Guidable Thermophoretic Janus Micromotors Containing Gold Nanocolorifiers for Infrared Laser Assisted Tissue Welding

Turning Polysaccharides into Injectable and Rapid Self-Healing Antibacterial Hydrogels for Antibacterial Treatment and Bacterial-Infected Wound Healing

Great efforts have been devoted to the development of novel and multifunctional wound dressing materials to meet the different needs of wound healing. Herein, we covalently grafted quaternary ammonium groups (QAGs) containing 12-carbon straight-chain alkanes to the dextran polymer skeleton. We then oxidized the resulting product into oxidized quaternized dextran (OQD). The obtained OQD polymer is rich in antibacterial QAGs and aldehyde groups. It can react with glycol chitosan (GC) via the Schiff-base reaction to form a multifunctional GC@OQD hydrogel with good self-healing behavior, hemostasis, injectability, inherent superior antibacterial activity, biocompatibility, and excellent promotion of healing of methicillin-resistant Staphylococcus aureus (MRSA)-infected wounds. The biosafe and nontoxic GC@OQD hydrogel with a three-dimensional porous network structure possesses an excellent swelling rate and water retention capacity. It can be used for hemostasis and treating irregular wounds. The designed GC@OQD hydrogel with inherent antibacterial activity possesses good antibacterial efficacy on both S. aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria), as well as MRSA bacteria, with antibacterial activity greater than 99%. It can be used for the treatment of wounds infected by MRSA and significantly promotes the healing of wounds. Thus, the multifunctional antibacterial GC@OQD hydrogel has the potential to be applied in clinical practice as a wound dressing.

Features of Anisotropic Drug Delivery Systems

Natural materials are anisotropic. Delivery systems occurring in nature, such as viruses, blood cells, pollen, and many others, do have anisotropy, while delivery systems made artificially are mostly isotropic. There is apparent complexity in engineering anisotropic particles or capsules with micron and submicron sizes. Nevertheless, some promising examples of how to fabricate particles with anisotropic shapes or having anisotropic chemical and/or physical properties are developed. Anisotropy of particles, once they face biological systems, influences their behavior. Internalization by the cells, flow in the bloodstream, biodistribution over organs and tissues, directed release, and toxicity of particles regardless of the same chemistry are all reported to be factors of anisotropy of delivery systems. Here, the current methods are reviewed to introduce anisotropy to particles or capsules, including loading with various therapeutic cargo, variable physical properties primarily by anisotropic magnetic properties, controlling directional motion, and making Janus particles. The advantages of combining different anisotropy in one entity for delivery and common problems and limitations for fabrication are under discussion.

Janus Micromotors for Photophoretic Motion and Photon Upconversion Applications Using a Single Near-Infrared Wavelength

External stimuli can trigger changes in temperature, concentration, and momentum between micromotors and the medium, causing their propulsion and enabling them to perform different tasks with improved kinetic efficiencies. Light-activated micromotors are attractive systems that achieve improved motion and have the potential for high spatiotemporal control. Photophoretic swarming motion represents an attractive means to induce micromotor movement through the generation of temperature gradients in the medium, enabling the micromotors to move from cold to hot regions. The micromotors studied herein are assembled with Fe3O4 nanoparticles, and NaGdF4:Yb3+,Er3+/NaGdF4:Yb3+ and LiYF4:Yb3+,Tm3+ upconverting nanoparticles. The Fe3O4 nanoparticles were localized to one hemisphere to produce a Janus architecture that facilitates improved upconversion luminescence with the upconverting nanoparticles distributed throughout. Under 976 nm excitation, Fe3O4 nanoparticles generate the temperature gradient, while the upconverting nanoparticles produce visible light that is used for micromotor motion tracking and triggering of reactive oxygen species generation. As such, the motion and application of the micromotors are achieved using a single excitation wavelength. To demonstrate the practicality of this system, curcumin was adsorbed to the micromotor surface and degradation of Rhodamine B was achieved with kinetic rates that were over twice as fast as the static micromotors. The upconversion luminescence was also used to track the motion of the micromotors from a single image frame, providing a convenient means to understand the trajectory of these systems. Together, this system provides a versatile approach to achieving light-driven motion while taking advantage of the potential applications of upconversion luminescence such as tracking and detection, sensing, nanothermometry, particle velocimetry, photodynamic therapy, and pollutant degradation.

Focus on the performance enhancement of micro/nanomotor-based biosensors

Micro/nanomotors (MNMs) emerge as a vital candidate for biosensing due to its nano-size structure, high surface-to-area ratio, directional mobility, biocompatibility, and ease of functionalization, therefore being able to detect objects with high efficiency, precision, and selectivity. The driving mode, nanostructure, materials property, preparation technique, and biosensing applications have been thoroughly discussed in publications. To promote the MNMs-based biosensors from in vitro to in vivo, it is necessary to give a comprehensive discussion from the perspective of sensing performances enhancement. However, until now, there is few reviews dedicated to the systematic discussion on the multiple performance enhancement schemes and the current challenges of MNMs-based biosensors. Bearing it in mind and based on our research experience in this field, we summarized the enhancement methods for biosensing properties such as sensitivity, selectivity, detection time, biocompatibility, simplify system operation, and environmental availability. We hope that this review provides the readers with fundamental understanding on performance enhancement schemes for MNMs-based biosensors.

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.

Swarming Multifunctional Heater-Thermometer Nanorobots for Precise Feedback Hyperthermia Delivery

Micro-/nanorobots (MNRs) are envisioned to act as "motile-targeting" platforms for biomedical tasks due to their ability to propel and navigate in challenging, hard-to-reach biological environments. However, it remains a great challenge for current swarming MNRs to accurately report and regulate therapeutic doses during disease treatment. Here we present the development of swarming multifunctional heater-thermometer nanorobots (HT-NRs) and their application in precise feedback photothermal hyperthermia delivery. The HT-NRs are designed as photothermal-responsive photonic nanochains consisting of magnetic Fe3O4 nanoparticles arranged periodically in one dimension and encapsulated in a temperature-responsive hydrogel shell. The HT-NRs exhibit energetic and controllable swarming motions under a rotating magnetic field, while simultaneously functioning as motile nanoheaters and nanothermometers, utilizing their photothermal conversion and (photo)thermal-responsive structural color changes (photothermochromism). Consequently, the HT-NRs can be quickly deployed to a remote target area (e.g., a superficial tumor lesion) using their collective motion and selectively eliminate diseased cells in a specific targeted region by utilizing their self-reporting photothermochromism as visual feedback for precisely regulating external light irradiation. This work may inspire the development of intelligent multifunctional theranostic micro-/nanorobots and their practical applications in precise disease treatment.

