A comparison of charged and uncharged stabilizers on the loading of hydrophilic low and high molecular weight synthetic charged molecules in the LeciPlex® system

Abstract

The present investigation aims to evaluate the loading of hydrophilic molecules with varying physicochemical properties in LeciPlex®. Polysorbate 80, taurocholate, and dioctadecyldimethylammonium bromide (DODAB) were used to prepare non-ionic, anionic and cationic LeciPlex® respectively, and their interactions with two model hydrophilic compounds differing in molecular weight, surface charge and structural features are explored. A negatively charged peptide, daptomycin was encapsulated via passive loading, while a positively charged amphipathic base, acridine orange required a remote loading. All formulations were characterized for particle size, zeta potential, and entrapment efficiency. Daptomycin and acridine orange LeciPlex® were further characterized by transmission electron microscopy (TEM) and evaluated for in vitro release profiles by dialysis bag method. In addition to the above characterizations, daptomycin-loaded LeciPlex® was further evaluated for thermal behavior using differential scanning calorimetry (DSC), antimicrobial efficacy via the resazurin assay, haemocompatibility and physicochemical stability. The type of stabilizer and phospholipid concentration directly influenced the particle size and entrapment of daptomycin LeciPlex®. The average particle size of daptomycin-loaded LeciPlex® was lower compared to the acridine orange-loaded LeciPlex®. Acridine orange entrapment (55–80 %) increased with cholesterol incorporation. TEM revealed uni or oligo lamellar vesicles. DSC confirmed the interaction of daptomycin with lipid in all three daptomycin-LeciPlex® systems. Both daptomycin and acridine orange LeciPlex® systems demonstrated sustained release profiles and improved stability. Daptomycin LeciPlex® showed comparable antimicrobial efficacy to that of the solution and exhibited minimal haemolysis. Present study demonstrated the successful encapsulation of structurally diverse hydrophilic molecules into LeciPlex® using a simplified and scalable approach.