Acupuncture Needle-Based Biosensors: Interface Engineering, Sensing Strategies, and Applications

Acupuncture needles, conventionally employed as therapeutic tools in Chinese medicine, have emerged as compelling substrates for constructing minimally invasive sensing platforms. Acupuncture needles' unique attributes, including small size, sharp tip geometry, mechanical robustness, biocompatibility, and ease of insertion into tissue, render them attractive for in vivo, real-time monitoring applications. This review provides an overview of the recent advances in acupuncture needle-based biosensors (ANBSs), focusing on three interconnected aspects: interface engineering approaches, sensing strategies, and representative applications. We demonstrate electrochemical and surface-enhanced Raman spectroscopy (SERS)-based platforms as two principal classes of acupuncture needle-based biosensors, and survey their applications in neurotransmitter monitoring, disease biomarker detection, therapeutic drug monitoring, metabolite profiling, acupoint initiation investigation, as well as environmental contaminant screening and food safety assessment. Finally, we also discuss current challenges, including long-term instability, inadequate active sites, biofouling, signal drift, and insufficient reproducibility, while offering perspectives on future directions such as optimization of materials, miniaturization and multifunction, intelligent sensing strategies and clinical translation proposal. By bridging traditional acupuncture needles and advanced analytical science, this review not only provides a coherent framework for researchers in biosensors but also inspires the next generation of minimally invasive point-of-care diagnostic tools.