Plasmonic Nanostructure Engineering with Shadow Growth

Physical shadow growth is a vacuum deposition technique that permits a wide variety of 3D-shaped nanoparticles and structures to be fabricated from a large library of materials. Recent advances in the control of the shadow effect at the nanoscale expand the scope of nanomaterials from spherical nanoparticles to complex 3D shaped hybrid nanoparticles and structures. In particular, plasmonically active nanomaterials can be engineered in their shape and material composition so that they exhibit unique physical and chemical properties. Here, the recent progress in the development of shadow growth techniques to realize hybrid plasmonic nanomaterials is discussed. The review describes how fabrication permits the material response to be engineered and highlights novel functions. Potential fields of application with a focus on photonic devices, biomedical, and chiral spectroscopic applications are discussed.

Active Micro/Nanoparticles in Colloidal Microswarms

Colloidal microswarms have attracted increasing attention in the last decade due to their unique capabilities in various complex tasks. Thousands or even millions of tiny active agents are gathered with distinctive features and emerging behaviors, demonstrating fascinating equilibrium and non-equilibrium collective states. In recent studies, with the development of materials design, remote control strategies, and the understanding of pair interactions between building blocks, microswarms have shown advantages in manipulation and targeted delivery tasks with high adaptability and on-demand pattern transformation. This review focuses on the recent progress in active micro/nanoparticles (MNPs) in colloidal microswarms under the input of an external field, including the response of MNPs to external fields, MNP-MNP interactions, and MNP-environment interactions. A fundamental understanding of how building blocks behave in a collective system provides the foundation for designing microswarm systems with autonomy and intelligence, aiming for practical application in diverse environments. It is envisioned that colloidal microswarms will significantly impact active delivery and manipulation applications on small scales.

Janus polymer-grafted nanoparticles mimicking membrane repair proteins for the prevention of lipid membrane rupture

Plasma membrane rupture often leads to cell damage, especially when there is a lack of membrane repair proteins near the wounds due to genetic mutations in organisms. To efficiently promote the repair of the injured lipid membrane, nanomedicines may act as a promising alternative to membrane repair proteins, but the related research is still in its infancy. Herein, using dissipative particle dynamics simulations, we designed a class of Janus polymer-grafted nanoparticles (PGNPs) that can mimic the function of membrane repair proteins. The Janus PGNPs comprise both hydrophobic and hydrophilic polymer chains grafted on nanoparticles (NPs). We track the dynamic process of the adsorption of Janus PGNPs at the damaged site in the lipid membrane and systematically assess the driving forces for this process. Our results reveal that tuning the length of the grafted polymer chains and the surface polarity of the NPs can efficiently enhance the adsorption of Janus PGNPs at the site of the damaged membrane to reduce membrane stress. After repair, the adsorbed Janus PGNPs can be successfully detached from the membrane, leaving the membrane untouched. These results provide valuable guidelines for designing advanced nanomaterials for the repair of damaged lipid membranes.

Small-Scale Robotics with Tailored Wettability

Small-scale robots (SSRs) have emerged as promising and versatile tools in various biomedical, sensing, decontamination, and manipulation applications, as they are uniquely capable of performing tasks at small length scales. With the miniaturization of robots from the macroscale to millimeter-, micrometer-, and nanometer-scales, the viscous and surface forces, namely adhesive forces and surface tension have become dominant. These forces significantly impact motion efficiency. Surface engineering of robots with both hydrophilic and hydrophobic functionalization presents a brand-new pathway to overcome motion resistance and enhance the ability to target and regulate robots for various tasks. This review focuses on the current progress and future perspectives of SSRs with hydrophilic and hydrophobic modifications (including both tethered and untethered robots). The study emphasizes the distinct advantages of SSRs, such as improved maneuverability and reduced drag forces, and outlines their potential applications. With continued innovation, rational surface engineering is expected to endow SSRs with exceptional mobility and functionality, which can broaden their applications, enhance their penetration depth, reduce surface fouling, and inhibit bacterial adhesion.

In vivo applications of micro/nanorobots

Untethered robots in the size range of micro/nano-scale offer unprecedented access to hard-to-reach areas of the body. In these challenging environments, autonomous task completion capabilities of micro/nanorobots have been the subject of research in recent years. However, most of the studies have presented preliminary in vitro results that can significantly differ under in vivo settings. Here, we focus on the studies conducted with animal models to reveal the current status of micro/nanorobotic applications in real-world conditions. By a categorization based on target locations, we highlight the main strategies employed in organs and other body parts. We also discuss key challenges that require interest before the successful translation of micro/nanorobots to the clinic.

Optical Manipulation Heats up: Present and Future of Optothermal Manipulation

Optothermal manipulation is a versatile technique that combines optical and thermal forces to control synthetic micro-/nanoparticles and biological entities. This emerging technique overcomes the limitations of traditional optical tweezers, including high laser power, photon and thermal damage to fragile objects, and the requirement of refractive-index contrast between target objects and the surrounding solvents. In this perspective, we discuss how the rich opto-thermo-fluidic multiphysics leads to a variety of working mechanisms and modes of optothermal manipulation in both liquid and solid media, underpinning a broad range of applications in biology, nanotechnology, and robotics. Moreover, we highlight current experimental and modeling challenges in the pursuit of optothermal manipulation and propose future directions and solutions to the challenges.

