A pH-Responsive Polyetheretherketone Implant Modified with a Core–Shell Metal–Organic Framework to Promote Antibacterial and Osseointegration Abilities

Polyetheretherketone (PEEK) is considered to be a potential material for oral implants due to its elastic modulus being similar to that of human cortical bone. However, the poor antibacterial, anti-inflammatory, and osseointegration properties of bioinert PEEK have hindered its clinical application. Therefore, this study designed and constructed a pH-responsive PEEK implant with a bilayer core-shell zeolitic imidazolate framework-8 (ZIF-8) structure loaded on its surface, with an antimicrobial peptide (KR12) encapsulated in the outer shell and an osteogenic peptide (osteogenic growth peptide ) encapsulated in its inner core. In this study, the bilayer core-shell ZIF-8 structure was confirmed to have pH-responsive properties. In vitro studies proved that the implant could promote bone marrow mesenchymal stem cells' proliferation and differentiation and the M1 phenotype to M2 phenotype conversion of RAW 264.7 and could inhibit bacterial adhesion and proliferation. By constructing rats' distal femur with/without infection models, it was further demonstrated that the novel implant could effectively inhibit bacterial adhesion and growth, inhibit inflammation, and promote peri-implant osseointegration, which was more substantial when the local area was infected and the pH was lower than that of normal tissue. Collectively, the results suggest that this novel pH-responsive PEEK implant loaded with a bilayer core-shell ZIF-8 structure is a promising peptide delivery implant system, which is well suited for dental applications and offers a potential solution for the prevention of infection during the early phase after implantation.