Micro/Nanorobots for Biomedicine: Delivery, Surgery, Sensing, and Detoxification

Strategies to enhance the penetration of nanomedicine in solid tumors

Nanomedicine was previously regarded as a promising solution in the battle against cancer. Over the past few decades, extensive research has been conducted to exploit nanomedicine for overcoming tumors. Unfortunately, despite these efforts, nanomedicine has not yet demonstrated its ability to cure tumors, and the research on nanomedicine has reached a bottleneck. For a significant period of time, drug delivery strategies have primarily focused on targeting nanomedicine delivery to tumors while neglecting its redistribution within solid tumors. The uneven distribution of nanomedicine within solid tumors results in limited therapeutic effects on most tumor cells and significantly hampers the efficiency of drug delivery and treatment outcomes. Therefore, this review discusses the challenges faced by nanomedicine in penetrating solid tumors and provides an overview of current nanotechnology strategies (alleviating penetration resistance, size regulation, tumor cell transport, and nanomotors) that facilitate enhanced penetration of nanomedicine into solid tumors. Additionally, we discussed the potential role of nanobionics in promoting effective penetration of nanomedicine.

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.

Magnetically driven lipid vesicles for directed motion and light-triggered cargo release

Targeted drug delivery and precision medicine offer great promise for enhancing therapeutic efficacy while minimizing systemic toxicity. Among various platforms, lipid-based delivery systems have attracted significant interest due to their intrinsic biocompatibility and their ability to transport hydrophilic, hydrophobic, and amphiphilic compounds. With recent advances in bottom-up synthetic biology and microfluidics, giant unilamellar vesicles (GUVs) have emerged as a versatile candidate for drug delivery. However, achieving controlled and directed motion of GUVs remains a critical challenge. In this study, we conduct a systematic experimental investigation of GUVs encapsulating magnetic particles (magGUVs) subjected to inhomogeneous magnetic fields. We develop a lattice Boltzmann simulation framework to model the propulsion of GUVs driven by an internally encapsulated particle under a constant force, and compare the simulated speeds with experimental measurements. Furthermore, we demonstrate a proof-of-concept integrating directed motion of magGUVs with controlled, localized release of encapsulated contents via light-induced asymmetric oxidation. This work provides a foundation for the design of lipid-based drug delivery vehicles that combine navigational control with on-demand release capabilities, advancing targeted therapeutic strategies in precision medicine.

Light-powered phagocytic macrophage microrobot (phagobot): both in vitro and in vivo

Micro/nanorobots based on immune cells show great potential for addressing challenging biological and biomedical conditions. However, their powerful innate immune functions, particularly the phagocytosis capabilities, remain a big challenge to fully leverage with the current designs of immune cell-based microrobots. Herein, we report a light-powered phagocytic macrophage microrobot (phagobot), which is capable of robotic navigation toward specific foreign bio-threats and executing precise phagocytosis of these targeted entities under light control. Without genetic modification or nanoengineering of macrophages, the phagobot's "wake-up" program is achieved through direct activation of a resting-state macrophage by a tightly focused near-infrared (NIR) light beam. The phagobot exhibits robotic steering and directional navigation controlled by optical manipulation of the extended pseudopodia within the activated macrophage. It can further execute targeted phagocytic clearance tasks via engulfing various foreign bio-threats, including nanoplastics, microbials, and cancer cell debris. Notably, the phagobot can be constructed in a living larval zebrafish through optical activation and manipulation of the endogenous macrophage, which also exhibits controllable navigation and targeted phagocytic capabilities in vivo. With the intrinsic immune functions of macrophages, our light-powered phagobot represents a novel form of intelligent immune cell-based microrobots, holding many new possibilities for precise immune regulation and treatment for immune-related diseases.

