Publications

Biological barriers present a significant obstacle to treatment, especially when drugs are administered locally to increase their concentrations at the target site while minimizing unintended off-target effects. Among these barriers, mucus presents a challenge, as it serves as a protective layer in the respiratory, urogenital, and gastrointestinal tracts. Its role is to shield the underlying epithelial cells from pathogens and toxic compounds but also impedes the efficient delivery of drugs. Despite the exploration of mucolytic agents to improve drug delivery, overcoming this protective barrier remains a significant hurdle. In our study, we investigate an alternative approach involving the use of catalase-powered nanobots. We use an in vitro model that simulates intestinal mucus secretion to demonstrate the dual functionality of our nanobots. This includes their ability to disrupt mucus, which we confirmed through in vitro and ex vivo validation, as well as their self-propulsion to overcome the mucus barrier, resulting in a 60-fold increase compared with passive nanoparticles. Therefore, our findings highlight the potential utility of catalase-powered nanobots as carriers for therapeutic agents since they could enhance drug delivery efficiency by penetrating the mucus barrier.

JTD Keywords: Biological barrier, Biological barriers, Drug-delivery, Growth, Hydrogen-peroxide, Muci, Mucus, Nanobots, Nanomedicine, Nanomotors, Transport

Photocatalytic nanomotors have attracted a lot of attention because of their unique capacity to simultaneously convert light and chemical energy into mechanical motion with a fast photoresponse. Recent discoveries demonstrate that the integration of optical and magnetic components within a single nanomotor platform offers novel advantages for precise motion control and enhanced photocatalytic performance. Despite these advancements, the impact of magnetic fields on energy transfer dynamics in photocatalytic nanomotors remains unexplored. Here, we introduce dual-responsive rod-like nanomotors, made of a TiO2/NiFe heterojunction, able to (i) self-propel upon irradiation, (ii) align with the direction of an external magnetic field, and (iii) exhibit enhanced photocatalytic performance. Consequently, when combining light irradiation with a homogeneous magnetic field, these nanomotors exhibit increased velocities attributed to their improved photoactivity. As a proof-of-concept, we investigated the ability of these nanomotors to generate phenol, a valuable chemical feedstock, from benzene under combined optical and magnetic fields. Remarkably, the application of an external magnetic field led to a 100% increase in the photocatalytic phenol generation in comparison with light activation alone. By using various state-of-the-art techniques such as photoelectrochemistry, electrochemical impedance spectroscopy, photoluminescence, and electron paramagnetic resonance, we characterized the charge transfer between the semiconductor and the alloy component, revealing that the magnetic field significantly improved charge pair separation and enhanced hydroxyl radical generation. Consequently, our work provides valuable insights into the role of magnetic fields in the mechanisms of light-driven photocatalytic nanomotors for designing more effective light-driven nanodevices for selective oxidations.

JTD Keywords: Charge transfer, Dual-responsive nanomotors, Magnetic properties, Photoactive nanomotors, Photocatalysis, Selective oxidations

Over the past decades, the development of nanoparticles (NPs) to increase the efficiency of clinical treatments has been subject of intense research. Yet, most NPs have been reported to possess low efficacy as their actuation is hindered by biological barriers. For instance, synovial fluid (SF) present in the joints is mainly composed of hyaluronic acid (HA). These viscous media pose a challenge for many applications in nanomedicine, as passive NPs tend to become trapped in complex networks, which reduces their ability to reach the target location. This problem can be addressed by using active NPs (nanomotors, NMs) that are self-propelled by enzymatic reactions, although the development of enzyme-powered NMs, capable of navigating these viscous environments, remains a considerable challenge. Here, the synergistic effects of two NMs troops, namely hyaluronidase NMs (HyaNMs, Troop 1) and urease NMs (UrNMs, Troop 2) are demonstrated. Troop 1 interacts with the SF by reducing its viscosity, thus allowing Troop 2 to swim more easily through the SF. Through their collective motion, Troop 2 increases the diffusion of macromolecules. These results pave the way for more widespread use of enzyme-powered NMs, e.g., for treating joint injuries and improving therapeutic effectiveness compared with traditional methods. The conceptual idea of the novel approach using hyaluronidase NMs (HyaNMs) to interact with and reduce the viscosity of the synovial fluid (SF) and urease NMs (UrNMs) for a more efficient transport of therapeutic agents in joints.image

