Amino Acid-Based Zwitterionic Polymer Surfaces Highly Resist Long-Term Bacterial Adhesion

The surfaces or coatings that can effectively suppress bacterial adhesion in the long term are of critical importance for biomedical applications. Herein, a group of amino acid-based zwitterionic polymers (pAAZ) were investigated for their long-term resistance to bacterial adhesion. The polymers were derived from natural amino acids including serine, ornithine, lysine, aspartic acid, and glutamic acid. The pAAZ brushes were grafted on gold via the surface-initiated photoiniferter-mediated polymerization (SI-PIMP). Results show that the pAAZ coatings highly suppressed adsorption from the undiluted human serum and plasma. Long-term bacterial adhesion on these surfaces was investigated, using two kinds of representative bacteria [Gram-positive Staphylococcus epidermidis and Gram-negative Pseudomonas aeruginosa] as the model species. Results demonstrate that the pAAZ surfaces were highly resistant to bacterial adhesion after culturing for 1, 5, 9, or even 14 days, representing at least 95% reduction at all time points compared to the control unmodified surfaces. The bacterial accumulation on the pAAZ surfaces after 9 or 14 days was even lower than on the surfaces grafted with poly[poly(ethyl glycol) methyl ether methacrylate] (pPEGMA), one of the most common antifouling materials known to date. The pAAZ brushes also exhibited excellent structural stability in phosphate-buffered saline after incubation for 4 weeks. The bacterial resistance and stability of pAAZ polymers suggest they have good potential to be used for those applications where long-term suppression to bacterial attachment is desired.