Ultrasmall Fe2O3 Tubular Nanomotors: The First Example of Swarming Photocatalytic Nanomotors Operating in High-Electrolyte Media

Self-propelled chemical micro/nanomotors (MNMs) have demonstrated considerable potential in targeted drug delivery, (bio)sensing, and environmental remediation due to their autonomous nature and possible intelligent self-targeting behaviors (e.g., chemotaxis and phototaxis). However, these MNMs are commonly limited by their primary propulsion mechanisms of self-electrophoresis and electrolyte self-diffusiophoresis, making them prone to quenching in high electrolyte environments. Thus, the swarming behaviors of chemical MNMs in high-electrolyte media remain underexplored, despite their potential to enable the execution of complex tasks in high-electrolyte biological media or natural waters. In this study, we develop ultrasmall tubular nanomotors that exhibit ion-tolerant propulsions and collective behaviors. Upon vertical upward UV irradiation, the ultrasmall Fe₂O₃ tubular nanomotors (Fe₂O₃ TNMs) demonstrate positive superdiffusive photogravitaxis and can further self-organize into nanoclusters near the substrate in a reversible manner. After self-organization, the Fe₂O₃ TNMs exhibit a pronounced emergent behavior, allowing them to switch from random superdiffusions to ballistic motions near the substrate. Even at a high electrolyte concentration (C_e), the ultrasmall Fe₂O₃ TNMs retain a relatively thick electrical double layer (EDL) compared to their size, and the electroosmotic slip flow in their EDL is strong enough to propel them and induce phoretic interactions among them. As a result, the nanomotors can rapidly concentrate near the substrate and then gather into motile nanoclusters in high-electrolyte environments. This work opens a gate for designing swarming ion-tolerant chemical nanomotors and may expedite their applications in biomedicine and environmental remediation.

Microrobots for Targeted Delivery and Therapy in Digestive System

Untethered miniature robots enable targeted delivery and therapy deep inside the gastrointestinal tract in a minimally invasive manner. By combining actuation systems and imaging tools, significant progress has been made toward the development of functional microrobots. These robots can be actuated by external fields and fuels while featuring real-time tracking feedback toward certain regions and can perform the therapeutic process by rational exertion of the local environment of the gastrointestinal tract (e.g., pH, enzyme). Compared with conventional surgical tools, such as endoscopic devices and catheters, miniature robots feature minimally invasive diagnosis and treatment, multifunctionality, high safety and adaptivity, embodied intelligence, and easy access to tortuous and narrow lumens. In addition, the active motion of microrobots enhances local penetration and retention of drugs in tissues compared to common passive oral drug delivery. Based on the dissimilar microenvironments in the various sections of the gastrointestinal tract, this review introduces the advances of miniature robots for minimally invasive targeted delivery and therapy of diseases along the gastrointestinal tract. The imaging modalities for the tracking and their application scenarios are also discussed. We finally evaluate the challenges and barriers that retard their applications and hint on future research directions in this field.

Reversible speed control of one-stimulus-double-response, temperature-sensitive asymmetric hydrogel micromotors

Soft, one-stimulus-double-response, thermo-sensitive, PNIPAm-based microgels are designed for controlled autonomous motion under stimuli. At higher temperature, the motors with physically encapsulated catalase move faster, while motors in which catalase is chemically linked to PNIPAm ceased moving. The phenomenon is reversible over multiple cycles of temperature.

Twin-Engine Janus Supramolecular Nanomotors with Counterbalanced Motion

Supramolecular nanomotors were created with two types of propelling forces that were able to counterbalance each other. The particles were based on bowl-shaped polymer vesicles, or stomatocytes, assembled from the amphiphilic block copolymer poly(ethylene glycol)-block-polystyrene. The first method of propulsion was installed by loading the nanocavity of the stomatocytes with the enzyme catalase, which enabled the decomposition of hydrogen peroxide into water and oxygen, leading to a chemically induced motion. The second method of propulsion was attained by applying a hemispherical gold coating on the stomatocytes, on the opposite side of the opening, making the particles susceptible to near-infrared laser light. By exposing these Janus-type twin engine nanomotors to both hydrogen peroxide (H₂O₂) and near-infrared light, two competing driving forces were synchronously generated, resulting in a counterbalanced, "seesaw effect" motion. By precisely manipulating the incident laser power and concentration of H₂O₂, the supramolecular nanomotors could be halted in a standby mode. Furthermore, the fact that these Janus stomatocytes were equipped with opposing motile forces also provided a proof of the direction of motion of the enzyme-activated stomatocytes. Finally, the modulation of the "seesaw effect", by tuning the net outcome of the two coexisting driving forces, was used to attain switchable control of the motile behavior of the twin-engine nanomotors. Supramolecular nanomotors that can be steered by two orthogonal propulsion mechanisms hold considerable potential for being used in complex tasks, including active transportation and environmental remediation.

Nanoswimmers Based on Capped Janus Nanospheres

Nanoswimmers are synthetic nanoscale objects that convert the available surrounding free energy to a directed motion. For example, bacteria with various flagella types serve as textbook examples of the minuscule swimmers found in nature. Along these lines, a plethora of artificial hybrid and non-hybrid nanoswimmers have been introduced, and they could find many uses, e.g., for targeted drug delivery systems (TDDSs) and controlled drug treatments. Here, we discuss a certain class of nanoparticles, i.e., functional, capped Janus nanospheres that can be employed as nanoswimmers, their subclasses and properties, as well as their various implementations. A brief outlook is given on different fabrication and synthesis methods, as well as on the diverse compositions used to prepare nanoswimmers, with a focus on the particle types and materials suitable for biomedical applications. Several recent studies have shown remarkable success in achieving temporally and spatially controlled drug delivery in vitro using Janus-particle-based TDDSs. We believe that this review will serve as a concise introductory synopsis for the interested readers. Therefore, we hope that it will deepen the general understanding of nanoparticle behavior in biological matrices.

Improving disease prevention, diagnosis, and treatment using novel bionic technologies

Increased human life expectancy, due in part to improvements in infant and childhood survival, more active lifestyles, in combination with higher patient expectations for better health outcomes, is leading to an extensive change in the number, type and manner in which health conditions are treated. Over the next decades as the global population rapidly progresses toward a super-aging society, meeting the long-term quality of care needs is forecast to present a major healthcare challenge. The goal is to ensure longer periods of good health, a sustained sense of well-being, with extended periods of activity, social engagement, and productivity. To accomplish these goals, multifunctionalized interfaces are an indispensable component of next generation medical technologies. The development of more sophisticated materials and devices as well as an improved understanding of human disease is forecast to revolutionize the diagnosis and treatment of conditions ranging from osteoarthritis to Alzheimer's disease and will impact disease prevention. This review examines emerging cutting-edge bionic materials, devices and technologies developed to advance disease prevention, and medical care and treatment in our elderly population including developments in smart bandages, cochlear implants, and the increasing role of artificial intelligence and nanorobotics in medicine.