JTD Keywords: Biological barrier, Clinical research, Clinical treatments, Collective motion, Collective motion,nanomotors,nanorobots,swarming,viscous medi, Collective motions, Complex networks, Enzymatic reaction, Enzymes, Hyaluronic acid, Hyaluronic-acid,ph,viscoelasticity,adsorption,barriers,behavior,ureas, Macromolecules, Medical nanotechnology, Nano robots, Nanomotors, Nanorobots, Swarming, Synovial fluid, Target location, Viscous media, Viscous medium

Micro/nanomotors (MNMs) have evolved from single self-propelled entities to versatile systems capable of performing one or multiple biomedical tasks. When single MNMs self-assemble into coordinated swarms, either under external control or triggered by chemical reactions, they offer advantages that individual MNMs cannot achieve. These benefits include intelligent multitasking and adaptability to changes in the surrounding environment. Here, we provide our perspective on the evolution of MNMs, beginning with the development of enzymatic MNMs since the first theoretical model was proposed in 2005. These enzymatic MNMs hold immense promise in biomedicine due to their advantages in biocompatibility and fuel availability. Subsequently, we introduce the design and application of single motors in biomedicine, followed by the control of MNM swarms and their biomedical applications. In the end, we propose viable solutions for advancing the development of MNM swarms and anticipate valuable insights into the creation of more intelligent and controllable MNM swarms for biomedical applications.; Micro/nanomotor swarms propelled by diverse mechanisms.

JTD Keywords: Active particles, Actuation, Behaviors, Biocompatibility, Biomedical applications, Coordination reactions, Design and application, Diffusion, External control, Medical applications, Micromotors, Motion, Nanomotors, Powered nanomotors, Propulsion, Self-assemble, Surrounding environment, Theoretical modeling, Versatile system, Viable solutions

Bladder cancer treatment via intravesical drug administration achieves reasonable survival rates but suffers from low therapeutic efficacy. To address the latter, self-propelled nanoparticles or nanobots have been proposed, taking advantage of their enhanced diffusion and mixing capabilities in urine when compared with conventional drugs or passive nanoparticles. However, the translational capabilities of nanobots in treating bladder cancer are underexplored. Here, we tested radiolabelled mesoporous silica-based urease-powered nanobots in an orthotopic mouse model of bladder cancer. In vivo and ex vivo results demonstrated enhanced nanobot accumulation at the tumour site, with an eightfold increase revealed by positron emission tomography in vivo. Label-free optical contrast based on polarization-dependent scattered light-sheet microscopy of cleared bladders confirmed tumour penetration by nanobots ex vivo. Treating tumour-bearing mice with intravesically administered radio-iodinated nanobots for radionuclide therapy resulted in a tumour size reduction of about 90%, positioning nanobots as efficient delivery nanosystems for bladder cancer therapy.© 2024. The Author(s).

JTD Keywords: cell, drug-delivery, nanomotors, tissue, Bladder cancers, Cancer therapy, Diseases, Drug administration, Drug delivery, Enhanced diffusion, Enhanced mixing, Ex-vivo, In-vivo, Mammals, Nanobots, Nanoparticles, Nanosystems, Oncology, Positron emission tomography, Radioisotopes, Silica, Survival rate, Therapeutic efficacy, Tumor penetration, Tumors

