Fundamentals and applications of enzyme powered micro/nano-motors

Anti-biopassivated Reticular Micromotors for Bladder Cancer Therapy

The limited lifespan of enzyme-powered micro/nanomotors (MNMs) hinders their biomedical applications due to the easy deactivation in tumor microenvironments. In this study, by taking advantage of hydrogen bond-rich metal-organic frameworks (MOFs), we design anti-biopassivated urease-powered MOF motors (Ur-MOFtors) with sustained motility for bladder cancer therapy. Such reticular Ur-MOFtors exhibited an exceptionally long locomotion lifespan exceeding 90 min in highly concentrated urea, which was an 18-fold enhancement compared with urease-adsorbed MOFs, resulting in excellent anti-biopassivation of MOFtors. The underlying molecular mechanism of persistent motion involves hydrogen bonding interaction between the MOF skeleton and the catalytic product, as identified by in situ infrared spectroscopy and density functional theory. Based on the preserved enzymatic activity comparable to native urease, the self-propulsion pathway of Ur-MOFtors is driven by ionic self-diffusiophoresis with the positive chemotactic motion toward urea. Benefiting from the persistent motion of Ur-MOFtors in physiological urea, a rapid bladder cancer therapy was achieved with few instillation sessions and short treatment cycles during intravesical administration. This hydrogen bond-rich framework presents a promising anti-biopassivated approach to overcoming the short lifespan and easy deactivation of enzymatic motors for advanced therapeutic robotics.

Single-Atom Colloidal Nanorobotics Enhanced Stem Cell Therapy for Corneal Injury Repair

Corneal repair using mesenchymal stem cell therapy faces challenges due to long-term cell survival issues. Here, we design cerium oxide with gold single-atom-based nanorobots (CeSAN-bots) for treating corneal damage in a synergistic combination with stem cells. Powered by glucose, CeSAN-bots exhibit enhanced diffusion and active motion due to the cascade reaction catalyzed by gold and cerium oxide. CeSAN-bots demonstrate a two-fold increase in cellular uptake efficiency into mesenchymal stem cells compared to passive uptake. CeSAN-bots possess intrinsic antioxidant and immunomodulatory properties, promoting corneal regeneration. Validation in a mouse corneal alkali burn model reveals an improvement in corneal clarity restoration when stem cells are incorporated with CeSAN-bots. This work presents a strategy for developing glucose-driven, enzyme-free, single-atom-based ultrasmall nanorobots with promising applications in targeted intracellular delivery in diverse biological environments.

Liquid Metal Amplified Charge Separation in Photocatalytic Micro/Nanomotors for Antibacterial Therapy

Photocatalytic micro/nanomotors (MNMs) driven by electrophoresis have attracted considerable attention by virtue of their active mobility and versatile functionality. However, the rapid recombination of photogenerated electron-hole pairs on light illumination severely compromises the involvement of charge species in the catalytic redox reactions of fuels, thus hindering both the propulsion and the application performance of photocatalytic MNMs. Herein, we report a facile strategy to amplify charge separation by incorporating liquid metal (LM) into the construction of photocatalytic MNMs, thereby strengthening the electrophoretic propulsion of MNMs and promoting the generation of reactive oxygen species (ROS) for antibacterial application. The MNMs are constructed with a gallium (Ga) LM core, coated with abundant graphite-phase carbon nitride (g-C3N4) nanosheets and half covered by a thin platinum layer. These MNMs exhibit self-propulsion in hydrogen peroxide (H2O2) solution, with their motion dynamics further enhanced by light irradiation. Theoretical calculations and simulations reveal that the composition between Ga and g-C3N4 forms an ohmic junction in the electronic energy band structure, which effectively improves the charge separation efficiency of electron-hole pairs. These results align well with the experimental electrochemical tests and consequently intensify the catalytic redox reactions of H2O2, as well as accelerate the charge migration across MNMs, contributing to the enhancement of their propulsion performance. Simultaneously, the amplified separation of electrons facilitates increased ROS generation, empowering the MNMs with motion-enhanced antibacterial activity against Escherichia coli. Finally, an in vivo wound healing experiment is conducted, verifying the superior antibacterial therapeutic performance of photocatalytic MNMs. This work not only provides insights into the role of charge species in phoretic motion of MNMs but also gives inspiration for developing photocatalytic MNMs with advanced biomedical applications.

Progress in enzyme-powered micro/nanomotors in diagnostics and therapeutics

Enzyme-powered micro/nanomotors (EMNMs) represent cutting-edge research taking advantage of enzymes as biocatalysts to provide a driving force for micro/nanomotors. Up to now, EMNMs have been designed to be powered by catalase, urease, lipase, collagenase, compound enzymes, etc. They not only have good biocompatibility and biosafety but also possess the unique ability to utilize physiologically relevant fuel to achieve autonomous propulsion through in vivo catalytic reactions. This innovation has opened exciting possibilities for medical applications of EMNMs. Given the fact that the human body is naturally abundant with substrates available for enzymatic reactions, EMNMs can effectively exploit the complex microenvironment associated with diseases, enabling the diagnosis and treatment of various medical conditions. In this review, we first introduce different kinds of EMNMs applied in specific environments for the diagnosis and treatment of diseases, while highlighting their advancements for revolutionizing healthcare practices. Then, we address the challenges faced in this rapidly evolving field, and at last, the potential future development directions are discussed. As the potential of EMNMs becomes increasingly evident, continued research and exploration are essential to unlock their full capabilities and to ensure their successful integration into clinical applications.

Recent Advances in Micro/Nanomotor for the Therapy and Diagnosis of Atherosclerosis

Atherosclerotic cardiovascular disease poses a significant global public health threat with a high incidence that can result in severe mortality and disability. The lack of targeted effects from traditional therapeutic drugs on atherosclerosis may cause damage to other organs and tissues, necessitating the need for a more focused approach to address this dilemma. Micro/nanomotors are self-propelled micro/nanoscale devices capable of converting external energy into autonomous movement, which offers advantages in enhancing penetration depth and retention while increasing contact area with abnormal sites, such as atherosclerotic plaque, inflammation, and thrombosis, within blood vessel walls. Recent studies have demonstrated the crucial role micro/nanomotors play in treating atherosclerotic cardiovascular disease. Hence, this review highlights the recent progress of micro/nanomotor technology in atherosclerotic cardiovascular disease, including the effective promotion of micro/nanomotors in the circulatory system, overcoming hemorheological barriers, targeting the atherosclerotic plaque microenvironment, and targeting intracellular drug delivery, to facilitate atherosclerotic plaque localization and therapy. Furthermore, we also describe the potential application of micro/nanomotors in the imaging of vulnerable plaque. Finally, we discuss key challenges and prospects for treating atherosclerotic cardiovascular disease while emphasizing the importance of designing individualized management strategies specific to its causes and microenvironmental factors.