Mechanically Optimize T Cells Activation by Spiky Nanomotors

T cell activation is vital for immune response initiation and modulation. Except for the strength of the interaction between T cell receptors (TCR) and peptides on major histocompatibility complex molecules (MHC), mechanical force, mediated by professional mechanosensitive ion channels, contributes to activating T cells. The intrinsic characteristic of synthetic micro/nanomotors that convert diverse energy sources into physical movement and force, opening up new possibilities for T cell regulation. In this work, Pd/Au nanomotors with spiky morphology were fabricated, and in the presence of low concentrations of hydrogen peroxide fuel, the motors exhibited continuous locomotion in the cellular biological environment. Physical cues (force and pressure) generated by the dynamic performance are sensed by mechanosensitive ion channels of T cells and trigger Ca2+ influx and subsequent activation. The successful demonstration that mechanical signals generated in the bio microenvironment can potentiate T cells activation, represents a potential approach for cell-based cancer immunotherapy.

Heat-Mediated Optical Manipulation

Progress in optical manipulation has stimulated remarkable advances in a wide range of fields, including materials science, robotics, medical engineering, and nanotechnology. This Review focuses on an emerging class of optical manipulation techniques, termed heat-mediated optical manipulation. In comparison to conventional optical tweezers that rely on a tightly focused laser beam to trap objects, heat-mediated optical manipulation techniques exploit tailorable optothermo-matter interactions and rich mass transport dynamics to enable versatile control of matter of various compositions, shapes, and sizes. In addition to conventional tweezing, more distinct manipulation modes, including optothermal pulling, nudging, rotating, swimming, oscillating, and walking, have been demonstrated to enhance the functionalities using simple and low-power optics. We start with an introduction to basic physics involved in heat-mediated optical manipulation, highlighting major working mechanisms underpinning a variety of manipulation techniques. Next, we categorize the heat-mediated optical manipulation techniques based on different working mechanisms and discuss working modes, capabilities, and applications for each technique. We conclude this Review with our outlook on current challenges and future opportunities in this rapidly evolving field of heat-mediated optical manipulation.

Bioinspired urease-powered micromotor as an active oral drug delivery carrier in stomach

Self-propelling micro- and nano-motors (MNMs) have been extensively investigated as an emerging oral drug delivery carrier for gastrointestinal (GI) tract diseases. However, the propulsion of current MNMs reported so far is mostly based on the redox reaction of metals (such as Zn and Mg) with severe propulsion gas generation, remaining non-degradable residue in the GI tract. Here, we develop a bioinspired enzyme-powered biopolymer micromotor mimicking the mucin penetrating behavior of Helicobacter pylori in the stomach. It converts urea to ammonia and the subsequent increase of pH induces local gel-sol transition of the mucin layer facilitating the penetration into the stomach tissue layer. The successful fabrication of micromotors is confirmed by high-resolution transmission electron microscopy, electron energy loss spectroscopy, dynamic light scattering analysis, zeta-potential analysis. In acidic condition, the immobilized urease can efficiently converted urea to ammonia, comparable with that of neutral condition because of the increase of surrounding pH during propulsion. After administration into the stomach, the micromotors show enhanced penetration and prolonged retention in the stomach for 24 h. Furthermore, histological analysis shows that the micromotors are cleared within 3 days without causing any toxicity in the GI tract. The enhanced penetration and retention of the micromotors as an active oral delivery carrier in the stomach would be successfully harnessed for the treatment of various GI tract diseases.

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Polydopamine (PDA) hollow microcapsules are biocompatible, biodegradable, and muco-adhesive.

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Urease-powered PDA micromotors are propelled by the decomposition of urea to ammonia and carbon dioxide.

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Micromotors increase the local pH to induce the gel-sol transition of the mucus layer.

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Micromotors result in enhanced penetration and prolonged retention in the stomach.

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Micromotors can be effectively used for oral drug delivery with complete clearance from the GI tract.

Multifunctional micro/nanomotors as an emerging platform for smart healthcare applications

Self-propelling micro- and nano-motors (MNMs) are emerging as a multifunctional platform for smart healthcare applications such as biosensing, bioimaging, and targeted drug delivery with high tissue penetration, stirring effect, and rapid drug transport. MNMs can be propelled and/or guided by chemical substances or external stimuli including ultrasound, magnetic field, and light. In addition, enzymatically powered MNMs and biohybrid micromotors have been developed using the biological components in the body. In this review, we describe emerging MNMs focusing on their smart propulsion systems, and diagnostic and therapeutic applications. Finally, we highlight several MNMs for in vivo applications and discuss the future perspectives of MNMs on their current limitations and possibilities toward further clinical applications.

Apoptotic Tumor DNA Activated Nanomotor Chemotaxis

Inspired by the tactic organisms in Nature that can self-direct their movement following environmental stimulus gradient, we proposed a DNase functionalized Janus nanoparticle (JNP) nanomotor system for the first time, which can be powered by ultralow nM to μM levels of DNA. The system exhibited interesting chemotactic behavior toward a DNA richer area, which is physiologically related with many diseases including tumors. In the presence of the subtle DNA gradient generated by apoptotic tumor cells, the cargo loaded nanomotors were able to sense the DNA signal released by the cells and demonstrate directional motion toward tumor cells. For our system, the subtle DNA gradient by a small amount (10 μL) of tumor cells is sufficient to induce the chemotaxis behavior of self-navigating and self-targeting ability of our nanomotor system, which promises to shed new light for tumor diagnosis and therapy.

