Biomolecular motors such as F1-adenosine triphosphate synthase (F1-ATPase) and myosin are similar in size, and they generate forces compatible with currently producible nanoengineered structures. We have engineered individual biomolecular motors and nanoscale inorganic systems, and we describe their integration in a hybrid nanomechanical device powered by a biomolecular motor. The device consisted of three components: an engineered substrate, an F1-ATPase biomolecular motor, and fabricated nanopropellers. Rotation of the nanopropeller was initiated with 2 mM adenosine triphosphate and inhibited by sodium azide.

Cells regulate active transport of intracellular cargo using motor proteins. Recent nanobiotechnology efforts aim to adapt motor proteins to power the movement and assembly of synthetic materials. A motor-protein-based nanoscale transport system (molecular shuttle) requires that the motion of the shuttles be guided along tracks. This study investigates the principles by which microtubules, serving as shuttle units, are guided along micrometer-scale kinesin-coated chemical and topographical tracks, where the efficiency of guidance is determined by events at the track boundary. Thus, we measure the probability of guiding as microtubules reach the track boundary of (1) a chemical edge between kinesin-coated and kinesin-free surfaces, (2) a topography-only wall coated completely with kinesin, and (3) a kinesin-free wall next to a kinesin-coated bottom surface (topography and chemistry combined). We present a guiding mechanism for each surface type that takes into account the physical properties of microtubule filaments and the surface properties (geometry, chemistry), and elucidate the contributions of surface topography and chemistry. Our experimental and theoretical results show that track edges that combine both topography and chemistry guide microtubules most frequently (approximately 90% of all events). By applying the principles of microtubule guidance by microfabricated surfaces, one may design and build motor-protein-powered devices optimized for transport.

Nature has evolved dynamic, non-equilibrium mechanisms for assembling hierarchical complexes of nanomaterials. A critical element to many of these assembly mechanisms involves the active and directed transport of materials by biomolecular motor proteins such as kinesin. In the present work, nanocrystal quantum dots (nQDs) were assembled and organized using microtubule (MT) filaments as nanoscale scaffolds. nQD density and localization were systematically evaluated by varying the concentration and distribution of functional groups within the MT structure. Confining nQD attachment to a central region within the MT enabled unaffected interaction with kinesin necessary to support active transport of nQD−MT composites. This active transport system will be further refined to control the optical properties of a surface by regulating the collective organization of nQD−MT composites.

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The integration of active transport into nanodevices greatly expands the scope of their applications. Molecular shuttles represent a nanoscale transport system driven by biomolecular motors that permits the transport of molecular cargo under user-control and along predefined paths. Specifically, we utilize functionalized microtubules as shuttles, which may be transported by kinesin motor proteins along photolithographically defined tracks on a surface. While it was thought that efficient guiding along these tracks requires a combination of surface chemistry and topography, we show here that channel-like tracks with a particular wall geometry can be created to efficiently guide microtubules in the absence of selectively adsorbed motor proteins. This new wall geometry consists of an undercut 200 nm high at the bottom of the channel wall fabricated by image reversal photolithography using AZ5214 photoresist. Microtubules move unencumbered in the undercut, suggesting applications for nanofluidic systems and for in vitro motility assays mimicking the restricted environment characteristic of intracellular transport. Because adsorbed kinesin supports motility on top and bottom surfaces of the guiding channels, this guiding mechanism may serve as a first step toward the development of three-dimensional architectures.

Biomolecular motors, in particular motor proteins, are ideally suited to introduce chemically powered movement of selected components into devices engineered at the micro- and nanoscale level. The design of such hybrid "bio/nano"-devices requires suitable synthetic environments, and the identification of unique applications. We discuss current approaches to utilize active transport and actuation on a molecular scale, and we give an outlook to the future.

Nuclear pore complexes (NPCs) regulate all cargo traffic across the nuclear envelope. The transport conduit of NPCs is highly enriched in disordered phenylalanine/glycine-rich nucleoporins (FG-Nups), which form a permeability barrier of still elusive and highly debated molecular structure. Here we present a microfluidic device that triggered liquid-to-liquid phase separation of FG-Nups, which yielded droplets that showed typical properties of a liquid state. On the microfluidic chip, droplets were perfused with different transport-competent or -incompetent cargo complexes, and then the permeability barrier properties of the droplets were optically interrogated. We show that the liquid state mimics permeability barrier properties of the physiological nuclear transport pathway in intact NPCs in cells: that is, inert cargoes ranging from small proteins to large capsids were excluded from liquid FG-Nup droplets, but functional import complexes underwent facilitated import into droplets. Collectively, these data provide an experimental model of how NPCs can facilitate fast passage of cargoes across an order of magnitude in cargo size.

Virus particles are captured and transported using kinesin‐driven, antibody‐functionalized microtubules. The functionalization was achieved through covalent crosslinking, which consequently enhanced the microtubule stability. The capture and transport of the virus particles was subsequently demonstrated in gliding motility assays in which antibody‐coated microtubules functioned as capture elements, and antibody‐coated microspheres served as fluorescent reporters (see Figure).