Dual-functional polyetheretherketone surface modification for enhanced osseointegration and antibacterial activity in pH-responsive manner

Polyetheretherketone (PEEK) has been recognized for its immense potential in hard tissue repair applications due to its mechanical properties resembling those of natural bones. However, the inherent bioinertness of pristine PEEK results in insufficient osseointegration. Moreover, implant-associated infection (IAI) has become a serious threat in orthopedic surgery. These risks usually lead to implant loosening, delayed healing, and even the failure of implantation, hampering many clinical applications of PEEK. In this study, we present a facile strategy to endow PEEK implants with enhanced osseointegration and pH-responsive antibacterial activity. Briefly, pristine PEEK was first treated with mixed acids to obtain a porous structure (referred to as SNPEEK), and then the metal-phenolic networks (MPN) coating was prepared using layer-by-layer (LbL) assembly consisting of Sr2+ and tannin acid (TA) (referred to as ST coating). The results demonstrated that the dual-functional PEEK displayed enhanced antibacterial activity in pH-responsive manner. At pH 7.4, the antibacterial ratios were 71.72% and 66.79% against Staphylococcus aureus (MSSA, ATCC 25923) and methicillin-resistant Staphylococcus aureus (MRSA, ATCC BAA-40), respectively. Remarkably, at pH 5.5, the antibacterial activities significantly increased, resulting in killing ratios of 99.98% and 100%, respectively. Furthermore, the dual-functional PEEK promoted osteogenic differentiation of pre-osteoblasts (MC3T3-E1) and migration of human umbilical vascular endothelial cells (HUVECs). In addition, the dual-functional PEEK demonstrated effective anti-infection ability and desirable new bone formation ability in vivo compared to both pristine PEEK and SNPEEK implants. Overall, this study provides a promising strategy to endow PEEK implants with effective osseointegration and anti-infective ability, representing a prospective solution to address current clinical challenges associated with PEEK implants.