MXene Chemistries for Biomedicine: On-Body, In-Body, and Beyond

: MXenes, a rapidly expanding family of two-dimensional transition-metal carbides, nitrides, and carbonitrides, have gained considerable attention as highly versatile nanomaterials for biomedical applications owing to their high electrical conductivity, chemically tunable surfaces, mixed ionic-electronic transport, and controllable redox activity. This review provides a structured overview of MXene-based biomedical technologies, organized by their functional interaction with the human body. We first examine on-body applications, highlighting MXene-enabled wearable, epidermal, and implantable bioelectronics. We then discuss in-body applications, including regenerative medicine, advanced cancer therapies, and antimicrobial strategies, emphasizing how MXene chemistry regulates biological interactions and therapeutic performance. Finally, we address applications outside the body, such as biosensing and diagnostic platforms, where MXenes enhance sensitivity, signal transduction, and imaging capabilities. Beyond summarizing recent advances, this review critically analyzes current gaps in knowledge, including long-term biocompatibility, degradation pathways, immune interactions, and structure-activity relationships, which currently limit clinical translation. We conclude by outlining key future directions, including sustainable synthesis, oxidation-resistant and fluorine-free MXenes, and the integration of artificial intelligence to accelerate materials discovery and application-specific design. Together, these insights position MXenes as chemistry-programmable nanoplatforms with strong potential to bridge on-body, in-body, and outside-the-body biomedical technologies.