The drug loading capacity of an engineered lipoprotein (eLP1) and the colloidal stability of drug-loaded eLP1s were assessed with 12 drugs with different charges/hydrophobicities. The capacity was largely correlated with their log P values, and the binding to the protein moiety was suggested for two drugs. The size of drug-loaded eLP1 formulations after freeze-drying followed by resolubilization hardly changed. The eLP1 formulation of travoprost, a clinically used drug in eye drop formulations, maintained its small size (19 nm) for 1 h at 37 °C in an artificial tear solution, whereas the liposome counterpart of 112 nm in diameter aggregated.
Keywords: Drug loading; colloidal stability; eye drop; freeze-drying; liposomes.