Exploring the potential of antifungal-loaded proniosomes to consolidate corneal permeation in fungal keratitis: A comprehensive investigation from laboratory characterization to microbiological evaluation

This work aimed to prepare Terconazole loaded proniosomes (TCZ-PNS) utilizing modified coacervation technique for the management of fungal keratitis. Terconazole (TCZ) is a potent antifungal with poor aqueous solubility posing intricacies in its incorporation in ocular formulations. A 2³ factorial design was adopted to probe independent formulation variables including A: Lecithin: cholesterol ratio, B: Surfactant: cholesterol ratio and C: Span® 80 contribution (% of total SAA). The formulae, generated by the design, were prepared and scrutinized regarding entrapment efficiency (%EE), particle size (PS), polydispersity index (PDI) and zeta potential (ZP). Numerical desirability algorithms selected an optimum TCZ-PNS which boasted plausible %EE (89.51 % ± 0.94 %), nanoscale vesicles consistent with TEM measurements (247.9 ± 0.42 nm), a sufficiently high ZP (-43.42 ± 0.85 mV), and an in-vitro biphasic release profile that remained stable even after Gamma irradiation and short-term storage. The transcorneal ex-vivo permeation of TCZ-PNS was higher than that of TCZ suspension (≈ 2-fold). The formulation was further evaluated for pH, corneal hydration threshold, and histopathological safety, confirming its suitability for ocular application. Confocal laser microscopy revealed substantial corneal uptake (approximately twice as deep as of TCZ suspension). Additionally, microbiological assessments of the optimal TCZ-PNS compared to TCZ suspension demonstrated an inhibition zone nearly 50 % larger, a significantly lower MIC and MFC (64-fold reduction), and enhanced biofilm inhibition activity across most tested concentrations. These findings suggest that TCZ-PNS could be a propitious treatment choice to deeply deliver antifungal therapy for the eradication of deeply rooted and inaccessible fungal keratitis.