Ti₃C₂T_x MXene Nanosheets: Bridging High-Performance Energy Storage and Comprehensive In Vivo Biocompatibility...

Owing to advancements in implantable bioelectronic devices, there has been an increase in demand for biocompatible energy sources with long-term electrochemical and mechanical stability. In this study, we present the fabrication of a flexible asymmetric supercapacitor (MXene//AC) based on two-dimensional Ti₃C₂T_x MXene nanosheets. The supercapacitor demonstrates excellent electrochemical performance with an areal capacitance of 66.43 mF cm^-2, energy density of 13.2 Wh kg^-1, and a high power density of 2300 W kg^-1. The supercapacitor retained 95% capacitance after 5000 charge-discharge cycles and displayed negligible performance degradation under various bending angles, highlighting its mechanical suitability for wearable electronics. Density functional theory (DFT) analysis revealed that the metallic Ti-C backbone of Ti3C2T_x MXene and its O/F terminations work synergistically to enable rapid electron transport and reversible proton-coupled surface redox, supporting predominantly surface-controlled charge storage with a significant pseudocapacitive contribution. To complement device-level studies, we assessed the in vivo safety profile and antioxidant potential of Ti₃C₂T_x MXene nanosheets in Sprague-Dawley (SD) rats through acute dermal, subchronic oral, and subchronic intraperitoneal toxicity evaluations. Acute dermal exposure up to 100 mg kg^-1 caused mild skin responses without necrosis, while subchronic administration for 28 days revealed no considerable abnormalities in biochemical parameters (alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, creatinine), inflammatory markers (IL-1β, IL-6), or oxidative stress biomarkers (malondialdehyde, glutathione). Histopathological evaluations confirmed the absence of structural damage or inflammation in vital organs. Additionally, MXene nanosheets demonstrated antioxidant activity by scavenging 2,2-azino-bis(3-ethyl)benzothiazoline-6-sulfonic acid free radicals in a dose-dependent manner, highlighting their potential to reduce oxidative stress in biomedical applications. Overall, this dual-focused study demonstrates that MXene nanosheets are not only highly effective for developing flexible, stable asymmetric supercapacitors but also exhibit favorable in vivo biocompatibility and antioxidant properties at the tested doses. These findings emphasize the potential of MXene-based materials as next-generation, fully biocompatible energy storage devices for advanced implantable bioelectronic systems.