Mw 38 000–54 000), 1-ethyl-3-(3-(dimethylamino)propyl)
carbodiimide (EDC), N-hydroxysuccinimide (NHS), triethylamine
(TEA), low-density lipoproteins (LDL), and a cholesterol quantitation
kit were purchased from Sigma-Aldrich (St. Louis, MO, USA). Methotrexate
(MTX) was bought by AlfaAesar (Haverhill, MA, USA). 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[succinyl(polyethylene
glycol)-2000] (DSPE-PEG-COOH), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine
(DSPE_NH2), and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine
(DPPC) were purchased from Avanti Polar Lipid (Alabaster, AL, USA).
All reagents and solvents were used without further purification.