Protein Adsorption of Ultrafine Metal Oxide and Its Influence on Cytotoxicity toward Cultured Cells

Abstract

Many investigations about the cellular response by metal oxide nanoparticles in vitro have been reported. However, the influence of the adsorption ability of metal oxide nanoparticles toward cells is unknown. The aim of this study is to understand the influence of adsorption by metal oxide nanoparticles on the cell viability in vitro. The adsorption abilities of six kinds of metal oxide nanoparticles, namely, NiO, ZnO, TiO2, CeO2, SiO2, and Fe2O3, to Dulbecco's modified Eagle's medium supplemented with a 10% fetal bovine serum (DMEM-FBS) component such as serum proteins and Ca2) were estimated. All of the metal oxide nanoparticles adsorbed proteins and Ca2+ in the DMEM-FBS; in particular, TiO2, CeO2, and ZnO showed strong adsorption abilities. Furthermore, the influence of the depletion of medium components by adsorption to metal oxide nanoparticles on cell viability and proliferation was examined. The particles were removed from the dispersion by centrifugation, and the supernatant was applied to the cells. Both the cell viability and the proliferation of human keratinocyte HaCaT cells and human lung carcinoma A549 cells were affected by the supernatant. In particular, cell proliferation was strongly inhibited by the supernatant of TiO2 and CeO2 dispersions. The supernatant showed depletion of serum proteins and Ca2+ by adsorption to metal oxide nanoparticles. When the adsorption effect was blocked by the pretreatment of particles with FBS, the inhibitory effect was lost. However, in NiO and ZnO, which showed ion release, a decrease of inhibitory effect by pretreatment was not shown. Furthermore, the association of the primary particle size and adsorption ability was examined in TiO2. The adsorption ability of TiO2 depended on the primary particle size. The TiO2 nanoparticles were size dependently absorbed with proteins and Ca2+, thereby inducing cytotoxicity. In conclusion, the adsorption ability of metal oxide nanoparticles is an important factor for the estimation of cytotoxicity in vitro for low-toxicity materials.

Effect of particle size onin vitrocytotoxicity of titania and alumina nanoparticles

“…While the concentrations used in this study were relatively high, they are comparable to those used in previous nanotoxicity studies (0.5-5 mg/mL) utilising A549 cells [8,9,35,36]. In [35], for example, the viability of A549 cells was found to significantly decrease (580% relative to the control group), following incubation with 7 nm TiO 2 NPs at concentrations greater than 5 mg/mL. Similarly, Kim et al [36] observed a 20% decrease in colony numbers (viability) after the A549 cells were exposed to 0.5 mg/mL of 20-40 nm TiO 2 or 20 nm Al 2 O 3 NPs for 10 days, as measured by the clonogenic assay.…”

“…Horie et al [35] concluded that the adsorption of medium components (e.g. serum proteins and Ca 2þ ) must be taken into account when evaluating the cytotoxicity of low-toxicity materials like TiO 2 .…”

Big Signals from Small Particles: Regulation of Cell Signaling Pathways by Nanoparticles

“…For instance, Horie et al 35 have described relationships between physico-chemical NP properties and the biological responses they evoke. They suggested a five step in vitro !…”

Implications of the stability behavior of zinc oxide nanoparticles for toxicological studies

“…However, examples of in vitro tests using human cells showed gaps in the understanding of parameters that control ZnO behavior, dissolution and hence toxicity. Especially under physiological conditions, the ZnO behavior, mainly its dissolution, is influenced by constituents of the cell culture media [15,16]. With respect to surface charge and zeta potential and their influence on the toxicity, several hypotheses have been proposed [4,11,14].…”