WO2025038371A1 - Salt-loaded solid lipid nanoparticles loaded with an active agent - Google Patents

Abstract

A solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine, (c) cholesterol, and (d) 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt; a SLN comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in dimethyldidodecylammonium bromide or 1,2-dioleoyl-3-trimethylammonium-propane; pharmaceutical compositions comprising the SLNs; and methods of making the SLNs.

Description

69951-03 SALT-LOADED SOLID LIPID NANOPARTICLES LOADED WITH AN ACTIVE AGENT CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. provisional patent application no. 63/532,230, which was filed August 11, 2023, and U.S. provisional patent application no. 63/653,261, which was filed May 30, 2024, both of which are hereby incorporated by reference in their entireties. TECHNICAL FIELD [0002] The present disclosure relates to solid lipid nanoparticles comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in a cationic form of a lipid as an ionic complex or salt, pharmaceutical compositions comprising same, and methods of making. BACKGROUND [0003] Liposomes and lipid-based nanomedicines have been important drug-delivery vehicles for many years [1-4]. Solid lipid-based nanosystems loaded with drugs have been successfully used to treat various cancers since Doxil was introduced more than 20 years ago. Abraxane, which is an albumin-coated nanoparticle of the neutral drug paclitaxel, has increased activity (33% when combined with carboplatin) over paclitaxel (25% when combined with carboplatin). Doxil, which is doxorubicin in liposomal form, has lower heart toxicity than doxorubicin (Gyongyosi, Card. Res.116: 970 (2020)). [0004] The structure of liposomes, solid lipid nanoparticles (SLN), nanolipid carriers and the like is not well understood. Many diagrams and cartoons showing the structures of these species have been presented including simple liposomes with a bilayer with nucleic acids inside, double loaded bilayers containing an outer bilayer and an inner compartment loaded with nucleic acids, and even a bilayer with nucleic acids adhering to the outside. There has been a large amount of work on nucleic acid- and RNA-loaded carriers including, of course, the COVID-19 vaccine, which contains a carrier composed of a cationic lipid, a helper lipid, cholesterol, and a 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol (DMG- 69951-03 PEG) lipid loaded with mRNA. There has been surprisingly little work on drug-loaded carriers and no reports of the properties and characterization of COVID-19 carriers loaded with anionic drugs including phosphates, carboxylates, and phenolates. This is surprising since anionic drugs can form ionic complexes/salts with the cationic lipids that make up a large percentage of the composition of an SLN carrier, such as the SLN carrier used to vaccinate against COVID-19. [0005] In view of the above, it is an object of the present disclosure to provide solid lipid nanoparticles (SLNs) loaded with an anionic active agent. This and other objects and advantages, as well as inventive features, will be apparent from the detailed description. SUMMARY [0006] Provided is a solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine (DSPC), (c) cholesterol, and (d) 1,2-dimyristoyl-rac-glycero- 3-methoxypolyethylene glycol-2000 (DMG- PEG-2000) or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt. The ionic complex or salt is formed in ethanol, or another nonaqueous solvent is used for the reaction. The anionic form of the drug can be salified with sodium or triethylamine hydrochloride prior to entrapment in the carrier. The SLN carrier can be stable for at least about 29 days in a refrigerator at about 1.7-3.3 °C. The drug can be an anti-cancer drug, such as fludarabine phosphate, etoposide phosphate, or a flavone anion, for example. When the drug is fludarabine phosphate, the proton NMR spectrum of the SLN in suspension does not show fludarabine phosphate signals at about 6-6.5 ppm or about 8 to 8.5 ppm using tetramethylsilane (TMS) as a reference standard in ethanol – d₆ + D₂O with pre-saturation. The drug can be an anti-infective drug, such as an anti-infective drug comprising a phenolic anion, for example. [0007] A pharmaceutical composition is also provided. The pharmaceutical composition comprises an above-described SLN and a pharmaceutically acceptable carrier. [0008] Further provided is a method of making a SLN comprising an anionic form of a 69951-03 drug, which comprises a phosphate, a phenolate or a carboxylate, entrapped in (a) a cationic form of the lipid SM- 102 or a cationic form of the lipid ALC-0315, (b) DSPC, (c) cholesterol, and (d) DMG-PEG- 2000 or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or salt. The method comprises (i) mixing the anionic form of the drug dissolved in 100% ethanol with a cationic salt of ethoxide (e.g., sodium ethoxide) dissolved in ethanol, followed by stirring, filtering, evaporating as needed, and powdering as needed to obtain a powder or a residue; (ii) (a) mixing the powder or the residue obtained in (i) with ethanol and either of SM-102 or ALC- 0315 at a drug-lipid molar ratio of about 0.7:1 to about 1.5:1 until dissolved, (b) separately mixing DSPC, cholesterol, and either of DMG-PEG-2000 or ALC-0159 in ethanol until dissolved, and (c) mixing (a) and (b) together to obtain a solution; and (iii) adding the solution obtained in (ii) to water or a solution comprising water and a buffer; whereupon the SLN comprising an anionic form of a drug entrapped in either of SM-102 or ALC-0315 is obtained. The cationic form can be sodium or triethylamine. The drug can be an anti- cancer drug, such as fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion, for example. The drug can be an anti-infective drug, such as an anti-infective drug comprising a phenolic anion, for example. [0009] Still further provided is another method of making a SLN comprising an anionic form of a phosphate drug entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) DSPC, (c) cholesterol, and (d) DMG-PEG-2000 or ALC- 0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or salt. The method comprises (i) mixing the phosphate drug dissolved in 100% ethanol with (a) SM-102 or ALC-0315, (b) DSPC, (c) cholesterol, and (d) DMG- PEG-2000 or ALC-0159 in ethanol until dissolved to obtain a solution; and (ii) adding the solution obtained in (i) to water or a solution comprising water and a buffer; whereupon the SLN comprising an anionic form of a drug entrapped in either of SM-102 or ALC-0315 is obtained. The cationic form can be sodium or triethylamine. The drug can be an anti- cancer drug, such as fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion, for example. The drug can be an anti-infective drug, such as an anti-infective drug comprising a phenolic anion, for example. [00010] Even still further provided is a SLN comprising an anionic form of a drug, which 69951-03 comprises a phosphate, a phenolate, or a carboxylate, entrapped in dimethyldidodecylammonium bromide (DDAB) or 1,2-dioleoyl-3-trimethylammonium- propane (DOTAP). The anionic form of the drug can be salified with sodium or triethylamine hydrochloride. The SLN can be stable for at least about 29 days in a refrigerator at about 1.7-3.3 °C. The drug can be an anti-cancer drug, such as fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion, for example. The drug can be an anti-infective drug, such as an anti-infective drug comprising a phenolic anion, for example. The anti-infective drug can be quercetin. When the drug is quercetin, for example, it can produce a differential scanning calorimetry peak at 46 +/- 3 °C. [00011] A pharmaceutical composition is also provided. The pharmaceutical composition comprises an above-described SLN and a pharmaceutically acceptable carrier. [00012] Also provided is a method of making a SLN comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in DDAB or DOTAP. The method comprises (i) mixing the anionic form of a drug and either (a) DDAB in ethanol or (b) DOTAP in ethanol, followed by stirring, filtering, evaporating as needed, and powdering as needed; and (ii) adding the solution (or dissolving the powder to form the solution) to water or a second solution comprising water and a buffer; whereupon the SLN comprising the anionic form of a drug entrapped in DDAB or DOTAP is obtained. The anionic form of the drug can be salified with sodium or triethylamine hydrochloride. The drug can be an anti-cancer drug, such as fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. The drug can be an anti-infective drug, such as an anti- infective drug comprising a phenolic anion, for example. FIGURES [00013] Fig.1 shows the reaction to form the salt of nanoparticles. In the reaction, the ratio of quercetin to SM-102 was 1:1. The lipids were in the ratio 50:10:38.5:1.5. [00014] Fig.2 shows the TEM images of nanoparticles formed by reacting quercetin sodium with the lipid mix containing the cationic lipid SM-102. [00015] Fig.3 shows the reaction of the triethylamine salt of quercetin with the ionizable lipid SM-102. [00016] Fig.4 shows the TEM images of the dispersion and the supernatant formed by 69951-03 reaction of the quercetin triethylamine salt and SM-102 (with the other lipids). [00017] Fig.5 shows the reaction of benzoyl chloride with quercetin to form quercetin benzoate. [00018] Fig.6 shows the TEM images of nanoparticles loaded with quercetin benzoate. [00019] Fig.7 shows the reaction of dimethyldidodecylammonium bromide (DDAB) with quercetin sodium by salt exchange. [00020] Fig.8 shows the TEM images of quercetin sodium DDAB⁺ nanoparticles. [00021] Fig.9A shows the structure of etoposide phosphate. [00022] Fig.9B shows the structure of fludarabine phosphate. [00023] Fig.9C shows the structure of niclosamide. [00024] Fig.9D shows the structure of niclosamide phosphate. [00025] Fig.9E shows the structure of a salt of niclosamide phosphate and a cationic lipid. [00026] Fig.10 shows the differential scanning calorimetry (DSC) of quercetin (Q)- DDAB nanoparticles at different ratios of quercetin and DDAB. A is QNa-DDAB (1:1.25) nanoparticles, enthalpy (normalized) 69.384 J/g, peak temperature 51.84 °C, onset 45.08 °C. B is QNa-DDAB (1:1.5) nanoparticles, enthalpy (normalized) 75.440 J/g, peak temperature 50.66 °C, onset 43.99 °C. C is QNa-DDAB (1:1.75) nanoparticles, enthalpy (normalized) 74.541 J/g, peak temperature 49.68 °C, onset 43.53 °C. D is DDAB nanoparticles, enthalpy (normalized) 14.422 J/g, peak temperature 53.81 °C, onset 50.76 °C, and enthalpy (normalized) 46.442 J/g, peak temperature 67.62 °C, onset 65.07 °C. E is DDAB, enthalpy (normalized) 136.23 J/g, peak temperature 89.26 °C, onset 85.43 °C. [00027] Fig.11 shows the solution nuclear magnetic resonance (NMR) spectrum of fludarabine phosphate (FP) – COVID-19 nanoparticles and FP-SM-102 nanoparticles. A is FP + SM-102 + (distearoylphosphatidylcholine) DSPC + cholesterol + 1,2-dimyristoyl-rac- glycero-3-methoxypolyethylene glycol-2000 (DMG-PEG-2000) (FP - SM-102 = 1:1.5). B is FP + SM-102 (1:1.5). C is SM-102, and D is FP. DETAILED DESCRIPTION [00028] The present disclosure is predicated on the discovery that salt chemistry can be used to load and stabilize solid lipid nanoparticles (SLNs) (e.g., a COVID-19 vaccine type carrier) with an active agent. By way of example, quercetin sodium was formed in pure 69951-03 ethanol by reacting sodium ethoxide with quercetin (a weak acid). The quercetin sodium salt was then used to form nanoparticles with the cationic lipid SM-102 (the cationic lipid used in Moderna’s SARS-CoV-2 vaccine) and with dimethyldioctadecylammonium (bromide salt) (DDAB; a cationic lipid). The quercetin sodium salt and DDAB formed lipid nanoparticles without using other lipids. The quercetin salt also formed nanoparticles with a COVID-19-type mixture of SM-102, cholesterol, 1,2-distearoyl-s,n-glycero-3- phosphocholine (DSPC; a neutral lipid), and 1,2-dimyristoyl-rac-glycero-3-methoxy- polyethylene glycol 2000 (DMP-PEG-2000) in a ratio of 50:38.5:10:1.5. The formation of nanoparticles using this salt chemistry approach was established by particle size, transmission electron microscopy (TEM) analyses, nuclear magnetic resonance (NMR) analysis, and differential scanning calorimetry (DSC) analysis, and entrapment efficiency was determined using high pressure liquid chromatography (HPLC). Quercetin sodium was also reacted with benzoyl chloride to form benzoyl quercetin. The reaction product could be entrapped in a nanoparticle, but the entrapment efficiency was 28%, likely because the reaction with benzoyl chloride was not complete, allowing some ionic drug to be entrapped. [00029] By way of a second example, fludarabine phosphate and SM-102 were reacted in ethanol to form the salt/ionic complex as detected by dissolution of fludarabine phosphate. DSPC, cholesterol and DMG-PEG-2000 were dissolved in another portion of pure ethanol, and the two ethanol portions were mixed. This drug-lipid solution in ethanol was injected into aqueous phase (deionized water or 10 mM, pH 5.0, acetate buffer) under stirring to form the COVID-19-type SLN with a composition different from the COVID-19 nanoparticles because of the presence of the fludarabine phosphate. The solution was dialyzed and lyophilized with sucrose added to give a solid SLN. The formation of nanoparticles using this salt chemistry approach was established by particle size and NMR analysis. [00030] Additional examples are provided in more detail in the Examples section. [00031] Advantages of SLNs salt-loaded with an active agent can include one or more of the following: improved solubility, increased absorption, slower metabolism and elimination, more stable plasma levels, increased drug stability, high drug payload, enhanced activity or efficacy, reduced toxicity, improved tolerability, large-scale production, and the ability to make controlled-release products. 69951-03 [00032] In view of the above, provided is a SLN (e.g., a COVID-19 vaccine type carrier) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine (DSPC), (c) cholesterol, and (d) 1,2- dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 (DMG-PEG-2000) or ALC- 0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt. The ionic complex or salt is formed in ethanol, or another nonaqueous solvent, such as acetone or tetrahydrofuran (THF), is used for the reaction. The anionic form of the drug can be salified, for example, with sodium or triethylamine hydrochloride, prior to entrapment in the carrier. The SLN carrier can be stable for at least about 29 days in a refrigerator at about 1.7-3.3 °C. The drug can be an anti-cancer drug, such as fludarabine phosphate, etoposide phosphate, or a flavone anion, for example. Examples of flavone anions include, but are not limited to, those based on flavones derived from plants (see, e.g., Tsimogiannis and Oreopoulou, “Classification of Phenolic Compounds in Plants,” in Polyphenols in Plants, 2^nd ed., Isolation, Purification, and Extract Preparation, pp.263-284, Academic Press (2019)), apigenin, apigenin C-glycoside, apigenin O-glycoside, luteolin, luteolin C-glycoside, luteolin O-glycoside, diosmetin C- glycoside, diosmetin O-glycoside, chrysoeriol C-glycoside, chrysoeriol O-glycoside, acacetin O-glycoside, myricetin, chrysin, baicalein, scutellarein, hispidulin, tricetin, sinensetin, tangeretin, serpyllin, nobiletin, scaposin, and genkwanin. When the drug is fludarabine phosphate, the proton NMR spectrum of the SLN in suspension does not show fludarabine phosphate signals at about 6-6.5 ppm or about 8-8.5 ppm using tetramethylsilane (TMS) as a reference standard in ethanol – d₆ + D₂O with pre-saturation. The drug can be an anti-infective drug, such as an anti-infective drug comprising a phenolic anion, for example. Phenolic anions can be based on phenolic acids derived from plants, such as, for example, polyphenolic compounds, such as flavonoids, galangin, campaverol, cinnamic acid, P-coumaric acid, ferulic acid, sinapic acid, caffeic acid, benzoic acid, 4- hydroxy-benzoic acid, vanillic acid, syringic acid, protocatechuic acid, tannic acid, epicatechin, epigallocatechin, gallic acid, resveratrol, resveratryl triacetate, catechol, catechin, epicatechin-3-gallate, epigallocatechin gallate, ellagic acid, punicalagin, protocatechuic aldehyde, afzelin, formononetin, quercetin, pyrogallol, capsaicin, Wrightia 69951-03 dione, thespesin, chamazulene/matricin, silymarin, hydroxytyrosol, chlorogenic acid, luteolin, EGCG, hesperetin, daidzein, myricetin, apigenin, curcumin, stilbene, benzoic acid, and kaempferol. The cationic lipid SM-102 has already been utilized in medicines (e.g., the COVID-19 vaccine), and this utilization will facilitate regulatory approval of new medicines containing SM-102. Nanoparticles of another anti-infective drug, niclosamide, can necessitate the addition of an agent that retards/prevents agglomeration, an example of which is mannitol. [00033] A pharmaceutical composition is also provided. The pharmaceutical composition comprises an above-described SLN and a pharmaceutically acceptable carrier. [00034] Further provided is a method of making a SLN comprising an anionic form of a drug, which comprises a phosphate, a phenolate or a carboxylate, entrapped in (a) a cationic form of the lipid SM- 102 or a cationic form of the lipid ALC-0315, (b) DSPC, (c) cholesterol, and (d) DMG-PEG-2000 or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or salt. The method comprises (i) mixing the anionic form of the drug dissolved in 100% ethanol with a cationic salt of ethoxide (e.g., sodium ethoxide) dissolved in ethanol, followed by stirring, filtering, evaporating as needed, and powdering as needed to obtain a powder or a residue; (ii) (a) mixing the powder or the residue obtained in (i) with ethanol and either of SM-102 or ALC- 0315 at a drug-lipid molar ratio of about 0.7:1 to about 1.5:1 until dissolved, (b) separately mixing DSPC, cholesterol, and either of DMG-PEG-2000 or ALC-0159 in ethanol until dissolved, and (c) mixing (a) and (b) together to obtain a solution; and (iii) adding the solution obtained in (ii) to water or a solution comprising water and a buffer (e.g., at a pH of about 5); whereupon the SLN comprising an anionic form of a drug entrapped in either of SM-102 or ALC-0315 is obtained. The cationic form can be sodium or triethylamine, for example. The drug can be an anti-cancer drug, such as fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion, for example. Examples of flavone anions include, but are not limited to, those based on flavones derived from plants (see, e.g., Tsimogiannis and Oreopoulou, “Classification of Phenolic Compounds in Plants,” in Polyphenols in Plants, 2^nd ed., Isolation, Purification, and Extract Preparation, pp.263-284, Academic Press (2019)), apigenin, apigenin C-glycoside, apigenin O-glycoside, luteolin, luteolin C- glycoside, luteolin O-glycoside, diosmetin C-glycoside, diosmetin O-glycoside, chrysoeriol 69951-03 C-glycoside, chrysoeriol O-glycoside, acacetin O-glycoside, myricetin, chrysin, baicalein, scutellarein, hispidulin, tricetin, sinensetin, tangeretin, serpyllin, nobiletin, scaposin, and genkwanin. The drug can be an anti-infective drug, such as an anti-infective drug comprising a phenolic anion, for example. Phenolic anions can be based on phenolic acids derived from plants, such as, for example, polyphenolic compounds, such as flavonoids, galangin, campaverol, cinnamic acid, P-coumaric acid, ferulic acid, sinapic acid, caffeic acid, benzoic acid, 4-hydroxy-benzoic acid, vanillic acid, syringic acid, protocatechuic acid, tannic acid, epicatechin, epigallocatechin, gallic acid, resveratrol, resveratryl triacetate, catechol, catechin, epicatechin-3-gallate, epigallocatechin gallate, ellagic acid, punicalagin, protocatechuic aldehyde, afzelin, formononetin, quercetin, pyrogallol, capsaicin, Wrightia dione, thespesin, chamazulene/matricin, silymarin, hydroxytyrosol, chlorogenic acid, luteolin, EGCG, hesperetin, daidzein, myricetin, apigenin, curcumin, stilbene, benzoic acid, and kaempferol. Another anti- infective drug, niclosamide, can necessitate the addition of an agent that retards/prevents agglomeration, an example of which is mannitol. [00035] The reaction steps shown below illustrate this process with etoposide phosphate. [00036] Still further provided is another method of making a SLN comprising an anionic form of a phosphate drug entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) DSPC, (c) cholesterol, and (d) DMG-PEG-2000 or ALC- 0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or salt. The method comprises (i) mixing the phosphate drug dissolved in 100% ethanol with (a) SM-102 or ALC-0315, (b) DSPC, (c) cholesterol, and (d) DMG- PEG-2000 or ALC-0159 in ethanol until dissolved to obtain a solution; and (ii) adding the solution obtained in (i) to water or a solution comprising water and a buffer (e.g., at a pH of about 5); whereupon the SLN comprising an anionic form of a drug entrapped in either of SM-102 or ALC-0315 is obtained. The cationic form can be sodium or triethylamine, for 69951-03 example. The drug can be an anti-cancer drug, such as fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion, for example. Examples of flavone anions include, but are not limited to, those based on flavones derived from plants (see, e.g., Tsimogiannis and Oreopoulou, “Classification of Phenolic Compounds in Plants,” in Polyphenols in Plants, 2^nd ed., Isolation, Purification, and Extract Preparation, pp.263-284, Academic Press (2019)), apigenin, apigenin C-glycoside, apigenin O-glycoside, luteolin, luteolin C- glycoside, luteolin O-glycoside, diosmetin C-glycoside, diosmetin O-glycoside, chrysoeriol C-glycoside, chrysoeriol O-glycoside, acacetin O-glycoside, myricetin, chrysin, baicalein, scutellarein, hispidulin, tricetin, sinensetin, tangeretin, serpyllin, nobiletin, scaposin, and genkwanin. The drug can be an anti-infective drug, such as an anti-infective drug comprising a phenolic anion, for example. Phenolic anions can be based on phenolic acids derived from plants, such as, for example, polyphenolic compounds, such as flavonoids, galangin, campaverol, cinnamic acid, P-coumaric acid, ferulic acid, sinapic acid, caffeic