Enzymatic/Magnetic Hybrid Micromotors for Synergistic Anticancer Therapy

Micro/nanomotors (MNMs), which propel by transforming various forms of energy into kinetic energy, have emerged as promising therapeutic nanosystems in biomedical applications. However, most MNMs used for anticancer treatment are only powered by one engine or provide a single therapeutic strategy. Although double-engined micromotors for synergistic anticancer therapy can achieve more flexible movement and efficient treatment efficacy, their design remains challenging. In this study, we used a facile preparation method to develop enzymatic/magnetic micromotors for synergetic cancer treatment via chemotherapy and starvation therapy (ST), and the size of micromotors can be easily regulated during the synthetic process. The enzymatic reaction of glucose oxidase, which served as the chemical engine, led to self-propulsion using glucose as a fuel and ST via a reduction in the energy available to cancer cells. Moreover, the incorporation of Fe₃O₄ nanoparticles as a magnetic engine enhanced the kinetic power and provided control over the direction of movement. Inherent pH-responsive drug release behavior was observed owing to the acidic decomposition of drug carriers in the intracellular microenvironment of cancer cells. This system displayed enhanced anticancer efficacy owing to the synergetic therapeutic strategies and increased cellular uptake in a targeted area because of the improved motion behavior provided by the double engines. Therefore, the demonstrated micromotors are promising candidates for anticancer biomedical microsystems.

Near-Infrared Light-Driven Multifunctional Tubular Micromotors for Treatment of Atherosclerosis

One of the difficulties in atherosclerosis treatment is that the ablation of inflammatory macrophages, repair of vascular endothelial injury, and anti-tissue proliferation should be considered. However, there are few studies that can solve the abovementioned problems simultaneously. Herein, we present a kind of near-infrared (NIR) light-driven multifunctional mesoporous/macroporous tubular micromotor which can rapidly target the damaged blood vessels and release different drugs. Their motion effect can promote themselves to penetrate into the plaque site, and the generated heat effect caused by NIR irradiation can realize the photothermal ablation of inflammatory macrophages. Furthermore, these micromotors can rapidly release the vascular endothelial growth factor for endothelialization and slowly release paclitaxel for antiproliferation to achieve synergistic treatment of atherosclerosis. In vivo results demonstrated that the micromotors can achieve a good therapeutic effect for atherosclerosis. This kind of micro/nanomotor technology with a complex porous structure for drug loading will bring a more potential treatment platform for the disease.

Biosafety, Functionalities, and Applications of Biomedical Micro/nanomotors

Due to their unique ability to actively move, micro/nanomotors offer the possibility of breaking through the limitations of traditional passive drug delivery systems for the treatment of many diseases, and have attracted the increasing attention of researchers. However, at present, the realization of many advantages of micro/nanomotors in disease treatment in vivo is still in its infancy, because of the complexity and particularity of diseases in different parts of human body. In this Minireview, we first focus on the biosafety and functionality of micro/nanomotors as a biomedical treatment system. Then, we address the treatment difficulties of various diseases in vivo (such as ophthalmic disease, orthopedic disease, gastrointestinal disease, cardiovascular disease, and cancer), and then review the research progress of biomedical micro/nanomotors in the past 20 years, Finally, we propose the challenges in this field and possible future development directions.

Six-Degree-of-Freedom Steerable Visible-Light-Driven Microsubmarines Using Water as a Fuel: Application for Explosives Decontamination

Micro/nanomotors are capable of a wide variety of tasks related, i.e., to biomedical or environmental applications. Light-driven semiconductor-based micromotors are especially appealing, as they can split surrounding water via light irradiation, and therefore, they can move infinitely. However, their motion is typically limited to in-plane motion with four degrees of freedom (4DoF) or even pseudo-1D motion with 2DoF. Herein, magnetically steerable tubular TiO₂ /Fe₃ O₄ /CdS micromotors, termed microsubmarines, with 6DoF motion, based on a fuel-free design where surrounding water acts as fuel upon visible light irradiation, are presented, with an average velocity of 7.9 µm s^-1 . Besides, the generation of radicals via such water splitting aids the photocatalytic chemicals degradation with the potential to use solar radiation. A light-induced self-electrophoretic mechanism is responsible for the self-propulsion and can be used to predict the motion direction based on the structure and composition. Finally, the TiO₂ /Fe₃ O₄ /CdS microsubmarines are tested in a proof-of-concept application of high-energy explosive, e.g., picric acid, photocatalytic degradation, with the best performance owing to the versatility of 6DoF motion, the surface coating with amorphous TiO₂ layer, and UV light. The results can help optimize light-active micromotor design for potential national security and environmental application, hydrogen evolution, and target cargo delivery.

Endoscopy-assisted magnetic navigation of biohybrid soft microrobots with rapid endoluminal delivery and imaging

High-precision delivery of microrobots at the whole-body scale is of considerable importance for efforts toward targeted therapeutic intervention. However, vision-based control of microrobots, to deep and narrow spaces inside the body, remains a challenge. Here, we report a soft and resilient magnetic cell microrobot with high biocompatibility that can interface with the human body and adapt to the complex surroundings while navigating inside the body. We achieve time-efficient delivery of soft microrobots using an integrated platform called endoscopy-assisted magnetic actuation with dual imaging system (EMADIS). EMADIS enables rapid deployment across multiple organ/tissue barriers at the whole-body scale and high-precision delivery of soft and biohybrid microrobots in real time to tiny regions with depth up to meter scale through natural orifice, which are commonly inaccessible and even invisible by conventional endoscope and medical robots. The precise delivery of magnetic stem cell spheroid microrobots (MSCSMs) by the EMADIS transesophageal into the bile duct with a total distance of about 100 centimeters can be completed within 8 minutes. The integration strategy offers a full clinical imaging technique-based therapeutic/intervention system, which broadens the accessibility of hitherto hard-to-access regions, by means of soft microrobots.

Biomedical Micro-/Nanomotors: From Overcoming Biological Barriers to In Vivo Imaging

Self-propelled micro- and nanomotors (MNMs) have shown great potential for applications in the biomedical field, such as active targeted delivery, detoxification, minimally invasive diagnostics, and nanosurgery, owing to their tiny size, autonomous motion, and navigation capacities. To enter the clinic, biomedical MNMs request the biodegradability of their manufacturing materials, the biocompatibility of chemical fuels or externally physical fields, the capability of overcoming various biological barriers (e.g., biofouling, blood flow, blood-brain barrier, cell membrane), and the in vivo visual positioning for autonomous navigation. Herein, the recent advances of synthetic MNMs in overcoming biological barriers and in vivo motion-tracking imaging techniques are highlighted. The challenges and future research priorities are also addressed. With continued attention and innovation, it is believed that, in the future, biomedical MNMs will pave the way to improve the targeted drug delivery efficiency.

