Loading and unloading of molecular cargo by DNA-conjugated microtubule

Ce-based solid-phase catalysts for phosphate hydrolysis as new tools for next-generation nanoarchitectonics

This review comprehensively covers synthetic catalysts for the hydrolysis of biorelevant phosphates and pyrophosphates, which bridge between nanoarchitectonics and biology to construct their interdisciplinary hybrids. In the early 1980s, remarkable catalytic activity of Ce4+ ion for phosphate hydrolysis was found. More recently, this finding has been extended to Ce-based solid catalysts (CeO2 and Ce-based metal-organic frameworks (MOFs)), which are directly compatible with nanoarchitectonics. Monoesters and triesters of phosphates, as well as pyrophosphates, were effectively cleaved by these catalysts. With the use of either CeO2 nanoparticles or elegantly designed Ce-based MOF, highly stable phosphodiester linkages were also hydrolyzed. On the surfaces of all these solid catalysts, Ce4+ and Ce3+ coexist and cooperate for the catalysis. The Ce4+ activates phosphate substrates as a strong acid, whereas the Ce3+ provides metal-bound hydroxide as an eminent nucleophile. Applications of these Ce-based catalysts to practical purposes are also discussed.

Localization analysis of essential oils in perilla herb (Perilla frutescens var. crispa) using derivatized mass spectrometry imaging

The localization of essential oils, including flavor components, in perilla herb (Perilla frutescens var. crispa) were visually determined using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) imaging. The surface of a perilla leaf was peeled using a cyanoacrylate adhesion compound and contained oil glands that retained their morphology and chemical properties. We imaged the three essential oils perillaldehyde, β-caryophyllene, and rosmarinic acid (RA). Perillaldehyde was derivatized using glycine to prevent evaporation and allow its detection and imaging while localized in oil glands. β-caryophyllene also localized in the oil glands and not in the epidermis region. RA was detected throughout the leaf, including the oil glands. Quantitative data for the three essential oils were obtained by gas chromatography- or liquid chromatography-MS. The concentrations of perillaldehyde, β-caryophyllene, and RA were 12.6 ± 0.62, 0.27 ± 0.02, and 0.16 ± 0.02 [mg/g] in the paste sample of perilla herb. Peeling using a cyanoacrylate adhesion compound, and derivatization of a target such as an aroma component have great potential for mass spectrometry imaging for multiple essential oils.

Targeted Activation of Molecular Transportation by Visible Light

Regulated transportation of nanoscale objects with a high degree of spatiotemporal precision is a prerequisite for the development of targeted molecular delivery. In vitro integration of the kinesin-microtubule motor system with synthetic molecules offers opportunities to develop controllable molecular shuttles for lab-on-a-chip applications. We attempted a combination of the kinesin-microtubule motor system with push-pull type azobenzene tethered inhibitory peptides (azo-peptides) through which reversible, spatiotemporal control over the kinesin motor activity was achieved locally by a single, visible wavelength. The fast thermal relaxation of the cis-isomers of azo-peptides offered us quick and complete resetting of the trans-state in the dark, circumventing the requirement of two distinct wavelengths for two-way switching of kinesin-driven microtubule motility. Herein, we report the manipulation of selected, single microtubule movement while keeping other microtubules at complete rest. The photoresponsive inhibitors discussed herein would help in realizing complex bionanodevices.

Spatiotemporal control of kinesin motor protein by photoswitches enabling selective single microtubule regulations

Artificial control of bio-nanomachines should have a major impact on the development of controllable transport systems for specific cargo transport on chips. Precise spatiotemporal control and local regulation of the bio-motor activity will, however, be necessary if we are to accomplish such a goal. In this study, we exploited the photoswitching properties of azobenzene-based high-energy molecules and inhibitors to control a single kinesin-driven microtubule that has potential to work as a nanocarrier for molecular cargos. In particular, we could influence the local concentration and dispersion of the microtubules at any desired position and time by irradiating a local area of the motility system at one wavelength, while irradiating the entire area at another wavelength, to enrich either cis or trans isomers of photoswitches in the selected region. Furthermore, various regulations (e.g., transporting, bending, breaking) of single microtubules were possible while almost arresting ambient microtubules-all without the need for any surface patterning.

pH responsive ATP carriers to drive kinesin movement

Multilayer film coated CaCO3 microspheres were employed as pH responsive ATP carriers to drive kinesin movement. The production of oxygen scavengers in a kinesin-microtubule system induces the decomposition of ATP-loaded CaCO3 microspheres and then leads to the release of ATP.