On-Demand Photoactivation of DNA-Based Motor Motion

A major challenge in the field of synthetic motors relates to mimicking the precise, on-demand motion of biological motor proteins, which mediates processes such as cargo transport, cell locomotion, and cell division. To address this challenge, we developed a system to control the motion of DNA-based synthetic motors using light. DNA motors are composed of a central chassis particle modified with DNA "legs" that hybridize to RNA "fuel", and move upon enzymatic consumption of RNA. We first concealed RNA fuel sites using photocleavable oligonucleotides that block DNA leg binding. Upon UV activation, the RNA blocking strands dissociate, exposing the RNA fuel and initiating active, directional motion. We also created a "brake" system using photocleavable DNA stalling strands, anchoring the motors until UV light removes the "brake" while simultaneously "fueling" the motors, initiating spatiotemporally controlled stop → go motion. Additionally, we modified the "brake" system to activate the motors via a chemical input, while an optical input is required to fuel the motors. This dual-input approach, functioning as an "AND" gate, demonstrates the potential for DNA motors to perform light-triggered computational tasks. Our work provides a proof of concept for enhancing the complexity and functionality of synthetic motors.

Dual-Responsive MnO2-Loaded Carbonaceous Nanobottle Motors Fabricated by Interfacial Superassembly for On-The-Fly MicroRNA Sensing

Diverse nanomotors with advanced motion manipulation have been proposed to revolutionize the way problems in many fields are solved. However, rational and controllable synthetic methods of multifunctional nanomotor are still limited. Herein, dual-responsive MnO2-loaded carbonaceous nanobottle motors (MnO2 NBMs) are developed through an interfacial superassembly strategy. Asymmetric carbonaceous nanobottles are first synthesized, and the reductive carbonaceous shell induces an oxidation-reduction reaction with KMnO4 for in-situ growth of MnO2 nanosheets, which enables the nanomotor to perform either self-diffusiophoretic or self-thermophoretic motion in response to H2O2 and near-infrared light, respectively. Inspired by bioaffinity sensing, the nanomotors are sequentially assembled with functional nanoparticles and hairpin DNA to construct swimming functional MnO2 NBMs (MnO2 FNBMs) probes. The probes can move around complex samples to improve target miRNA transport and accelerate receptor-target interaction. Coupling with the photocurrent-signal amplification, the self-assembly of photoelectrochemical (PEC) biosensors has been achieved for sensitive microRNA detection. Trace amounts of miRNA-155 can be quickly detected with a wide detection range (100 fM to 100 nM). Moreover, the direct detection of microRNA in tumor cell lysates by the biosensor is demonstrated. Given the merits of automation and miniaturization, the proposed strategy provides a promising method for fast and effective self-assembly of biosensors.

Breaking Through Physiological Barriers: Nanorobotic Strategies for Active Drug Delivery

Self-propelled micro/nanomotors (MNMs) represent a groundbreaking advancement in precision drug delivery, offering potential solutions to persistent challenges such as systemic toxicity, limited bioavailability, and nonspecific distribution. By transforming various energy sources into mechanical motion, MNMs are able to autonomously navigate through complex physiological environments, facilitating targeted delivery of therapeutic agents to previously inaccessible regions. However, to achieve efficient in vivo drug delivery, biomedical MNMs must demonstrate their ability to overcome crucial physiological barriers encompassing mucosal surfaces, blood flow dynamics, vascular endothelium, and cellular membrane. This review provides a comprehensive overview of the latest strategies developed to address these obstacles while also analyzing the broader challenges and opportunities associated with clinical translation. Our objective is to establish a solid foundation for future research in medical MNMs by focusing on enhancing drug delivery efficiency and advancing precision medicine, ultimately paving the way for practical theragnostic applications and wider clinical adoption.

Transport and energetics of bacterial rectification

Randomly moving active particles can be herded into directed motion by asymmetric geometric structures. Although such a rectification process has been extensively studied due to its fundamental, biological, and technological relevance, a comprehensive understanding of active matter rectification based on single particle dynamics remains elusive. Here, by combining experiments, simulations, and theory, we study the directed transport and energetics of swimming bacteria navigating through funnel-shaped obstacles-a paradigmatic model of rectification of living active matter. We develop a microscopic parameter-free model for bacterial rectification, which quantitatively explains experimental and numerical observations and predicts the optimal geometry for the maximum rectification efficiency. Furthermore, we quantify the degree of time irreversibility and measure the extractable work associated with bacterial rectification. Our study provides quantitative solutions to long-standing questions on bacterial rectification and establishes a generic relationship between time irreversibility, particle fluxes, and extractable work, shedding light on the energetics of nonequilibrium rectification processes in living systems.

Application of Micro/Nanomotors in Environmental Remediation: A Review

The advent of self-propelled micro/nanomotors represents a paradigm shift in the field of environmental remediation, offering a significant enhancement in the efficiency of conventional operations through the exploitation of the material phenomenon of active motion. Despite the considerable promise of micro/nanomotors for applications in environmental remediation, there has been a paucity of reviews that have focused on this area. This review identifies the current opportunities and challenges in utilizing micro/nanomotors to enhance contaminant degradation and removal, accelerate bacterial death, or enable dynamic environmental monitoring. It illustrates how mobile reactors or receptors can dramatically increase the speed and efficiency of environmental remediation processes. These studies exemplify the wide range of environmental applications of dynamic micro/nanomotors associated with their continuous motion, force, and function. Finally, the review discusses the challenges of transferring these exciting advances from the experimental scale to larger-scale field applications.

Miniature Robots for Battling Bacterial Infection

Micro/nanorobots have shown great promise for minimally invasive bacterial infection therapy. However, bacterial infections usually form biofilms inside the body by aggregation and adhesion, preventing antibiotic penetration and increasing the likelihood of recurrence. Moreover, a substantial portion of the infection happens in those hard-to-access regions, making delivery of antibiotics to infected sites or tissues difficult and exacerbating the challenge of addressing bacterial infections. Micro/nanorobots feature exceptional mobility and controllability, are able to deliver drugs to specific sites (targeted delivery), and enhance drug penetration. In particular, the emergence of bioinspired microrobot surface design strategies have provided effective alternatives for treating infections, thereby preventing the possible development of bacterial resistance. In this paper, we review the recent advances in design, mechanism, and actuation modalities of micro/nanorobots with exceptional antimicrobial features, highlighting active therapy strategies for bacterial infections and derived complications at various organs, from the laboratory bench to in vivo applications. The current challenges and future research directions in this field are summarized. Those breakthroughs in micro/nanorobots offer a huge potential for clinical translation for bacterial infection therapy.

Micro/nanorobots for gastrointestinal tract

The application of micro/nanomotors (MNMs) in the gastrointestinal tract has become a Frontier in the treatment of gastrointestinal diseases. These miniature robots can enter the gastrointestinal tract through oral administration, achieving precise drug delivery and therapy. They can traverse mucosal layers and tissue barriers, directly targeting tumors or other lesion sites, thereby enhancing the bioavailability and therapeutic effects of drugs. Through the application of nanotechnology, these MNMs are able to accomplish targeted medication release, regulating drug release in response to either external stimuli or the local biological milieu. This results in reduced side effects and increased therapeutic efficacy. This review summarizes the primary classifications and power sources of current MNMs, as well as their applications in the gastrointestinal tract, providing inspiration and direction for the treatment of gastrointestinal diseases with MNMs.

