(601a) New Surface Strategies to Resist, Remove and Recover Bacteria

Bacterial contamination and infection has been a critical issue in both industry and medicine. The objectives of this work are to develop multifunctional materials for protection and de-contamination and to provide a fundamental understanding of the origin for bacteria adhesion.

In this talk, three new material-based approaches will be presented to achieve long-term bacterial adhesion and biofilm formation and to remove or recover bacteria. The first one is to develop zwittterionic sulfobetaine(SB) and carbobetain (CB) polymer-brush coated surfaces via atomic transfer radical polymerization (ATRP). The extensive hydration of the zwitterionic polymer coating has been shown to dramatically reduce bacteria adhesion onto the surfaces. Our Results show that pCBMA coatings reduced long-term biofilm formation of P. aeruginosa up to 240 hours by 95% at 25oC, and for 64 hours by 93% at 37oC. In addition to monofunctional nonfouling polymer coating, our second approach is to integrate antimicrobial and nonfouling strategies. For example, we use hydrolysable cationic zwitterionic precursor grafted onto a surface via ATRP. The antibacterial property of the positively charged surfaces can kill 99.9% of E.coli attached, and, with the gradual hydrolysis of polymer coating, 98% of the dead cells will detach from the surface. After this conversion, the nonfouling nature of hydrolysized zwitterionic coating will prevent further attachment of microbial cells. The third approach is to attach and release bacteria by controlling the environmental pH. In this work, we prepare mix charge copolymers that are neutral at medium or high pH, but bear a positive charge at low pH, thus attracting negatively charged bacteria under acid conditions then releasing the cells once higher pH values are restored. Our results showed that six times more bacterial cells will adhere onto the mixed charge polymer-coated surfaces at low pH as compared to neutral or basic pH conditions. Furthermore, attached bacterial cells can be easily recollected from the surfaces after switching to higher pH. This unique property makes it valuable for the detection of biological warfare agents.

In this talk, the role of Exocellular polysaccharide (EPS) on bacterial adhesion will also be presented. As the major species of biomacromolecule on bacteria surfaces, EPS is expected to play an important role in multiple stages of bacteria adhesion processes. P.aeruginosa PA01 isogenic strains were used to study the connections between EPS production and bacteria adhesion. Regular SPR was used to study preconditioning of biomacromolecules in bacteria culture while long-range SPR to study the transient interactions between bacteria cells and surfaces. Finally, a flow-chamber approach was used to observe long-term bacteria adhesion and biofilm formation. Preliminary results suggest that extensive EPS adsorption onto materials of different surface chemistries is crucial to preconditioning processes.