External Power-Driven Microrobotic Swarm: From Fundamental Understanding to Imaging-Guided Delivery

Untethered micro/nanorobots have been widely investigated owing to their potential in performing various tasks in different environments. The significant progress in this emerging interdisciplinary field has benefited from the distinctive features of those tiny active agents, such as wireless actuation, navigation under feedback control, and targeted delivery of small-scale objects. In recent studies, collective behaviors of these tiny machines have received tremendous attention because swarming agents can enhance the delivery capability and adaptability in complex environments and the contrast of medical imaging, thus benefiting the imaging-guided navigation and delivery. In this review, we summarize the recent research efforts on investigating collective behaviors of external power-driven micro/nanorobots, including the fundamental understanding of swarm formation, navigation, and pattern transformation. The fundamental understanding of swarming tiny machines provides the foundation for targeted delivery. We also summarize the swarm localization using different imaging techniques, including the imaging-guided delivery in biological environments. By highlighting the critical steps from understanding the fundamental interactions during swarm control to swarm localization and imaging-guided delivery applications, we envision that the microrobotic swarm provides a promising tool for delivering agents in an active, controlled manner.

Visible Light-Driven Micromotor with Incident-Angle-Controlled Motion and Dynamic Collective Behavior

Light-driven micromotor has become one of the research focuses in the past decade, and its motion behavior is usually controlled by light intensity, polarization, and light wavelength. Herein, the light incident angle is utilized to control the motion behavior of silica/Au/pentacene (SiO₂/Au/PEN) spherical Janus micromotor. Under tilted irradiation, a single micromotor shows positive phototactic moving behavior without the addition of external chemical fuels, which relies on the photocatalytic reactions and the self-electrophoresis mechanism. Interestingly, when the incident light is tuned to the vertical angle, the SiO₂/Au/PEN micromotor stops moving. Similarly, a number of SiO₂/Au/PEN micromotors exhibit the same "on-off" motion change, which is dependent on the light incident angle. More interestingly, the "on-off" motion of the SiO₂/Au/PEN microparticles under vertical light irradiation results in the formation of the agglomeration with position and size precisely controlled by light. In addition, the resulting aggregation exhibits light-controlled dynamic migration behavior. The incident angle control thus opens up new opportunities for the motion control of the micromotors for diverse applications.

Magnetically actuated intelligent hydrogel-based child-parent microrobots for targeted drug delivery

Small intestine-targeted drug delivery by oral administration has aroused the growing interest of researchers. In this work, the child-parent microrobot (CPM) as a vehicle protects the child microrobots (CMs) under a gastric acid environment and releases them in the small intestinal environment. The intelligent hydrogel-based CPMs with sphere, mushroom, red blood cell, and teardrop shapes are fabricated by an extrusion-dripping method. The CPMs package uniform CMs, which are fabricated by designed microfluidic (MF) devices. The fabrication mechanism and tunability of CMs and CPMs with different sizes and shapes are analyzed, modeled, and simulated. The shape of CPM can affect its drug release efficiency and kinetic characteristics. A vision-feedback magnetic driving system (VMDS) actuates and navigates CPM along the predefined path to the destination and continuously releases drug in the simulated intestinal fluid (SIF, a low Reynolds number (Re) regime) using a new motion control method with the tracking-learning-detection (TLD) algorithm. The newly designed CPM combines the advantages of powerful propulsion, good biocompatibility, and remarkable drug loading and release capacity at the intestinal level, which is expected to be competent for oral administration of small intestine-targeted therapy in the future.

A Journey of Nanomotors for Targeted Cancer Therapy: Principles, Challenges, and a Critical Review of the State-of-the-Art

A nanomotor is a miniaturized device that converts energy stored in the environment into mechanical motion. The last two decades have witnessed a surge of research interests in the biomedical applications of nanomotors, but little clinical translation. To accelerate this process, targeted cancer therapy is used as an example to describe a "survive, locate, operate, and terminate" (SLOT) mission of a nanomotor, where it must 1) survive in the unfriendly in vivo environment, 2) locate its target as well as be located by human operators, 3) carry out specific operations, and 4) terminate after the mission is completed. Along this journey, the challenges presented to a nanomotor, including to power, navigate, steer, target, release, control, image, and communicate are discussed, and how state-of-the-art nanomotors meet or fall short of these requirements is critically reviewed. These discussions are then condensed into a table for easy reference. In particular, it is argued that chemically powered nanomotors are intrinsically ill-positioned for targeted cancer therapy, while nanomotors powered by magnetic fields or ultrasound show more promises. Following this argument, a tentative nanomotor design is then presented in the end to conform to the SLOT guideline, and to inspire practical, functional nanorobots that are yet to come.

Trends in Micro-/Nanorobotics: Materials Development, Actuation, Localization, and System Integration for Biomedical Applications

Micro-/nanorobots (m-bots) have attracted significant interest due to their suitability for applications in biomedical engineering and environmental remediation. Particularly, their applications in in vivo diagnosis and intervention have been the focus of extensive research in recent years with various clinical imaging techniques being applied for localization and tracking. The successful integration of well-designed m-bots with surface functionalization, remote actuation systems, and imaging techniques becomes the crucial step toward biomedical applications, especially for the in vivo uses. This review thus addresses four different aspects of biomedical m-bots: design/fabrication, functionalization, actuation, and localization. The biomedical applications of the m-bots in diagnosis, sensing, microsurgery, targeted drug/cell delivery, thrombus ablation, and wound healing are reviewed from these viewpoints. The developed biomedical m-bot systems are comprehensively compared and evaluated based on their characteristics. The current challenges and the directions of future research in this field are summarized.

Engineering the Interaction Dynamics between Nano-Topographical Immunocyte-Templated Micromotors across Scales from Ions to Cells

Manufacturing mobile artificial micromotors with structural design factors, such as morphology nanoroughness and surface chemistry, can improve the capture efficiency through enhancing contact interactions with their surrounding targets. Understanding the interplay of such parameters targeting high locomotion performance and high capture efficiency at the same time is of paramount importance, yet, has so far been overlooked. Here, an immunocyte-templated nano-topographical micromotor is engineered and their interactions with various targets across multiple scales, from ions to cells are investigated. The macrophage templated nanorough micromotor demonstrates significantly increased surface interactions and significantly improved and highly efficient removal of targets from complex aqueous solutions, including in plasma and diluted blood, when compared to smooth synthetic material templated micromotors with the same size and surface chemistry. These results suggest that the surface nanoroughness of the micromotors for the locomotion performance and interactions with the multiscale targets should be considered simultaneously, for they are highly interconnected in design considerations impacting applications across scales.

