Polymeric Hydrogels Loaded with ZnO Nanoparticles as Promising Tools for Tacking Viral Skin Disorders

Zinc oxide nanoparticles (ZnO NPs) have attracted growing interest in several fields, including topical biomedical applications, due to their stability, biocompatibility and therapeutic potential. In this study, chitosan (Ch), gelatin (G) and arabic gum (AG) were combined to formulate hydrogels loaded with different ZnO NP concentrations. The main aim is to assess the synergy between the properties of biopolymers and ZnO moieties in terms of antiviral activity. ZnO NPs were synthesized via co-precipitation. Hydrogels were prepared using the freeze–thaw method, and the loading of 2.5, 5 and 7.5% w/w of ZnO NPs with respect to Ch was promoted by ultrasonication. The structural, morphological, surface and thermal properties of hydrogels loaded with ZnO NPs (HZ 2.5, HZ 5 and HZ 7.5) and the control matrix (H) were characterized using FTIR spectroscopy, confirming the successful incorporation and interaction of ZnO NPs with the polymeric network. Low ZnO NP concentrations enhanced the swelling degree of the hydrogels (from 1044% to 1253%), improving their thermal stability and solubility (96 h vs. 48 h HZ 7.5 and 14 h in the case of H). This behavior could be ascribed to the aggregation of ZnO NPs with increasing amounts, which was verified through FESEM. Virucidal activity was tested against herpes simplex virus type 1 (HSV-1) and bovine coronavirus (BCoV), demonstrating a substantial enhancement when the ZnO NPs are added independently of the concentration. An almost 100% viral inhibition was recorded when the HZs were analyzed, whereas the H matrix showed an inhibition of about 40% against the same virus. Antioxidant activity was evaluated via the DPPH free radical inhibition method, revealing an improvement with the loading of NPs.