Trienzyme-in-One Nanoparticle Making Multifunctional Synergistic Nanorobot for Tumor Therapy

Current nanoparticle-based drug delivery systems for tumor therapy face significant challenges in intratumoral penetration and cellular internalization, leading to poor therapeutic efficacy. Herein, it is demonstrated that the sequential integration of glucose oxidase (GOx), catalase (CAT), and urease (URE) onto the half surface of biotin-modified Janus nanoparticles via the chemical coupling way produces nanorobots of multifunctionality and synergistic effect (denoted as UCGPJNRs). They can autonomously and powerfully move in tumor microenvironment (TME) by using endogenous urea as a fuel, enabling to penetrate deeper than 0.55 mm into tumor tissues, ≈5.5-fold of the previous counterparts. The UCGPJNRs perform motion-enhanced biotin receptor-mediated endocytosis and endoplasmic reticulum/Golgi apparatus pathway-mediated exocytosis, greatly improving the internalization efficiency of tumor cells. They release NH3 when moving to produce selective toxicity against tumor cells in hypoxic TME. Further, they enhance the glucose consumption by ≈three times due to the motion-accelerated GOx/CAT cascade reaction, disrupting the metabolism against tumor cells on a large area. After intratumorally injecting into tumor-bearing mice, UCGPJNRs can significantly amplify the in vivo tumor growth inhibition rate through their synergistic effect. This work provides a plausible strategy to overcome current limitations in tumor treatment by anchoring multiple bioenzymes on one nanoparticle.

Designing optimal elastic filaments for viscous propulsion

The propulsion of many eukaryotic cells is generated by flagella, flexible slender filaments that are actively oscillating in space and time. The dynamics of these biological appendages have inspired the design of many types of artificial microswimmers. The magnitude of the filament's viscous propulsion depends on the time-varying shape of the filament, and that shape depends in turn on the spatial distribution of the bending rigidity of the filament. In this work, we rigorously determine the relationship between the mechanical (bending) properties of the filament and the viscous thrust it produces using mathematical optimisation. Specifically, by considering a model system (a slender elastic filament with an oscillating slope at its base), we derive the optimal bending rigidity function along the filament that maximises the time-averaged thrust produced by the actuated filament. Instead of prescribing a specific functional form, we use functional optimisation and adjoint-based variational calculus to formally establish the link between the distribution of bending rigidity and propulsion. The optimal rigidities are found to be stiff near the base, and soft near the distal end, with a spatial distribution that depends critically on the constraints used in the optimisation procedure. These findings may guide the optimal design of future artificial swimmers.

Harnessing optical forces with advanced nanophotonic structures: principles and applications

Non-contact mechanical control of light has given rise to optical manipulation, facilitating diverse light-matter interactions and enabling pioneering applications like optical tweezers. However, the practical adoption of versatile optical tweezing systems remains constrained by the complexity and bulkiness of their optical setups, underscoring the urgent requirement for advancements in miniaturization and functional integration. In this paper, we present innovations in optical manipulation within the nanophotonic domain, including fiber-based and metamaterial tweezers, as well as their emerging applications in manipulating cells and artificial micro-nano robots. Furthermore, we explore interdisciplinary on-chip devices that integrate photonic crystals and optofluidics. By merging optical manipulation with the dynamism of nanophotonics and metamaterials, this work seeks to chart a transformative pathway for the future of optomechanics and beyond.

Rapid Blood Clot Removal via Remote Delamination and Magnetization of Clot Debris

Micro/nano-scale robotic devices are emerging as a cutting-edge approach for precision intravascular therapies, offering the potential for highly targeted drug delivery. While employing micro/nanorobotics for stroke treatment is a promising strategy due to its ability to localize therapy and minimize drug dosage, current methods require prolonged treatment durations, increasing the risk of nerve tissue necrosis from extended hypoxia. Here a programmable colloidal microswarm capable of rapidly detaching blood clots from the vessel wall is developed, enabling swift recanalization without the need for complete clot degradation. More importantly, the detached clot debris, despite their random shapes, functions as magnetic "debris-robots" and can be efficiently propelled through helical swimming within flowing vessels, followed by retrieval using catheter suction. The entire process-including catheter delivery, controlled locomotion, clot detachment, and retrieval-can be completed in approximately half an hour, significantly saving time compared to the critical "Golden 6 hours" window for stroke treatment. This retrieval procedure greatly minimizes nanoparticle exposure in the bloodstream and lowers the risk of secondary clotting in distal vessels, marking a significant advancement in robotic-assisted thrombolysis.