Targeted drug delivery depends on the ability of nanocarriers to reach the target site, which requires the penetration of different biological barriers. Penetration is usually low and slow because of passive diffusion and steric hindrance. Nanomotors (NMs) have been suggested as the next generation of nanocarriers in drug delivery due to their autonomous motion and associated mixing hydrodynamics, especially when acting collectively as a swarm. Here, we explore the concept of enzyme-powered NMs designed as such that they can exert disruptive mechanical forces upon laser irradiation. The urease-powered motion and swarm behavior improve translational movement compared to passive diffusion of state-of-the-art nanocarriers, while optically triggered vapor nanobubbles can destroy biological barriers and reduce steric hindrance. We show that these motors, named Swarm 1, collectively displace through a microchannel blocked with type 1 collagen protein fibers (barrier model), accumulate onto the fibers, and disrupt them completely upon laser irradiation. We evaluate the disruption of the microenvironment induced by these NMs (Swarm 1) by quantifying the efficiency by which a second type of fluorescent NMs (Swarm 2) can move through the cleared microchannel and be taken up by HeLa cells at the other side of the channel. Experiments showed that the delivery efficiency of Swarm 2 NMs in a clean path was increased 12-fold in the presence of urea as fuel compared to when no fuel was added. When the path was blocked with the collagen fibers, delivery efficiency dropped considerably and only depicted a 10-fold enhancement after pretreatment of the collagen-filled channel with Swarm 1 NMs and laser irradiation. The synergistic effect of active motion (chemically propelled) and mechanical disruption (light-triggered nanobubbles) of a biological barrier represents a clear advantage for the improvement of therapies which currently fail due to inadequate passage of drug delivery carriers through biological barriers.

JTD Keywords: drug delivery, enzyme catalysis, nanoparticles, swarming, vapor nanobubbles, Drug carriers, Drug delivery, Drug delivery systems, Enzyme catalysis, Hela cells, Humans, Nanomotors, Nanoparticles, Swarming, Vapor nanobubbles

Although an increasing number of micro/nanomotors have been designed for environmental remediation in the past decade, the construction of contaminants-fueled nanomotors for synergistically degrading multiple pollutants simultaneously remains a challenge. Herein, laccase-powered Fe3O4@silica nanomotors are fabricated, assisted with lipase enzyme for the enhanced degradation of multiple contaminants using the contaminants themselves as fuels. Notably, we demonstrate that representative industrial phenols and polycyclic aromatic pollutants possess the ability of triggering the enhanced Brownian motion of laccase nanomotors (De of 1.16 mu m(2)/s in 220 mu M biphenol A (BPA), 1.40 mu m(2)/s in 375 mu M Congo red (CR)). Additionally, the k(cat) value of lipase-assisted laccase-powered nanomotors increased over 1.4 times, enhancing their Brownian motion, while leading to the efficient degradation of multiple contaminants such as BPA, CR, and triacetin droplets within 40 min, simultaneously. Ultimately, the lipase-assisted laccase nanomotors exhibit great advantages over free laccase, free lipase, lipase nanomotors, or laccase nanomotors in K-m, k(cat), catalytic stability, recycling property, and the degradation efficiency of contaminants. Therefore, our work further broadens the library of enzyme-powered nanomotors and provides deep insights in synergistical enzymatic catalysis, thus paving avenues for environmental remediation based on enzyme-powered micro/nanomotors. (C) 2022 Elsevier Ltd. All rights reserved.

JTD Keywords: core, dye, environmental remediation, enzyme catalysis, hybrid, light, microspheres, motors, pollutants removal, propulsion, removal, self-propulsion, shell, Core, Dye, Environmental remediation, Enzyme catalysis, Hybrid, Light, Micro/nanomotors, Micromotors, Microspheres, Motors, Pollutants removal, Propulsion, Removal, Self-propulsion, Shell

Nature has inspired the creation of artificial micro- and nanomotors that self-propel converting chemical energy into mechanical action. These tiny machines have appeared as promising biomedical tools for treatment and diagnosis and have also been used for environmental, antimicrobial or sensing applications. Among the possible catalytic engines, enzymes have emerged as an alternative to inorganic catalysts due to their biocompatibility and the variety and bioavailability of fuels. Although the field of enzyme-powered micro- and nano-motors has a trajectory of more than a decade, a comprehensive framework on how to rationally design, control and optimize their motion is still missing. With this purpose, herein we performed a thorough bibliographic study on the key parameters governing the propulsion of these enzyme-powered devices, namely the chassis shape, the material composition, the motor size, the enzyme type, the method used to incorporate enzymes, the distribution of the product released, the motion mechanism, the motion media and the technique used for motion detection. In conclusion, from the library of options that each parameter offers there needs to be a rational selection and intelligent design of enzymatic motors based on the specific application envisioned.