acid, benzoic acid, 4-hydroxy-benzoic acid, vanillic acid, syringic acid, protocatechuic acid, tannic acid, epicatechin, epigallocatechin, gallic acid, resveratrol, resveratryl triacetate, catechol, catechin, epicatechin-3-gallate, epigallocatechin gallate, ellagic acid, punicalagin, protocatechuic aldehyde, afzelin, formononetin, quercetin, pyrogallol, capsaicin, Wrightia dione, thespesin, chamazulene/matricin, silymarin, hydroxytyrosol, chlorogenic acid, luteolin, EGCG, hesperetin, daidzein, myricetin, apigenin, curcumin, stilbene, benzoic acid, and kaempferol. Another anti-infective drug, niclosamide, can necessitate the addition of an agent that retards/prevents agglomeration, such as mannitol. [00037] Even still further provided is a SLN comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in dimethyldidodecylammonium bromide (DDAB) or 1,2-dioleoyl-3-trimethylammonium- propane (DOTAP). The anionic form of the drug can be salified, for example, with sodium or triethylamine hydrochloride. The SLN can be stable for at least about 29 days in a refrigerator at about 1.7-3.3 °C. The drug can be an anti-cancer drug, such as fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion, for example. Examples of flavone anions include, but are not limited to, those based on flavones derived from plants (see, e.g., Tsimogiannis and Oreopoulou, “Classification of Phenolic Compounds in Plants,” in Polyphenols in Plants, 2^nd ed., Isolation, Purification, and Extract Preparation, 69951-03 pp.263-284, Academic Press (2019)), apigenin, apigenin C-glycoside, apigenin O- glycoside, luteolin, luteolin C-glycoside, luteolin O-glycoside, diosmetin C-glycoside, diosmetin O-glycoside, chrysoeriol C-glycoside, chrysoeriol O-glycoside, acacetin O- glycoside, myricetin, chrysin, baicalein, scutellarein, hispidulin, tricetin, sinensetin, tangeretin, serpyllin, nobiletin, scaposin, and genkwanin. The drug can be an anti-infective drug, such as a phenolic anion, for example. Phenolic anions can be based on phenolic acids derived from plants, such as, for example, polyphenolic compounds, such as flavonoids, galangin, campaverol, cinnamic acid, P-coumaric acid, ferulic acid, sinapic acid, caffeic acid, benzoic acid, 4-hydroxy-benzoic acid, vanillic acid, syringic acid, protocatechuic acid, tannic acid, epicatechin, epigallocatechin, gallic acid, resveratrol, resveratryl triacetate, catechol, catechin, epicatechin-3-gallate, epigallocatechin gallate, ellagic acid, punicalagin, protocatechuic aldehyde, afzelin, formononetin, quercetin, pyrogallol, capsaicin, Wrightia dione, thespesin, chamazulene/matricin, silymarin, hydroxytyrosol, chlorogenic acid, luteolin, EGCG, hesperetin, daidzein, myricetin, apigenin, curcumin, stilbene, benzoic acid, and kaempferol. The anti-infective drug can be quercetin. When the drug is quercetin, for example, it can produce a differential scanning calorimetry peak at 46 +/- 3 °C. [00038] A pharmaceutical composition is also provided. The pharmaceutical composition comprises an above-described SLN and a pharmaceutically acceptable carrier. [00039] Also provided is a method of making a SLN comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in DDAB or DOTAP. The method comprises (i) mixing the anionic form of a drug and either (a) DDAB in ethanol or (b) DOTAP in ethanol, followed by stirring, filtering, evaporating as needed, and powdering as needed; and (ii) adding the solution (or dissolving the powder to form the solution) to water or a second solution comprising water and a buffer (e.g., at a pH of about 5); whereupon the SLN comprising the anionic form of a drug entrapped in DDAB or DOTAP is obtained. The anionic form of the drug can be salified, for example, with sodium or triethylamine hydrochloride. The drug can be an anti-cancer drug, such as fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. Examples of flavone anions include, but are not limited to, those based on flavones derived from plants (see, e.g., Tsimogiannis and Oreopoulou, “Classification of Phenolic Compounds in Plants,” in Polyphenols in Plants, 2^nd ed., Isolation, Purification, and Extract Preparation, 69951-03 pp.263-284, Academic Press (2019)), apigenin, apigenin C-glycoside, apigenin O- glycoside, luteolin, luteolin C-glycoside, luteolin O-glycoside, diosmetin C-glycoside, diosmetin O-glycoside, chrysoeriol C-glycoside, chrysoeriol O-glycoside, acacetin O- glycoside, myricetin, chrysin, baicalein, scutellarein, hispidulin, tricetin, sinensetin, tangeretin, serpyllin, nobiletin, scaposin, and genkwanin. The drug can be an anti-infective drug, such as an anti-infective drug comprising a phenolic anion, for example. Phenolic anions can be based on phenolic acids derived from plants, such as, for example, polyphenolic compounds, such as flavonoids, galangin, campaverol, cinnamic acid, P- coumaric acid, ferulic acid, sinapic acid, caffeic acid, benzoic acid, 4-hydroxy-benzoic acid, vanillic acid, syringic acid, protocatechuic acid, tannic acid, epicatechin, epigallocatechin, gallic acid, resveratrol, resveratryl triacetate, catechol, catechin, epicatechin-3-gallate, epigallocatechin gallate, ellagic acid, punicalagin, protocatechuic aldehyde, afzelin, formononetin, quercetin, pyrogallol, capsaicin, Wrightia dione, thespesin, chamazulene/matricin, silymarin, hydroxytyrosol, chlorogenic acid, luteolin, EGCG, hesperetin, daidzein, myricetin, apigenin, curcumin, stilbene, benzoic acid, and kaempferol. Another anti-infective drug, niclosamide, can necessitate the addition of an agent that retards/prevents agglomeration, such as mannitol. [00040] By “cationic lipid” is meant a lipid species that carries a net positive charge at a selected pH, such as physiological pH (e.g., a pH of about 7.0). Cationic lipids comprising alkyl chains with multiple sites of unsaturation, e.g., at least two or three sites of unsaturation, can be particularly useful for forming lipid particles with increased membrane fluidity. [00041] By “neutral lipid” is meant a lipid species that exists either in an uncharged or neutral zwitterionic form at a selected pH, such as physiological pH (e.g., a pH of about 7.0). [00042] By “salt” is meant an association or ionic complex of a cationic molecule and an anionic molecule. The reaction of an acid and a base forms a salt. [00043] Examples of cholesterol derivatives include, but are not limited to, cholestanol, cholestanone, cholestenone, coprostanol, cholesteryl-2’-hydroxyethyl ether, cholesteryl-4’- hydroxybutyl ether, and mixtures thereof. [00044] The drug can be any anionic active agent, such as an anti-cancer drug or an anti- 69951-03 infective drug (e.g., anti-viral, anti-bacterial, anti-parasitic). Examples of anionic anti- cancer drugs include, but are not limited to, etoposide, etoposide phosphate and fludarabine phosphate (see Fig.11 for structures). Examples of anionic anti-viral drugs include, but are not limited to, niclosamide (which may be require the addition of an agent that retards/prevents agglomeration, such as mannitol), acyclovir, salicylamides, curcumin, quercetin, flavonoids, and phosphates of any of the foregoing. [00045] Homogenization, ultrasound, and antisolvent mixing can be used for formulation (Mehnert et al., Adv Drug Deliv Rev 64: 83-101 (2012)). Hot homogenization has been used for formulations containing stearic acid and tristearin, which melt during the process. High temperatures can result in smaller particles due to decreased viscosity. Solvent emulsification is another powerful method involving precipitation of oil:water emulsions by solvent evaporation. In some cases, the emulsion is formed with high-pressure homogenization. Of course, the lipid, the emulsifier, and the manufacturing procedure all play a role in the properties of the SLNs produced. Spray drying is potentially a powerful method for making SLN because it yields a powder that can usually be filled into capsules. Additionally, if the product is to be sterilized by heat, then this step's effect on the SLN needs to be assessed. Sterilization by gamma irradiation can also produce changes. A sterilization method needs to be developed after the final structure and formulation of the SLN is established. [00046] A critical part of SLN manufacture is determination of the structure of SLNs and their quality. Typical characterization methods are: (1) particle size; (2) zeta potential; (3) crystallinity of the components; (4) thermal analysis; and (4) nuclear magnetic resonance (NMR). Particle size is typically measured using dynamic light scattering methods. Zeta potential measures particle movement when exposed to an electric field. Crystallinity is measured using X-ray diffraction and pair distribution function analysis as described in more detail below. Thermal analysis is measured in a differential scanning calorimeter and can be used to determine crystallinity. NMR is a powerful method for determining the association of molecules and mobility. A combination of X-ray pair distribution analysis and NMR can illustrate the domain structure of the solid lipid nanoparticles. [00047] Typically, SLNs are less toxic than polymeric nanoparticles. Overall, SLN are expected to be non-toxic because they contain physiological compounds, and metabolic 69951-03 pathways exist for the formulation components. The SLN are typically phagocytized. [00048] Pharmaceutical compositions can be prepared for any suitable route of administration. Examples of suitable routes include, but are not limited to, oral, parenteral, subcutaneous, inhalation, depot, and topical. The characteristics of the SLN for each route of administration may differ, but in cases where the SLN is stable, a single SLN composition can be administered by multiple routes. Lipases can degrade SLNs and exist in multiple organs in the body (Mehnert et al. (2012), supra). The degradation routes for SLNs are determined empirically. EXAMPLES [00049] The following examples serve to illustrate the present disclosure. The examples are not intended to limit the scope of the claimed invention in any way. Example 1. Preparation of solid lipid nanoparticles (SLNs) [00050] SLNs were prepared following the injection procedure described in the literature [7,8]. Alternatively, SLNs can be prepared using a confined impinging jet mixer - CIJ mixer (Holland Applied Technologies, P0288404). [00051] The lipids and drugs were purchased commercially. Cholesterol, quercetin, and pure ethanol were available in the laboratory. [00052] The particle size was determined using Malvern Zetasizer Nano ZX (Malvern Panalytical). Transmission electron microscopy (TEM) imaging was done using a 200 kV transmission electron microscope (Tecnai G2 T20, FEI). Drug entrapment efficiency was determined using Agilent 1100 Series high pressure liquid chromatography (HPLC). The nuclear magnetic resonance (NMR) spectra were measured on a Bruker Avance-III 800 MHz NMR equipped with a QCI cryoprobe. The entrapment efficiency of quercetin in the nanoparticles was determined using HPLC under the chromatographic conditions [9] in Table 1. 69951-03 Table 1. Chromatographic Conditions Parameter Description Column HiQ Sil C18HS [00053