A Clinically Feasible Diagnostic Electrochemical Micronano Motors Biosensor Built on Miniature Swimmer for Multiplex Detection and Grading of Breast Cancer Biomarkers

Estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2 (HER2), and Ki67 are four crucial biomarkers used in the clinical diagnosis of breast cancer. Accurate detection of these biomarkers is essential for an effective diagnosis and treatment. MOF-based micronano motors (MOFtors) are promising for various applications, including environmental remediation, targeted nanosurgery, and biomarker detection. This paper presents a clinically feasible diagnostic electrochemical micronano motor biosensor, built on a miniature swimmer, for the multiplex detection and grading of breast cancer biomarkers. We designed a biosensor, named MOFtor-MSEM, incorporating aptamers and antibodies functionalized on SiO2@Co-Fe-MOF, which acts as a miniature swimmer in solution. The SiO2@Co-Fe-MOF serves as the body, while complementary double-chain-linked antibodies function as paddles. In a homogeneous solution, when a positive voltage is applied to the working electrode, the electrostatic interaction between the neutral SiO2@Co-Fe-MOF and the negatively charged complementary double-linked antibody causes the antibody to move toward the electrode and then regress due to water resistance. This back-and-forth motion propels the miniature swimmer, enabling it to move the target analyte through the solution. The sensor features an automatic "sample-amplifying signal-output" process, achieving simultaneous signal amplification and output of four electrochemical signals on a single nanomaterial, a significant challenge in electrochemical sensing. The biosensor boasts a short detection time of 40 min, compared to approximately 1 week for current clinical tissue testing. Additionally, the bioplatform selectively detects HER2, ER, Ki67, and PR in the range of 0-1500 pg/mL, with detection limits of 0.01420, 0.03201, 0.01430, and 0.01229 pg/mL, respectively.

Challenges of enzyme therapy: Why two players are better than one

Enzyme-based therapy has garnered significant attention for its current applications in various diseases. Despite the notable advantages associated with the use of enzymes as therapeutic agents, that could have high selectivity, affinity, and specificity for the target, their application faces challenges linked to physico-chemical and pharmacological properties. These limitations can be addressed through the encapsulation of enzymes in nanoplatforms as a comprehensive solution to mitigate their degradation, loss of activity, off-target accumulation, and immunogenicity, thus enhancing bioavailability, therapeutic efficacy, and circulation time, thereby reducing the number of administrations, and ameliorating patient compliance. The exploration of novel nanomedicine-based enzyme therapeutics for the treatment of challenging diseases stands as a paramount goal in the contemporary scientific landscape, but even then it is often not enough. Combining an enzyme with another therapeutic (e.g., a small molecule, another enzyme or protein, a monoclonal antibody, or a nucleic acid) within a single nanocarrier provides innovative multidrug-integrated therapy and ensures that both the actives arrive at the target site and exert their therapeutic effect, leading to synergistic action and superior therapeutic efficacy. Moreover, this strategic approach could be extended to gene therapy, a field that nowadays has gained increasing attention, as enzymes acting at genomic level and nucleic acids may be combined for synergistic therapy. This multicomponent therapeutic approach opens opportunities for promising future developments. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Magnetic motors in interphases: Motion control and integration in soft robots

Magnetic motors are a class of out-of-equilibrium particles that exhibit controlled and fast motion overcoming Brownian fluctuations by harnessing external magnetic fields. The advances in this field resulted in motors that have been used for different applications, such as biomedicine or environmental remediation. In this Perspective, an overview of the recent advancements of magnetic motors is provided, with a special focus on controlled motion. This aspect extends from trapping, steering, and guidance to organized motor grouping and degrouping, which is known as swarm control. Further, the integration of magnetic motors in soft robots to actuate their motion is also discussed. Finally, some remarks and perspectives of the field are outlined.

Thermal-Accelerated Urease-Driven Bowl-Like Polydopamine Nanorobot for Targeted Photothermal/Photodynamic Antibiotic-Free Antibacterial Therapy

The problem of antibiotic resistance seriously affects the treatment of bacterial infections, so there is an urgent need to develop novel antibiotic-independent antimicrobial strategies. Herein, a urease-driven bowl-like mesoporous polydopamine nanorobot (MPDA@ICG@Ur@Man) based on single-wavelength near-infrared (NIR) remote photothermal acceleration to achieve antibiotic-free phototherapy(photothermal therapy, PTT, plus photodynamic therapy, PDT) is first reported. The smart nanorobots can perform active movement by decomposing urea to produce carbon dioxide and ammonia. Particularly, the elevated local temperature during PTT can increase urease activity to enhance the autonomous movement and thus increase the contact between the antimicrobial substance and bacteria. Compared with a nanomotor propelled by urea only, the diffusion coefficient (De) of photothermal-accelerated nanorobots is increased from 1.10 to 1.26 µm2 s-1. More importantly, urease-driven bowl-like nanorobots with photothermal enhancement can specifically identify Escherichia coli (E. coli) and achieve simultaneous PTT/PDT at a single wavelength with 99% antibactericidal activity in vitro. In a word, the urease-driven bowl-like nanorobots guided by photothermal-accelerated strategy could provide a novel perspective for increasing PTT/PDT antibacterial therapeutic efficacy and be promising for various antibiotic-free sterilization applications.

Polysaccharide-Based Micro/Nanomotors for Active Ingredient Delivery in Food

Micro/nanomotors (MNMs) are miniature devices that can generate energy through chemical reactions or physical processes, utilizing this energy for movement. By virtue of their small size, self-propulsion, precise positioning within a small range, and ability to access microenvironments, MNMs have been applied in various fields including sensing, biomedical applications, and pollutant adsorption. However, the development of food-grade MNMs and their application in food delivery systems have been scarcely reported. Currently, there are various issues with the decomposition, oxidation, or inability to maintain the activity of some nutrients or bioactive substances, such as the limited application of curcumin (Cur) in food. Compared to traditional delivery systems, MNMs can adjust the transport speed and direction as needed, effectively protecting bioactive substances during delivery and achieving efficient transportation. Therefore, this study utilizes polysaccharides as the substrate, employing a simple, rapid, and pollution-free template method to prepare polysaccharide-based microtubes (PMTs) and polysaccharide-based micro/nanomotors (PMNMs). PMNMs can achieve multifunctional propulsion by modifying ferrosoferric oxide (Fe3O4), platinum (Pt), and glucose oxidase (GOx). Fe-PMNMs and Pt-PMNMs exhibit excellent photothermal conversion performance, showing promise for applications in photothermal therapy. Moreover, PMNMs can effectively deliver curcumin, achieving the effective delivery of nutrients and exerting the anti-inflammatory performance of the system.

