Single-walled carbon nanotubes (SWNTs) have drawn great attention worldwide for their unique electronic, mechanical and optical properties. This dissertation details studies of some of the most important areas including: (1) Single-stranded DNA (ssDNA) assisted separation of SWNTs using high performance liquid chromatography; (2) Optical sensitivity and kinetic studies of redox reaction of ssDNA functionalized SWNTs with hydrogen peroxide (H₂O₂); (3) Effects of Ag⁺ on the redox reaction of ssDNA-encased SWNTs with hydrogen peroxide; (4) Single-walled carbon nanotube based optical sensors for DNA detection; and (5) SWNTs as scaffolds for promoting stem cell differentiation into bone forming cells.

By using size-exclusion chromatography (SEC) and ion-exchange chromatography (IEC) for ssDNA assisted SWNT separations, enrichment for nanotubes of a few single types, including (6, 5), (8, 4), and (10, 5) nanotubes has been demonstrated. The redox reaction and the reaction kinetics of ssDNA functionalized SWNT hybrids with H₂O₂ under different environments including different buffer constituents and transition metal ions have been studied for developing optical sensors for H₂O₂ detection with a detection limit determined to be 0.28 ppm. The reaction between ssDNA-SWNTs and H₂O₂ has been found to be pH and buffer dependent, and can be affected by Ag⁺ ions which play a dual role in the reaction. By taking advantage of SWNT's unique near infrared optical properties and Raman features, SWNT-based optical DNA detection schemes have been developed for breast cancer diagnostics. With their robust mechanical properties and rich surface chemistry, it has been demonstrated that SWNTs are a promising scaffold material for promoting stem cell differentiation.