Enhancing the proliferation of MC3T3-E1 cells on casein phosphopeptide-biofunctionalized 3D reduced-graphene oxide/polypyrrole scaffolds

In bone tissue engineering, the 3D macro-scaffold plays an indispensable role as a matrix for cell proliferation, differentiation and tissue formation, for which a bioactive surface is required. Previously, we successfully prepared the 3D macro-reduced graphene oxide/polypyrrole (3D rGO/PPY) scaffold; in the present study, by using casein phosphopeptide (CPP) as a bioactive molecule, we have developed a 3D rGO/PPY/CPP composite scaffold through a simple, but low-cost electrostatic self-assembly method and have explored the application of the composite scaffold in bone tissue engineering. The results have indicated that the CPP successfully modified the backbone of the scaffold, and demonstrated that the developed 3D rGO/PPY/CPP scaffold has excellent hydrophilic behavior and water uptake performance, much better than that of 3D rGO/PPY. In the biomimetic mineralization experiment, the CPP-modified matrix, particularly 3D rGO/PPY/CPP20, could promote the rapid formation of hydroxyapatite in simulated body fluid solution on just the 1st soaking day. On co-culturing with the MC3T3-E1 cells, the 3D rGO/PPY/CPP20 kept the cells at a higher proliferation state of 5.07 times that of the control group, superior to that of the 3D rGO/PPY/CPP10 (3.88 times) and the 3D rGO/PPY group (2.07 times). The excellent osteoblastic performance of the 3D rGO/PPY/CPP20 composite scaffold can be attributed to the good biological properties of CPP, and the unique 3D macro-structure with a high specific surface area. Our findings suggest that the 3D rGO/PPY/CPP20 can be considered as an attractive scaffold for bone healing and regeneration in the future.