Integration of Photodiagnosis and Therapy Guided by Micro/Nanorobots

Micro/Nanorobots(MNRs)integrated with phototherapy represent an emerging approach to cancer treatment and hold significant potential for addressing bacterial infections, neurological disorders, cardiovascular diseases, and related conditions. By leveraging micro/nanoscale motor systems in conjunction with phototherapy, these robots enable real-time guidance and monitoring of therapeutic processes, improving drug delivery precision and efficiency. This integration not only enhances the effectiveness of phototherapy but also minimizes damage to surrounding healthy tissues. Nevertheless, clinical translation of MNRs-assisted phototherapy still faces numerous challenges. In this review, recent key developments in the field are comprehensively summarized, the critical roles of MNRs-assisted phototherapy in clinical applications are highlighted, and insights into future directions and the pathway toward large-scale clinical implementation are provided.

Magnetically driven biohybrid blood hydrogel fibres for personalized intracranial tumour therapy under fluoroscopic tracking

Small materials with pliability and untethered mobility are particularly suitable for minimally invasive medical interventions inside the body. However, the capabilities and applicability of such soft 'robots' are restricted by foreign-body responses to them and by the need to get them cleared from the body after the intervention. Here we report the development of biodegradable magnetized biohybrid blood hydrogel fibres that evade immune recognition, and their applicability for targeted intracranial tumour therapy with real-time tracking through X-ray fluoroscopy. The gel fibres can be made of the patient's own blood mixed with a small amount of magnetic particles and can be produced in about 15 min. We show that the locomotion of intracranially injected gel fibres through cerebrospinal fluid can be remotely controlled under a magnetic field and fluoroscopically tracked, and that a drug encapsulated in the gels can be released on demand under magnetic control, as we show for the delivery of doxorubicin to intracranial tumours in the minipigs. Biodegradable soft actuatable materials that avoid foreign-body responses may aid the development of personalized targeted interventions.

Polymersome-based nanomotors: preparation, motion control, and biomedical applications

Polymersome-based nanomotors represent a cutting-edge development in nanomedicine, merging the unique vesicular properties of polymersomes with the active propulsion capabilities of synthetic nanomotors. As a vesicular structure enclosed by a bilayer membrane, polymersomes can encapsulate both hydrophilic and hydrophobic cargoes. In addition, their physical-chemical properties such as size, morphology, and surface chemistry are highly tunable, which makes them ideal for various biomedical applications. The integration of motility into polymersomes enables them to actively navigate biological environments and overcome physiological barriers, offering significant advantages over passive delivery platforms. Recent breakthroughs in fabrication techniques and motion control strategies, including chemically, enzymatically, and externally driven propulsion, have expanded their potential for drug delivery, biosensing, and therapeutic interventions. Despite these advancements, key challenges remain in optimizing propulsion efficiency, biocompatibility, and in vivo stability to translate these systems into clinical applications. In this perspective, we discuss recent advancements in the preparation and motion control strategies of polymersome-based nanomotors, as well as their biomedical-related applications. The molecular design, fabrication approaches, and nanomedicine-related utilities of polymersome-based nanomotors are highlighted, to envisage the future research directions and further development of these systems into effective, precise, and smart nanomedicines capable of addressing critical biomedical challenges.

Breaking the Limitation of Laminar Flow in Thrombolytic Therapy with Reconfigurable Vortex-Like Nanobot Swarms

Laminar blood flow represents the normal physiological state of blood circulation, but it also acts as a natural physiological barrier for the effective diffusion of drugs to the lesion site. Here, we report a bioinspired strategy in which reconfigurable vortex-like swarms of magnetic swimming nanobots actively disrupt the laminar flow to deliver drugs in a manner similar to how bacteria seek food. The drug was released from the cavity of biodegradable, submicron pentosan flask-like nanobots, aggregates as the dynamic rotating drug fluid under a rotating magnetic field. The vortex-like nanobot swarm successfully overcame the laminar barrier near the thrombus in a rat inferior vena cava stenosis thrombosis model, which was observed by ultrasound blood flow imaging. Furthermore, the clinical feasibility of nanobots swarm for enhancing thrombolytic efficacy through drug aggregation after breaking the laminar flow was further confirmed in a rat deep vein thrombosis model. This bionic active targeting approach overcomes the laminar flow barrier and restricts the release of drugs by the swarm-induced vortex fluid to facilitate targeted drug delivery, which is expected to be an innovative method to enhance drug delivery efficiency.

