One-step preparation of the engineered titanium implant by rationally designed linear fusion peptides with spacer-dependent antimicrobial, anti-inflammatory and osteogenic activities

Biomaterial-associated infection (BAI) and delayed osseointegration are two major limitations for orthopeadic titanium implants, which are highly required in clinic implants. Herein, we rationally design a series of novel fusion peptides (FPs) based on HHC36 and BFP1 with different polyethylene glycol (PEG) spacers, and covalently immobilize them onto titanium implants via a one-step reaction between thiol groups and titanium hydroxyl groups. All FP-engineered implants show improved biocompatibility and osteogenic activity with hBMSCs. But interestingly, they display spacer-dependent antimicrobial and anti-inflammatory activities. Specifically, implants engineered with FPs containing no more than 12 units of PEG spacers exhibit strong antimicrobial activity against clinical bacteria (S. aureus, E. coli, P. aeruginosa, S. epidermidis and MRSA) and mediated macrophages transitions towards M2 polarization. However, implants engineered with FPs containing long PEG spacers (24 units) show negligible levels of the abovementioned activities. By all-atom molecular dynamics simulation, we demonstrate that the loss of activity is due to low exposure of antimicrobial sequence (HHC36) and high exposure of PEG. In vivo assays show that optimized FP-engineered implants inhibit S. aureus by 97.89%, while promoting osseointegration. This research provides great potential to resolve BAI and delayed osseointegration issues for orthopeadic implants.