Realization of a Nano-voyager in Human Blood
-Ambarish Ghosh, Centre for Nano Science and Engineering
The idea of tiny vessels roaming around in human blood vessels working as surgical nanorobots was first proposed by Richard Feynman: a vision that has triggered imagination in scientists and non-scientists alike. With current advances in nanotechnology, there have been several strategies to realize this dream of a “nano-voyager”, aiming to move artificial nanostructures in biological environments in a controllable manner. Unfortunately, most externally driven nanomotors have so far been actuated in de-ionized water, and in a few cases, in media of biological relevance, such as serum. The question then arises: why has there not been any demonstration of an artificial nanomotor being driven in unmodified human blood, and what are the steps to be taken to achieve the same?
As shown in a recent paper published in Nano Letters, this limitation is related to fuel requirement, corrosion, and liquid viscosity, which have limited the motion of nanomotors to model systems such as water, serum, or bio-fluids diluted with toxic chemical fuels, such as hydrogen peroxide. As demonstrated in a massive collaborative effort involving research groups from CeNSE and MRC, integrating conformal ferrite coatings with magnetic nanohelices offer a promising combination of functionalities for having controlled motion in practical biological fluids, such as chemical stability, cytocompatibility and the generated thrust. These coatings were found to be stable in various bio-fluids, even after overnight incubation, and did not have significant influence on the propulsion efficiency of the magnetically driven nanohelices, thereby facilitating the first successful “voyage” of artificial nanomotors in human blood. The motion of the “nano-voyager” was found to show interesting stick-slip dynamics, an effect originating in the colloidal jamming of blood cells in the plasma. The system of magnetic “nano-voyagers” was found to be cytocompatible with C2C12 mouse myoblast cells, as confirmed using MTT assay and fluorescence microscopy observations of cell morphology.
Interestingly, ferrites display large magnetic hysteresis (therefore large specific absorption rate), implying that the present system can be readily used in applications pertaining to magnetic hyperthermia. It will be interesting to see if this and various other in vivo biological applications can be realized with this powerful system of magnetic nano-voyagers.
Reference: Conformal Cytocompatible Ferrite Coatings Facilitate the Realization of a Nano-voyager in Human Blood, Pooyath Lekshmy Venugopalan, Ranajit Sai, Yashoda Chandorkar, Bikramjit Basu, Srinivasrao Shivashankar, and Ambarish Ghosh, Published in Nano Letters (DOI: http://dx.doi.org/10.1021/nl404815q)