Light-Driven Artificial Cell Micromotors for Degenerative Knee Osteoarthritis

Combining artificial cellular compartmentalization and intelligent motion benefits of micro/nanomotors, light is used as energy input to construct an artificial cell-based micromotor capable of photosynthetic anabolism and intelligent directional movement. This system is assembled from phospholipids functionalized with F-ATP synthase and molybdenum disulfide (MoS2) nanoparticles (Vesical@MoS2-ATPase). The underlying mechanism involves the generation of protons (H+) through photo-hydrolysis of MoS2 nanoparticles within vesicles, which generates a local electroosmotic flow inside the vesicles and drives the negatively charged MoS2 toward light. The established proton gradient across the phospholipid membrane, in turn, drives the ATP synthase to catalyze ATP production. Both in vitro and in vivo models demonstrate that the micromotor can elevate local intracellular ATP levels upon light and improve the metabolism of denatured chondrocytes. This cell mimicry, with capabilities of migration and biosynthesis, emerges as a promising platform for the next generation of functional bio-interface.

Treatment of lung diseases via nanoparticles and nanorobots: Are these viable alternatives to overcome current treatments?

Challenges

Respiratory diseases remain challenging to treat, with current efforts primarily focused on managing symptoms rather than maintaining overall lung health. Traditional treatment methods, such as oral or parenteral administration of antiviral, antibacterial, and anti-inflammatory drugs, face limitations. These include difficulty in delivering therapeutic agents to pathogens residing deep in the airways and the risk of severe side effects due to high systemic drug concentrations. The growing threat of drug-resistant pathogens further complicates infection management.

Advancements

The lung's large surface area offers an attractive target for inhalation-based drug delivery. Nanoparticles (NP) enable uniform and sustained drug distribution across the alveolar network, overcoming challenges posed by complex lung anatomy. Recent breakthroughs in nanorobots (NR) have demonstrated precise navigation through biological environments, delivering therapies directly to affected lung areas with enhanced accuracy. Nanotechnology has also shown promise in treating lung cancer, with nanoparticles engineered to overcome biological barriers, improve drug solubility, and enable controlled drug release.

Future scope

This review explores the progress of NP and NR in addressing challenges in pulmonary drug delivery. These innovations allow targeted delivery of nucleic acids, drugs, or peptides to the pulmonary epithelium with unprecedented accuracy, offering significant potential for improving therapeutic effectiveness in respiratory disorders.

Nanobots: The current scenario

The detection and treatment of cancer could be completely transformed by the application of nanotechnology. New nanoscale targeting methods have emerged as a result of advancements in materials science and protein engineering, giving cancer patients new hope. Only a small number of nanocarriers have been approved for clinical usage in targeting cancer cells, despite the fact that many have been licensed for human studies. We examine a few of the approved formulations in this study and talk about the difficulties in transferring laboratory results to clinical settings. This review emphasises the inherent challenges in cancer therapy as well as the different nanocarriers and chemicals that can be used for specific tumour targeting. Future advancements in cancer detection and therapy could be facilitated by nanotechnology, but still the area remains vast and more clinical as well as laboratory trails are the need of the hour to overcome the present barriers and align the discovery of the potential application of nanobots from a mere lab work to a full-fledged clinical and translational work.

A Bibliometric Analysis and Systematic Review of Research Advances in In Situ Gel Drug Delivery Systems from 2003 to 2023

Objective: We aimed analyze research trends in in situ gel drug delivery systems. Methods: Studies from 2003 to 2023 were systematically obtained from the Web of Science database and analyzed using VOSviewer software to evaluate publication trends, citation patterns, and collaborative networks. Results: A total of 990 articles were reviewed. There has been a significant increase in publications since 2019, with the highest number of publications occurring in 2023. China was the leading country in terms of publication output. Cairo University and King Abdulaziz University were identified as the top contributing institutions. Key researchers included Zhao, Xia, Hosny, and Kim. The research primarily focused on developing new formulations, optimizing materials (e.g., biocompatible and biodegradable materials), and exploring clinical applications such as nasal-brain delivery for Alzheimer's treatment. Conclusions: In situ gel systems have gained widespread use in clinical practice due to their ability to provide prolonged drug release and enhance patient compliance. This area remains crucial for future research, particularly in formulation design and administration methods.

