Safe-by-design gelatin-modified zinc oxide nanoparticles

We report an innovative low-cost wet precipitation synthesis method for gelatin-modified zinc oxide nanoparticles (GM ZnO NPs) at the interface between the gelatin hydrogel and aqueous electrolyte. Diffusion of ammonia through the hydrogel matrices with different gelatin contents induced precipitation of the product in contact with the surface of the aqueous solution of zinc ions. The obtained precipitate was subjected to thermal treatment to partially decompose the adsorbed gelatin in the NP structure. Physicochemical properties of obtained GM ZnO NPs were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), thermogravimetry (TG), photon correlation spectroscopy (PCS), zeta potential measurements, and inductively coupled plasma-mass spectrometry (ICP-MS). The estimated mean crystallite size of GM ZnO NP powders was in the range from 5.8 to 12.1 nm. The synthesized NPs exhibited nanosheet morphology and arranged into flake-like aggregates. The toxic potential was investigated in vitro in human hepatocellular carcinoma cell line HepG2. The thiazolyl blue tetrazolium bromide (MTS) assay was used to assess cell viability, 2′,7′-dichlor-fluorescein-diacetate (DCFH-DA) assay to examine the formation of intracellular reactive oxygen species (ROS), and comet assay to evaluate the genotoxic response. GM ZnO NPs slightly reduced HepG2 cell viability, did not induce ROS formation, and showed low genotoxic potential at very high doses (100 µg mL−1). ZnO NPs fabricated and modified using the proposed methodology deserve further study as potential candidates for antibacterial agents or dietary supplements with low overall toxicity.