Recent advances in micro/nanomotors for antibacterial applications

Currently, the rapid spread of multidrug-resistant bacteria derived from the indiscriminate use of traditional antibiotics poses a significant threat to public health worldwide. Moreover, established bacterial biofilms are extremely difficult to eradicate because of their high tolerance to traditional antimicrobial agents and extraordinary resistance to phagocytosis. Hence, it is of universal significance to develop novel robust and efficient antibacterial strategies to combat bacterial infections. Micro/nanomotors exhibit many intriguing properties, including enhanced mass transfer and micro-mixing resulting from their locomotion, intrinsic antimicrobial capabilities, active cargo delivery, and targeted treatment with precise micromanipulation, which facilitate the targeted delivery of antimicrobials to infected sites and their deep permeation into sites of bacterial biofilms for fast inactivation. Thus, the ideal antimicrobial activity of antibacterial micro/nanorobots makes them desirable alternatives to traditional antimicrobial treatments and has aroused extensive interest in recent years. In this review, recent advancements in antibacterial micro/nanomotors are briefly summarized, focusing on their synthetic methods, propulsion mechanism, and versatile antibacterial applications. Finally, some personal insights into the current challenges and possible future directions to translate proof-of-concept research to clinic application are proposed.

Exploring the Synthesis of Self-Organization and Active Motion

Proteins, genetic material, and membranes are fundamental to all known organisms, yet these components alone do not constitute life. Life emerges from the dynamic processes of self-organization, assembly, and active motion, suggesting the existence of similar artificial systems. Against this backdrop, our Perspective explores a variety of chemical phenomena illustrating how nonequilibrium self-organization and micromotors contribute to life-like behavior and functionalities. After explaining key terms, we discuss specific examples including enzymatic motion, diffusiophoretic and bubble-driven self-propulsion, pattern-forming reaction-diffusion systems, self-assembling inorganic aggregates, and hierarchically emergent phenomena. We also provide a roadmap for combining self-organization and active motion and discuss possible outcomes through biological analogs. We suggest that this research direction, deeply rooted in physical chemistry, offers opportunities for further development with broad impacts on related sciences and technologies.

Supramolecular Modular Assembly of Imaging-Trackable Enzymatic Nanomotors

Self-propelled micro/nanomotors (MNMs) have shown great application potential in biomedicine, sensing, environmental remediation, etc. In the past decade, various strategies or technologies have been used to prepare and functionalize MNMs. However, the current preparation strategies of the MNMs were mainly following the pre-designed methods based on specific tasks to introduce expected functional parts on the various micro/nanocarriers, which lacks a universal platform and common features, making it difficult to apply to different application scenarios. Here, we have developed a modular assembly strategy based on host-guest chemistry, which enables the on-demand construction of imaging-trackable nanomotors mounted with suitable driving and imaging modules using a universal assembly platform, according to different application scenarios. These assembled nanomotors exhibited enhanced diffusion behavior driven by enzymatic reactions. The loaded imaging functions were used to dynamically trace the swarm motion behavior of assembled nanomotors with corresponding fuel conditions both in vitro and in vivo. The modular assembly strategy endowed with host-guest interaction provides a universal approach to producing multifunctional MNMs in a facile and controllable manner, which paves the way for the future development of MNMs systems with programmable functions.

Putting Hybrid Nanomaterials to Work for Biomedical Applications

Hybrid nanomaterials have found use in many biomedical applications. This article provides a comprehensive review of the principles, techniques, and recent advancements in the design and fabrication of hybrid nanomaterials for biomedicine. We begin with an introduction to the general concept of material hybridization, followed by a discussion of how this approach leads to materials with additional functionality and enhanced performance. We then highlight hybrid nanomaterials in the forms of nanostructures, nanocomposites, metal-organic frameworks, and biohybrids, including their fabrication methods. We also showcase the use of hybrid nanomaterials to advance biomedical engineering in the context of nanomedicine, regenerative medicine, diagnostics, theranostics, and biomanufacturing. Finally, we offer perspectives on challenges and opportunities.

Experimental and Molecular Docking Studies on Enzyme-Driven Biohybrid-Inspired Micromotors Based on Amylose-b-(PEG-co-PBA) Inclusion Complexes

Amylose is a linear polysaccharide with a unique ability to form helical inclusion complexes with the appropriate guest components. Numerous studies have been conducted on encapsulation of bioactive compounds for various applications. In the biomedical field, biohybrid micro/nanomotors (MNMs) have emerged as innovative candidates due to their excellent biocompatible and biodegradable properties. This study was inspired by the biohybrid- and enzymatic-propelled MNMs and explored the potential of amylose inclusion complexes (ICs) in creating these MNMs. The study developed a new type of micromotor made from (PEG-co-PBA)-b-amylose. Nanoprecipitation, dimethyl sulfoxide (DMSO), and ultrasound-treated methods were employed to create spherical, thick crystalline, and rod-bacterial-like morphologies, respectively. Candida antarctica lipase B (CALB) was used as the catalytic fuel to induce the motion by the enzymatic degradation of ester linkages in the polymeric segment. Optical microscopy was utilized to observe the motion of the motors following incubation with enzyme concentrations of 5, 10, and 20% (w/w). The results demonstrated that the velocity of the motors increased proportionally with the percentage of added enzyme. Additionally, a comprehensive molecular docking evaluation with PyRx software provided insight into the interaction of the CALB enzyme with polymeric moieties and demonstrated a good affinity between the enzyme and polymer in the binding site. This study provides novel insight into the design and development of enzymatically driven polymeric micromotors and nanomotors.

Bidirectional Regulation of Intracellular Enzyme Activity Using Light-Driven Nano-Inhibitors

Photochemical regulation provides precise control over enzyme activities with high spatiotemporal resolution. A promising approach involves anchoring "photoswitches" at enzyme active sites to modulate substrate recognition. However, current methods often require genetic mutations and irreversible enzyme modifications for the site-specific anchoring of "photoswitches", potentially compromising the enzyme activities. Herein, we present a pioneering reversible nano-inhibitor based on molecular imprinting technique for bidirectional regulation of intracellular enzyme activity. The nano-inhibitor employs a molecularly imprinted polymer nanoparticle as its body and azobenzene-modified inhibitors ("photoswitches") as the arms. By using a target enzyme as the molecular template, the nano-inhibitor acquires oriented binding sites on its surface, resulting in a high affinity for the target enzyme and non-covalently firm anchoring of the azobenzene-modified inhibitor to the enzyme active site. Harnessing the reversible isomerization of azobenzene units upon exposure to ultraviolet and visible light, the nano-inhibitor achieves bidirectional enzyme activity regulation by precisely docking and undocking inhibitor at the active site. Notably, this innovative approach enables the facile in situ regulation of intracellular endogenous enzymes, such as carbonic anhydrase. Our results represent a practical and versatile tool for precise enzyme activity regulation in complex intracellular environments.

