Harnessing Novel Tetra-Synergistic Bilosomes for Effective Otomycosis Management: Integrated In-Vitro, Microbiological and In-vivo Studies

Abstract This study introduces and statistically optimizes novel Tetra-Synergistic Bilosomes (TSB), an advanced nano-platform for topical delivery of voriconazole (VOR) in otomycosis therapy. The term “Tetra-Synergistic” reflects the incorporation of four complementary components: Cremophor® EL, sodium deoxycholate, Brij® 58, and Brij® S2, working in synergy to enhance therapeutic efficacy. TSB was fabricated using the thin-film hydration method and optimized through a 2 3 D-optimal design. Three formulation factors were investigated: Cremophor® EL: VOR ratio, sodium deoxycholate: cholesterol ratio, and Brij® 58: Brij® S2 ratio, with the optimization goal of maximizing EE%, minimizing vesicular size, and maintaining ZP within the acceptable stability range. The model demonstrated excellent predictability, achieving a desirability value of 0.888. The optimized TSB exhibited high EE% (91.6%), a suitably small VS (217.9nm), and stable ZP (− 24.1mV). FTIR confirmed VOR entrapment, while TEM revealed nano-sized spherical vesicles. Moreover, TSB displayed a biphasic In-vitro release profile and remained stable for three months under refrigeration. Importantly, microbiological evaluation confirmed the superior antifungal performance of TSB. Compared with VOR suspension, TSB showed a larger inhibition zone, a lower minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC), and a faster fungicidal effect, eradicating fungal growth in 33% less time. Ex-vivo permeation studies revealed a 2.18-fold enhancement ratio, supported by confocal laser scanning microscopy confirming deeper tissue penetration. Histopathological analysis further validated the safety of topical application without any tissue damage. Collectively, these results establish TSB as a pioneering, microbiologically potent, and clinically promising nano-vesicular system for the effective management of otomycosis.