Dopamine-assisted immobilization of peptide arginine–glycine–aspartic acid to enhance the cellular performances of MC3T3-E1 cells of carbon–carbon composites

Due to their excellent biocompatibility and suitable elastic modulus, carbon–carbon composites have excellent prospects for a wide range of applications such as artificial joints and bone replacements. However, the hydrophobicity and poor bioactivity limit their application in bone repair and substitution. Herein, a two-step surface modification of carbon–carbon composites was proposed to overcome these disadvantages. A polydopamine (PDA) layer was first deposited on the surface of carbon–carbon composites, followed by covalent coupling with arginine–glycine–aspartic acid (RGD) in varying concentrations. The surface-modified materials were characterized using a variety of techniques including water contact angle, scanning electron microscopy, atomic force microscopy, and protein adsorption. In addition, the cellular proliferation, alkaline phosphatase activity, and real-time quantitative PCR (RT-PCR) analysis were further tested in vitro. The results indicated that polydopamine and RGD nanoparticles formed on the surface, which significantly enhanced the hydrophilicity following modification. The RGD–PDA-coated carbon–carbon composites exhibited excellent roughness, protein adsorption behavior, and uniform morphology when a concentration of 50 µg/mL RGD was used, unlike blank and polydopamine-modified carbon–carbon composites. The in vitro cell co-culture experiments demonstrated that proliferation and alkaline phosphatase expression in osteoblasts was greatly improved after RGD–PDA coating. The RT-PCR results revealed that the expression of differentiation markers (alkaline phosphatase and osteocalcin) in cells on the RGD–PDA-coated carbon–carbon composites was higher than that on the blank and polydopamine-modified carbon–carbon composites, indicating that the RGD–PDA coating could support cell proliferation and promote osteogenic differentiation of MC3T3-E1 cells. In particular, the cells cultured on this material grew linearly along the morphological features of the material, which was effective for the subsequent regulation of cell growth. Our study suggested that the RGD–PDA coating was an effective method of enhancing the hydrophobicity and the cellular bioactivity of carbon–carbon composites, thus extending applications of carbon–carbon composites to the bone repair field.