Objectives: The aim of the present study is the synthesis of zinc oxide nanoparticles (ZnO NPs) and their loading onto a hydrogel based on marine biopolymers (sodium alginate, chitosan, and kappa-carrageenan), as well as investigating the effects of these nanoparticles on thermal stability, swelling behavior, antioxidant capacity, selective antibacterial activity, and pH-dependent release pattern.
methodology: The hydrogel was prepared at optimized ratios, and the zinc oxide nanoparticles were synthesized via the hydrothermal method. Characterization was performed using Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), simultaneous thermal analysis (STA), and X-ray diffraction (XRD). Additionally, antibacterial assays including disk diffusion (zone of inhibition), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were conducted against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Furthermore, the DPPH free radical scavenging assay and drug release studies were carried out.
Findings: It was observed that upon adding zinc oxide (ZnO) nanoparticles to the hydrogel, the swelling percentage of the hydrogel containing ZnO nanoparticles was lower than that of the pure hydrogel across all investigated time intervals, and it reached stability 60 minutes earlier. The hydrogel samples exhibited approximately 20% antioxidant activity at concentrations ranging from 20 to 2000 µg/mL. In the disk diffusion (zone of inhibition) test, no clear zone (halo) free of microbial growth was observed around the hydrogel samples containing ZnO nanoparticles. However, the results of the antibacterial assays for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) showed that the ZnO nanoparticle-loaded hydrogel had an MBC of 75 and an MIC of 75 against Gram-positive bacteria, and an MBC of 35 and an MIC of 6.25 against Gram-n