Negative differential electrical resistance of a rotational organic nanomotor

A robust, nanoelectromechanical switch is proposed based upon an asymmetric pendant moiety anchored to an organic backbone between two C60 fullerenes, which in turn are connected to gold electrodes. Ab initio density functional calculations are used to demonstrate that an electric field induces rotation of the pendant group, leading to a nonlinear current-voltage relation. The nonlinearity is strong enough to lead to negative differential resistance at modest source-drain voltages.

Nanoshuttles propelled by motor proteins sequentially assemble molecular cargo in a microfluidic device

Nanoshuttles powered by the molecular motor kinesin have the potential to capture and concentrate rare molecules from solution as well as to transport, sort and assemble them in a high-throughput manner. One long-thought-of goal has been the realisation of a molecular assembly line with nanoshuttles as workhorses. To harness them for this purpose might allow the community to engineer novel materials and nanodevices. The central milestone towards this goal is to expose nanoshuttles to a series of different molecules or building blocks and load them sequentially to build hierarchical structures, macromolecules or materials. Here, we addressed this challenge by exploiting the synergy of two so far mostly complementary techniques, nanoshuttle-mediated active transport and pressure-driven passive transport, integrated into a single microfluidic device to demonstrate the realisation of a molecular assembly line. Multiple step protocols can thus be miniaturised to a highly parallelised and autonomous working lab-on-a-chip: in each reaction chamber, analytes or building blocks are captured from solution and are then transported by nanoshuttles across fluid flow boundaries in the next chamber. Cargo can thus be assembled, modified, analysed and eventually unloaded in a procedure that requires only one step by its operator.

Transportation of nanoscale cargoes by myosin propelled actin filaments

Myosin II propelled actin filaments move ten times faster than kinesin driven microtubules and are thus attractive candidates as cargo-transporting shuttles in motor driven lab-on-a-chip devices. In addition, actomyosin-based transportation of nanoparticles is useful in various fundamental studies. However, it is poorly understood how actomyosin function is affected by different number of nanoscale cargoes, by cargo size, and by the mode of cargo-attachment to the actin filament. This is studied here using biotin/fluorophores, streptavidin, streptavidin-coated quantum dots, and liposomes as model cargoes attached to monomers along the actin filaments (“side-attached”) or to the trailing filament end via the plus end capping protein CapZ. Long-distance transportation (>100 µm) could be seen for all cargoes independently of attachment mode but the fraction of motile filaments decreased with increasing number of side-attached cargoes, a reduction that occurred within a range of 10–50 streptavidin molecules, 1–10 quantum dots or with just 1 liposome. However, as observed by monitoring these motile filaments with the attached cargo, the velocity was little affected. This also applied for end-attached cargoes where the attachment was mediated by CapZ. The results with side-attached cargoes argue against certain models for chemomechanical energy transduction in actomyosin and give important insights of relevance for effective exploitation of actomyosin-based cargo-transportation in molecular diagnostics and other nanotechnological applications. The attachment of quantum dots via CapZ, without appreciable modulation of actomyosin function, is useful in fundamental studies as exemplified here by tracking with nanometer accuracy.

A photochromic ATP analogue driving a motor protein with reversible light-controlled motility: controlling velocity and binding manner of a kinesin-microtubule system in an in vitro motility assay

We synthesized two photochromic ATP analogues (ATP-Azos) featuring azobenzene derivatives tethered at the 2' position of the ribose ring. In the presence of the ATP-Azo tethering p-tert-butylazobenzene, we observed reversible photo-control of the motility, velocity and binding manner, of a kinesin-microtubule system in an in vitro motility assay.

