[In vitro study on the osteogenic potential of sulfonated and osteogenic growth peptide co-modified carbon fiber-reinforced polyetheretherketone].

Objective: To determine an optimal surface modification protocol for carbon fiber-reinforced polyether ether ketone (CFR-PEEK), this study investigated the enhancement of material bioactivity and osteogenic properties. This was achieved by constructing a porous structure via sulfonation and polydopamine (PDA) modification and subsequently grafting osteogenic growth peptides (OGP) onto the surface. Methods: Using CFR-PEEK as the control group, CFR-PEEK specimens were sequentially subjected to 6 minute of sulfonation, hydrothermal treatment (SPK group), and PDA modification (SPD group), followed by grafting with 25, 50, or 100 μg/ml OGP (SPO25, SPO50, SPO100 groups). Surface morphology, functional groups, elemental composition, and hydrophilicity of each test specimen group were analyzed using scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle testing. Mouse osteoprogenitor cells (MC3T3-E1) were cultured on the surfaces of each group. Cell adhesion, proliferation, and osteogenic differentiation capabilities were evaluated through cell proliferation assays, immunofluorescence staining, alkaline phosphatase (ALP) and alizarin red staining, quantitative analysis, and real-time fluorescence quantitative PCR (RT-qPCR). Results: SEM revealed that the surface of the specimens formed a uniform three-dimensional porous structure after sulfonation treatment. ATR-FTIR and XPS revealed distinct characteristic peaks in the SPD and SPO groups; contact angle measurements demonstrated significantly superior hydrophilicity in all SPO groups compared to CFR-PEEK and SPK, with SPO50 group exhibiting optimal hydrophilicity (surface contact angle: 35.3°±2.5°), showing statistically significant differences from other groups (all P<0.05). Cell proliferation assays demonstrated no cytotoxicity in the SPK, SPD, and SPO groups, with all significantly promoting cell proliferation (compared to CFR-PEEK). Among these, the SPO50 group exhibited significantly higher cell proliferation (1.365±0.049) on day 5 than other groups (P<0.05), showing the best efficacy. SPK and SPD groups exhibited good cell spreading, while SPO groups (especially SPO50 and SPO100) demonstrated optimal cell adhesion properties. ALP staining and alizarin red staining results, along with their quantitative analysis, revealed that the SPO50 group exhibited the deepest ALP staining at both 7 and 14 d of osteogenic induction, and also demonstrated the deepest alizarin red staining at 14 days. Correspondingly, its 14-day ALP activity (0.057±0.001) and alizarin red quantitative value (0.246±0.006) were significantly higher than those of other groups (all P<0.05), indicating that the SPO50 group exhibited the optimal in vitro osteogenic differentiation-promoting performance. RT-qPCR revealed that all SPO groups exhibited significantly higher expression of Runt-related transcription factor-2 (RUNX2) and type Ⅰ collagen compared to the CFR-PEEK group during early osteogenesis (7 d). At 14 d postinduction, the SPO50 group reached peak expression levels for RUNX2 and osteopontin (3.325±0.225 and 2.550±0.107, respectively), significantly exceeding all other groups (all P<0.05). Conclusions: Sulfonated PDA modification enables the construction of porous structures on CFR-PEEK surfaces and efficient grafting of OGP. The SPO50 group demonstrated optimal cell adhesion, proliferation, and osteogenic differentiation capacity.