Exposure of the Yeast Saccharomyces cerevisiae to Functionalized Polystyrene Latex Nanoparticles: Influence of Surface Charge on Toxicity

Abstract

Novel nanoparticles with unique physicochemical characteristics are being developed with increasing frequency, leading to higher probability of nanoparticle release and environmental accumulation. Therefore, it is important to assess the potential environmental and biological adverse effects of nanoparticles. In this study, we investigated the toxicity and behavior of surface-functionalized nanoparticles toward yeast (Saccharomyces cerevisiae). The colony count method and confocal microscopy were used to examine the cytotoxicity of manufactured polystyrene latex (PSL) nanoparticles with various functional groups (amine, carboxyl, sulfate, and nonmodified). S. cerevisiae were exposed to PSL nanoparticles (40 mg/L) dispersed in 5-154 mM NaCl solutions for 1 h. Negatively charged nanoparticles had little or no toxic effect. Interestingly, nanoparticles with positively charged amine groups (p-Amine) were not toxic in 154 mM NaCl, but highly toxic in 5 mM NaCl. Confocal microscopy indicated that in 154 mM NaCl, the p-Amine nanoparticles were internalized by endocytosis, whereas in 5 mM NaCl they covered the dead cell surfaces. This demonstrates that nanoparticle-induced cell death might to be related to their adhesion to cells rather than their internalization. Together, these findings identify important factors in determining nanoparticle toxicity that might affect their impact on the environment and human health.

Adhesion and internalization of functionalized polystyrene latex nanoparticles toward the yeast Saccharomyces cerevisiae

“…It is believed that the rate of adhesion of the NPs onto the cell surface by the electrostatic interactions and the rate of the uptake of NPs via endocytosis affect the colloidal behavior of the NPs (i.e., the adhesion and internalization). Furthermore, similar results were obtained for PSL NPs with a nominal diameter of 100 nm [27]. Thus the effect of NP size on the toxicity and the uptake of NPs was small when the NP diameter was less than 100 nm.…”

Comparison of the cytotoxic effect of polystyrene latex nanoparticles on planktonic cells and bacterial biofilms

“…The zeta potentials of NC-glass (Yoshihara et al 2014) and PDA-glass used as the substratum for biofilm formation were -3.6 and 0.4 mV, respectively. The hydrodynamic diameter and zeta potential of PSL NPs were 105 nm and 14.3 mV, respectively (Nomura et al 2013). …”

“…Cell viability was estimated according to surface coverage assuming that the cell was a sphere and that the surface was covered with NPs in a close-packed single layer. The NP concentration required to achieve single layer coverage (C p ) was estimated using the following equation (Nomura et al 2013(Nomura et al , 2015: C p = 0.605pq p D p D c 2 N c , where q p is the particle density (=1030 kg/m 3 ), D p is the particle diameter, D c is the cell diameter, and N c is the number of cells. The surface coverage can be obtained by dividing the NP concentration by C p .…”

Effects of SiO2 nanoparticles on phospholipid membrane integrity and fluidity

“…The biological effects of NPs are well known to closely relate to their properties. Positively-charged NPs have been reported to interact strongly with cell membrane and induce cytotoxicity [17][18][19], which show the role of electrostatic interaction. However, in a study on gold NPs both the positively-and negatively-charged NPs induce membrane leakage [20], indicating that electrostatic interaction is not the only factor.…”