From Autonomous Chemical Micro-/Nanomotors to Rationally Engineered Bio-Interfaces

Developing micro-/nanomotors that convert a chemical energy input into a local gradient field and motion is an appealing but challenging task that holds particular promise for the intersection of materials and nanoengineering. Over the past two decades, remarkable advancements have refined these out-of-equilibrium chemically powered micro-/nanomotors, enabling them to orchestrate in situ chemical transformations that dynamically change local environments. The ionic products, radicals, gases, and electric fields from these active materials reshape the microenvironment, paving the way for ecofriendly disease interventions. This review discusses the state-of-the-art reactions that propel these energy-consuming micro-/nanomotors and elucidates the emerging implications of their products on biological systems. Particular emphasis has been placed on their potential for neural modulation, reactive oxygen species (ROS) regulation, synergistic tumor therapy, antibacterial strategies, and tissue regeneration. Collectively, these sketches provide a landscape of therapeutic modalities, heralding a new era of biomedicine. By harnessing the in situ product field of this active matter, we envision a paradigm shift toward active therapies that transcend conventional approaches, promising breakthroughs in disease diagnosis, treatment, and prevention.

Application of photosensitive microalgae in targeted tumor therapy

Microalgae present a novel and multifaceted approach to cancer therapy by modulating the tumor-associated microbiome (TAM) and the tumor microenvironment (TME). Through their ability to restore gut microbiota balance, reduce inflammation, and enhance immune responses, microalgae contribute to improved cancer treatment outcomes. As photosynthetic microorganisms, microalgae exhibit inherent anti-tumor, antioxidant, and immune-regulating properties, making them valuable in photodynamic therapy and tumor imaging due to their capacity to generate reactive oxygen species. Additionally, microalgae serve as effective drug delivery vehicles, leveraging their biocompatibility and unique structural properties to target the TME more precisely. Microalgae-based microrobots further expand their therapeutic potential by autonomously navigating complex biological environments, offering a promising future for precision-targeted cancer treatments. We position microalgae as a multifunctional agent capable of modulating TAM, offering novel strategies to enhance TME and improve the efficacy of cancer therapies.

Bacteria Flagella-Mimicking Polymer Multilayer Magnetic Microrobots

Mass production of biomedical microrobots demands expensive and complex preparation techniques and versatile biocompatible materials. Learning from natural bacteria flagella, the study demonstrates a magnetic polymer multilayer cylindrical microrobot that bestows the controllable propulsion upon an external rotating magnetic field with uniform intensity. The magnetic microrobots are constructed by template-assisted layer-by-layer technique and subsequent functionalization of magnetic particles onto the large opening of the microrobots. Geometric variables of the polymer microrobots, such as the diameter and wall thickness, can be controlled by selection of porous template and layers of assembly. The microrobots perform controllable propulsion through the manipulation of magnetic field. The comparative analysis of the movement behavior reveals that the deformation of microrobots may be attributed to the propulsion upon rotating magnetic field, which is similar to that of natural bacteria. The influence of actuation and frequency on the velocity of the microrobots is studied. Such polymer multilayer magnetic microrobots may provide a novel concept to develop rapidly delivering drug therapeutic agents for diverse practical biomedical uses.

