In 2003, invasive breast cancer will attack approximately 190,000 US women, and this malignancy will take the lives of approximately 41,000 patients. Breast cancer is the leading cause of cancer in US women (excluding skin cancers). Diagnostic systems that can detect cancer at an early stage can be a priceless gift to patients suffering from this disease. With progress in the area of nanotechnology, it is now possible to synthesize nanoparticles, nanotubes, and nanowires approaching the size of proteins or DNA or other functional biological molecules (1.5 nm to 10 nm). Keeping these rapid advances in mind, this proposal presents a revolutionary approach of developing a nano-biohybrid system where nanoparticles, nanowires, and nanotubes are used as probes for detecting and killing cancer cells by assembling specific anti-oncogene antibodies on nanowire/nanoparticle/nanotube surfaces for detecting overexpressed cell surface receptors called Her2 in cancer cells. The hypothesis used is that assembling antibodies on the nanowire/nanoparticle/nanotube surfaces will change the electronic properties of the material that can be detected using tunneling microscopic techniques. This would be a significant step in the area of biomedical nanotechnology and could revolutionize cancer diagnostic systems as we will be able to nanoelectronically detect a single cancer cell. Further, the success of this technology can result in cancer diagnostic systems for various other types of cancer based on similar principles that can be used in a clinical set-up for early detection of cancer.