Nanoparticles in Polyelectrolyte Multilayer Layer-by-Layer (LbL) Films and Capsules—Key Enabling Components of Hybrid Coatings

Originally regarded as auxiliary additives, nanoparticles have become important constituents of polyelectrolyte multilayers. They represent the key components to enhance mechanical properties, enable activation by laser light or ultrasound, construct anisotropic and multicompartment structures, and facilitate the development of novel sensors and movable particles. Here, we discuss an increasingly important role of inorganic nanoparticles in the layer-by-layer assembly—effectively leading to the construction of the so-called hybrid coatings. The principles of assembly are discussed together with the properties of nanoparticles and layer-by-layer polymeric assembly essential in building hybrid coatings. Applications and emerging trends in development of such novel materials are also identified.

Medical Micro/Nanorobots in Precision Medicine

Advances in medical robots promise to improve modern medicine and the quality of life. Miniaturization of these robotic platforms has led to numerous applications that leverages precision medicine. In this review, the current trends of medical micro and nanorobotics for therapy, surgery, diagnosis, and medical imaging are discussed. The use of micro and nanorobots in precision medicine still faces technical, regulatory, and market challenges for their widespread use in clinical settings. Nevertheless, recent translations from proof of concept to in vivo studies demonstrate their potential toward precision medicine.

On the shape-dependent propulsion of nano- and microparticles by traveling ultrasound waves

We address the propulsion mechanism of ultrasound-propelled nano- and microparticles that are exposed to a traveling ultrasound wave. Based on direct computational fluid dynamics simulations, we study the effect of two important aspects of the particle shape on the propulsion: rounded vs. pointed and filled vs. hollow shapes. We also study the flow field generated around such particles. Our results reveal that pointedness leads to an increase of the propulsion speed, whereas it is not significantly affected by hollowness. Furthermore, we show that the flow field near to ultrasound-propelled particles can look similar to the flow field generated by pusher squirmers.

Confined Bubble-Propelled Microswimmers in Capillaries: Wall Effect, Fuel Deprivation, and Exhaust Product Excess

Self-propelled autonomous nano/microswimmers are at the forefront of materials science. These swimmers are expected to operate in highly confined environments, such as between the grains of soil or in the capillaries of the human organism. To date, little attention is paid to the problem that in such a confined environment the fuel powering catalytic nano/microswimmers can be exhausted quickly and the space can be polluted with the product of the catalytic reaction. In addition, the motion of the nano/microswimmers may be influenced by the confinement. These issues are addressed here, showing the influence of the size of the capillary and length of the micromotor on the motion and the influence of the depletion of the fuel and excess of the exhaust products. Theoretical modeling is provided as well to bring further insight into the observations. This article shows challenges that these systems face and stimulates research to overcome them.

Urease-Powered Polydopamine Nanomotors for Intravesical Therapy of Bladder Diseases

Intravesical therapeutic delivery has been extensively investigated for various bladder diseases such as bladder cancer, overactive bladder, urinary incontinence, and interstitial cystitis. However, conventional drug carriers have a low therapeutic delivery efficiency because of the passive diffusion of drug molecules in a bladder and the rapid clearance by periodic urination. Here, we report biocompatible and bioavailable enzyme-powered polymer nanomotors which can deeply penetrate into a mucosa layer of the bladder wall and remain for a long-term period in the bladder. The successful fabrication of nanomotors was confirmed by high-resolution transmission electron microscopy, energy-dispersive X-ray mapping, zeta-potential analysis, Fourier transform infrared spectroscopy, and urease activity and nanomotor trajectory analyses. After injection into the bladder, urease-immobilized nanomotors became active, moving around in the bladder by converting urea into carbon dioxide and ammonia. The nanomotors resulted in the facilitated penetration to the mucosa layer of the bladder wall and the prolonged retention in the bladder even after repeated urination. The enhanced penetration and retention of the nanomotors as a drug delivery carrier in the bladder would be successfully harnessed for treating a variety of bladder diseases.

Stimuli-Responsive Microarray Films for Real-Time Sensing of Surrounding Media, Temperature, and Solution Properties via Diffraction Patterns

Stimuli-responsive polymers have attracted increasing attention over the years due to their ability to alter physiochemical properties upon external stimuli. However, many stimuli-responsive polymer-based sensors require specialized and expensive equipment, which limits their applications. Here an inexpensive and portable sensing platform of novel microarray films made of stimuli-responsive polymers is introduced for the real-time sensing of various environmental changes. When illuminated by laser light, microarray films generate diffraction patterns that can reflect and magnify variations of the periodical microstructure induced by surrounding invisible parameters in real time. Stimuli-responsive polyelectrolyte complexes are structured into micropillar arrays to monitor the pH variation and the presence of calcium ions based on reversible swelling/shrinking behaviors of the polymers. A pH hysteretic effect of the selected polyelectrolyte pair is determined and explained. Furthermore, polycaprolactone microchamber arrays are fabricated and display a thermal-driven structural change, which is exploited for photonic threshold temperature detection. Experimentally observed diffraction patterns are additionally compared with rigorous coupled-wave analysis simulations that prove that induced diffraction pattern alterations are solely caused by geometrical microstructure changes. Microarray-based diffraction patterns are a novel sensing platform with versatile sensing capabilities that will likely pave the way for the use of microarray structures as photonic sensors.

Terahertz three-dimensional monitoring of nanoparticle-assisted laser tissue soldering

In view of minimally-invasive clinical interventions, laser tissue soldering assisted by plasmonic nanoparticles is emerging as an appealing concept in surgical medicine, holding the promise of surgeries without sutures. Rigorous monitoring of the plasmonically-heated solder and the underlying tissue is crucial for optimizing the soldering bonding strength and minimizing the photothermal damage. To this end, we propose a non-invasive, non-contact, and non-ionizing modality for monitoring nanoparticle-assisted laser-tissue interaction and visualizing the localized photothermal damage, by taking advantage of the unique sensitivity of terahertz radiation to the hydration level of biological tissue. We demonstrate that terahertz radiation can be employed as a versatile tool to reveal the thermally-affected evolution in tissue, and to quantitatively characterize the photothermal damage induced by nanoparticle-assisted laser tissue soldering in three dimensions. Our approach can be easily extended and applied across a broad range of clinical applications involving laser-tissue interaction, such as laser ablation and photothermal therapies.

