Carbon nanotube (CNT) is increasingly finding numerous applications even in medical and biological markets. In some applications, CNT could be injected or implanted into the human body for intercellular molecular delivery vehicles. CNT may be harmful if it is kept for a longer time in the human body. The toxicity concerns are highly relevant as an increasing number of products containing CNTs are being introduced, and chances of free CNTs getting released into the body during their life cycle has increased mostly during production or disposal. Researchers from India’s Tata Institute of Fundamental Research have demonstrated a novel, optical tweezers based approach to scavenge CNTs from biological fluids such as blood. This method may potentially be of use in scavenging, transporting and dispersal of potentially toxic CNTs in biologically relevant environment. The team has succeeded in using a low-power infrared laser in an optical tweezers set-up to generate micro-bubbles in flowing, biologically-relevant fluids, including human whole blood. These micro-bubbles are formed upon very localized heating of small bundles of carbon nanotubes that are suspended in the flowing fluid. The localized nature of the heating causes enormous temperature gradients to be set up in the fluid that in turn set up surface tension gradients that give rise to complex flow patterns in the immediate vicinity of the microbubble. Thus, proximate CNTs are attracted towards the microbubble and appear to adhere to the bubble surface.The physical manipulation of such CNT-encrusted bubbles enables the physical manipulation of CNTs by optical means – something that is generally not feasible under normal circumstances, as it is not possible to optically trap CNTs using infrared laser light. A key feature of his team's experiments is the use of very low power (5 mW) light in the infrared region (1064 nm wavelength) obtained from a continuous wave laser. (Source Courtsey: Nanowerk)