Effects of potential environmental interferents on kinesin-powered molecular shuttles

Biomolecular motor-powered active transport represents an alternate means for analyte processing in nanoscale biosensors and bioanalytical devices. For example, a prototype "smart dust" biosensor has recently been reported in which the motor protein kinesin processes antibody-functionalized microtubules (MTs) to capture and separate optically tagged protein analytes. A potential limitation of this technology, however, involves the inhibition of transport function by interfering compounds that may be present in raw samples. Here we characterized the response of kinesin-MT transport to a range of potential interferents including solvents, acids, oxidizers, and environmental contaminants. The results of kinesin motility assays suggest that, among the tested interferents, only acetic acid and sodium hypochlorite adversely affected MT transport, primarily due to depolymerization of MT filaments. While negative effects were not observed for the remaining compounds tested, enhancement in motility was observed in the presence of acetone, antifreeze, and organic matter. Overall, the data suggest that kinesin-MT transport is resilient against a variety of common interferents, but primarily susceptible to failure due to significant changes in pH or the presence of an oxidizer.

Synthesis and Characterization of Functionalized Magnetic Nanoparticles for the Detection of Pesticide

We synthesized magnetic nanoparticles (MNPs) by mixing aqueous solutions of 3d transition metal chlorides (MCl2·nH2O) and a sodium metasilicate nonahydrate (Na2SiO3·9H2O) in order to produce monodispersed MNPs in a single step. The particle size can be controlled by adjusting the annealing temperature. We characterized the MNPs by X-ray diffraction (XRD), superconducting quantum interference device (SQUID), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and zeta-potential measurement. Paramagnetic and superparamagnetic behaviors were found for the obtained samples depending on the particle size (d=3.0–4.6 nm). The synthesized MNPs could be modified with the amino-, phenyl-, and carboxy- groups on MNPs' surface by silanization procedure, respectively. The purpose of functionalizing the surface of the nanoscale magnetic particles was to realize subsequent capture and detection with desired other molecules by nanoparticle assisted laser ionization/desorption mass spectrometry.

Proadrenomedullin N-terminal 20 peptide increases kinesin's velocity both in vitro and in vivo

Intracellular cargo transport relies on microtubules and motor proteins such as kinesins and dyneins. Currently we have ample knowledge of the mechanisms by which motor proteins propel themselves along the microtubules, but little is known about intracellular factors that regulate motor speed. Here we show that proadrenomedullin N-terminal 20 peptide (PAMP) increases kinesin velocity and ATP consumption in a dose-dependent manner, using a variety of human kinesins. Structure-activity studies found that the terminal amide of PAMP is required for modulating kinesin activity and that the smallest peptide fragment retaining this role is PAMP₁₂₋₂₀. On the other hand, peptide fragments as small as PAMP₁₈₋₂₀ maintained the ability of delaying tubulin polymerization, another function previously described for PAMP, indicating that these two activities depend on different regions of the molecule. To demonstrate that these observations are also relevant in vivo, hippocampal neurons were isolated from mice lacking the gene coding for PAMP and from wild type littermates. Intravital stains followed by time-lapse microscopy analysis revealed that mitochondrial speed inside neurons lacking PAMP was significantly slower than in cells expressing the peptide. External addition of synthetic PAMP reversed this phenotype in PAMP-null neurons. Besides the obvious implications for better understanding cell biology, these results may be also relevant for the rapidly evolving discipline of nanotechnology because PAMP may be used as an accelerator of nanodevices based on microtubules and motor proteins.

