Surface Modification of Titanium with EGCG and Hexamethylenediamine Coating for BMP‑2 Grafting: An Investigation of Osteogenic Properties
Osseointegration between titanium implants and surrounding bone is essential for the long-term success of implant surgery. However, mechanical injury during implantation can induce local oxidative stress, which compromises peri-implant osteogenesis. In this study, we developed a multifunctional titanium surface by codepositing epigallocatechin gallate (EGCG) and hexamethylenediamine (HD) to form a phenolic-amine coating with tunable amino-group density, followed by covalent grafting of bone morphogenetic protein-2 (BMP-2) via carbodiimide chemistry. Surface characterization confirmed the successful fabrication of the coatings, which exhibited improved hydrophilicity and pronounced radical-scavenging activity. In vitro experiments showed that the modified surfaces promoted osteoblast adhesion and spreading and enhanced osteogenic differentiation, as demonstrated by increased alkaline phosphatase (ALP) activity, enhanced extracellular matrix mineralization, and upregulated expression of osteogenesis-related genes and proteins, including Runx2, ALP, and OPN. Among the tested groups, the coating prepared with EGCG and HD at 0.4 mg/mL followed by BMP-2 grafting showed the strongest osteogenic performance. These findings suggest that the EGCG/HD/BMP-2 coating is a promising surface-engineering strategy for titanium implants by simultaneously improving the oxidative microenvironment and promoting osteogenesis.