ug s oc so u o s we e p epa e a g co ce a o e hanol. Calibration plots were prepared in the range of 2-50 μg/ml. The drug entrapment efficiency (%EE) was determined using Agilent 1100 Series HPLC by analyzing the drug content in the whole nanoparticle dispersion and the supernatant collected after ultracentrifugation of nanoparticle dispersion using the Beckman Coulter® Optima^TM MAX-XP Ultracentrifuge. The nanoparticle dispersion (1 ml) was added to 1.5 ml centrifuge tubes and centrifuged at 100,000 rpm (rcf of 543,000 x g) for 15 min at 4⁰C. The whole dispersion and the supernatant were analyzed using HPLC. The injection samples were prepared by diluting the nanoparticle dispersion 10x with methanol and mixing until a clear solution was obtained. The supernatant sample was prepared by diluting 5x with methanol. The drug entrapment efficiency was calculated using the formula: % EE = (amount of drug in whole dispersion – amount of drug in supernatant)/theoretical q^{uercetin amount in nanoparticles x 100} T_{he nanoparticles were imaged using the Tecnai G220 Transmission Electron} ^Microscope and a 200 KV LaB6 filament transmission electron microscope, fitted with a Fischione HAADF detector and equipped with software (FEI and SerialEM) for automated electron tomography, together with a Fischione 2020 high-tilt holder. The CCD camera was a bottom mount Gatan US10002K x 2K. The samples were stained using 2% uranyl acetate 69951-03 on 400 mesh copper grids coated with carbon film. [00054] Solid lipid nanoparticles were lyophilized using mannitol or sucrose as the cytooprotectant keeping the nanoparticles-mannitol/sucrose ratio of 1:1. Mannitol was dissolved in the nanoparticles dispersion by stirring. The dispersion was frozen at -80 ⁰C for 48 hours. The frozen sample was put through a freeze-drying cycle (cooling at -80 ⁰C at <0.05 mBar for 96 hours). The lyophilized product was stored at -20 ⁰C. Example 2. Preparation of quercetin sodium – DDAB nanoparticles [00055] Quercetin sodium (~ 90% pure) and triethylamine hydrochloride (1:4 molar ratio) were added to pure ethanol and sonicated until the quercetin sodium dissolved. Dimethyldidodecylammonium bromide (DDAB) was separately dissolved in pure ethanol and added to the quercetin solution. The drug-lipid solution was injected into the aqueous phase (deionized water or 10 mM, pH 5.0, acetate buffer) under stirring using a magnetic stirrer. The ethanol (and buffer salts, if prepared in 10 mM, pH 5.0, acetate buffer as antisolvent) in the formulation was removed by dialysis in deionized water using a 10K MWCO Slide-A-Lyzer dialysis cassette (ThermoFisher Scientific). The quercetin sodium- DDAB nanoparticles had a drug loading of 15-25% and encapsulation efficiency of 75- 100%. The aqueous nanoparticle suspension was lyophilized at -80⁰C and <0.1 mbar in a Labconco® benchtop lyophilizer (freeze-drying time: 5 days). Dried nanoparticles were obtained. The dialysis and lyophilization did not reduce the encapsulation efficiency. Example 3. Preparation of quercetin sodium-DOTAP nanoparticles [00056] The procedure of Example 2 was used to prepare quercetin sodium-1,2-dioleoyl-3- trimethylammonium-propane (DOTAP) nanoparticles. Example 4. Preparation of quercetin sodium-DDAB/DOTAP-DSPC-cholesterol-DMG- PEG-2000 nanoparticles [00057] Quercetin sodium (~ 90% pure) and triethylamine hydrochloride (1:4 molar ratio) were added to pure ethanol and sonicated until the quercetin sodium was dissolved. DDAB/DOTAP was separately dissolved in pure ethanol and added to the quercetin sodium solution.1,2-distearoyl-s,n-glycero-3-phosphocholine (DSPC), cholesterol and 1,2- 69951-03 dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 (DMG-PEG-2000) were dissolved in another portion of pure ethanol and also added to the quercetin sodium solution. The drug-lipid solution was injected into the aqueous phase (deionized water or 10 mM pH 5.0 acetate buffer) under stirring using a magnetic stirrer. Example 5. Preparation of quercetin COVID-19-type lipid nanoparticles starting with quercetin sodium instead of quercetin [00058] Quercetin sodium (prepared as described above) and SM-102 (a synthetic, ionizable amino lipid) were stirred in pure ethanol at 1:1 drug-lipid molar ratio until the drug was completely dissolved. DSPC, cholesterol and DMG-PEG-2000 were separately dissolved in pure ethanol keeping the SM-102, DSPC, cholesterol, and DMG-PEG-2000 lipid mix molar ratio at 50:10:38.5:1.5 by weight. The two solutions were mixed. The total solid content was 6 mg/ml, and the drug-total lipid weight ratio was 19:81. The solvent phase volume and the antisolvent phase (pH 5.0 acetate buffer, 10 mM) were measured to keep the solvent-antisolvent ratio of 1:3. The solvent phase was injected into the antisolvent phase under stirring using a 20G syringe, which was kept under the surface of the antisolvent phase while injecting. Stirring was continued for 15 minutes. [00059] The reaction to form the salt of nanoparticles is shown in Fig.1. In the reaction, the ratio of quercetin to SM-102 was 1:1. The lipids were in the ratio of 50:10:38.5:1.5. These nanoparticles contained 18.6%, 40.7%, 8.1%, 31.3% and 1.2% quercetin sodium:SM102:cholesterol:DSPC: DMG-PEG-2000. Unlike the quercetin nanoparticles, the quercetin sodium nanoparticles were stable. This is likely because of the stronger negative charge on the phenolic oxygen atom of quercetin due to the formation of the sodium salt, which readily loses the sodium ion in the acidic pH used in manufacturing the formulation. This leads to a stronger interaction with the cationic SM-102 compared to free quercetin. The particle size, PDI, zeta potential, and entrapment efficiency are shown in Table 2. 69951-03 Table 2. Particle size, PDI, zeta potential and entrapment efficiency for nanoparticles formed by the reaction of quercetin sodium with the lipid mix containing the cationic lipid SM-102 Particle size (Z-Avg, d.nm) 96.5