JTD Keywords: Catalase, Hydrogen-peroxide, Micro/nanomotors, Micromotors, Movement, Nanomotors, Propulsion, Surfactants, Therapy, Tumor microenvironment

The increasing resistance of bacteria to existing antibiotics constitutes a major public health threat globally. Most current antibiotic treatments are hindered by poor delivery to the infection site, leading to undesired off-target effects and drug resistance development and spread. Here, we describe micro- and nanomotors that effectively and autonomously deliver antibiotic payloads to the target area. The active motion and antimicrobial activity of the silica-based robots are driven by catalysis of the enzyme urease and antimicrobial peptides, respectively. These antimicrobial motors show micromolar bactericidal activity in vitro against different Gram-positive and Gram-negative pathogenic bacterial strains and act by rapidly depolarizing their membrane. Finally, they demonstrated autonomous anti-infective efficacy in vivo in a clinically relevant abscess infection mouse model. In summary, our motors combine navigation, catalytic conversion, and bactericidal capacity to deliver antimicrobial payloads to specific infection sites. This technology represents a much-needed tool to direct therapeutics to their target to help combat drug-resistant infections.

JTD Keywords: antibiotic-resistance, antimicrobial peptides, autonomous treatment, bacterial infection, delivery, ll-37, nanomotors, nanoparticles, peptide, self-propulsion, tissue, vitro, wasp venom, Antibiotic-resistance, Antimicrobial peptides, Autonomous treatment, Bacterial infection, Delivery, Ll-37, Mesoporous silica nanoparticles, Nanomotors, Nanoparticles, Peptide, Self-propulsion, Tissue, Vitro, Wasp venom

© 2021 Wiley Periodicals LLC. Biohybrid robotics is a field in which biological entities are combined with artificial materials in order to obtain improved performance or features that are difficult to mimic with hand-made materials. Three main level of integration can be envisioned depending on the complexity of the biological entity, ranging from the nanoscale to the macroscale. At the nanoscale, enzymes that catalyze biocompatible reactions can be used as power sources for self-propelled nanoparticles of different geometries and compositions, obtaining rather interesting active matter systems that acquire importance in the biomedical field as drug delivery systems. At the microscale, single enzymes are substituted by complete cells, such as bacteria or spermatozoa, whose self-propelling capabilities can be used to transport cargo and can also be used as drug delivery systems, for in vitro fertilization practices or for biofilm removal. Finally, at the macroscale, the combinations of millions of cells forming tissues can be used to power biorobotic devices or bioactuators by using muscle cells. Both cardiac and skeletal muscle tissue have been part of remarkable examples of untethered biorobots that can crawl or swim due to the contractions of the tissue and current developments aim at the integration of several types of tissue to obtain more realistic biomimetic devices, which could lead to the next generation of hybrid robotics. Tethered bioactuators, however, result in excellent candidates for tissue models for drug screening purposes or the study of muscle myopathies due to their three-dimensional architecture. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

JTD Keywords: bacteria-bots, based biorobots, biorobots, bots, enzymatic nanomotors, hybrid robotics, muscle‐, Bacteria‐, Bacteria-bots, Biorobots, Enzymatic nanomotors, Hybrid robotics, Muscle-based biorobots