Polyoxometalate-Nanozyme-Integrated Nanomotors (POMotors) for Self-Propulsion-Promoted Synergistic Photothermal-Catalytic Tumor Therapy

Enzyme-powered nanomotors have demonstrated promising potential in biomedical applications, especially for catalytic tumor therapy, owing to their ability of self-propulsion and bio-catalysis. However, the fragility of natural enzymes limits their environmental adaptability and also therapeutic efficacy in catalysis-enabled tumor therapy. Herein, polyoxometalate-nanozyme-based light-driven nanomotors were designed and synthesized for targeted synergistic photothermal-catalytic tumor therapy. In this construct, the peroxidase-like activity of the P2 W18 Fe4 polyoxometalates-based nanomotors can provide self-propulsion and facilitate their production of reactive oxygen species thus killing tumor cells, even in the weakly acidic tumor microenvironment. Conjugated polydopamine endows the nanomotors with the capability of light-driven self-propulsion behavior. After 10 min of NIR (808 nm) irradiation, along with the help of epidermal growth factor receptor antibody, the targeted accumulation and penetration of nanomotors in the tumor enabled highly efficient synergistic photothermal-catalytic therapy. This approach overcomes the disadvantages of the intrinsically fragile nature of enzyme-powered nanomotors in physiological environments and, more importantly, provides a motility-behavior promoted synergistic anti-tumor strategy.

Urease-Powered Black TiO2 Micromotors for Photothermal Therapy of Bladder Cancer

Urease-powered nano/micromotors can move at physiological urea concentrations, making them useful for biomedical applications, such as treating bladder cancer. However, their movement in biological environments is still challenging. Herein, Janus micromotors based on black TiO2 with urease asymmetric catalytic coating were designed to take benefit of the optical properties of black TiO2 under near-infrared light and the movement capability in simulated bladder environments (urea). The black TiO2 microspheres were half-coated with a thin layer of Au, and l-Cysteine was utilized to attach the urease enzyme to the Au surface using its thiol group. Biocatalytic hydrolysis of urea through urease at biologically relevant concentrations provided the driving force for micromotors. A variety of parameters, such as urea fuel concentration, viscosity, and ionic character of the environment, were used to investigate how micromotors moved in different concentrations of urea in water, PBS, NaCl, and urine. The results indicate that micromotors are propelled through ionic self-diffusiophoresis caused by urea enzymatic catalysis. Due to their low toxicity and in vitro anticancer effect, micromotors are effective agents for photothermal therapy, which can help kill bladder cancer cells. These promising results suggest that biocompatible micromotors hold great potential for improving cancer treatment and facilitating diagnosis.

Effects of Size and Asymmetry on Catalase-Powered Silica Micro/nanomotors

Enzyme-powered micro/nanomotors that can autonomously move in biological environment are attractive in the fields of biology and biomedicine. The fabrication of enzyme-powered micro/nanomotors normally focuses on constructing Janus structures of micro/nanomaterials, based on the intuition that the Janus coating of enzymes can generate driving force from asymmetric catalytic reactions. Here, in the fabrication of catalase-powered silica micro/nanomotors (C-MNMs), an archetypical model of enzyme-powered micro/nanomotors, we find the silica size rather than asymmetric coating of catalase determines the motion ability of C-MNMs. The effects of size and asymmetry have been investigated by a series of C-MNMs at various sizes (0.5, 2, 5 and 10 μm) and asymmetric levels (full-, half- and most-coated with catalase). The motion performance indicates that 500 nm and 2 μm C-MNMs show obvious increases (varying from 134% to 618%) of diffusion coefficient, but C-MNMs bigger than 5 μm have no self-propulsion behaviour at all, regardless of asymmetric levels. In addition, although asymmetry facilitates enhanced diffusion of C-MNMs, only 2 μm C-MNMs are sensitive to asymmetric level. This work elucidates the primary and secondary roles of size and asymmetry in the preparation of C-MNMs, paving the way to fabricate enzyme-powered micro/nanomotors with high motion performance in future.

Antibacterial micro/nanomotors: current research progress, challenges, and opportunities

Bacterial infections remain a formidable threat to human health, a situation exacerbated by the escalating problem of antibiotic resistance. While alternative antibacterial strategies such as oxidants, heat treatments, and metal nanoparticles (NPs) have shown potential, they come with significant drawbacks, ranging from non-specificity to potential environmental concerns. In the face of these challenges, the rapid evolution of micro/nanomotors (MNMs) stands out as a revolutionary development in the antimicrobial arena. MNMs harness various forms of energy and convert it into a substantial driving force, offering bright prospects for combating microbial threats. MNMs' mobility allows for swift and targeted interaction with bacteria, which not only improves the carrying potential of therapeutic agents but also narrows the required activation range for non-drug antimicrobial interventions like photothermal and photodynamic therapies, substantially improving their bacterial clearance rates. In this review, we summarized the diverse propulsion mechanisms of MNMs employed in antimicrobial applications and articulated their multiple functions, which include direct bactericidal action, capture and removal of microorganisms, detoxification processes, and the innovative detection of bacteria and associated toxins. Despite MNMs' potential to revolutionize antibacterial research, the translation from laboratory to clinical use remains challenging. Based on the current research status, we summarized the potential challenges and possible solutions and also prospected several key directions for future studies of MNMs for antimicrobial purposes. Collectively, by highlighting the important knowns and unknowns of antimicrobial MNMs, our present review would help to light the way forward for the field of antimicrobial MNMs and prevent unnecessary blindness and detours.

Recent advancements in Mg-based micromotors for biomedical and environmental applications

Synthetic micro/nanomotors have attracted considerable attention due to their promising potential in the field of biomedicine. Despite their great potential, major micromotors require chemical fuels or complex devices to generate external physical fields for propulsion. Therefore, for future practical medical and environmental applications, Mg-based micromotors that exhibit water-powered movement and thus eliminate the need for toxic fuels, and that display optimal biocompatibility and biodegradability, are attracting attention. In this review, we summarized the recent microarchitectural design of Mg-based micromotors for biomedical applications. We also highlight the mechanism for realizing their water-powered motility. Furthermore, recent biomedical and environmental applications of Mg-based micromotors are introduced. We envision that advanced Mg-based micromotors will have a profound impact in biomedicine.

Covalent Organic Framework-Based Nanomotor for Multimodal Cancer Photo-Theranostics

Developing efficient integrated diagnosis and treatment agents based on fuel-free self-movement nanomotors remains challenging in antitumor therapy. In this study, a covalent organic framework (COF)-based biomimetic nanomotor composed of polypyrrole (PPy) core, porphyrin-COF shell, and HCT116 cancer cell membrane coating is reported. Under near-infrared (NIR) light irradiation, the obtained mPPy@COF-Por can overcome Brownian motion and achieves directional motion through self-thermophoretic force generated from the PPy core. The HCT116 cancer cell membrane coating enables the nanomotor to selectively recognize the source cell lines and reduces the bio-adhesion of mPPy@COF-Por in a biological medium, endowing with this NIR light-powered nanomotor good mobility. More importantly, such multifunctional integration allows the COF-based nanomotor to be a powerful nanoagent for cancer treatment, and the high infrared thermal imaging/photoacoustic imaging/fluorescence trimodal imaging-guided combined photothermal/photodynamic therapeutic effect on HCT116 tumor cell is successfully achieved. The results offer considerable promise for the development of COF nanomotors with integrated imaging/therapy modalities in biomedical applications.

