Effect of Al2O3 nanoparticles on bacterial membrane amphiphilic biomolecules

Lipopolysaccharide (LPS) and l-α-phosphatidyl-ethanolamine (PE) are amphiphilic biomolecules that are key constituents in the outer cell membranes of Gram-negative bacteria. In this study, micelles and vesicles of LPS/PE were used as cell membrane models to evaluate nanoparticle (NP) effects on membrane structure. Using atomic force microscopy and sorption experiments, we observed that LPS vesicles were dispersed by Al2O3 NPs because of the strong attachment between LPS polysaccharide chain and oxide surface. LPS coated on the Al2O3 NPs, and formed a layer of tens of nanometer as shown from atom force microscopy (AFM) images. High pH, ionic strength and sulfate concentration inhibited the adsorption of LPS molecules on NPs. The features of PE vesicles were changed after exposing to Al2O3 NPs, inducing large round vesicles with detectable thickness as revealed by AFM, resulting in the increase of vesicle diameter. The aqueous stability of PE was disturbed when adding Al2O3 NPs, but was enhanced by increasing pH. The interaction between NPs and membrane amphiphilic biomolecules may affect membrane fluidity, integrity and lateral organization, which is important for NP safety evaluation and for new NP designs in biological and biomedical applications.