Catalytically powered micro/nanobots (MNBs) can perform active movement by harnessing energy from in situ chemical reactions and show tremendous potential in biomedical applications. However, the development of imageable MNBs that are driven by bioavailable fuels and possess multiple therapeutic functions remains challenging. To resolve such issues, we herein propose enzyme (urease) powered liquid metal (LM) nanobots that are naturally of multiple therapeutic functions and imaging signals. The main body of the nanobot is composed of a biocompatible LM nanoparticle encapsulated by polydopamine (PDA). Urease enzyme needed for the powering and desired drug molecules, e.g., cefixime trihydrate antibiotic, are grafted on external surfaces of the PDA shell. Such a chemical composition endows the nanobots with dual-mode ultrasonic (US) and photoacoustic (PA) imaging signals and favorable photothermal effect. These LM nanobots exhibit positive chemotaxis and therefore can be collectively guided along a concentration gradient of urea for targeted transportation. When exposed to NIR light, the LM nanobots would deform and complete the function change from active drug carriers to photothermal reagents, to achieve synergetic antibacterial treatment by both photothermal and chemotherapeutic effects. The US and PA properties of the LM nanoparticle can be used to not only track and monitor the active movement of the nanobots in a microfluidic vessel model but also visualize their dynamics in the bladder of a living mouse in vivo. To conclude, the LM nanobots demonstrated herein represent a proof-of-concept therapeutic nanosystem with multiple biomedical functionalities, providing a feasible tool for preclinical studies and clinical trials of MNB-based imaging-guided therapy.

JTD Keywords: cell, chemo-photothermal therapy, chemotaxis, image tracking, liquid metal nanobots, nanomotors, tracking, Chemo-photothermal therapy, Chemotaxis, Image tracking, Liquid metal nanobots, Nanomotors

The low efficacy of current conventional treatments for bacterial infections increases mortality rates worldwide. To alleviate this global health problem, we propose drug-free enzyme-based nanomotors for the treatment of bacterial urinary-tract infections. We develop nanomotors consisting of mesoporous silica nanoparticles (MSNPs) that were functionalized with either urease (U-MSNPs), lysozyme (L-MSNPs), or urease and lysozyme (M-MSNPs), and use them against nonpathogenic planktonic Escherichia coli. U-MSNPs exhibited the highest bactericidal activity due to biocatalysis of urea into NaHCO3 and NH3, which also propels U-MSNPs. In addition, U-MSNPs in concentrations above 200 μg/mL were capable of successfully reducing 60% of the biofilm biomass of a uropathogenic E. coli strain. This study thus provides a proof-of-concept, demonstrating that enzyme-based nanomotors are capable of fighting infectious diseases. This approach could potentially be extended to other kinds of diseases by selecting appropriate biomolecules.

JTD Keywords: biofilms, carbonate, e. coli, enzymatic nanomotors, infections, lysozyme, micromotors, nanomachines, proteins, self-propulsion, Anti-bacterial agents, Biocatalysis, Biofilms, Canavalia, Drug carriers, E. coli, Eliminate escherichia-coli, Enzymatic nanomotors, Escherichia coli, Escherichia coli infections, Humans, Infections, Muramidase, Nanomachines, Nanoparticles, Self-propulsion, Silicon dioxide, Urease, Urinary tract infections

© 2020 Wiley-VCH GmbH Self-propelled particles and, in particular, those based on mesoporous silica, have raised considerable interest due to their potential applications in the environmental and biomedical fields thanks to their biocompatibility, tunable surface chemistry and large porosity. Although spherical particles have been widely used to fabricate nano- and micromotors, not much attention has been paid to other geometries, such as nanorods. Here, we report the fabrication of self-propelled mesoporous silica nanorods (MSNRs) that move by the catalytic decomposition of hydrogen peroxide by a sputtered Pt layer, Fe2O3 nanoparticles grown within the mesopores, or the synergistic combination of both. We show that motion can occur in two distinct sub-populations characterized by two different motion dynamics, namely enhanced diffusion or directional propulsion, especially when both catalysts are used. These results open up the possibility of using MSNRs as chassis for the fabrication of self-propelled particles for the environmental or biomedical fields.

