Physicochemical Characteristics of Nanocomposite Hydrogels Based on Carboxymethylcellulose and Zinc Oxide Nanoparticles and Study Its Sun Protection Properties and Antibacterial Activity

ABSTRACT The conditions for synthesizing a polymer‐metal complex hydrogel containing zinc oxide nanoparticles (ZnO NPs) of various sizes and shapes, using chemical methods from solutions of purified sodium‐carboxymethylcellulose (Na‐CMC) with a degree of substitution of 0.97 and a degree of polymerization of 1000, along with aqueous solutions of zinc nitrate hexahydrate at 80°C, were determined. It was found that mixing of those solutions led to ionic‐coordinate cross‐linking binding of the zinc ions (Zn 2+ ) with the carboxylate anions (R‐COO − ) of Na‐CMC. The physicochemical properties of the hydrogel containing ZnO NPs of various sizes and shapes, stabilized by Na‐CMC macromolecules, were examined using FT‐IR, UV–Vis spectroscopy, AFM, SEM, TEM, XRD diffraction, and dynamic light scattering (DLS) analysis methods. It was found that increasing the initial concentration of Zn(NO 3 ) 2 in Na‐CMC hydrogel results in the formation of ZnO NPs with various sizes, contents, and shapes during chemical reduction. Additionally, DLS and zeta potential measurements confirmed the stability of ZnO NPs with a ζ potential of −38.3 mV in Na‐CMC hydrogel during 72 days of storage times. A strong sunscreen effect was observed in the CMC/ZnO NPs hydrogel containing 0.0324% ZnO NPs sized 35–95 nm, compared with the commercial “Floresan” sunscreen cream. The antibacterial activity of the hydrogel containing ZnO NPs with sizes of 35–95 nm was tested using two assays against the bacterium Staphylococcus epidermidis and the fungus Candida albicans . The hydrogel exhibited a strong bactericidal “nano effect,” achieving a 100% kill rate compared to the control and the commercial “Floresan” sunscreen cream. Na‐CMC hydrogels incorporating ZnO NPs have potential for broad use in medical and cosmetic applications, serving as sunscreens with antibacterial properties.