Magnetite-based Janus nanoparticles, their synthesis and biomedical applications

The advent of Janus nanoparticles has been a great breakthrough in the emerging field of nanomaterials. Janus nanoparticles refer to a single structure with two distinct chemical functions on either side. Owing to their asymmetric structures, they can be utilized in a variety of applications where monomorphic particles are insufficient. In the last decade, a wide variety of materials have been employed to fabricate Janus nanoparticles, and due to the great advantages of magnetite (Iron-oxide) NPs, they have been considered as one of the best candidates. With the main benefit of magnetic controlling, magnetite Janus nanoparticles fulfill great promises, especially in biomedical areas such as bioimaging, cancer therapies, theranostics, and biosensing. The intrinsic characteristics of magnetite Janus nanoparticles (MJNPs) even hold great potential in magnetite Janus forms of micro-/nanomotors. Despite the great interest and potential in magnetic Janus NPs, the need for a comprehensive review on MJNPs with a concentration on magnetite NPs has been overlooked. Herein, we present recent advancements in the magnetite-based Janus nanoparticles in the flourishing field of biomedicine. First, the synthesis and fabrication methods of Janus nanoparticles are discussed. Then we will delve into their intriguing biomedical applications, with a separate section for magnetite Janus micro-/nanomotors in biomedicine. And finally, the challenges and future outlook are provided. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > In Vitro Nanoparticle-Based Sensing.

Asymmetry-Enhanced Motion of Urease-Powered Micromotors from Double Emulsion-Templated Microcapsules

Autonomous motion of enzyme-powered motors has important implications for drug delivery, cell-cell communication, and protocell engineering. Although many of these systems are inspired by the motion of biological cells, most of them lack key structural features, like micrometer-sized boundaries and aqueous compartments, and rely on bubble propulsion to generation motion. In this study, we use droplet microfluidics to generate large populations of cell-sized microcapsules with poly(lactic-co-glycolic acid) shells and functionalize their surfaces with the enzyme urease to drive their motion. We adjust the number of surface functional groups for urease conjugation by preparing microcapsules with two different surfactants, poly(vinyl alcohol) (PVA) and poly(ethylene-alt-maleic anhydride) (PEMA). We also tune the surface roughness of the microcapsules by varying the concentration of silica nanoparticles in the droplet middle phase. We find that PEMA plays a crucial role in increasing the grafting density of urease on the surface of smooth microcapsules, leading to active motion in the presence of urea. In addition, rough microcapsules prepared with PEMA and loaded with comparable amounts of urease move up to three times faster than their smooth counterparts, which we believe is due to an asymmetric distribution of urease on the surface, giving rise to a preferred direction of motion. Taken together, these results provide new insights into the role that various stabilizing agents play in the induction of motion by enzymatic motors prepared from microfluidics, which is a potentially powerful tool for future preparation of motile protocells in biomedicine.

Progress on Physical Field-Regulated Micro/Nanomotors for Cardiovascular and Cerebrovascular Disease Treatment

Cardiovascular and cerebrovascular diseases (CCVDs) are two major vasculature-related diseases that seriously affect public health worldwide, which can cause serious death and disability. Lack of targeting effect of the traditional CCVD treatment drugs may damage other tissues and organs, thus more specific methods are needed to solve this dilemma. Micro/nanomotors are new materials that can convert external energy into driving force for autonomous movement, which can not only enhance the penetration depth and retention rates, but also increase the contact areas with the lesion sites (such as thrombus and inflammation sites of blood vessels). Physical field-regulated micro/nanomotors using the physical energy sources with deep tissue penetration and controllable performance, such as magnetic field, light, and ultrasound, etc. are considered as the emerging patient-friendly and effective therapeutic tools to overcome the limitations of conventional CCVD treatments. Recent efforts have suggested that physical field-regulated micro/nanomotors on CCVD treatments could simultaneously provide efficient therapeutic effect and intelligent control. In this review, various physical field-driven micro/nanomotors are mainly introduced and their latest advances for CCVDs are highlighted. Last, the remaining challenges and future perspectives regarding the physical field-regulated micro/nanomotors for CCVD treatments are discussed and outlined.

Magnetically Actuated Biodegradable Nanorobots for Active Immunotherapy

An efficient and cost-effective therapeutic vaccine is highly desirable for the prevention and treatment of cancer, which helps to strengthen the immune system and activate the T cell immune response. However, initiating such an adaptive immune response efficiently remains challenging, especially the deficient antigen presentation by dendritic cells (DCs) in the immunosuppressive tumor microenvironment. Herein, an efficient and dynamic antigen delivery system based on the magnetically actuated OVA-CaCO3 -SPIO robots (OCS-robots) is rationally designed for active immunotherapy. Taking advantage of the unique dynamic features, the developed OCS-robots achieve controllable motion capability under the rotating magnetic field. Specifically, with the active motion, the acid-responsiveness of OCS-robots is beneficial for the tumor acidity attenuating and lysosome escape as well as the subsequent antigen cross-presentation of DCs. Furthermore, the dynamic OCS-robots boost the crosstalk between the DCs and antigens, which displays prominent tumor immunotherapy effect on melanoma through cytotoxic T lymphocytes (CTLs). Such a strategy of dynamic vaccine delivery system enables the active activation of immune system based on the magnetically actuated OCS-robots, which presents a plausible paradigm for incredibly efficient cancer immunotherapy by designing multifunctional and novel robot platforms in the future.

Bladder microenvironment actuated proteomotors with ammonia amplification for enhanced cancer treatment

Enzyme-driven micro/nanomotors consuming in situ chemical fuels have attracted lots of attention for biomedical applications. However, motor systems composed by organism-derived organics that maximize the therapeutic efficacy of enzymatic products remain challenging. Herein, swimming proteomotors based on biocompatible urease and human serum albumin are constructed for enhanced antitumor therapy via active motion and ammonia amplification. By decomposing urea into carbon dioxide and ammonia, the designed proteomotors are endowed with self-propulsive capability, which leads to improved internalization and enhanced penetration in vitro. As a glutamine synthetase inhibitor, the loaded l-methionine sulfoximine further prevents the conversion of toxic ammonia into non-toxic glutamine in both tumor and stromal cells, resulting in local ammonia amplification. After intravesical instillation, the proteomotors achieve longer bladder retention and thus significantly inhibit the growth of orthotopic bladder tumor in vivo without adverse effects. We envision that the as-developed swimming proteomotors with amplification of the product toxicity may be a potential platform for active cancer treatment.

