Photothermally enhanced drug release and anti-inflammatory effects of allantoin-loaded chitosan-based biomaterials incorporating melanin for transdermal drug delivery.

Transdermal drug delivery system has attracted considerable attention as non-invasive alternatives to conventional drug administration routes. However, their therapeutic efficacy is often limited by insufficient drug penetration and the inability of controllable release behavior. In this study, photothermally responsive allantoin (AT)-loaded chitosan (CS)-based biomaterial patches incorporating melanin (MEL) were prepared to improve transdermal drug delivery and anti-inflammatory effects. The novelty of this study combines the intrinsic therapeutic potential of AT with the photothermal effect of MEL in a biodegradable CS-based patch platform, enabling externally triggered drug release under near-infrared (NIR) irradiation. The prepared MEL-added biomaterial patches exhibited a marked photothermal response, reaching 42-44 °C under NIR irradiation, leading to 1.20-2.45-fold higher AT release compared to non-irradiated conditions. Release kinetics using the Fickian diffusion and Korsmeyer-Peppas models revealed that AT release in buffer solution followed Fickian diffusion behavior (R2 = 0.990-0.999), and AT release in artificial and porcine skin models was governed by a non-Fickian mechanism (n = 0.55-0.98), indicating the combined contribution of drug diffusion and polymer relaxation. In addition, the prepared biomaterial patches demonstrated enhanced antioxidant activity, with radical-scavenging efficiencies of approximately 55-65%, as well as antibacterial activity against Escherichia coli and Bacillus subtilis. Cytocompatibility tests confirmed high cell viability (> 90%), and anti-inflammatory evaluation showed a significant reduction in nitric oxide production by approximately 40-60% compared with the lipopolysaccharide-treated group. Overall, these findings suggest that MEL-incorporated AT-loaded CS-based biomaterial patches may serve as multifunctional and stimuli-responsive transdermal platforms for controlled drug delivery and anti-inflammatory applications.