Cholesteryl stearate

PEA (Opti-PEA) was supplied by Innexus Nutraceuticals (Nijmegen, The Netherlands). Stearic acid, cholesteryl stearate, Span 85, Pluronic F68, and mannitol were purchased from Sigma-Aldrich Co. (St. Louis, MO, USA). Coumarin-6 was purchased from Acros Organics (Bridgewater, NJ, USA).
Simulated lung fluid type 3 (SLF) at pH 7.4, used for in vitro drug dissolution, was prepared according to the method described by Marques [47 (link)], as reported in the Supplementary Materials (Table S2).
For the cytotoxicity and cell internalization investigations, an MH-S cell line from IZSLER (Brescia, Italy), cell culture reagents RPMI-1640 medium, and phosphate-buffered saline (PBS) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Trypsin EDTA and L-Glutamine from Lonza (Bornem, Belgium), penicillin-streptomycin (P/S) from Cambrex Bio Science Verviers (Liège, Belgium), fetal bovine serum (FBS) from PAN-Biotech (Aidenbach, Germany), paraformaldehyde from Sigma-Aldrich (St. Louis, MO, USA), Hoechst 33,342 from ThermoFisher (Monza, Italy), and thiazolyl blue tetrazolium bromide (MTT) from Panreac Applichem ITW Reagents (Milan, Italy) were employed.
All the other chemicals were of analytical grade.

Stigmasterol (≥95%), stearic acid (≥98.5%), oleic acid (≥99%), linoleic acid (≥99%), linolenic acid (≥99%), all solvents, sodium hydroxide, anhydrous pyridine, the catalysts-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP), high-purity silica gel 70–230 mesh, standards of cholesteryl stearate (96%), oleate (98%), linoleate (98%), linolenate (97%), 5α-cholestane and heptadecanoic acid methyl ester were purchased from Sigma-Aldrich (St. Louis, MO, USA). The silylation mixture Sylon BTZ was supplied by Fluka Analytical (Buchs, Switzerland). The internal standard 19-hydroxycholesterol was purchased from Steraloids (Newport, RI, USA). The silylation mixture of BSTFA [N,O-Bis(trimethylsilyl) trifluoroacetamide] with 1% TMCS (trimethylchlorosilane) was obtained from Fluka Chemie, while the SEP-PAK amino cartridges were sourced from Waters (Milford, USA).