Nanotechnology enables the engineering of materials at molecular scales to achieve novel physical, optical, and biochemical functionalities. In biomedicine, nanoscale platforms such as carbon nanotubes, nanoparticles, and protein-based microspheres offer highly customizable architectures for integrated sensing, imaging, and therapeutic applications. Carbon nanotubes support near-infrared fluorescence and Raman-based detection, enabling real-time, in vivo molecular sensing of chemotherapeutics, redox activity, and tumor microenvironment dynamics. Protein-shell microspheres, fabricated through layer-by-layer surface functionalization, act as adaptable carriers for magnetic nanoparticles, optical dyes, and targeting ligands—supporting multimodal imaging and potential therapeutic delivery. These nanotechnologies have been deployed in cancer diagnostics, intraoperative imaging, and physiological biologging, demonstrating broad utility across disease monitoring and intervention. This work advances a vision of nanoscale tools as clinically relevant platforms for precision diagnostics, targeted therapy, and next-generation biomedical device development.