p ig.2. Example 6. Results for drug loading, %EE, stability, size, PDI [00061] The drug loading, encapsulation efficiency (EE), particle size and polydispersity index (PDI) for QS are summarized in the table below (Table 3). Table 3. Drug Loading, %EE, Stability, Size, PDI for quercetin sodium (QS) Drug loading %EE Storage Size PDI Com osition (% w/w) eriod (nm) 6 1 1 0 5 9 2 4 4 1

69951-03 Example 7. NMR spectroscopy of quercetin sodium-DDAB-SLN dispersion [00062] The SLN dispersion (drug-DDAB or pure DDAB) prepared using the procedure outlined above was then subjected to three cycles of ultrafiltration using the 4 ml Amicon Ultra Centrifugal Filters (MilliporeSigma). The concentrated dispersion was diluted with deuterium oxide (D2O) (99.9%) at each stage until essentially all the ethanol had been removed and water had been exchanged for D₂O. For the pure drug spectrum, quercetin sodium was dissolved in a 1:3 mixture of ethanol-d6 (99%) and D₂O (99.9%). Bruker Avance-III 800 MHz NMR equipped with a QCI cryoprobe was used for all analysis. The disappearance or near disappearance of some peaks of drug and the lipid in the nanoparticle spectrum was observed and indicates quercetin sodium-DDAB interaction. The disappearance of the quercetin signals in the salt suggests the quercetin anion may be immobilized in the lipid bilayer formed by DDAB. Example 8. Differential scanning calorimetry of the freeze-dried quercetin-DDAB nanoparticles [00063] Since the lyophilized pure nanoparticles were completely dry, it was possible to study the thermal behavior of the nanoparticles using DSC. It was observed that the pure lipid (DDAB) had a single melting endotherm at 89⁰C but the pure DDAB nanoparticles (prepared using the same method as the drug-lipid nanoparticles) showed two melting endotherms at 54⁰C and 68⁰C. The drug-lipid nanoparticles showed none of these peaks, while a new single melting endotherm was observed at around 50⁰C. The melting peak showed a small, gradual shift towards a lower melting point with decreasing drug load (51.84⁰C for 1:1.25, 50.66⁰C for 1:1.5 and 49.68⁰C quercetin sodium-DDAB molar ratio). The disappearance of the pure lipid melting peaks indicates that the drug is present as an ionic complex with the cationic lipid. Fig.10 and Table 4 show the DSC data for this ionic complex/salt. In this ionic complex (salt) the sodium that was originally associated with the quercetin anion was replaced by the DDAB cation, giving a different composition from the original molecules that were mixed together. 69951-03 Table 4. Relationship between drug loading and enthalpy in the DSC of DDAB:quercetin nanoparticles Drug Loading (quercetin:DDAB molar ratio) Enthalpy of DSC Peak in J/g 0.7:1 0.60

. [00064] Powder x-ray diffraction patterns of the DDAB:quercetin SLNs and the components show that quercetin sodium gives an amorphous pattern, showing that it is non- crystalline. The DDAB nanoparticle gives a crystalline pattern consistent with the DSC tracing showing endotherms. The quercetin sodium:DDAB nanoparticles show an amorphous pattern, which is different from the quercetin sodium starting material. Example 10. Stability of quercetin sodium nanoparticles [00065] The stability of SLN is important since the two SLN-based, COVID-19 vaccines had to be stored at -80 ⁰C. The initial study of the quercetin:SLN stability was carried out using particle size growth as the marker for instability. Particle size is a good marker for the instability of liposomes and nanoparticles, since adverse events from particle growth in liposomal products have been known for over 20 years. Table 5 reports the stability of quercetin SLN with SM-102, DSPC, cholesterol, and DMG-PEG. Table 5 also reports the stability of quercetin:DDAB nanoparticles. In both cases, the SLN-quercetin composition was stable for 29 days at refrigerator conditions.

69951-03 Table 5. Particle size and PDI of quercetin sodium nanoparticles initially and after 29 days. The small change in these parameters indicates a stable nanoparticle. Other data indicate that unstable preparations of other drugs change particle size within one day. Drug pKa (strongest Formulation Stability Z-Avg F l ti PDI 8 3 3 9

Example 11. Attempted preparation of COVID-19-type nanoparticles with the neutral drug Quercetin. [00066] Quercetin-filled nanoparticles were prepared and contained 17.5%, 41.2%, 8.2%, 31.7% and 1.2% quercetin:SM-102:DSPC:cholesterol:DMG-PEG-2000. These nanoparticles were not stable as evidenced by the large average particle size and high polydispersity index (PDI). The average particle size, PDI, zeta potential, and entrapment efficiency for these nanoparticles are shown in Table 6.

69951-03 Table 6. Particle size, PDI, zeta potential, and entrapment efficiency for the nanoparticles formed by the reaction of quercetin with the lipid mix containing the cationic lipid SM-102 Particle size (Z-Avg, d.nm) 545.1

wo hours. [00068] Quercetin sodium appeared, in some experiments, to be less than 100% soluble in pure ethanol. To investigate whether higher entrapment efficiency of a drug can be obtained using a different cation, quercetin sodium was converted to the triethylamine salt of quercetin. This triethylamine salt was then reacted with the same lipid mixture containing SM-102 in a 1:1 ratio. The overall lipid ratio for this reaction was 50:10:38.5:1.5 (SM-102:DSPC:cholesterol:DMG- PEG-2000). The chemical reaction is shown in Fig.3. In this reaction, the entrapment efficiency was higher than that for the sodium salt of quercetin. Table 7 shows the particle size, polydispersity, zeta potential, and entrapment efficiency of over 70%. This is higher than the entrapment efficiency for either quercetin or quercetin sodium unreacted with triethylamine hydrochloride. This is likely because the amine helps improve the solubility of quercetin sodium in pure ethanol, improving the efficiency of the interaction with SM-102. Table 7. Particle size, PDI, zeta potential, and entrapment efficiency of the triethylamine salt of quercetin and SM-102 in the lipid mixture Particle size (Z-Avg, d.nm) 93.4

