Conjugation and transport of quantum dots and nanoparticles by microtubule-associated kinesin motor proteins

In contrast to synthetic materials that passively assemble to form static structures through equilibrium dynamics, Nature has evolved complex, nonequilibrium strategies for the active assembly, reconfiguration and trafficking of nanomaterials. Microtubule-associated kinesin motor proteins play important roles in cell division, intracellular transport, and material assembly/reconfiguration in eukaryotic organisms. The primary goals of our work are to (1) integrate kinesin-microtubule shuttles for transporting synthetic nanoparticles, and (2) utilize the unique properties of these molecular shuttles to design dynamic and adaptive materials at synthetic interfaces. Towards this end, we are currently developing schemes by which kinesin-microtubule complexes are utilized in the transport of inorganic nanoparticles. Microtubule copolymers have been prepared from unlabeled and biotinylated tubulin and conjugated with streptavidin-coated gold nanoparticles and CdSe quantum dots. A variety of composite structures, ranging from centrosome-like assemblies to fully decorated microtubules, have been observed, and appear to be dependent on both the degree of biotinylation as well as the ratio of microtubules to quantum dots. Further, we have observed that these nanoparticle-laden microtubules can be transported by surface bound kinesins with an efficiency comparable to dye-labeled microtubules. To further facilitate microtubule-based nanoparticle transport, we have modified the microtubule polymerization and composition to create unique areas for attachment of nanoparticles and increase the efficacy for nanoparticle transport. Overall, these data demonstrate the ability to efficiently assemble and transport inorganic nanoparticle arrays using biological transport mechanisms, and provide a platform for the further development of dynamic nanomaterials based on these strategies.