Innovative materials that behave like robots to combat plastic pollution

The growing plastic pollution crisis demands novel approaches, with innovative materials that mimic robotic behaviors emerging as a promising solution. This approach explores the development and application of smart materials that can autonomously engage in plastic waste removal, functioning like robots under various environmental conditions. We focus on materials activated by light, magnetic fields, chemical fuels, and ion exchange, which are designed to target and remove plastic waste efficiently. The key properties of these materials, such as self-activation, adaptability, and precision that enable them to function autonomously in waste management systems, are examined. The integration of these innovative materials offers significant advantages, including faster waste processing, reduced human exposure to hazardous waste, and enhanced sorting accuracy. Additionally, this review evaluates the environmental impact, scalability, and cost-effectiveness of these materials in comparison to traditional methods. Finally, the potential of these materials to play a central role in sustainable plastic waste management and contribute to a circular economy is discussed.

Harnessing Photon Recoil for Enhanced Torque on Light-Driven Metarotors

Contact-free rotation of microscopic objects in aqueous environments based on optical forces is a powerful concept in the development of light-driven microrobots, micromachines, torque transducers, and rheological sensors. Here, we demonstrate freely movable quasi-two-dimensional metasurface rotors with lateral dimensions up to 100 μm while still exhibiting controllable and steady rotation when submerged in water. The metarotors utilize photon recoil to produce strong optical torque by deflecting low-intensity laser light toward high angles via long lever arms, which amplify the creation of orbital angular momentum. We find that the torque generated by a single metarotor can be used to rotate hundreds of passive microparticles present in solution, suggesting potential applications as particle mixers in microfluidics and microbiology. Further development might involve utilizing metarotors as components in future microrobots for biomedicine and beyond.

Particle-armored liquid robots

It is challenging to emulate biological forms and functions with artificial machines: Fluidity and adaptability seen in cellular organisms, characterized by their ability to deform, split, merge, and engulf, are hard to recapitulate with traditional rigid robotic structures. A promising avenue to tackle this problem is harnessing the supreme deformability of liquids while providing stable yet flexible shells around them. Here, we report a highly robust liquid-particle composite, named a Particle-armored liquid roBot (PB), featuring a liquid blob coated with unusually abundant superhydrophobic particles. The enhanced deformability and structural stability of our millimetric PBs enable a range of versatile robotic functions, such as navigating through complex environments, engulfing and transporting cargoes, merging, and adapting to various environments. We use both theoretical analysis and experimental approaches to develop a framework for predicting the shape evolution, dynamics, and robotic functions of PBs. The forms and functions of our liquid robots mark an essential hallmark toward miniature biomachines that perform like cells.

Externally controlled intermittent randomization enables complex navigation of multiple nanobots

Selective control of single untethered robots within a collection is trivial in macroscale robotics since it is possible to address and actuate individual entities using various communication schemes. This strategy does not work at reduced (sub-µm) length scales, where the global field cannot differentiate or control a single nanobot selectively from within a collection of indistinguishable objects. Here, we propose and demonstrate strategies where identical magnetic nanobots can be selectively and independently actuated using global control fields.

Vortex reversal is a precursor of confined bacterial turbulence

Active turbulence, or chaotic self-organized collective motion, is often observed in concentrated suspensions of motile bacteria and other systems of self-propelled interacting agents. To date, there is no fundamental understanding of how geometrical confinement orchestrates active turbulence and alters its physical properties. Here, by combining large-scale experiments, computer modeling, and analytical theory, we have identified a generic sequence of transitions occurring in bacterial suspensions confined in cylindrical wells of varying radii. With increasing the well's radius, we observed that persistent vortex motion gives way to periodic vortex reversals, four-vortex pulsations, and then well-developed active turbulence. Using computational modeling and analytical theory, we have shown that vortex reversal results from the nonlinear interaction of the first three azimuthal modes that become unstable with the radius increase. The analytical results account for our key experimental findings. To further validate our approach, we reconstructed equations of motion from experimental data. Our findings shed light on the universal properties of confined bacterial active matter and can be applied to various biological and synthetic active systems.

