Biomimetic PEEK implants with hierarchical mechanics and enhanced bioactivity

Polyetheretherketone (PEEK) exhibits significant potential in orthopedic implant applications due to its elastic modulus closely resembling that of natural bone; however, its inherently bioinert surface limits the efficacy of osseointegration. Inspired by natural biomineralization processes, this study developed an innovative coating strategy based on microbially induced calcium carbonate precipitation (MICP). Through sulfonation treatment of PEEK (SPEEK), a calcium carbonate bioactive coating enriched with calcium and magnesium elements was constructed on its surface using Sporosarcina pasteurii. Characterization results revealed that the coating exhibited a microporous structure, superhydrophilicity, and a depth-dependent modulus gradient (decreasing from 6.5 GPa to 4.5 GPa) along with mechanical heterogeneity from the surface to the substrate, successfully mimicking the hierarchical mechanical architecture of native bone. In vitro cellular experiments demonstrated that SPEEK-MICP-6D significantly enhanced the proliferation, viability, and expression of osteogenesis-related genes (ALP, Runx2, Col1, BSP) in MC3T3-E1 preosteoblasts. This enhanced bioactivity was primarily attributed to the sustained release of calcium and magnesium ions from the coating, coupled with its biomimetic mechanical microenvironment. The MICP modification method offers advantages of low cost, sustainability, and scalability, providing a highly promising platform for the development of next-generation PEEK orthopedic implants that integrate biomimetic mechanical properties with enhanced bioactivity.