GOx-Powered Janus Platelet Nanomotors for Targeted Delivery of Thrombolytic Drugs in Treating Thrombotic Diseases

Low efficiency of targeting and delivery toward the thrombus site poses challenges to using thrombolytic drugs. Inspired by the biomimetic system of platelet membranes (PMs) and glucose oxidase (GOx) modification technologies, we develop a novel GOx-powered Janus nanomotor by asymmetrically attaching the GOx to polymeric nanomotors coated with the PMs. Then the PM-coated nanomotors were conjugated with urokinase plasminogen activators (uPAs) on their surfaces. The PM-camouflaged design conferred excellent biocompatibility to the nanomotors and improved their targeting ability to thrombus. The Janus distribution of GOx also allows the uneven decomposition of glucose in biofluids to produce a chemophoretic motion, increasing the drug delivery efficiency of nanomotors. In addition, these nanomotors are located at the lesion site due to the mutual adhesion and aggregation of platelet membranes. Furthermore, thrombolysis effects of nanomotors are enhanced in static and dynamic thrombus as well as in mouse models. It is believed that the novel PM-coated enzyme-powered nanomotors represent a great value for thrombolysis treatment.

Construction of intelligent moving micro/nanomotors and their applications in biosensing and disease treatment

Micro/nanomotors are containers that pass through liquid media and carry cargo. Because they are tiny, micro/nanomotors exhibit excellent potential for biosensing and disease treatment applications. However, their size also makes overcoming random Brownian forces very challenging for micro/nanomotors moving on targets. Additionally, to achieve desired practical applications, the expensive materials, short lifetimes, poor biocompatibility, complex preparation methods, and side effects of micro/nanomotors must be addressed, and potential adverse effects must be evaluated both in vivo and in practical applications. This has led to the continuous development of key materials for driving micro/nanomotors. In this work, we review the working principles of micro/nanomotors. Metallic and nonmetallic nanocomplexes, enzymes, and living cells are explored as key materials for driving micro/nanomotors. We also consider the effects of exogenous stimulations and endogenous substance conditions on micro/nanomotor motions. The discussion focuses on micro/nanomotor applications in biosensing, treating cancer and gynecological diseases, and assisted fertilization. By addressing micro/nanomotor shortcomings, we propose directions for further developing and applying micro/nanomotors.

Steering Micromotors via Reprogrammable Optoelectronic Paths

Steering micromotors is important for using them in practical applications and as model systems for active matter. This functionality often requires magnetic materials in the micromotor, taxis behavior of the micromotor, or the use of specifically designed physical boundaries. Here, we develop an optoelectronic strategy that steers micromotors with programmable light patterns. In this strategy, light illumination turns hydrogenated amorphous silicon conductive, generating local electric field maxima at the edge of the light pattern that attracts micromotors via positive dielectrophoresis. As an example, metallo-dielectric Janus microspheres that self-propelled under alternating current electric fields were steered by static light patterns along customized paths and through complex microstructures. Their long-term directionality was also rectified by ratchet-shaped light patterns. Furthermore, dynamic light patterns that varied in space and time enabled more advanced motion controls such as multiple motion modes, parallel control of multiple micromotors, and the collection and transport of motor swarms. This optoelectronic steering strategy is highly versatile and compatible with a variety of micromotors, and thus it possesses the potential for their programmable control in complex environments.

Ultrasmall Enzyme-Powered Janus Nanomotor Working in Blood Circulation System

Injectable chemically powered nanomotors may revolutionize biomedical technologies, but to date, it is a challenge for them to move autonomously in the blood circulation system and they are too large in size to break through the biological barriers therein. Herein, we report a general scalable colloidal chemistry synthesis approach for the fabrication of ultrasmall urease-powered Janus nanomotors (UPJNMs) that have a size (100-30 nm) meeting the requirement to break through the biological barriers in the blood circulation system and can efficiently move in body fluids with only endogenous urea as fuel. In our protocol, the two hemispheroid surfaces of eccentric Au-polystyrene nanoparticles are stepwise grafted with poly(ethylene glycol) brushes and ureases via selective etching and chemical coupling, respectively, forming the UPJNMs. The UPJNMs have lasting powerful mobility with ionic tolerance and positive chemotaxis, while they are able to be dispersed steadily and self-propelled in real body fluids, as well as demonstrate good biosafety and a long circulation time in the blood circulation system of mice. Thus, the as-prepared UPJNMs are promising as an active theranostics nanosystem for future biomedical applications.

Smart micro- and nanorobots for water purification

Less than 1% of Earth's freshwater reserves is accessible. Industrialization, population growth and climate change are further exacerbating clean water shortage. Current water-remediation treatments fail to remove most pollutants completely or release toxic by-products into the environment. The use of self-propelled programmable micro- and nanoscale synthetic robots is a promising alternative way to improve water monitoring and remediation by overcoming diffusion-limited reactions and promoting interactions with target pollutants, including nano- and microplastics, persistent organic pollutants, heavy metals, oils and pathogenic microorganisms. This Review introduces the evolution of passive micro- and nanomaterials through active micro- and nanomotors and into advanced intelligent micro- and nanorobots in terms of motion ability, multifunctionality, adaptive response, swarming and mutual communication. After describing removal and degradation strategies, we present the most relevant improvements in water treatment, highlighting the design aspects necessary to improve remediation efficiency for specific contaminants. Finally, open challenges and future directions are discussed for the real-world application of smart micro- and nanorobots.

On Nanomachines and Their Future Perspectives in Biomedicine

Nano/micromotors are a class of active matter that can self-propel converting different types of input energy into kinetic energy. The huge efforts that are made in this field over the last years result in remarkable advances. Specifically, a high number of publications have dealt with biomedical applications that these motors may offer. From the first attempts in 2D cell cultures, the research has evolved to tissue and in vivo experimentation, where motors show promising results. In this Perspective, an overview over the evolution of motors with focus on bio-relevant environments is provided. Then, a discussion on the advances and challenges is presented, and eventually some remarks and perspectives of the field are outlined.

Active therapy based on the byproducts of micro/nanomotors

Different from traditional colloidal particles based on Brownian motion, micro/nanomotors are micro/nanoscale devices capable of performing complex tasks in liquid media via transforming various energy sources into mechanical motion or actuation. Such unique self-propulsion endows motors with fantastic capabilities to access and enter the deep layer of targeted diseased tissue, which in turn breaks through the limitation of the poor permeability of traditional pharmaceutical preparations, thus providing giant prospects for active therapy. It is noteworthy that recently several studies, which utilized the byproducts generated in situ by micro/nanomotors to achieve active therapy, in a truly green zero-waste manner, have been carried out. In this minireview, we highlight the recent efforts with respect to active therapy based on the byproducts of micro/nanomotors, expecting to motivate readers to expand the practical biomedical application scope of micro/nanomotors in a broader horizon. Accompanied by ever booming enthusiasm and persevering exploration, micro/nanomotors are on their way to revolutionize conventional fields.

