Detrimental impact of silica nanoparticles on the nanomechanical properties of Escherichia coli, studied by AFM

Abstract

Despite great innovative and technological promises, nanoparticles (NPs) can ultimately exert an antibacterial activity by affecting the cell envelope integrity. This envelope, by conferring the cell its rigidity and protection, is intimately related to the mechanical behavior of the bacterial surface. Depending on their size, surface chemistry, shape, NPs can induce damages to the cell morphology and structure among others, and are therefore expected to alter the overall mechanical properties of bacteria. Although Atomic Force Microscopy (AFM) stands as a powerful tool to study biological systems, with high resolution and in near physiological environment, it has rarely been applied to investigate at the same time both morphological and mechanical degradations of bacteria upon NPs treatment. Consequently, this study aims at quantifying the impact of the silica NPs (SiO-NPs) on the mechanical properties of E. coli cells after their exposure, and relating it to their toxic activity under a critical diameter. Cell elasticity was calculated by fitting the force curves with the Hertz model, and was correlated with the morphological study. SiO-NPs of 100 nm diameter did not trigger any significant change in the Young modulus of E. coli, in agreement with the bacterial intact morphology and membrane structure. On the opposite, the 4 nm diameter SiO-NPs did induce a significant decrease in E. coli Young modulus, mainly associated with the disorganization of lipopolysaccharides in the outer membrane and the permeation of the underlying peptidoglycan layer. The subsequent toxic behavior of these NPs is finally confirmed by the presence of membrane residues, due to cell lysis, exhibiting typical adhesion features.

Lipoprotein Lpp regulates the mechanical properties of the E. coli cell envelope

“…For WT cells, analysis of the curves using the Hertz model ( Fig. 5b, d) yielded E of 3.5 ± 1.6 MPa (mean ± SD, n = 15 cells), in agreement with previously published values ranging from 1 to few MPa on E. coli [22][23][24] . The k b values were found to be 0.02 ± 0.01 N m −1 (Fig.…”

Lignin for Nano‐ and Microscaled Carrier Systems: Applications, Trends, and Challenges

“…Ag NPs are well known for their antibacterial effects . Recent studies also reported silica particles, SWCNTs, and fullerene for antibacterial activity. The majority of antibacterial lignin materials make use of Ag ions or Ag NPs, as active payload.…”

Fast automated processing of AFM PeakForce curves to evaluate spatially resolved Young modulus and stiffness of turgescent cells

“…This equation further approximates the sample as a linear elastic and isotropic material, which is an obvious and well-recognized approximation for bacterial cell envelopes. 57 For the lack of better, this model is however widely used in AFM literature, and our purpose is here to test its applicability for capturing or not the power-law indentation-dependence of forces measured by PeakForce tapping mode on bacteria. Given these elements, eqn (1) may be rewritten in terms of the contact point CP (eqn (6)):…”