Impacts of Hematite Nanoparticle Exposure on Biomechanical, Adhesive, and Surface Electrical Properties of Escherichia coli Cells

Abstract

cDespite a wealth of studies examining the toxicity of engineered nanomaterials, current knowledge on their cytotoxic mechanisms (particularly from a physical perspective) remains limited. In this work, we imaged and quantitatively characterized the biomechanical (hardness and elasticity), adhesive, and surface electrical properties of Escherichia coli cells with and without exposure to hematite nanoparticles (NPs) in an effort to advance our understanding of the cytotoxic impacts of nanomaterials. Both scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that E. coli cells had noticeable deformation with hematite treatment for 45 min with a statistical significance. The hematite-treated cells became significantly harder or stiffer than untreated ones, as evidenced by indentation and spring constant measurements. The average indentation of the hematite-treated E. coli cells was 120 nm, which is significantly lower (P < 0.01) than that of the untreated cells (approximately 400 nm). The spring constant of hematite-treated E. coli cells (0.28 ؎ 0.11 nN/nm) was about 20 times higher than that of untreated ones (0.01 ؎ 0.01 nN/nm). The zeta potential of E. coli cells, measured by dynamic light scattering (DLS), was shown to shift from ؊4 ؎ 2 mV to ؊27 ؎ 8 mV with progressive surface adsorption of hematite NPs, a finding which is consistent with the local surface potential measured by Kelvin probe force microscopy (KPFM). Overall, the reported findings quantitatively revealed the adverse impacts of nanomaterial exposure on physical properties of bacterial cells and should provide insight into the toxicity mechanisms of nanomaterials.

E. coli Surface Properties Differ between Stream Water and Sediment Environments

“…However, our results indicate only a very weak correlation between net charge and zeta potential with r = 0.008 with p -value = 0.316. Thus our results may temper the conclusions of some previous research in which zeta potential has been used to estimate surface charge (Alves et al, 2010; Zhang et al, 2012). …”

Influences of Surface Coating, UV Irradiation and Magnetic Field on the Algae Removal Using Magnetite Nanoparticles

“…First, surface attachment of MNPs may lead to the changes to surface charge and other physicochemical properties of algae. 40 This is supported by the zeta potential shift from −38.5 ± 3.8 to −0.1 ± 0.6 mV for algae after mixing with PEIcoated MNPs. Second, as magnetite (F 3 O 4 ) NPs are a semiconductor material with the band gap of 2.2−2.3 eV, which is less than the photoenergy (3.3−4.9 eV) of UV 365 or UV 254 .…”

Adsorption of MS2 on oxide nanoparticles affects chlorine disinfection and solar inactivation

“…On the other hand, due to the high surface area, NPs possess higher adsorption capacity than particles in microscale. Thus, the reductions of virus viability may also result from direct surface interactions such as adsorption onto NPs Zhang et al, 2012b). For instance, the adsorption of bacteriophage phiX174 onto a-Fe 2 O 3 , g-Fe 2 O 3 , and Al 2 O 3 NPs affected the infectivity against the host bacteria (You et al, 2011).…”