Design of biomass-based renewable materials for environmental remediation

Various materials have been used to remove environmental contaminants for decades and have been an effective strategy for environmental cleanups. The current nonrenewable materials used for this purpose could impose secondary hazards and challenges in further downstream treatments. Biomass-based materials present viable, renewable, and sustainable solutions for environmental remediation. Recent biotechnology advances have developed biomaterials with new capacities, such as highly efficient biodegradation and treatment train integration. This review systemically discusses how biotechnology has empowered biomass-derived and bioinspired materials for environmental remediation sustainably and cost-effectively.

Intelligent Micro-/Nanorobots for Cancer Theragnostic

Cancer is one of the most intractable diseases owing to its high mortality rate and lack of effective diagnostic and treatment tools. Advancements in micro-/nanorobot (MNR)-assisted sensing, imaging, and therapeutics offer unprecedented opportunities to develop MNR-based cancer theragnostic platforms. Unlike ordinary nanoparticles, which exhibit Brownian motion in biofluids, MNRs overcome viscous resistance in an ultralow Reynolds number (Re << 1) environment by effective self-propulsion. This unique locomotion property has motivated the advanced design and functionalization of MNRs as a basis for next-generation cancer-therapy platforms, which offer the potential for precise distribution and improved permeation of therapeutic agents. Enhanced barrier penetration, imaging-guided operation, and biosensing are additionally studied to enable the promising cancer-related applications of MNRs. Herein, the recent advances in MNR-based cancer therapy are comprehensively addresses, including actuation engines, diagnostics, medical imaging, and targeted drug delivery; promising research opportunities that can have a profound impact on cancer therapy over the next decade is highlighted.

Dual-Mode-Driven Micromotor Based on Foam-like Carbon Nitride and Fe3O4 with Improved Manipulation and Photocatalytic Performance

Micro/nanomotors have emerged as a vibrant research topic in biomedical and environmental fields due to their attractive self-propulsion as well as small-scale functionalities. However, single actuated micro/nanomotors are not adaptive in facing intricate natural and industrial environments. Herein, we propose a new dual-mode-driven micromotor based on foam-like carbon nitride (f-C₃N₄) with precipitated Fe₃O₄ nanoparticles, namely, Fe₃O₄/f-C₃N₄, powered by chemical/magnetic stimuli for rapid reduction of organic pollutants. The Fe₃O₄/f-C₃N₄ motor composed of a three-dimensional (3D) porous "foam-like" structure and precipitated Fe₃O₄ nanoparticles (ca. 50 nm) not only exhibits efficient photocatalytic performance under visible light but also shows versatile and programmable motion behavior under the control of external magnetic fields. The aggregation of the micromotor under an external rotating magnetic field further enhances the catalytic activity by the increased local catalyst concentration. Furthermore, the magnetic property endows the micromotor with easy recyclability. This study provides a novel dual-mode-driven micromotor for antibiotics removal with magnetic field and light-enhanced performance in industrial wastewater treatment at a low cost.

Micro/nanomotor technology: the new era for food safety control

Food poisoning caused by eating contaminated food remains a threat to global public health. Making the situation even worse is the aggravated global environmental pollution, which poses a major threat to the safety of agricultural resources. Food adulteration has been rampant owing to negligent national food safety regulations. The speed at which contaminated food is detected and disposed of determines the extent to which consumers' lives are safeguarded and agricultural economic losses are prevented. Micro/nanomotors offer a high-speed mobile loading platform that substantially increases the chemical reaction rates and, accordingly, exhibit great potential as alternatives to conventional detection and degradation techniques. This review summarizes the propulsion modes applicable to micro/nanomotors in food systems and the advantages of using micro/nanomotors, highlighting examples of their potential use in recent years for the detection and removal of food contaminants. Micro/nanomotors are an emerging technology for food applications that is moving toward mass production, simple preparation, and important functions.

Micro‐ and Nanorobots Meet DNA

DNA, the well‐known molecule that carries the genetic information of almost all forms of life, represents a pivotal element in formulating intelligent and versatile micro/nanorobotic systems. DNA‐functionalized micro/nanorobots have opened new and exciting opportunities in many research areas due to the synergistic combination of self‐propulsion at the micro/nanoscale and the high specificity and programmability of DNA interactions. Here, their designs and applications are critically reviewed, which span from the use of DNA as the fuel to chemotactically power nanorobots toward cancer cells to DNA as the main building block for sophisticated phototactic biorobots, DNA nanodevices to self‐monitor microrobots’ activity status, DNA and RNA sensing, nucleic acids isolation, gene therapy, and water purification. The perspective on future directions of the field is also shared, envisioning DNA‐mediated reconfigurable assemblies of nanorobotic swarms.

Enzyme-powered micro- and nano-motors: key parameters for an application-oriented design

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.

Diffusion coefficient and power spectrum of active particles with a microscopically reversible mechanism of self-propelling

Catalytically active macromolecules are envisioned as key building blocks in development of artificial nanomotors. However, theory and experiments report conflicting findings regarding their dynamics. The lack of consensus is mostly caused by a limited understanding of specifics of self-propulsion mechanisms at the nanoscale. Here, we study a generic model of a self-propelled nanoparticle that does not rely on a particular mechanism. Instead, its main assumption is the fundamental symmetry of microscopic dynamics of chemical reactions: the principle of microscopic reversibility. Significant consequences of this assumption arise if we subject the particle to an action of an external time-periodic force. The particle diffusion coefficient is then enhanced compared to the unbiased dynamics. The enhancement can be controlled by the force amplitude and frequency. We also derive the power spectrum of particle trajectories. Among new effects stemming from the microscopic reversibility are the enhancement of the spectrum at all frequencies and sigmoid-shaped transitions and a peak at characteristic frequencies of rotational diffusion and external forcing. The microscopic reversibility is a generic property of a broad class of chemical reactions, therefore we expect that the presented results will motivate new experimental studies aimed at testing of our predictions. This could provide new insights into dynamics of catalytic macromolecules.

Laminar flow-assisted synthesis of amorphous ZIF-8-based nano-motor with enhanced transmigration for photothermal cancer therapy

Because of their biocompatibility, there are promising applications in various fields for enzyme-powered nano-motors. However, enzymes can undergo denaturation under harsh conditions. Here, we report the flow-assisted synthesis of an enzyme-based amorphous ZIF-8 nano-motor (A-motor; Pdop@urease@aZIF-8) for enhanced movement and protection of polydopamine and enzymes. Multiple laminar flow types with varied input ratios effectively entrapped enzymes into amorphous ZIF-8 shells in a serial flow with a momentary difference. The obtained A-motor exhibited superior enzymatic activity and photothermal ablation properties with excellent durability due to the protection the amorphous shell offers from the external environment. Furthermore, in the bio-mimic 2D membrane model, the enhanced mobility of the A-motor afforded high transmigration (>80%), which had a powerful effect on bladder cancer cell ablation via photothermal therapy. This work envisages that the rapid flow approach will facilitate scalable manufacturing of the nano-motors under low stress to vulnerable biomolecules, which would be extended to nano-biomedical applications in various body environments.