Biophysical Characterization and In Vitro Evaluation of Doxycycline-Loaded Egg Yolk Phospholipid Liposomes

Antimicrobial resistance represents not only a biological challenge but also a physicochemical limitation associated with antibiotic transport, membrane interaction, and local availability. In this preliminary study, a liposome-encapsulated doxycycline delivery system was developed using egg yolk-derived phospholipids, and its biophysical properties and release behavior were investigated. Phospholipids were isolated from egg yolk and used to prepare doxycycline-loaded liposomes via a thin-film hydration method combined with freeze–thaw processing. Liposome morphology was characterized by atomic force microscopy (AFM), while encapsulation efficiency was quantified by reversed-phase high-performance liquid chromatography (RP-HPLC). In vitro release kinetics were evaluated using a dialysis diffusion method, and antibacterial activity was assessed as a functional indicator of drug availability using minimum inhibitory concentration (MIC) assays against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). The prepared liposomes exhibited morphology with diameters of approximately 153 nm (PDI = 0.223). The encapsulation efficiency of doxycycline hyclate was 8.41%, and complete drug release was achieved within 48 h. Liposome-encapsulated doxycycline demonstrated a two-fold reduction in MIC values compared with free doxycycline. These findings offer preliminary insight to support further optimization and expanded investigation of liposome-encapsulated antibiotic delivery systems.