Dual-functional sulfonated PEEK implants via graphene oxide–mediated BMP-2 gene delivery: enhanced osteogenic and antibacterial performance in vitro

Introduction Polyetheretherketone (PEEK) is a promising orthopedic implant material due to its bone-mimetic mechanical properties; however, its bioinert surface and susceptibility to bacterial colonization limit its clinical efficacy. Strategies to enhance osteointegration while providing antibacterial functionality are urgently needed. Methods Graphene oxide (GO) was functionalized with polyethylene glycol (PEG) and complexed with a plasmid encoding bone morphogenetic protein-2 (pBMP-2) to form a GO-PEG/pBMP-2 complex. This complex was coated onto sulfonated PEEK (SPEEK) via freeze-drying, yielding SPEEK-(GO-PEG/pBMP-2) composites. The materials were systematically compared with pristine PEEK, SPEEK, and SPEEK-GO-PEG controls. Surface chemistry, morphology, hydrophilicity, gene loading efficiency, and coating uniformity were characterized. In vitro assessments included cell adhesion, proliferation, viability, alkaline phosphatase (ALP) activity, mineralized matrix deposition, osteogenic gene expression, and antibacterial activity against Staphylococcus aureus and Escherichia coli . Results Successful PEGylation of GO and efficient pBMP-2 loading were confirmed, with uniform coating and significantly improved hydrophilicity on SPEEK-(GO-PEG/pBMP-2). This composite markedly enhanced osteoblast adhesion, proliferation, and viability, along with elevated ALP activity, increased mineralized nodule formation, and upregulated expression of key osteogenic genes (e.g., Runx2, OPN, OCN). Both GO-containing coatings—SPEEK-GO-PEG and SPEEK-(GO-PEG/pBMP-2)—exhibited strong antibacterial effects against both Gram-positive and Gram-negative bacteria, with no significant difference attributable to BMP-2 loading. Conclusion The SPEEK-(GO-PEG/pBMP-2) platform simultaneously promotes osteogenesis through localized BMP-2 gene delivery and provides robust antibacterial protection via GO. This dual-functional design addresses two major limitations of PEEK implants, offering a promising strategy for next-generation orthopedic biomaterials.