[00069] The dispersion and the supernatant formed by reaction of the quercetin triethylamine salt and SM-102 (with the other lipids) is shown in Fig.4. 69951-03 Example 12. Attempted preparation of quercetin benzoate nanoparticles [00070] Quercetin benzoate was prepared to test the entrapment efficiency of a neutral quercetin molecule in an SM-102 cationic solid lipid nanoparticle with the other lipids. Quercetin sodium was reacted with benzoyl chloride for this study, as shown in Fig.5. Then the quercetin benzoate was reacted with SM-102 and the other lipids in the same ratio (50:10:38.5:1.50) to form nanoparticles. The drug-lipid weight ratio was 19:81. The solvent phase volume and the antisolvent phase (pH 5.0 acetate buffer) were kept at a solvent-antisolvent ratio of 1:3. The solvent phase was injected into the antisolvent phase under stirring using a 20G syringe, which was kept under the surface of the antisolvent phase while injecting. The particle size, polydispersity, zeta potential and entrapment efficiency are shown in Table 8. Notably, the entrapment efficiency is much lower in this case, likely due to the neutral charge on the ester reducing the proportion of the drug available for ionic interaction with the lipid. [00071] Quercetin sodium was stirred in pure ethanol, and benzoyl chloride was added at a 1:1 molar ratio. The mixture was stirred until the drug was completely dissolved. A product with a distinct fruity odor was formed. The product was a yellow-colored solution, rather than the reddish-brown color of quercetin sodium. Table 8. Particle size, PDI, zeta potential, and entrapment efficiency of quercetin benzoate nanoparticles Particle size (Z-Avg, d.nm) 108.8

[00072] The TEM of quercetin benzoate loaded particles is shown in Fig.6. Example 13. Preparation of fludarabine phosphate-DDAB nanoparticles [00073] Fludarabine phosphate and triethylamine (1:2 molar ratio) were added to pure ethanol and sonicated until the fludarabine phosphate dissolved. DDAB was separately 69951-03 dissolved in pure ethanol and added to the fludarabine phosphate solution. The drug-lipid solution was injected into the aqueous phase (deionized water or 10 mM, pH 5.0, acetate buffer) under stirring using a magnetic stirrer. The ethanol (and buffer salts, if prepared in 10 mM, pH 5.0, acetate buffer as antisolvent) in the formulation was removed by dialysis in deionized water using a 10K MWCO Slide-A-Lyzer dialysis cassette (ThermoFisher Scientific). The fludarabine phosphate-DDAB nanoparticles had a drug loading of 15-25% and encapsulation efficiency of 75-100%. Example 14. Preparation of fludarabine phosphate-DOTAP nanoparticles [00074] The procedure of Example 13 was used to prepare Fludarabine phosphate- DOTAP nanoparticles. Example 15. Preparation of fludarabine phosphate-DOTAP-DSPC-cholesterol- DMG- PEG-2000 nanoparticles [00075] Fludarabine phosphate and triethylamine (1:2 molar ratio) were added to pure ethanol and sonicated until the fludarabine phosphate dissolved. DOTAP was separately dissolved in pure ethanol and added to the fludarabine phosphate solution. DSPC, cholesterol and DMG-PEG-2000 were dissolved in another portion of pure ethanol and added to the fludarabine phosphate solution. The drug-lipid solution was injected into the aqueous phase (deionized water or 10 mM, pH 5.0, acetate buffer) under stirring using a magnetic stirrer. Example 16. Preparation of fludarabine phosphate-SM-102-DSPC-cholesterol-DMG- PEG-2000 nanoparticles [00076] Fludarabine phosphate and SM-102 were added to pure ethanol and sonicated until the fludarabine phosphate dissolved. DSPC, cholesterol and DMG-PEG-2000 were dissolved in another portion of pure ethanol and added to the fludarabine phosphate solution. The drug-lipid solution was injected into the aqueous phase (deionized water or 10 mM, pH 5.0, acetate buffer) under stirring using a magnetic stirrer. The nanoparticles obtained had a drug loading of 10-17% and encapsulation efficiency of 52- 83%. The ethanol (and buffer salts if prepared in 10 mM, pH 5.0, acetate buffer as 69951-03 antisolvent) in the formulation was removed by dialysis in deionized water using a 10K MWCO Slide-A-Lyzer dialysis cassette (ThermoFisher Scientific). The aqueous nanoparticle suspension was lyophilized at -80⁰C and <0.1 mbar in a Labconco® benchtop lyophilizer with 2.5% w/v or 5% w/v sucrose added (freeze-drying time: 7 days). Example 17. Lyophilization of SLN [00077] SLNs containing fludarabine phosphate – SM-102 (1:1.5) – DSPC – Chol – DMG-PEG-2000 were lyophilized with no sucrose, 2.5% sucrose, and 5% sucrose and reconstituted. The nanoparticles showed only a small amount of particle growth as shown in Table 5. The drug loading (DL), encapsulation efficiency (EE), particle size and polydispersity index (PDI) after lyophilization are shown in Table 9. Table 9. Drug loading (DL), encapsulation efficiency (EE), particle size and polydispersity index (PDI) after lyophilization of fludarabine phosphate nanoparticles C_{omposition %DL %EE} ^Storage Size r_{i d (nm)} ^PDI 5 7 3 5 1 5 3 5 8 9 4 4 0 3 3 5

69951-03 2 days 117.6 0.0783

I ii l 7923 01027 5 2 1 8 0 9

Example 18. NMR spectroscopy of fludarabine phosphate-SM-102 SLN dispersion [00078] The SLN dispersions (drug-SM-102, pure SM-102, and drug-SM-102-DSPC- Cholesterol-DMG-PEG-2000) were prepared using the procedure outlined and replacing the regular solvents with deuterated solvents and using ethanol-d6 (99%) as the solvent phase and D2O (99.9%) as the antisolvent phase. All samples were prepared keeping the drug concentration of 1 mM and the SM-102 concentration of 1.6 mM. The SLN dispersion was directly analyzed after preparation. For the pure drug spectrum, fludarabine phosphate was dissolved in a 1:3 mixture of ethanol-d (99%) and D2O (99.9%). Bruker Avance-III 800 MHz NMR equipped with a QCI cryoprobe was used for all analysis. The disappearance or attenuation of component (drug or lipid) peaks was seen, which indicates drug-lipid interaction. Example 19. Preparation of etoposide phosphate-SM-102-DSPC-cholesterol-DMG-PEG- 2000 nanoparticles [00079] SM-102 (50 mg) and etoposide phosphate (8 mg) were dissolved in ethanol (2 mL). Cholesterol (38.5 mg), DSPC (10 mg) and DMG-PEG 2000 (1.5 mg) were added to the ethanol solution. The lipid-etoposide phosphate solution was slowly added to rapidly stirred water (8 mL, 1,200 rpm) via syringe and 22 ga. needle to give solid lipid 69951-03 nanoparticles. [00080] Alternatively, the SLNs were prepared using a confined impinging jet mixer (CIJ) and a syringe pump. The lipid-etoposide phosphate solution, prepared as described above, was rapidly mixed with an equal volume of water using a CIJ mixer (Holland Applied Technologies, P0288404). The mixed stream of solid lipid nanoparticles was collected in water (6 mL). Table 10. Particle size and polydispersity index (PDI) for etoposide phosphate nanoparticles Composition Method of Particle Size PDI manufacture (NM)

