ZnO nanoparticle preparation route influences surface reactivity, dissolution and cytotoxicity

Abstract

ZnO nanoparticles (nZnO) are commonly used in nanotechnology applications despite their demonstrated cytotoxicity against multiple cell types. This underscores the significant need to determine the physicochemical properties that influence nZnO cytotoxicity. In this study, we analyzed six similarly sized nZnO formulations, along with SiO-coated nZnO, bulk ZnO and ZnSO as controls. Four of the nZnO samples were synthesized using various wet chemical methods, while three employed high-temperature flame spray pyrolysis (FSP) techniques. X-ray diffraction and optical analysis demonstrated the lattice parameters and electron band gap of the seven nZnO formulations were similar. However, electrophoretic mobility measures, hydrodynamic size, photocatalytic rate constants, dissolution potential, reactive oxygen species (ROS) production and, more importantly, the cytotoxicity of the variously synthesized nZnO towards Jurkat leukemic and primary CD4 T cells displayed major differences. Surface structure analysis using FTIR, X-ray photoelectron spectroscopies (XPS) and dynamic light scattering (DLS) revealed significant differences in the surface-bound chemical groups and the agglomeration tendencies of the samples. The wet chemical nZnO, with higher cationic surface charge, faster photocatalytic rates, increased extracellular dissolution and ROS generation demonstrated greater cytotoxicity towards both cell types than those made with FSP techniques. Furthermore, principal component analysis (PCA) suggests that the synthesis procedure employed influences which physicochemical properties contribute more to the cytotoxic response. These results suggest that the synthesis approach results in unique surface chemistries and can be a determinant of cellular cytotoxicity and oxidative stress responses.

Defect Engineering of ZnO Nanoparticles for Bioimaging Applications

“…As seen in Figure 9, the untreated cells have little to no apparent fluorescence in the nZnO channel. After 2 hours of incubation, a few nZnO are seen in the same plane as the cells and appear to have begun the agglomeration and sedimentation process commonly seen with NPs, [49][50][51] causing association with the lipid membrane on the surface of the cells. No apparent changes in cellular morphology were noted at this time point.…”

A Method to Assess the Relevance of Nanomaterial Dissolution during Reactivity Testing

“…It remains an open question therefore as to whether the measured reactivity derives from the reactive processes on the particle surface or whether it originates from interactions with dissolved ions. Especially for ZnO and CuO particles, the debate has been recurring over whether or not the observed reactivity is due to the ions or due to the remaining particles [6,16]. Grouping of NFs by their "surface reactivity" or "oxidative potential" is not robust without knowing the main contributor (the particle or the ions) for ROS generation.…”

ZnO nanocrystals derived from organometallic approach: Delineating the role of organic ligand shell on physicochemical properties and nano-specific toxicity

“…Some recent scientific reports indicate that positively charged NCs usually penetrate cells more readily 28–30 or induce higher endothelial cells leakiness 31,32 . Nevertheless, both systematic studies on toxicological profiles of surface-modified ZnO NCs and the nano-specific toxicity defined by multiparametric structure-property relationship remain highly challenging 33 . Most of published toxicological studies concern ZnO nanostructured materials derived from inorganic sol-gel procedures 11,12,17 , which provide ZnO NCs with highly corrugated surface structure and coated with ‘swollen’ organic ligand shell (Fig.…”