Post-treatment with biogenic silver nanoparticles modulates hydration and polymer structure in soft contact lenses: An FTIR-chemometric study

Abstract

Silver nanoparticles (AgNPs) are promising modifiers of ophthalmic biomaterials; however, their concentration-dependent effects on commercial contact lenses remain poorly understood. This study investigates molecular and physicochemical alterations in hydrogel contact lenses following 24-hour exposure to biogenic AgNPs (0.5–100 μg/ml) using Fourier transform infrared (FTIR) spectroscopy combined with advanced chemometric analyses. Synthesized AgNPs exhibited spherical morphology with an average size of 19 ± 1.8 nm and a zeta potential of −31 mV, confirming high colloidal stability. FTIR analysis revealed concentration-dependent shifts in OH stretching (3600–3200 cm −1 ), carbonyl (1713–1689 cm −1 ), and siloxane vibrational bands, indicating modulation of hydrogen bonding, polymer chain mobility, and network organization. Water-related spectral indices demonstrated increased hydration at intermediate concentrations (5–15 μg/ml), while higher concentrations (50–100 μg/ml) induced structural reorganization with enhanced oxygen permeability. Chemometric analyses showed perfect discrimination between treated and untreated lenses, with principal component analysis explaining 95.04% of variance and receiver operating characteristic curves yielding area under the curve values ≈ 1.0. Parallel factor analysis resolved three independent components corresponding to native polymer structure, nanoparticle-induced modification, and hydration dynamics, revealing distinct concentration-dependent interaction regimes. These findings demonstrate that biogenic AgNPs modulate key physicochemical properties of contact lenses and establish a quantitative, data-driven framework for optimizing nanoparticle-polymer interactions in ophthalmic applications.