Phosphonate/quaternary ammonium copolymers as high-efficiency antibacterial coating for metallic substrates

Designing a coating material with efficient bactericidal property to cope with bacterial associated infections is highly desirable for metallic implants and devices. Here, we report phosphonate/quaternary ammonium copolymers, p(DEMMP-co-TMAEMA), as the new type of metal anchorable high-efficiency antibacterial coating. Seven p(DEMMP-co-TMAEMA) polymers with varied cationic components were precisely prepared via random radical polymerization. Copolymers were constructed on titanium alloy (TC4) substrates based on strong covalent bonding between the phosphonate group and metallic substrates through a one-step process as evidenced by XPS and water contact angle tests. A robust relationship between the composition of the copolymers and the bactericidal ability endowed to TC4 substrates was established. Results showed that the copolymer, with the pDEMMP content even as low as 6.3%, was able to anchor onto TC4 substrates. With the increase of cationic pTMAEMA content from 4.0 to 93.7% in the coating copolymer, the bactericidal ability endowed to the TC4 substrates was steadily increased from 39.4 to 98.8% for S. aureus and from 70.0 to 99.4% for E. coli after 8 h's of contacting. All p(DEMMP-co-TMAEMA) coating on TC4 substrates showed limited cytotoxicity to C2C12 cells. Notably, the phosphonate/quaternary amine copolymers can be easily constructed on diverse biomedical metals such as titanium (Ti), stainless steel (SS), and Ni/Cr alloys with significantly increased antibacterial performance, demonstrating the potency of the copolymer as the general high-efficiency antibacterial coating for diverse bio-metals.