In Vitro Antifungal Activity of Amphotericin B-Encapsulated Silk Fibroin-Chitosan Nanoparticles Against Fusarium solani Isolates from Keratitis Patients

Background: Fungal keratitis is a serious ophthalmic problem due to low antifungal medication penetration and bioavailability at the ocular surface, necessitating novel delivery strategies for successful therapeutic outcomes. This study created amphotericin B-loaded silk fibroin nanoparticles (AmB-SFNs) as a targeted drug delivery platform for long-term ocular antifungal therapy. Methods: Silk fibroin-chitosan nanoparticles were produced using a precipitation technique, with chitosan coating for mucoadhesion and polyethylene glycol-400 surface stability. Clinical fungal isolates from keratitis patients were identified as species by morphological and molecular analysis, followed by in vitro antifungal susceptibility testing. Results: The optimized formulation produced spherical AmB-SFNs with an average diameter of 220 nm, a positive zeta potential of +34 mV, and a maximum amphotericin B entrapment effectiveness of 76%. Molecular identification confirmed that all five clinical isolates were Fusarium solani. AmB-SFNs showed strong antifungal activity against all tested isolates, with a minimum inhibitory dose of 50 μg/mL (0.25% w/v). Conclusions: The developed nanoparticulate system has optimal characteristics for enhanced corneal drug delivery, such as appropriate particle size for tissue penetration and mucoadhesive properties for prolonged ocular residence time, suggesting that this nanoparticulate system warrants further investigation in vivo to evaluate its potential for clinical translation in treating Fusarium keratitis and as a platform for topical ophthalmic therapies.