Electrospun hydrogel-forming nanofibres embedded in a pH-responsive film for the prevention of sexually transmitted infections

Sexually transmitted infections (STIs) remain a major global health challenge, highlighting the urgent need for effective and user-friendly vaginal prevention strategies. This study presents a novel composite system for vaginal application, consisting of mucoadhesive electrospun nanofibres with inherent antiviral potential embedded within a pH-responsive film. The film is designed to preserve the integrity of the nanofibres in the acidic vaginal environment and to dissolve rapidly upon contact with seminal fluid - released during sexual intercourse -, triggering nanofibre hydration and interaction with the mucosal surface. Electrospinning successfully produced uniform and defect-free nanofibres consisting of polyvinyl alcohol (PVA) blended with either κ- or ι-carrageenans (CAR), sulphated polysaccharides known for their mucoadhesive, gelling and intrinsic antiviral properties. Different solutions containing Eudragit® polymers (EL100 or EL100-55) and plasticisers (polyethylene glycol or glycerol) were prepared and cast to identify the most suitable composition for developing the composite system. Solutions capable of forming films with optimal mechanical flexibility and rapid solubility under mildly alkaline conditions were selected. The composite system was fabricated by embedding nanofibres between two partially dried layers of the selected pH-responsive solutions, forming a uniform composite structure that ensured complete fibre incorporation. The outer film effectively protected the nanofibrous core in acidic environments; upon pH increase (pH ∼7.5), the film rapidly dissolved, allowing the nanofibres to hydrate and form a cohesive, strongly mucoadhesive hydrogel, potentially enhancing their retention within the vaginal cavity. Overall, the composite system exhibited good structural integrity, pH-responsiveness, biocompatibility and antiviral potential, offering a promising, non-hormonal strategy for on-demand STI prevention.