Tea Polyphenol–Functionalized Graphene/Chitosan as an Experimental Platform with Improved Mechanical Behavior and Bioactivity

In this study, water-soluble, one-step highly reduced and functionalized graphene oxide was prepared via a facile, environment-friendly method by using tea polyphenol (TP), which acted as both reducing agent and stabilizer. The product obtained, that is, tea polyphenol–reduced graphene oxide (TPG), was used as a reinforcing building block for the modification of a mechanically weak chitosan (CS), TPG/CS. The morphology and physicochemical and mechanical properties of the composite were examined by various characterizations. The tensile strength and elastic modulus of CS were greatly improved by TPG, as compared to the findings for GO incorporation. Additionally, to our knowledge, this study is an in-depth analysis of the osteoblast functions of CS/TPG, including aspects such as cell cytotoxicity, proliferation, and expression of ossification genes, alkaline phosphatase (ALP), and Runt-related transcription factor (Runx2), which showed advantages in favorably modulating cellular activity. It was concluded that TPG/CS showed a higher elastic modulus, better hydrophilicity, and excellent biocompatibility than the pristine chitosan for promoting the proliferation and differentiation of osteoblasts, as well as for accelerating the expression of ALP and Runx2 (as shown by reverse transcription polymerase chain reaction (RT-PCR)). These results may provide new prospects for the use of TPG in the modification of biomaterials and for broadening the application of TPG in biological fields.