Leukocyte Membrane-Coated Liquid Metal Nanoswimmers for Actively Targeted Delivery and Synergistic Chemophotothermal Therapy

We report a leukocyte membrane-coated gallium nanoswimmer (LMGNS) capable of ultrasound-propelled motion, antibiofouling, and cancer cell recognition and targeting. The LMGNS consists of a needle-shaped gallium core encapsulating an anticancer drug and a natural leukocyte membrane shell. Under the propulsion of an ultrasound field, LMGNSs could autonomously move in biological media with a speed up to 108.7 μm s^-1. The velocity and motion direction of the LMGNSs can be modulated by regulating the frequency and voltage of the applied ultrasound field. Owing to the leukocyte membrane coating, LMGNSs can not only avoid biofouling during the motion in blood but also possess cancer cell recognition capability. These LMGNSs could actively seek, penetrate, and internalize into the cancer cells and achieve enhanced anticancer efficiency by combined photothermal and chemical therapy. Such biofunctionalized liquid metal nanoswimmer presents a new type of multifunctional platform for biomedical applications.

Stabilization and Rheological Behavior of Fly Ash-Water Slurry Using a Natural Dispersant in Pipeline Transportation

Effective transportation of fly ash-water slurry through a pipeline from its generation site, a power plant, to a storage site by replacing commercial surfactants such as cetyl trimethyl ammonium bromide and sodium dodecyl sulfate by a natural dispersant extracted from Sapindus laurifolia was studied. The stability of fly ash slurry was determined from its rheological parameters, dispersant concentration, and stabilization mechanism. From surface tensiometric data, the critical micelle concentration of the dispersant was obtained to be 0.017 g/cc. The stabilization of high-concentration fly ash slurry has been studied through its rheological behavior by variation of temperature and dispersant and ash concentration. The rheological result obtained for fly ash concentrations in the range of 50-65% slurry was best justified by the Bingham plastic model. The wettability of fly ash particles is increased in the presence of dispersants, which is inferred from reduction of the surface tension value. The stabilization mechanism of the slurry is explained by a steric factor as indicated by the decrease in the zeta potential value. Air pollution is minimized at its destination site due to agglomeration of fly ash particles, which is confirmed from the SEM microphotograph.

Surface Wettability-Directed Propulsion of Glucose-Powered Nanoflask Motors

Chemically driven colloidal motors capable of implementing different movements under a common environment are of great importance for various complex tasks. However, the key parameters underlying different motion behaviors are incompletely understood. Here, we demonstrate that carbonaceous nanoflask (CNF) motors move spontaneously in glucose powered by the cascade reaction of glucose oxidase and catalase, and their directional propulsion can be premeditated by controlling the surface wettability of nanomotors. The hydrophilic CNF motors move from the round-bottom to the opening neck (backward), whereas the hydrophobic CNF motors swim from the opening neck to the round-bottom (forward). We demonstrate that the backward motion of the hydrophilic CNF motors is driven by the local glucose gradient due to self-diffusiophoresis, and the forward movement of the hydrophobic CNF motors is caused by the locally produced glucose acid gradient. The fluid simulation reveals that the hydrophilic and hydrophobic CNF motors correspond to the puller and pusher models, respectively. Our study offers a minimal strategy to manipulate the direction of motion of motors for specific applications and to change the hydrodynamic behaviors of glucose-powered motors.

Near-Infrared Light-Triggered Porous AuPd Alloy Nanoparticles To Produce Mild Localized Heat To Accelerate Bone Regeneration

The treatment of massive bone defects is still a significant challenge for orthopedists. Here we have engineered synthetic porous AuPd alloy nanoparticles (pAuPds) as a hyperthermia agent for in situ bone regeneration through photothermal therapy (PTT). After being swallowed by cells, pAuPds produced a mild localized heat (MLH) (40-43 °C) under the irradiation of a near-infrared laser, which can greatly accelerate cell proliferation and bone regeneration. Almost 97% of the cranial defect area (8 mm in diameter) was covered by the newly formed bone after 6 weeks of PTT. RNA sequencing analysis was used to obtain insight into the molecular mechanism of the MLH on cell proliferation and bone formation. These results demonstrated that the Wnt signaling pathway was involved in the MLH. This Letter provides a unique strategy with mild heat stimulation and high efficiency for in situ bone regeneration.

Biocompatibility of artificial micro/nanomotors for use in biomedicine

The advent of micro/nanomotors (MNMs) has shed light on the innovation of active biomedical systems or devices that might bring revolutionary solutions to traditional biomedical strategies. In spite of development beyond expectation over the last decade with a fair number of proof-of-concept demonstrations, the in vivo practical application of MNMs for clinical use is still in its infancy. The biocompatibility of MNMs is the first consideration before realizing practicality, taking into account the complicated interactions between the self-propelled MNMs and biological systems. Therefore, in this review, we focused on the biocompatibility of MNMs with regard to the fabrication materials and propulsion mechanisms by means of in-depth discussions on the advantages and limitations of MNMs for operating under physiological conditions. The future prospective and suggestions on the development of MNMs toward practical biomedical applications will also be proposed.

Overview on the Evolution of Laser Welding of Vascular and Nervous Tissues

Laser welding presents a core position in the health sector. This process has had an outstanding impact on the surgical procedures from many medical areas, such as on vascular and nervous surgeries. The aim of the present research is to present an overview on the evolution of laser welding of vascular and nervous tissues. These surgeries present many advantages, such as an absence of foreign-body reactions and aneurysms and good tensile strengths. However, despite the sutureless nature of the process, complementary sutures have been applied to support the procedure success. An important concern in vascular and nervous laser welding is the thermal damage. The development of temperature-controlled feedback systems has reduced this concern with a very precise control of the laser parameters. The bonding strength of vascular and nerve laser welds can be enhanced with the application of solder solutions, bonding materials, and laser-activated dyes. Alternative techniques to laser welding, such as photochemical tissue bonding and electrosurgical high-frequency technologies, have also been tested for vascular and nervous repairs.