JTD Keywords: Mesoporous silica, Nanomotors, Nanorods, Porous materials, Self-propulsion

Self-propelled particles and, in particular, those based on mesoporous silica, have raised considerable interest due to their potential applications in the environmental and biomedical fields thanks to their biocompatibility, tunable surface chemistry and large porosity. Although spherical particles have been widely used to fabricate nano- and micromotors, not much attention has been paid to other geometries, such as nanorods. Here, we report the fabrication of self-propelled mesoporous silica nanorods (MSNRs) that move by the catalytic decomposition of hydrogen peroxide by a sputtered Pt layer, Fe2O3 nanoparticles grown within the mesopores, or the synergistic combination of both. We show that motion can occur in two distinct sub-populations characterized by two different motion dynamics, namely enhanced diffusion or directional propulsion, especially when both catalysts are used. These results open up the possibility of using MSNRs as chassis for the fabrication of self-propelled particles for the environmental or biomedical fields

JTD Keywords: Mesoporous silica, Nanomotors, Nanorods, Porous materials, Self-propulsion

Micro/nanomotors (MNMs) are miniaturized machines that can perform assigned tasks at the micro/nanoscale. Over the past decade, significant progress has been made in the design, preparation, and applications of MNMs that are powered by converting different sources of energy into mechanical force, to realize active movement and fulfill on-demand tasks. MNMs can be navigated to desired locations with precise controllability based on different guidance mechanisms. A considerable research effort has gone into demonstrating that MNMs possess the potential of biomedical cargo loading, transportation, and targeted release to achieve therapeutic functions. Herein, the recent advances of self-propelled MNMs for on-demand biomedical cargo transportation, including their self-propulsion mechanisms, guidance strategies, as well as proof-of-concept studies for biological applications are presented. In addition, some of the major challenges and possible opportunities of MNMs are identified for future biomedical applications in the hope that it may inspire future research.

JTD Keywords: Biomedical applications, Cargo transportation, Guidance strategies, Micro/nanomotors, Self-propulsion

The introduction of stimuli-responsive cargo release capabilities on self-propelled micro- and nanomotors holds enormous potential in a number of applications in the biomedical field. Herein, we report the preparation of mesoporous silica nanoparticles gated with pH-responsive supramolecular nanovalves and equipped with urease enzymes which act as chemical engines to power the nanomotors. The nanoparticles are loaded with different cargo molecules ([Ru(bpy)3]Cl2 (bpy = 2,2′-bipyridine) or doxorubicin), grafted with benzimidazole groups on the outer surface, and capped by the formation of inclusion complexes between benzimidazole and cyclodextrin-modified urease. The nanomotor exhibits enhanced Brownian motion in the presence of urea. Moreover, no cargo is released at neutral pH, even in the presence of the biofuel urea, due to the blockage of the pores by the bulky benzimidazole:cyclodextrin-urease caps. Cargo delivery is only triggered on-command at acidic pH due to the protonation of benzimidazole groups, the dethreading of the supramolecular nanovalves, and the subsequent uncapping of the nanoparticles. Studies with HeLa cells indicate that the presence of biofuel urea enhances nanoparticle internalization and both [Ru(bpy)3]Cl2 or doxorubicin intracellular release due to the acidity of lysosomal compartments. Gated enzyme-powered nanomotors shown here display some of the requirements for ideal drug delivery carriers such as the capacity to self-propel and the ability to “sense” the environment and deliver the payload on demand in response to predefined stimuli.

JTD Keywords: Controlled release, Drug delivery, Enzymatic catalysis, Gatekeepers, Nanocarriers, Nanomotors, Stimuli-responsive nanomaterials

