Biological applications of carbon nanotubes: Paving the way to nanotube-based delivery vehicles and therapies for living systems

There is a growing interest in developing novel interfaces between nanomaterials and biological systems. The interactions between single-walled carbon nanotubes (SWNT) and cellular systems are studied here and the ability of SWNT to act as a transport and delivery system for cellular delivery is reported. Covalent and non-covalent techniques are employed to yield SWNT conjugates that are highly stable in aqueous environments. Functionalization schemes are also developed to incorporate cleavable bonds needed for cargo release, loading multiple cargos on the nanotube transporter and allowing SWNT to selectively target specific cells. The SWNT-based delivery system is shown to be compatible for the delivery of various proteins as well as biologically relevant species such as short interfering RNA (siRNA). Gene knock-down of oncongenes is observed in cells that are exposed with SWNT-siRNA conjugates at a level that is superior to that of a commercial transfection agent. Exploiting the intrinsic optical physical properties of SWNTs has also been explored and can be utilized to cause local heating inside cells and trigger cell death. SWNT transporters have no apparent cytotoxic effects or detrimental effect on biological functionality of the cargo post-internalization. SWNT are emerging as a new class of cellular transporters for applications in drug delivery, protein delivery, gene therapy and cancer therapy. Taken together, these factors elevate carbon nanotubes as an excellent candidate for providing new solutions to current biomedical problems. However, the investigation of carbon nanotubes in-vivo is crucial to determining the actual merits of this new material in clinical settings.