Poly(hexamethylene biguanide) (PHMB) as high-efficiency antibacterial coating for titanium substrates

Bacterial associated infection is a remaining urgent challenge in clinic application of metallic implants and devices. Here, we developed a new strategy to combat the bacterial associated infection of titanium alloy (TC4). Novel phosphonate/active ester block polymers (pDEMMP-b-pNHSMA) with identical phosphonate segments (DP = 29) as the metal anchorable ligand but varied active ester segments (DPs = 7, 29, and 64) as the conjugation site for poly(hexamethylene biguanide) (PHMB) were precisely prepared. Through a facile two-step process, the polymeric coating were successfully constructed on TC4 substrates as evidenced by water contact angle and XPS measurements. Through systematical in vitro antibacterial evaluations, robust relationship between the chemical structure of coating polymer and the antibacterial property endowed to the TC4 substrates has been established. Results showed that the block polymer, bearing an active ester segment of 64 repeat units, enabled dense packing of PHMB coating on the TC4 surface, which is able to kill 100% of both S. aureus and E. coli. that seeded without compromising the cytocompatibility of TC4 substrates. Furthermore, PHMB coating could significantly inhibit the colony of the bacteria and consequently reduce the bacterial associated inflammatory reaction as verified by a subcutaneous infection model on rat.