Biosynthesis of a Novel Composite Resin Incorporating Gamma Radiation Synthesized Pomegranate Extract–Coated Zinc Oxide Nanoparticles and In Vitro Assessment Against Streptococcus mutans Causing Dental Caries

Dental caries is a common disease widely known to be the main cause of tooth decay. This study evaluated the antibacterial properties of zinc oxide nanoparticles (ZnO NPs) against four Streptococcus mutans isolated from dental caries. ZnO NPs were biosynthesized from a mixture of zinc chloride (ZnCl₂) solution with various pomegranate peel extracts under different doses of gamma radiation. The antibacterial activity was evaluated using the agar-well diffusion method. The structure and elemental content of these artificial ZnO NPs were studied using X-ray diffraction (XRD), ultraviolet–visible absorption spectroscopy (UV–Vis), transmission electron microscope (TEM), and Fourier-transform infrared spectroscopy (FTIR). UV analysis revealed that the pomegranate/ZnO nanoparticles prepared at 60 kGy gamma irradiation dose had the highest intensity at absorption peaks between 395 and 445 nm compared to the other gamma doses. The biosynthesized ZnO NPs demonstrated a strong sensitivity toward Streptococcus mutans. FTIR analysis indicated the presence of specific peaks associated with the functional groups found in pomegranate, which play a role in the production, capping, and stabilization of the biosynthesized ZnO NPs. The presence of Zn–O bonds at 437, 505, 610, 1412, and 1623 cm⁻¹ confirmed the presence of ZnO NPs. TEM analyses revealed that the biosynthesized ZnO NPs were well dispersed and existed in three different shapes: spherical, rod-shaped, and triangular nanoparticles, with sizes of 17.95 nm, 10.29 nm, and 76.98 nm, respectively. XRD analysis gave a sharp peak at 31.68° related to the formed ZnO NPs. To ensure the safety of ZnO NPs, a sulforodamine B (SRB) assay was conducted. Ninety-nine percent of human oral epithelial cells (OEC) treated with different concentrations of ZnO NPs (0.01, 0.1, 1, 10, and 100 μg/ml) remained viable. The IC₅₀ value was more significant than 100 μg/ml. ZnO NPs with a percentage of 0.1% incorporated with composite resin were the minimal concentration to inhibit S. mutans. These findings suggest that ZnO NPs from pomegranate peel extracts could be a novel antibacterial and eco-friendly agent for preventing dental caries.

Biosynthesized Zinc Oxide nanoparticles (ZnO NPs) using Pomegranate peel extract (PPE) and gamma radiation.