Microsphere dynamics for actin based nanorobotic motility

Actin is the principle building block of the cytoskeleton. It provides eukaryotic cells with their characteristic shape, as well as the means to produce the force required for cell motility. Similarly, actin also provides the motile force behind the movement of prokaryotic organisms such as Listeria monocytogenes. Listeria's movement is achieved by hijacking the cytoskeleton proteins of the eukaryotic host through the use of its transmembrane protein, ActA, a nucleation factor which interacts with the host Arp2/3 complex, VASP, and Actin. Previous investigations with ActA have included microbead motility tests in cytoplasmic extract, and a prokaryotic over-expression system in an artificial motility media consisting of several essential actin binding proteins, (ABP's), ATP, and salt. From both of these studies, actin nucleation was observed at the bead surface interface with ActA, in the form of comet tails assembled from crosslinked microfilaments. Here we report comet tail formation using ActA coated microspheres in a motility system consisting of several key ABP's. This movement is being further characterized using a microcantilever-microsphere assembly, which we are using to measure the force output of our actin-based motility system. The ultimate objective of this research is to place the actin-based motility system into polymer vesicles and create an enclosed nanorobotic system, which produces a controllable amoeboid-like movement through an externally applied electric field.