Implantable and Biodegradable Power Sources for Accelerating Bone Regeneration

Bone defect repair remains a clinical challenge owing to the lack of implantable devices that provide sustained electrical stimulation without the need for external power sources or secondary surgical removal. Although enzymatic biofuel cells (EBFCs) offer a promising self-powered strategy, their nondegradability and unstable electrical output limit their application in bone tissue engineering. Here, we developed a degradable, self-powered hydrogel system (C/M/GB) based on an enzymatic biofuel cell that provides stable electrical stimulation for bone regeneration. To facilitate electron transfer within the electrode, MXene nanosheets are incorporated into the bioelectrodes to form a three-layer structure. The system exhibits favorable degradability, with approximately 49% retention at 8 weeks, and generates a stable self-powered output with a current of 27.2 μA and an electric field intensity of 94.3 mV/mm. In vitro experiments demonstrate that the system exhibits good biocompatibility, significantly promotes BMSC proliferation, and upregulates the expression of osteogenic genes. In a rat calvarial defect model, micro-CT imaging reveals a significant increase in bone volume/total volume (BV/TV) and trabecular number (Tb.N) after C/M/GB implantation. Histological and immunohistochemical analyses further confirm high expression of Runx2 and OPN, along with rapid bone formation, and no observable systemic toxicity. The self-powered, degradable, and biocompatible properties of this hydrogel system make it a promising therapeutic strategy for bone defect repair.