Non-RGD peptide H-ckrwwkwirw-NH₂ grafting accentuates antibacterial and osteoinductive properties of biopolymer coating

A coating on the surfaces of metallic implants to promote bone cell integration as well as prevent infection is highly desired for orthopedic surgeries. A novel antibacterial peptide was grafted onto an osteoinductive coating and the modified coating was tested for its antibacterial properties and biocompatibility with bone cells in vitro. A layer of chitosan hydrogel was chemically attached to the surface of a medical-grade titanium alloy and a novel non-RGD peptide (H-ckrwwkwirw-NH₂) was grafted on top of the coating through chemical cross-linking. The composite layer was tested for its surface wettability (contact angle), composition (energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy), antibacterial property, and bone cell biocompatibility. The successful grafting of the peptide onto the coating was confirmed by the increase of contact angle and nitrogen content (both p < .05) on the surface due to the presence of the hydrophobic amino acids. The modified coating successfully reduced the growth of Gram negative and positive (E. coli and S. aureus) bacteria by 74.2% and 52.4%, respectively (p < .01). The coating did not show any sign of cytotoxicity and unexpectedly improved osteoblast proliferation and mineralization compared to unmodified samples (all p < .01). An antimicrobial peptide successfully grafted onto the chitosan coating to enhance its bactericidal function. This non-RGD peptide, after chemical modification, not only preserved its bactericidal activity but also improved the biocompatibility of the coating.