Development and kinetic evaluation of vitamin C-loaded contact lenses prepared by a simple soaking technique

Conventional ocular drug delivery systems are often limited by low bioavailability and short residence times at the ocular surface, motivating the development of alternative delivery platforms. In this study, vitamin C-loaded contact lenses were prepared using a simple soaking technique and systematically evaluated. Two commercial lenses, Senofilcon A and Hilafilcon B, were immersed in vitamin C solutions, and their loading efficiency, release kinetics, stability, water content, and oxygen permeability were investigated. Vitamin C release was quantified using UV-Vis spectrometry and analyzed using zero-order, first-order, Higuchi, and Korsmeyer-Peppas models. Hilafilcon B exhibited higher vitamin C loading and cumulative release (∼14 µg/mL) than Senofilcon A (∼10 µg/mL), consistent with its higher hydrophilicity and equilibrium water content (∼56% compared to ∼29%). Kinetic analysis indicated that the vitamin C release from both lenses was best described by the Korsmeyer-Peppas model (Hilafilcon B, n = 0.610; Senofilcon A, n = 0.783), suggesting anomalous transport behavior. Vitamin C stability was strongly influenced by storage conditions, with refrigerated storage improving stability, while UV exposure accelerated degradation. Overall, these findings demonstrate that vitamin C incorporation via soaking provides a straightforward approach for developing antioxidant-loaded contact lenses with potential relevance for ocular drug delivery.