This chapter explores bio-nanotronics, an interdisciplinary field combining biology, nanotechnology, and electronics to develop advanced, ultra-sensitive sensor systems. By integrating functional nanomaterials—such as carbon nanotubes, graphene, quantum dots, and metallic nanoparticles—with biological recognition elements like enzymes, antibodies, and DNA, bio-nanotronic sensors enable precise, real-time detection of chemical and biological analytes. The chapter outlines the fundamental principles of signal transduction, diverse sensing mechanisms (optical, electrochemical, piezoelectric), and strategies for nanomaterial functionalization and device fabrication. Applications span healthcare diagnostics, environmental monitoring, food safety, agriculture, and defense. Special attention is given to wearable and implantable sensor technologies and lab-on-a-chip integration. Challenges such as sensitivity, reproducibility, large-scale manufacturing, and ethical considerations are also addressed. Additionally, the chapter discusses the future potential of bio-nanotronics in energy storage, suggesting a convergence of sensing and power systems. Overall, bio-nanotronics holds great promise for developing intelligent, biocompatible, and sustainable sensing platforms for next-generation technological solutions.