[00081] Pharmaceutical salts are normally considered to form when the pKa of the basic species (the cationic lipid, DDAB or ionizable lipid SM-102) differs from the pKa of the acidic species (quercetin) by two or more units. The listed pKa for quercetin is 6.3 [12]. SM-102 and related cationic lipids have been the subject of extensive study. Tilstra reported that ionizable lipids comprising a pure ethanolamine core with an apparent pKa between 6.6 and 6.9 maximize intramuscular mRNA delivery [13]. In a screening study of novel ionizable lipids, Lam reported that the pKa of SM-102 was 6.3, and that of ALC-0315 was 6.09 [14]. Since the anion of quercetin and SM-102 as a cation in acidic pH are likely in a complex, good entrapment was found. DDAB is a quaternary ammonium ion with no pKa but possesses a permanent positive charge on the nitrogen atom. It also shows good entrapment. [00082] The above examples show that it is possible to form stable SLNs by forming a sodium salt of a phenol with sodium ethoxide in ethanol and then reacting this sodium salt with ionizable/cationic lipids in an acidic environment with or without other lipids to form SLNs containing the drug and the cationic lipid — the ionic interaction between the drug and the lipid results in high entrapment efficiency and improved stability. This approach is 69951-03 attractive for designing stable SLNs for drugs containing a phenol group. This and related approaches provide a new approach to forming SLNs containing drugs that will likely be widely applicable to forming solid lipid nanoparticles of weakly acidic drugs like phenols and carboxylic acids. Salts formed in this way are expected to be injectable and can be readily tested in an investigational new drug (IND) trial. ENUMERATED EMBODIMENTS: [00083] The following enumerated embodiments show the claims with multiply dependent claims depending from multiply dependent claims for purposes of examination in those jurisdictions where such claim dependencies are permitted. 1. A solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine (DSPC), (c) cholesterol, and (d) 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 (DMG- PEG- 2000) or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt. 2. The SLN of claim 1, wherein the anionic form of the drug is salified with sodium. 3. The SLN of claim 1, wherein the anionic form of the drug is salified with triethylamine hydrochloride. 4. The SLN of any one of claims 1-3, wherein the SLN is stable for at least about 29 days in a refrigerator at about 1.7-3.3 °C. 5. The SLN of any one of claims 1-4, wherein the drug is an anti-cancer drug. 6. The SLN of claim 5, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 69951-03 7. The SLN of claim 6, wherein the anti-cancer drug is fludarabine phosphate and the proton NMR spectrum of the SLN in suspension does not show fludarabine phosphate signals at about 6-6.5 ppm or about 8 to 8.5 ppm using TMS as a reference standard in ethanol – d₆ + D2O with pre-saturation. 8. The SLN of any one of claims 1-4, wherein the drug is an anti-infective drug. 9. The SLN of claim 8, wherein the anti-infective drug comprises a phenolic anion. 10. A pharmaceutical composition comprising the SLN of any one of claims 1-9 and a pharmaceutically acceptable carrier. 11. A method of making a solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate or a carboxylate, entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine (DSPC), (c) cholesterol, and (d) 1,2-dimyristoyl-rac-glycero-3- methoxypolyethylene glycol-2000 (DMG-PEG-2000) or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt, which method comprises: (i) mixing the drug dissolved in 100% ethanol with a cationic salt of ethoxide (e.g., sodium ethoxide) dissolved in ethanol, followed by stirring, filtering, evaporating as needed, and powdering as needed to obtain a powder or a residue; (ii) (a) mixing the powder or the residue obtained in (i) with ethanol and either of SM- 102 or ALC-0315 at a drug-lipid molar ratio of about 0.7:1 to about 1.5:1 until dissolved, (b) separately mixing DSPC, cholesterol, and either of DMG-PEG-2000 or ALC-0159 in ethanol until dissolved, and (c) mixing (a) and (b) together to obtain a solution; and (iii) adding the solution obtained in (ii) to water or a solution comprising water and a buffer; whereupon the SLN comprising an anionic form of a drug entrapped in either of SM-102 or ALC-0315 is obtained. 69951-03 12. The method of claim 11, wherein the cationic form is sodium. 13. The method of claim 11, wherein the cationic form is triethylamine. 14. The method of any one of claims 11-13, wherein the drug is an anti-cancer drug. 15. The method of claim 14, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 16. The method of any one of claims 11-13, wherein the drug is an anti-infective drug. 17. The method of claim 16, wherein the anti-infective drug comprises a phenolic anion. 18. A method of making a solid lipid nanoparticle (SLN) comprising an anionic form of a phosphate drug entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine (DSPC), (c) cholesterol, and (d) 1,2- dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 (DMG-PEG-2000) or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt, which method comprises: (i) mixing the phosphate drug dissolved in 100% ethanol with (a) SM-102 or ALC- 0315, (b) DSPC, (c) cholesterol, and (d) DMG-PEG-2000 or ALC-0159 in ethanol until dissolved to obtain a solution; and (ii) adding the solution obtained in (i) to water or a solution comprising water and a buffer; whereupon the SLN comprising an anionic form of a phosphate drug entrapped in either of SM-102 or ALC-0315 is obtained. 19. The method of claim 18, wherein the cationic form is sodium. 69951-03 20. The method of claim 18, wherein the cationic form is triethylamine. 21. The method of any one of claims 18-20, wherein the drug is an anti-cancer drug. 22. The method of claim 22, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 23. The method of any one of claims 18-20, wherein the drug is an anti-infective drug. 24. The method of claim 23, wherein the anti-infective drug is niclosamide or an anti- infective drug comprising a phenolic anion. 25. A solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in dimethyldidodecylammonium bromide (DDAB) or 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). 26. The SLN of claim 25, wherein the anionic form of the drug is salified with sodium. 27. The SLN of claim 25, wherein the anionic form of the drug is salified with triethylamine hydrochloride. 28. The SLN of any one of claims 25-27, wherein the SLN is stable for at least about 29 days in a refrigerator at about 1.7 °C to about 3.3 °C. 29. The SLN of any one of claims 25-28, in which the drug is an anti-cancer drug. 30. The SLN of claim 29, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 31. The SLN of any one of claims 25-28, wherein the drug is an anti-infective drug. 69951-03 32. The SLN of claim 31, wherein the anti-infective drug comprises a phenolic anion. 33. The SLN of claim 32, wherein the drug is quercetin. 34. The SLN of claim 33, which produces a differential scanning calorimetry peak at 46 +/- 3 °C. 35. A pharmaceutical composition comprising the SLN of any one of claims 25-34 and a pharmaceutically acceptable carrier. 36. A method of making a solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in dimethyldidodecylammonium bromide (DDAB) or 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), which method comprises: (i) mixing the anionic form of a drug and either (a) DDAB in ethanol or (b) DOTAP in ethanol, followed by stirring, filtering, evaporating as needed, and powdering as needed; and (ii) adding the solution (or dissolving the powder to form the solution) to water or a second solution comprising water and a buffer; whereupon the SLN comprising the anionic form of a drug entrapped in DDAB is obtained. 37. The method of claim 36, wherein the anionic form of the drug is salified with sodium. 38. The method of claim 36, wherein the anionic form of the drug is salified with triethylamine hydrochloride. 39. The method of any one of claims 36-38, wherein the drug is an anti-cancer drug. 69951-03 40. The method of claim 39, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 41. The method of any one of claims 36-38, wherein the drug is an anti-infective drug. 42. The method of claim 41, wherein the anti-infective drug comprises a phenolic anion. References 1. Kumar, R., et al., Lipid based nanocarriers: Production techniques, concepts, and commercialization aspect. Journal of Drug Delivery Science and Technology, 2022: p. 103526. 2. Fraguas‐Sanchez, A., et al., Current status of nanomedicine for breast cancer treatment, in Targeted Nanomedicine for Breast Cancer Therapy.2022, Elsevier. p.65‐110. 3. Baldrick, P., Nonclinical Testing Evaluation of Liposomes as Drug Delivery Systems. International Journal of Toxicology, 2022: p.10915818221148436. 4. Inglut, C.T., et al., Immunological and toxicological considerations for the design of liposomes. Nanomaterials, 2020.10(2): p.190. 5. Palanikarasu, P., R.R. Surajambika, and N. Ramalakshmi, Chalcones and Flavones as Multifunctional Anticancer Agents‐A Comprehensive Review. Current Bioactive Compounds, 2022.18(10): p.84‐107. 6. Srinivasan, N., POLYPHENOLIC COMPOUNDS‐A PROMISING LEADS FOR ANTIVIRAL THERAPY. Pharmacophore, 2022.13(1). 7. Alabi, C.A., et al., Multiparametric approach for the evaluation of lipid nanoparticles for siRNA delivery. Proceedings of the National Academy of Sciences, 2013.110(32): p. 12881‐12886. 8. Zada, M.H., et al., Dispersible hydrolytically sensitive nanoparticles for nasal delivery of thyrotropin releasing hormone (TRH). J. Controlled Release, 2019.295: p.278‐289. 9. Sanghavi, N., S. Bhosale, and Y. Malode, RP‐HPLC method development and validation of Quercetin isolated from the plant Tridax procumbens L. Journal of Scientific and Innovative Research, 2014.3(6): p.594‐597. 10. Horhota, A., Mclaughlin,C., Cheney, J., Geldhof, B., Hrkach, J., Morre, M., Hoge, S., Preparation of lipid nanoparticles and methods of administration thereof. WO2020061457, 2020. 11. Huang, E., Tse, S., Iacovelli,J., Mckinney, K., Valkiante, N., IMMUNOMODULATORY THERAPEUTIC MRNA COMPOSITIONS ENCODING ACTIVATING ONCOGENE MUTATION PEPTIDES. WO2018144775 A1, 2018. 12. Malviya, R. and A. Sharma, Sources, Properties, and Pharmacological Effects of Quercetin. Current Nutrition & Food Science, 2022.18(5): p.457‐465. 13. Tilstra, G., Couture‐Senecal, j., Anson, Y.M. et al., Iterative Design of Ionizable Lipids for Intramuscular mRNA Delivery. J. Amer. Chem. Soc.145: p.2294‐2304. 14. Lam, K., et al., Unsaturated, Trialkyl Ionizable Lipids are Versatile Lipid‐Nanoparticle Components for Therapeutic and Vaccine Applications. Advanced Materials, 2023.35(15): p. 2209624. 69951-03   [00084] All patents, patent application publications, journal articles, textbooks, and other publications mentioned in the specification are indicative of the level of skill of those in the art to which the disclosure pertains. All such publications are incorporated herein by reference to the same extent as if each individual publication were specifically and individually indicated to be incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls. [00085] The invention illustratively described herein may be suitably practiced in the absence of any element(s) or limitation(s), which is/are not specifically disclosed herein. Thus, for example, each instance herein of any of the terms "comprising," "consisting essentially of," and "consisting of" may be replaced with either of the other two terms. Likewise, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, references to "the method" includes one or more methods and/or steps of the type, which are described herein and/or which will become apparent to those ordinarily skilled in the art upon reading the disclosure. The term "or" is used to refer to a nonexclusive "or" unless otherwise indicated. [00086] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art. The following terms and phrases shall have the meaning indicated. [00087] The term "about," when referring to a number or a numerical value or range (including, for example, whole numbers, fractions, and percentages), means that the number or numerical range referred to is an approximation within experimental variability (or within statistical experimental error) and thus the numerical value or range can vary between 1% and 15% of the stated number or numerical range (e.g., +/- 5 % to 15% of the recited value, such as within 10%, within 5%, or within 1% of a stated value or stated limit of a range) provided that one of ordinary skill in the art would consider equivalent to the recited value (e.g., having the same function or result). The term "substantially" can allow for a degree of variability in a value or range, for example, within 90%, within 95%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more of a stated value or of a stated 69951-03 limit of a range. [00088] In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting. Further, information that is relevant to a section heading may occur within or outside of that particular section.

