Catalytic Propulsion and Magnetic Steering of Soft, Patchy Microcapsules: Ability to Pick-Up and Drop-Off Microscale Cargo (original) (raw)
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Advanced Functional Materials, 2010
The control over micro-and nanoobjects has attracted great attention in several areas of science, such as nanotechnology and drug delivery. One of the major challenges is to achieve autonomous movement of micro-and nanoscale machines in a fluid and employ them to perform complex tasks such as drug delivery, transport, and assembly of micro-/nano-objects. [1] Richard Feynman in his 1959 speech ''There's Plenty of Room at the Bottom'' envisioned microscopic factories with tiny machines that could perform sophisticated tasks. [2] The dream of manufacturing nanomachines is to mimic biological motors that can convert chemical into mechanical energy and hence develop diverse functions. [3] Some fascinating examples in nature are DNA and RNA polymerase; [4] rotary motors such as ATP synthase; [5] cilia and flagella motors; [6] dyneins, [7] kinesins, [8] and myosins. [9] Catalytic synthetic micro-and nanomotors [10-13] and engines [14,15] are of growing interest because of their high locomotive power and easy control. [16] Several approaches have been focused on the improvement of the catalytic conversion of chemicals (e.g., hydrogen peroxide) into kinetic energy [17-19] and the control over the movement of nanomotors by different sources has been reported. [20] The transport of spherical particles used as cargo [21,22] was recently achieved by either using electrostatic, chemical, or magnetic interactions to attach the cargo. [21,22] Extra functionality has also been given to the cargo (e.g., magnetic properties, chemical modification for electrostatic binding) for loading into the nanomotors. In addition, practical applications require higher towing forces and general mechanisms to bind and unbind different cargo in an easy and controllable way. Recently, rolled-up tubular structures that accumulate gas, which is generated by the catalytic decomposition of a fuel, have been developed. [14] These tubular microjets enhance the power of synthetic micromachines reaching a speed of up to 50 body lengths per second. [15] In this work, we describe the use of rolled-up thin Ti/Fe/Pt films as microbots developing tasks that require full control over their motion and high propulsion power. Maneuvers of self-propelled microbots were wirelessly coordinated by an external magnetic field, which allows the selective manipulation of different microobjects randomly suspended in solution. The physical characteristics of these tubular microbots led to a high propulsion power and allowed more than sixty polymeric cargo-particles to be attached and transferred to a desired location. Moreover, we achieved the selective loading of metallic nanoplates with a ''large'' surface area, their transport and directed assembly into different configurations. These illustrative examples form an attractive concept of
Self-propelling capsules as artificial microswimmers
Current Opinion in Colloid & Interface Science
The mimicry of natural microswimmers by artificial nano-and micro-devices is extremely challenging because it is hard to achieve and control nanoscale actuation reproducibly and reversibly. In the context of recent developments, we shall review the basic phenomena of artificial swimming objects in the micrometer scale. Typically, these swimming devices were rigid, and up to now, the mechanisms of self-propulsion have only rarely been adapted to soft particles as microcapsules. The high flexibility of capsules is an important feature for more realistic descriptions of the basic swimming processes of biological cells. Additionally, micro-and nanocapsules show the advantage that they can store a defined amount of chemical or biological compounds in their core regions. This offers a high potential for the realization of diverse biological or medical applications (e.g. cargo transport and controlled drug delivery). The discussed phenomena are based on different chemical reactions or flow and diffusion principles, including bulk-and surface rheology, and they can be used to develop new ideas concerning the construction of advanced types of self-propelling microcapsules.
2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2013
Development of targeted drug delivery systems using magnetic microrobots increases the therapeutic indices of drugs. These systems have to be incorporated with precise motion controllers. We demonstrate closed-loop motion control of microrobots under the influence of controlled magnetic fields. Point-to-point motion control of a cluster of iron oxide nanoparticles (diameter of 250 nm) is achieved by pulling the cluster towards a reference position using magnetic field gradients. Magnetotactic bacterium (MTB) is controlled by orienting the magnetic fields towards a reference position. MTB with membrane length of 5 µm moves towards the reference position using the propulsion force generated by its flagella. Similarly, self-propelled microjet with length of 50 µm is controlled by directing the microjet towards a reference position by external magnetic torque. The microjet moves along the field lines using the thrust force generated by the ejecting oxygen bubbles from one of its ends. Our control system positions the cluster of nanoparticles, an MTB and a microjet at an average velocity of 190 µm/s, 28 µm/s, 90 µm/s and within an average region-of-convergence of 132 µm, 40 µm, 235 µm, respectively.
