Immobilization of Polyethyleneimine (PEI) on Flat Surfaces and Nanoparticles Affects Its Ability to Disrupt Bacterial Membranes

Abstract

Interactions between a widely used polycationic polymer, polyethyleneimine (PEI), and a Gram-negative bacteria, E. coli, are investigated using atomic force microscopy (AFM) quantitative imaging. The effect of PEI, a known membrane permeabilizer, is characterized by probing both the structure and elasticity of the bacterial cell envelope. At low concentrations, PEI induced nanoscale membrane perturbations all over the bacterial surface. Despite these structural changes, no change in cellular mechanics (Young’s modulus) was detected and the growth of E. coli is barely affected. However, at high PEI concentrations, dramatic changes in both structure and cell mechanics are observed. When immobilized on a flat surface, the ability of PEI to alter the membrane structure and reduce bacterial elasticity is diminished. We further probe this immobilization-induced effect by covalently attaching the polymer to the surface of polydopamine nanoparticles (PDNP). The nanoparticle-immobilized PEI (PDNP-PEI), though not able to induce major structural changes on the outer membrane of E. coli (in contrast to the flat surface), was able to bind to and reduce the Young’s modulus of the bacteria. Taken together, our data demonstrate that the state of polycationic polymers, whether bound or free—which greatly dictates their overall configuration—plays a major role on how they interact with and disrupt bacterial membranes.

Cationic cellulose filter papers modified with ZnO/Ag/GO nanocomposite as point of use gravity-driven filters for bacterial removal from water

“…Thus, PEI was used to form a layer with higher positive charge. PEI due to the presence of many amino groups, including primary, secondary, and tertiary ones along its chain can present a high positive charge density 41 . Performing PEI led to charge reversal and changed the zeta potential to + 22 mV.…”

“…It has been reported that some cationic polymers, including PDA and PEI, also have antibacterial activity and can destabilize the bacterial membrane. Their activity heavily depends on their structure, such as their molecular weight, type of functional groups, and form (linear or branched) 41 , 43 , 44 . Moreover, the combination of those cationic polymers with other antibacterial agents has led to the synergistic improvements in activity 45 .…”

In Situ Transformation of Electrospun Nanofibers into Nanofiber-Reinforced Hydrogels

“…It has recently gained significance as an adhesive antimicrobial coating material that binds to various inorganic and organic materials and can be formulated into drug delivery systems [ 43 ]. Furthermore, polyethylene imine (PEI), a cationic polymer with the ability to disrupt bacterial cell walls and membranes through pore formation, was crosslinked into the gelatin-PDA matrix in this study to confer antimicrobial activity to the fibers [ 41 , 44 , 45 , 46 ]. Due to its excellent gene encapsulation efficiency and its intrinsic endosomolytic activity, PEI is widely used for gene delivery purposes [ 47 ].…”