Oligonucleotide analysis by nanoparticle-assisted laser desorption/ionization mass spectrometry

We analyzed oligonucleotides by nanoparticle-assisted laser desorption/ionization (nano-PALDI) mass spectrometry (MS). To this end, we prepared several kinds of nanoparticles (Cr-, Fe-, Mn-, Co-based) and optimized the nano-PALDI MS method to analyze the oligonucleotides. Iron oxide nanoparticles with diammonium hydrogen citrate were found to serve as an effective ionization-assisting reagent in MS. The mass spectra showed both [M - H](-) and [M + xMe(2+)- H](-) (Me: transition metal) peaks. The number of metal-adducted ion signals depended on the length of the oligonucleotide. This phenomenon was only observed using bivalent metal core nanoparticles, not with any other valency metal core nanoparticles. Our pilot study demonstrated that iron oxide nanoparticles could easily ionize samples such as chemical drugs and peptides as well as oligonucleotides without the aid of an oligonucleotide-specific chemical matrix (e.g., 3-hydroxypicolinic acid) used in conventional MS methods. These results suggested that iron-based nanoparticles may serve as the assisting material of ionization for genes and other biomolecules.

Transport of single cells using an actin bundle-myosin bionanomotor transport system

The potential of using actin bundles for the transport of liposomes and single cells across myosin-coated surfaces is investigated. Compared to that observed with filamentous actin, the liposome transport using actin bundles was more linear in nature and able to occur over longer distances. Bundles, but not filamentous actin, were capable of moving single cells. Cargo unloading from bundles was achieved by incubation with Triton X-100. These data suggest that actin bundling may improve the ability of the myosin motor system for nanotransport applications.

Molecular shuttles powered by motor proteins: loading and unloading stations for nanocargo integrated into one device

A central challenge on the way to engineer novel materials and nanodevices comprising active transport by nanomotors is the integration of cargo loading and unloading stations on one chip. Exploiting DNA hybridization in zipping and shearing geometries, we demonstrate spatially distinct cargo pick-up and unload by "molecular shuttles" in an integrated device. With this approach, applications can be realized where motor-driven processes are needed to enable transport and active sorting of analytes and nanosystems, or the reconfiguration or self-repair of materials and devices.

Functionalized magnetic nanoparticles as an in vivo delivery system

We developed extremely small functionalized magnetic nanoparticles (MNPs) for use as an in vivo delivery system for pharmaceuticals and biomolecules. We functionalized the MNPs (d = 3 nm) by silanization of amino groups on the particles with (3-aminopropyl)triethoxysilane for subsequent cross-linking with pharmaceuticals and biomolecules. The MNPs were successfully introduced into living cells without any further modification, such as the use of cationic residues, to enhance endocytic internalization. The particles could be incorporated into the subcutaneous tissue of a mouse's ear through the skin of the ear and could be localized by application of an external magnetic field.We also developed a cell-specific delivery system that makes use of MNPs (d = 3 nm) conjugated with folic acid and a coumarin fluorophore for recognition by folate receptors on the cell surface. The modified MNPs were internalized by human pharyngeal cancer cells (KB cells) after an incubation time that was short compared with the time required for internalization of MNPs without folic acid. Cellular recognition of MNPs may lead to the development of other cell-specific delivery systems.These functionalized MNPs are expected to be useful as a new drug delivery tool.

Molecular Motors as Components of Future Medical Devices and Engineered Materials

A new frontier in the development of prosthetic devices is the design of nanoscale systems which replace, augment, or support individual cells. Similar to cells, such devices will require the ability to generate mechanical movement, either for transport or actuation. Here, the development of nanoscale transport systems, which integrate biomolecular motors, is reviewed. To date, close to 100 publications have explored the design of such “molecular shuttles” based on the integration of synthetic molecules, nano- and microparticles, and micropatterned structures with kinesin and myosin motors and their associated cytoskeletal filaments, microtubules, and actin filaments. Tremendous progress has been made in addressing the key challenges of guiding, loading, and controlling the shuttles, providing a foundation for the exploration of applications in medicine and engineering.

"Smart dust" biosensors powered by biomolecular motors

The concept of a microfabricated biosensor for environmental and biomedical monitoring applications which is composed of environmentally benign components is presented. With a built-in power source (the biological fuel ATP) and driven by biological motors (kinesin), sensing in the microdevice can be remotely activated and the presence of a target molecule or toxin remotely detected. The multifaceted progress towards the realization of such a device is described.

