Effects of Surface Charges on the Bactericide Activity of CdTe/ZnS Quantum Dots: A Cell Membrane Disruption Perspective

Abstract

The inhibitory effects of CdTe/ZnS quantum dots (QDs) modified with 3-mercaptopropionic acid (negatively charged) or cysteamine (positively charged) on the metabolic activity of Escherichia coli were investigated using biological microcalorimetry. Results show that the inhibitory ratio of positive QDs is higher than that of negative QDs. Transmission electron microscopy images indicate that QDs are prone to be adsorbed on the surface of E. coli. This condition disturbs the membrane structure and function of E. coli. Fluorescence anisotropy results demonstrate that positive QDs show a significant increase in the membrane fluidity of E. coli and dipalmitoylphosphatidylcholine (DPPC) model membrane. Furthermore, fluorescence anisotropy values of DPPC membrane in the gel phase decreased upon the addition of positive QDs. By contrast, anisotropy values in the liquid-crystalline phase are almost constant. The change in membrane fluidity is associated with the increased permeability of the membrane. Finally, the kinetics of dye leakage from liposomes demonstrate that the surface charge of QDs is crucial to the interaction between QDs and membrane.

Compressibility of Multicomponent, Charged Model Biomembranes Tunes Permeation of Cationic Nanoparticles

“…Earlier studies by us and others with both NPs on cell , and model uncharged multicomponent, phase-separated biomembranes − suggested domain-specific and enhanced binding compared to homogeneous membranes. In the case of phase-separated model membranes, it has been reported using various techniques like STED–fluorescence correlation spectroscopy, atomic force microscopy (AFM), quartz crystal microbalance with dissipation monitoring, and MD simulations , that either NPs bind to the phase boundaries of the lipid domains or there is a preferential binding to the more fluidic phase with membranes having domains/rafts with height variations, depending on the charge and hydrophilic/hydrophobic nature of the NPs.…”

Leakage and Rupture of Lipid Membranes by Charged Polymers and Nanoparticles

“…Another type of membrane disruptors are polymers and nanomaterials. ,− A comprehensive study was performed over a decade ago using phosphocholine (PC) bilayers supported on freshly cleaved mica. A wide range of cationic peptides, polymers, dendrimers, and inorganic nanoparticles were studied; all disrupted the supported membrane. − Some recent works were carried out using dye-loaded liposomes, also demonstrating cationic nanoparticles inducing more rapid leakage. , A thermodynamic model was proposed to explain the interaction between charged nanoparticles and membranes; although it did not specify the type of charge on nanoparticles, both cationic and anionic nanoparticles could interact with lipid membranes . Thus, it is unclear why cationic materials appeared more effective in leaking membranes.…”

Biosafety of micro/nanomotors towards medical application

“…Also, the subchronic toxicity study has to include toxicokinetic analysis to examine the level of systemic MNM uptake. 93 (6) As reported the cytotoxicity of micro/nanoparticles in both bacterial 94 and mammalian cells 95 is mainly attributed to plasma membrane damage. However, the complex interaction between MNMs and the plasma membrane has made it difficult to translate the cytotoxicity results to properties of MNMs.…”