Cancer is one of the main causes of death around the world, lacking efficient clinical treatments that generally present severe side effects. In recent years, various nanosystems have been explored to specifically target tumor tissues, enhancing the efficacy of cancer treatment and minimizing the side effects. In particular, bladder cancer is the ninth most common cancer worldwide and presents a high survival rate but serious recurrence levels, demanding an improvement in the existent therapies. Here, we present urease-powered nanomotors based on mesoporous silica nanoparticles that contain both polyethylene glycol and anti-FGFR3 antibody on their outer surface to target bladder cancer cells in the form of 3D spheroids. The autonomous motion is promoted by urea, which acts as fuel and is inherently present at high concentrations in the bladder. Antibody-modified nanomotors were able to swim in both simulated and real urine, showing a substrate-dependent enhanced diffusion. The internalization efficiency of the antibody-modified nanomotors into the spheroids in the presence of urea was significantly higher compared with antibody-modified passive particles or bare nanomotors. Furthermore, targeted nanomotors resulted in a higher suppression of spheroid proliferation compared with bare nanomotors, which could arise from the local ammonia production and the therapeutic effect of anti-FGFR3. These results hold significant potential for the development of improved targeted cancer therapy and diagnostics using biocompatible nanomotors.

JTD Keywords: 3D cell culture, Bladder cancer, Enzymatic catalysis, Nanomachines, Nanomotors, Self-propulsion, Targeting

We report lipase-based nanomotors that are capable of enhanced Brownian motion over long periods of time in triglyceride solution and of degrading triglyceride droplets that mimic “blood lipids”. We achieved about 40 min of enhanced diffusion of lipase-modified mesoporous silica nanoparticles (MSNPs) through a biocatalytic reaction between lipase and its corresponding water-soluble oil substrate (triacetin) as fuel, which resulted in an enhanced diffusion coefficient (ca. 50 % increase) at low triacetin concentration (<10 mm). Lipase not only serves as the power engine but also as a highly efficient cleaner for the triglyceride droplets (e.g., tributyrin) in PBS solution, which could yield potential biomedical applications, for example, for dealing with diseases related to the accumulation of triglycerides, or for environmental remediation, for example, for the degradation of oil spills.

JTD Keywords: Enzyme nanomotors, Lipase, Micromotors, Oil removal, Self-propulsion

Biocatalytic micro- and nanomotors have emerged as a new class of active matter self-propelled through enzymatic reactions. The incorporation of functional nanotools could enable the rational design of multifunctional micromotors for simultaneous real-time monitoring of their environment and activity. Herein, we report the combination of DNA nanotechnology and urease-powered micromotors as multifunctional tools able to swim, simultaneously sense the pH of their surrounding environment, and monitor their intrinsic activity. With this purpose, a FRET-labeled triplex DNA nanoswitch for pH sensing was immobilized onto the surface of mesoporous silica-based micromotors. During self-propulsion, urea decomposition and the subsequent release of ammonia led to a fast pH increase, which was detected by real-time monitoring of the FRET efficiency through confocal laser scanning microscopy at different time points (i.e., 30 s, 2 and 10 min). Furthermore, the analysis of speed, enzymatic activity, and propulsive force displayed a similar exponential decay, matching the trend observed for the FRET efficiency. These results illustrate the potential of using specific DNA nanoswitches not only for sensing the micromotors’ surrounding microenvironment but also as an indicator of the micromotor activity status, which may aid to the understanding of their performance in different media and in different applications.

JTD Keywords: Micromotors, DNA-nanoswitch, pH detection, Self-propulsion, Nanosensors, Nanomotors

The use of enzyme catalysis to power micro- and nanomotors exploiting biocompatible fuels has opened new ventures for biomedical applications such as the active transport and delivery of specific drugs to the site of interest. Here, urease-powered nanomotors (nanobots) for doxorubicin (Dox) anticancer drug loading, release, and efficient delivery to cells are presented. These mesoporous silica-based core-shell nanobots are able to self-propel in ionic media, as confirmed by optical tracking and dynamic light scattering analysis. A four-fold increase in drug release is achieved by nanobots after 6 h compared to their passive counterparts. Furthermore, the use of Dox-loaded nanobots presents an enhanced anticancer efficiency toward HeLa cells, which arises from a synergistic effect of the enhanced drug release and the ammonia produced at high concentrations of urea substrate. A higher content of Dox inside HeLa cells is detected after 1, 4, 6, and 24 h incubation with active nanobots compared to passive Dox-loaded nanoparticles. The improvement in drug delivery efficiency achieved by enzyme-powered nanobots may hold potential toward their use in future biomedical applications such as the substrate-triggered release of drugs in target locations.