Liquid-bodied antibiofilm robot with switchable viscoelastic response for biofilm eradication on complex surface topographies

Recalcitrant biofilm infections pose a great challenge to human health. Micro- and nanorobots have been used to eliminate biofilm infections in hard-to-reach regions inside the body. However, applying antibiofilm robots under physiological conditions is limited by the conflicting demands of accessibility and driving force. Here, we introduce a liquid-bodied antibiofilm robot constructed by a dynamically cross-linked magnetic hydrogel. Leveraging the viscoelastic response of the robot enables it to adapt to complex surface topographies such as medical meshes and stents. Upon actuation, the robot can mechanically destroy the biofilm matrix, chemically deactivate bacterial cells, and collect disrupted biofilm debris. The robot's antibiofilm performance is studied in vitro and demonstrated on a medical mesh and a biliary stent. Tracking and navigation under endoscopy and x-ray imaging in an ex vivo porcine bile duct are demonstrated. Last, in vivo antibiofilm treatment is conducted by indwelling infected stents into mice's abdominal cavity and clearing the biofilm infection using the proposed robot.

Photothermal Cavitation-Driven Micromotor to Penetrate Cell Membrane

Photothermally driven micro/nanomotors efficiently convert light into mechanical motion, making them highly attractive for biomedical applications due to their exceptional biocompatibility and safety. However, one mystery of the photothermally driven micro/nanomotor is the wide range of reported light intensities applied, ranging from 1 W cm-2 to over 105 W cm-2. To address this mystery, we systematically investigated the propulsion of a carbon microbottle-based micromotor under three illumination conditions: continuous laser, pulsed laser, and scanning laser, where a new cavitation-driven mechanism is identified. Using a high-speed camera, we find that the instantaneous deposition of laser energy on the micromotors can lead to transient and localized evaporation of the solvent, creating cavitation bubbles to drive micromotors with ultrafast speed, where instantaneous velocity over 1 m s-1 is observed. Through precise modulation of the scanning orientation and intensity of the laser, directional propulsion and targeted explosions of the microbottles are achieved, where the instant force is strong enough to penetrate live cell membranes. Finally, the cavitation-driven micromotors are exploited as gene transfection tools, where targeted cytoplasmic transfection is demonstrated.

Designing polymersomes with surface-integrated nanoparticles through hierarchical phase separation

Polymersomes with surface-integrated nanoparticles, in which a smaller sphere is attached to a larger capsule, are typically formed through complex processes like membrane deformation, polymerization, or membrane functionalization. This complexity restricts facile application of this unusual topology, for example in drug delivery or nanomotor science. Our study introduces a robust method for crafting polymersomes with surface-integrated nanoparticles using a hierarchical phase separation approach. By co-assembling block copolymers with aromatic aggregation-induced emission (AIE) moieties as side chains and photothermal-responsive guest molecules (PTM), spontaneous sequential phase separation processes occur that lead to their controlled formation. Polymer-rich liquid droplets form first, followed by internal phase separation of the guest molecules, which determines the formation of asymmetric morphology. This mechanism is elucidated in detail using liquid-phase transmission and cryogenic transmission electron microscopy (LP-TEM and cryo-TEM) and corroborated by theoretical simulations of the interaction forces between the block copolymers and guest molecules. Finally, the application potential of polymersomes with surface-integrated nanoparticles as nanomotors is demonstrated.

Micro- and Nanomotors: Engineered Tools for Targeted and Efficient Biomedicine

Over the past two decades, nanotechnology has made significant progress toward the development and applications of micromotors (MMs) and nanomotors (NMs). Characterized by their capability to self-propel and swim in fluids, they have emerged as promising tools in various fields, particularly in biomedicine. This Review presents an overview of the current state of MMs and NMs, their motion in viscous media and complex environments, their interaction with biological barriers, and potential therapeutical applications. We identify the choice of appropriate administration routes to reach their target location as a key aspect of the success of MMs and NMs in biomedical applications. Looking ahead, we envision NMs playing a key role in treating diverse medical disorders, as recent proof-of-concept in vivo studies demonstrate their distinct capabilities and versatility. However, addressing regulatory, scalability, biocompatibility, and safety concerns remains imperative for the successful translation of NMs into clinical trials and industrial-scale production. This work provides a guideline for researchers, guiding them through the current landscape, challenges, and prospects of using MMs and NMs in biomedicine, thereby encouraging their responsible development and positioning in the future of nanomedicine. Furthermore, we outline critical areas for further research, including studies on biocompatibility, safety, and methods to overcome physical obstacles.