Claims

69951-03 WHAT IS CLAIMED IS: 1. A solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine (DSPC), (c) cholesterol, and (d) 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 (DMG- PEG- 2000) or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt. 2. The SLN of claim 1, wherein the anionic form of the drug is salified with sodium. 3. The SLN of claim 1, wherein the anionic form of the drug is salified with triethylamine hydrochloride. 4. The SLN of claim 1, wherein the SLN is stable for at least about 29 days in a refrigerator at about 1.7-3.3 °C. 5. The SLN of any one of claims 1-4, wherein the drug is an anti-cancer drug. 6. The SLN of claim 5, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 7. The SLN of claim 6, wherein the anti-cancer drug is fludarabine phosphate and the proton NMR spectrum of the SLN in suspension does not show fludarabine phosphate signals at about 6-6.5 ppm or about 8 to 8.5 ppm using TMS as a reference standard in ethanol – d6 + D2O with pre-saturation. 8. The SLN of any one of claims 1-4, wherein the drug is an anti-infective drug. 9. The SLN of claim 8, wherein the anti-infective drug comprises a phenolic anion. 69951-03 10. A pharmaceutical composition comprising the SLN of any one of claims 1-4 and a pharmaceutically acceptable carrier. 11. A pharmaceutical composition comprising the SLN of claim 5 and a pharmaceutically acceptable carrier. 12. A pharmaceutical composition comprising the SLN of claim 6 and a pharmaceutically acceptable carrier. 13. A pharmaceutical composition comprising the SLN of claim 7 and a pharmaceutically acceptable carrier. 14. A pharmaceutical composition comprising the SLN of claim 8 and a pharmaceutically acceptable carrier. 15. A pharmaceutical composition comprising the SLN of claim 9 and a pharmaceutically acceptable carrier. 16. A method of making a solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate or a carboxylate, entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine (DSPC), (c) cholesterol, and (d) 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol- 2000 (DMG-PEG-2000) or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt, which method comprises: (i) mixing the drug dissolved in 100% ethanol with a cationic salt of ethoxide (e.g., sodium ethoxide, in which sodium is the cation and ethoxide is the anion) dissolved in ethanol, followed by stirring, filtering, evaporating as needed, and powdering as needed to obtain a powder or a residue; (ii) (a) mixing the powder or the residue obtained in (i) with ethanol and either of SM- 102 or ALC-0315 at a drug-lipid molar ratio of about 0.7:1 to about 1.5:1 until dissolved, (b) 69951-03 separately mixing DSPC, cholesterol, and either of DMG-PEG-2000 or ALC-0159 in ethanol until dissolved, and (c) mixing (a) and (b) together to obtain a solution; and (iii) adding the solution obtained in (ii) to water or a solution comprising water and a buffer; whereupon the SLN comprising an anionic form of a drug entrapped in either of SM-102 or ALC-0315 is obtained. 17. The method of claim 16, wherein the cationic form is sodium. 18. The method of claim 16, wherein the cationic form is triethylamine. 19. The method of any one of claims 16-18, wherein the drug is an anti-cancer drug. 20. The method of claim 19, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 21. The method of any one of claims 16-18, wherein the drug is an anti-infective drug. 22. The method of claim 21, wherein the anti-infective drug comprises a phenolic anion. 23. A method of making a solid lipid nanoparticle (SLN) comprising an anionic form of a phosphate drug entrapped in (a) a cationic form of the lipid SM-102 or a cationic form of the lipid ALC-0315, (b) distearoylphosphatidylcholine (DSPC), (c) cholesterol, and (d) 1,2- dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000 (DMG-PEG-2000) or ALC-0159, wherein the anionic form of the drug and the cationic form of the lipid of (a) form an ionic complex or a salt, which method comprises: (i) mixing the phosphate drug dissolved in 100% ethanol with (a) SM-102 or ALC- 0315, (b) DSPC, (c) cholesterol, and (d) DMG-PEG-2000 or ALC-0159 in ethanol until dissolved to obtain a solution; and (ii) adding the solution obtained in (i) to water or a solution comprising water and a buffer; 69951-03 whereupon the SLN comprising an anionic form of a phosphate drug entrapped in either of SM-102 or ALC-0315 is obtained. 24. The method of claim 23, wherein the cationic form is sodium. 25. The method of claim 23, wherein the cationic form is triethylamine. 26. The method of any one of claims 23-25, wherein the drug is an anti-cancer drug. 27. The method of claim 26, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 28. The method of any one of claims 23-25, wherein the drug is an anti-infective drug. 29. The method of claim 28, wherein the anti-infective drug is niclosamide or an anti- infective drug comprising a phenolic anion. 30. A solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in dimethyldidodecylammonium bromide (DDAB) or 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). 31. The SLN of claim 30, wherein the anionic form of the drug is salified with sodium. 32. The SLN of claim 30, wherein the anionic form of the drug is salified with triethylamine hydrochloride. 33. The SLN of claim 30, wherein the SLN is stable for at least about 29 days in a refrigerator at about 1.7 °C to about 3.3 °C. 34. The SLN of any one of claims 30-33, in which the drug is an anti-cancer drug. 69951-03 35. The SLN of claim 34, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 36. The SLN of any one of claims 30-33, wherein the drug is an anti-infective drug. 37. The SLN of claim 36, wherein the anti-infective drug comprises a phenolic anion. 38. The SLN of claim 37, wherein the drug is quercetin. 39. The SLN of claim 38, which produces a differential scanning calorimetry peak at 46 +/- 3 °C. 40. A pharmaceutical composition comprising the SLN of any one of claims 30-33 and a pharmaceutically acceptable carrier. 41. A pharmaceutical composition comprising the SLN of claim 34 and a pharmaceutically acceptable carrier. 42. A pharmaceutical composition comprising the SLN of claim 35 and a pharmaceutically acceptable carrier. 43. A pharmaceutical composition comprising the SLN of claim 36 and a pharmaceutically acceptable carrier. 44. A pharmaceutical composition comprising the SLN of claim 37 and a pharmaceutically acceptable carrier. 45. A pharmaceutical composition comprising the SLN of claim 38 and a pharmaceutically acceptable carrier. 69951-03 46. A pharmaceutical composition comprising the SLN of claim 39 and a pharmaceutically acceptable carrier. 47. A method of making a solid lipid nanoparticle (SLN) comprising an anionic form of a drug, which comprises a phosphate, a phenolate, or a carboxylate, entrapped in dimethyldidodecylammonium bromide (DDAB) or 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), which method comprises: (i) mixing the anionic form of a drug and either (a) DDAB in ethanol or (b) DOTAP in ethanol, followed by stirring, filtering, evaporating as needed, and powdering as needed; and (ii) adding the solution (or dissolving the powder to form the solution) to water or a second solution comprising water and a buffer; whereupon the SLN comprising the anionic form of a drug entrapped in DDAB is obtained. 48. The method of claim 47, wherein the anionic form of the drug is salified with sodium. 49. The method of claim 47, wherein the anionic form of the drug is salified with triethylamine hydrochloride. 50. The method of any one of claims 47-49, wherein the drug is an anti-cancer drug. 51. The method of claim 50, wherein the anti-cancer drug is fludarabine phosphate, etoposide, etoposide phosphate, or a flavone anion. 52. The method of any one of claims 47-49, wherein the drug is an anti-infective drug. 53. The method of claim 52, wherein the anti-infective drug comprises a phenolic anion.