JTD Keywords: Drug delivery, Enzymatic catalysis, Nanobots, Nanomachines, Nanomotors

The motion of nanomotors triggered by light sources will provide new alternative routes to power nanoarchitectures without the need of chemical fuels. However, most light-driven nanomotors are triggered by UV-light, near infrared reflection, or laser sources. It is demonstrated that nanocap shaped Au/TiO2 nanomotors (175 nm in diameter) display increased Brownian motion in the presence of broad spectrum visible light. The motion results from the surface plasmon resonance effect leading to self-electrophoresis between the Au and TiO2 layers, a mechanism called plasmonic photocatalytic effect in the field of photocatalysis. This mechanism is experimentally characterized by electron energy loss spectroscopy, energy-filtered transmission electron microscopy, and optical video tracking. This mechanism is also studied in a more theoretical manner using numerical finite-difference time-domain simulations. The ability to power nanomaterials with visible light may result in entirely new applications for externally powered micro/nanomotors.

JTD Keywords: Enhanced Brownian motion, Fuel-free nanomotors, Nanomachines, Self-electrophoresis, Visible light

Self-propelled micromotors have previously shown to enhance pollutant removal compared to non-motile nano-micro particles. However, these systems are expensive, difficult to scale-up and require surfactant for efficient work. Efficient and inexpensive micromotors are desirable for their practical applications in water treatment technologies. We describe cobalt-ferrite based micromotors (CFO micromotors) fabricated by a facile and scalable synthesis, that produce hydroxyl radicals via Fenton-like reaction and take advantage of oxygen gas generated during this reaction for self-propulsion. Once the reaction is complete, the CFO micromotors can be easily separated and collected due to their magnetic nature. The CFO micromotors are demonstrated for highly efficient advanced oxidative removal of tetracycline antibiotic from the water. Furthermore, the effects of different concentrations of micromotors and hydrogen peroxide on the antibiotic degradation were studied, as well as the generation of the highly reactive hydroxyl radicals responsible for the oxidation reaction.

JTD Keywords: Degradation, Fenton reaction, Microbots, Nanomotors, Self-propelled Micromotors, Water treatment

JTD Keywords: Drug delivery, Nanomachines, Nanomotors, Nanorobots, Target delivery

The development of synthetic nanomotors for technological applications in particular for life science and nanomedicine is a key focus of current basic research. However, it has been challenging to make active nanosystems based on biocompatible materials consuming nontoxic fuels for providing self-propulsion. Here, we fabricate self-propelled Janus nanomotors based on hollow mesoporous silica nanoparticles (HMSNPs), which are powered by biocatalytic reactions of three different enzymes: catalase, urease, and glucose oxidase (GOx). The active motion is characterized by a mean-square displacement (MSD) analysis of optical video recordings and confirmed by dynamic light scattering (DLS) measurements. We found that the apparent diffusion coefficient was enhanced by up to 83%. In addition, using optical tweezers, we directly measured a holding force of 64 ± 16 fN, which was necessary to counteract the effective self-propulsion force generated by a single nanomotor. The successful demonstration of biocompatible enzyme-powered active nanomotors using biologically benign fuels has a great potential for future biomedical applications.

JTD Keywords: Enzyme, Hollow mesoporous silica nanoparticles, Hybrid motors, Janus particles, Nanomotors, Optical tweezers

Chemically powered micro- and nanomotors are small devices that are self-propelled by catalytic reactions in fluids. Taking inspiration from biomotors, scientists are aiming to find the best architecture for self-propulsion, understand the mechanisms of motion, and develop accurate control over the motion. Remotely guided nanomotors can transport cargo to desired targets, drill into biomaterials, sense their environment, mix or pump fluids, and clean polluted water. This Review summarizes the major advances in the growing field of catalytic nanomotors, which started ten years ago.

JTD Keywords: Catalysis, Micromotors, Nanomotors, Robots, Self-propulsion