Manganese oxide nanoparticle-assisted laser desorption/ionization mass spectrometry for medical applications

We prepared and characterized manganese oxide magnetic nanoparticles (d =5.6 nm) and developed nanoparticle-assited laser desorption/ionization (nano-PALDI) mass spectrometry. The nanoparticles had MnO₂ and Mn₂O₃ cores conjugated with hydroxyl and amino groups, and showed paramagnetism at room temperature. The nanoparticles worked as an ionization assisting reagent in mass spectroscopy. The mass spectra showed no background in the low m/z. The nanoparticles could ionize samples of peptide, drug and proteins (approx. 5000 Da) without using matrix, i.e., 2,5-dihydroxybenzoic acid (DHB), 4-hydroxy-α-cinnamic acid (CHCA) and liquid matrix, as conventional ionization assisting reagents. Post source decay spectra by nano-PALDI mass spectrometry will yield information of the chemical structure of analytes.

Biomolecular-motor-based nano- or microscale particle translocations on DNA microarrays

We aimed to create autonomous on-chip systems that perform targeted translocations of nano- or microscale particles in parallel using machinery that mimics biological systems. By exploiting biomolecular-motor-based motility and DNA hybridization, we demonstrate that single-stranded DNA-labeled microtubules gliding on kinesin-coated surfaces acted as cargo translocators and that single-stranded DNA-labeled cargoes were loaded/unloaded onto/from gliding microtubules at micropatterned loading/unloading sites specified by DNA base sequences. Our results will help to create autonomous molecular sorters and sensors.

Multiplex transport and detection of cytokines using kinesin-driven molecular shuttles

The application of biomolecular active transport systems offers a potential route for downscaling multiple analyte assays for lab-on-a-chip applications. Recently, the capture and transport of a wide range of target analytes including proteins, virus particles, and DNA have been demonstrated using kinesin-driven molecular shuttles. The molecular shuttles consisted of microtubule (MT) filaments that were functionalized with either analyte-selective antibodies or complementary DNA, thus facilitating selective target capture and transport. In the present work, we have applied this microfluidic platform for the simultaneous detection of multiple target protein analytes. Multiplexing of molecular shuttles was achieved by immobilizing biotinylated antibodies against interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-alpha) on biotinylated MTs using a streptavidin bridge. Nanocrystal quantum dots of different sizes and spectral emissions were functionalized with IL-2 and TNF-alpha antibodies to facilitate multiplexed detection. In this paper we discuss the results of selectivity and motility in single and multiplexed assays.

A smart dust biosensor powered by kinesin motors

Biosensors can be miniaturized by either injecting smaller volumes into micro- and nanofluidic devices or immersing increasingly sophisticated particles known as 'smart dust' into the sample. The term 'smart dust' originally referred to cubic-millimetre wireless semiconducting sensor devices that could invisibly monitor the environment in buildings and public spaces, but later it also came to include functional micrometre-sized porous silicon particles used to monitor yet smaller environments. The principal challenge in designing smart dust biosensors is integrating transport functions with energy supply into the device. Here, we report a hybrid microdevice that is powered by ATP and relies on antibody-functionalized microtubules and kinesin motors to transport the target analyte into a detection region. The transport step replaces the wash step in traditional double-antibody sandwich assays. Owing to their small size and autonomous function, we envision that large numbers of such smart dust biosensors could be inserted into organisms or distributed into the environment for remote sensing.

[Development of bio-hybrid micro machines]

Living system use many types of micro or nano-mechanical systems, which are called "motor protein". Those biological motors have unique features, such as nano-meter scaled molecular motor, high efficiently energy transduction from chemical energy or having a capacity of self-assembly. The realization of bio-hybrid micro-machines to integrate such motor proteins and micro-or nano-structures fabricated of inorganic materials, would have some potential values that are not achieved by traditional electronic, magnetic or optical devices. In this paper, we discuss a possibility of motor proteins to use as driving unit for micro analysis systems, such as Lab on a chip or microTAS (micro Total Analysis System) devices.