Nano-biotechnology is a multidisciplinary field that bridges physical sciences with biological sciences via chemical tools. Carbon nanotubes with small sizes, unique one dimensional aromatic structure, and interesting inherent physical, especially optical, properties, have shown promise in biology and medicine. This thesis is a comprehensive study of using single walled carbon nanotubes (SWNT) for in vitro and in vivo biomedical applications. In vitro siRNA delivery by SWNTs into 'hard-to-transfect' cells is reported. Drug loading on functionalized SWNTs by supramolecular chemistry is developed for targeted delivery of aromatic cancer drugs to specific types of cancer cells. Next, in vivo biodistribution of SWNTs is monitored by a radiolabeling methodology, as well as ex-vivo Raman spectroscopy. The latter provides long-term fate and excretion information of SWNTs in mice. It is found that the surface chemistry of SWNTs largely governs their in vivo behaviors. Prolonged blood circulation, reduced uptake in reticuloendothelial systems (RES) and accelerated excretion are all achieved for SWNTs with superior biocompatible surface coating. Efficient in vivo tumor targeting is also realized by conjugating a targeting peptide to biocompatible SWNTs. After those fundamental explorations, in vivo cancer treatment by SWNT delivery is validated in xenograft mouse models with two chemotherapy drugs, paclitaxel and doxorubicin, loaded on nanotubes in two separate studies. Furthermore, isotope composition-dependent Raman spectroscopy signatures of SWNTs are used for multiple color Raman imaging. In addition to SWNTs, a novel carbon based nanomaterial, nano-graphene oxide, is synthesized and used for drug loading and delivery. Taken together, carbon nanotubes and related nano-biotechnologies are likely to provide new opportunities for challenging problems in biomedicine such as cancer treatment and imaging.