Catalytic Self-Propulsion of Supramolecular Capsules Powered by Polyoxometalate Cargos
Chemistry - A European Journal, 2014
Multicompartment, spherical microcontainers were engineered through a layer-by-layer polyelectrolyte deposition around a fluorescent core while integrating a ruthenium polyoxometalate (Ru 4 POM), as molecular motor, vis-à-vis its oxygenic, propeller effect, fuelled upon H 2 O 2 decomposition. The resulting chemomechanical system, with average speeds of up to 25 mm s À1 , is amenable for integration into a microfluidic set-up for mixing and displacement of liquids, whereby the propulsion force and the resulting velocity regime can be modulated upon H 2 O 2 -controlled addition.
Self-Propelled Polymer Nanomotors
ChemPhysChem, 2009
Molecular motors that use chemical reactions to drive directed motion are widespread in nature. In addition to biochemical motors, which play an important role in the biochemistry of the cell, a wide variety of synthetic molecular motors that make use of chemical energy, light, magnetic fields and other sources of energy to effect motion have been constructed. These include molecular motors that rely on asymmetrical conformational changes, similar to many biological motors or selfpropelled bacteria, as well as motors that make use of chemical catalysis and an asymmetrical distribution of reaction products to effect motion. The basic elements that are important for the operation and directed motion of these nonequi-A C H T U N G T R E N N U N G librium nanodevices are an intrinsic asymmetry and a power source that maintains the system out of equilibrium. Models for motors that operate by conformational changes and asymmetric gradients have been constructed and used to elucidate the nature of the propulsion mechanisms. Self-propelled nanodimers, which consist of linked catalytic and noncatalytic spheres, are simple examples of such molecular motors. A chemical reaction A!B occurs on the catalytic sphere. The asymmetric spatial distribution of the B molecules produced in the reaction gives rise to a directed force on the dimer that propels it in solution. This is a nonequilibrium nanodevice that consumes fuel in its environment, uses it to generate a non-A C H T U N G T R E N N U N G equilibrium local spatial distribution of products, which in turn gives rise to directed motion.
Colloidal Micromotors: Controlled Directed Motion
2008
Here we demonstrate a synthetic micro-engine, based on long-range controlled movement of colloidal particles, which is induced by a local catalytic reaction. The directed motion at long timescales was achieved by placing specially designed magnetic capped colloids in a hydrogen peroxide solution at weak magnetic fields. The control of the motion of the particles was provided by changes of the concentration of the solution and by varying the strength of the applied magnetic field. Such synthetic objects can then be used not only to understand the fundamental driving processes but also be employed as small motors in biological environments, for example, for the transportation of molecules in a controllable way.
Motion Control of Urea-Powered Biocompatible Hollow Microcapsules
ACS nano, 2016
The quest for biocompatible microswimmers powered by compatible fuel and with full motion control over their self-propulsion is a long-standing challenge in the field of active matter and microrobotics. Here, we present an active hybrid microcapsule motor based on Janus hollow mesoporous silica microparticles powered by the biocatalytic decomposition of urea at physiological concentrations. The directional self-propelled motion lasts longer than 10 min with an average velocity of up to 5 body lengths per second. Additionally, we control the velocity of the micromotor by chemically inhibiting and reactivating the enzymatic activity of urease. The incorporation of magnetic material within the Janus structure provides remote magnetic control on the movement direction. Furthermore, the mesoporous/hollow structure can load both small molecules and larger particles up to hundreds of nanometers, making the hybrid micromotor an active and controllable drug delivery microsystem.
Bubble-propelled micromotors for enhanced transport of passive tracers
Fluid convection and mixing induced by bubble-propelled tubular microengines are characterized using passive microsphere tracers. Enhanced transport of the passive tracers by bubble-propelled micromotors, indicated by their mean squared displacement (MSD), is dramatically larger than that observed in the presence of catalytic nanowires and Janus particle motors. Bubble generation is shown to play a dominant role in the effective fluid transport observed in the presence of tubular microengines. These findings further support the potential of using bubble-propelled microengines for mixing reagents and accelerating reaction rates. The study offers useful insights toward understanding the role of the motion of multiple micromotors, bubble generation, and additional factors (e.g., motor density and fuel concentration) upon the observed motor-induced fluid transport.
Current status of micro/nanomotors in drug delivery
Journal of Drug Targeting, 2020
Synthetic micro/nanomotors (MNMs) are novel, self-propelled nano or microscale devices that are widely used in drug transport, cell stimulation and isolation, bio-imaging, diagnostic and monitoring, sensing, photocatalysis and environmental remediation. Various preparation methods and propulsion mechanisms make MNMs "tailormade" nanosystems for the intended purpose or use. As the one of the newest members of nano carriers, MNMs open a new perspective especially for rapid drug transport and gene delivery. Although there exists limited number of in-vivo studies for drug delivery purposes, existence of in-vitro supportive data strongly encourages researchers to move on in this field and benefit from the maneuver capability of these novel systems. In this article, we reviewed the preparation and propulsion mechanisms of nanomotors in various fields with special attention to drug delivery systems.