Hybrid Biomembrane-Functionalized Nanorobots Penetrate the Vitreous Body of the Eye for the Treatment of Retinal Vein Occlusion

Intravitreal injections of antivascular endothelial growth factor (VEGF) agents are the primary method for treating retinal vein occlusion (RVO). However, the complex structure of eye anatomy presents ocular barriers that impede drug delivery. Additionally, these drugs only manage the complications associated with RVO and fail to address the underlying cause of vessel occlusions. Here, we describe a method that utilizes functionalized magnetically driven nanorobots to overcome ocular barriers and treat RVO. These nanorobots are developed using a hybrid biomembrane that combines stem cell membranes with liposome-derived membranes, enveloping perfluorohexane, iron oxide nanoparticles, and l-arginine. After intravitreal injection, the nanorobots can move directionally through and penetrate the vitreous body to reach the retina, driven by an external magnetic field. Subsequently, the nanorobots actively target the inflammation sites at occluded vessels due to the presence of stem cell membranes. In a rat model of RVO, enhanced targeting and accumulation in ischemic retinal vessels were demonstrated following intravitreal injections. Furthermore, the application of ultrasound triggers the release of l-arginine at the site of occlusion, stimulating the production of nitric oxide, which promotes vasodilation and restores blood flow, thereby achieving excellent therapeutic efficacy for RVO. We believe these methods hold significant promise for overcoming challenges in ocular drug delivery and effectively treating RVO in clinical applications.

Metareview: a survey of active matter reviews

In the past years, the amount of research on active matter has grown extremely rapidly, a fact that is reflected in particular by the existence of more than 1000 reviews on this topic. Moreover, the field has become very diverse, ranging from theoretical studies of the statistical mechanics of active particles to applied work on medical applications of microrobots and from biological systems to artificial swimmers. This makes it very difficult to get an overview over the field as a whole. Here, we provide such an overview in the form of a metareview article that surveys the existing review articles and books on active matter. Thereby, this article provides a useful starting point for finding literature about a specific topic.

Magnetic Micro/nanorobots in Cancer Theranostics: From Designed Fabrication to Diverse Applications

Cancer poses a substantial threat and a serious challenge to public human health, driving the promotion of sophisticated technologies for cancer therapy. While conventional chemotherapy has bottlenecks such as low delivery efficiency, strong toxic side effects, and tumor enrichment barriers, magnetic micro/nanorobots (MNRs) emerge as promising therapeutic candidates that provide alternative strategies for cancer therapy. MNR is a kind of human-made machine that is micro- or nanosized, is reasonably designed, and performs command tasks through self-actuated or externally controlled propulsion mechanisms, which can be potentially applied in cancer theranostics. Here, this review first introduces the components that constitute a typical magnetic MNR, including the body part, the driving part, the control part, the function part, and the sensing part. Subsequently, this review elucidates representative fabrication methods to construct magnetic MNRs from top-down approaches to bottom-up approaches, covering injection molding, self-rolling, melt electrospinning writing, deposition, biotemplate method, lithography, assembling, 3D printing, and chemical synthesis. Furthermore, this review focuses on multiple applications of magnetic MNRs facing cancer diagnosis and treatment, encompassing imaging, quantification, drug release, synergy with typical therapies, cell manipulation, and surgical assistance. Then, this review systematically elaborates on the biocompatibility and biosafety of magnetic MNRs. Finally, the challenges faced by magnetic MNRs are discussed alongside future research directions. This review is intended to provide scientific guidance that may improve the comprehension and cognition of cancer theranostics through the platform of magnetic MNRs, promoting and prospering the practical application development of magnetic MNRs.

NIR-II Fluorescent Thermophoretic Nanomotors for Superficial Tumor Photothermal Therapy

Peritumoral subcutaneous injection has been highly envisioned as an efficient yet low-risk administration of photothermal agents for superficial tumor photothermal therapy. However, obstructed by complex subcutaneous tissue, the delivery of injected photothermal agents to the specific tumor remains a critical issue. Herein, the study reports a polydopamine (PDA)-encapsulated spherical core/shell nanomotor with fluorescent indocyanine green (ICG) immobilized on its PDA shell. Upon the first near-infrared (NIR-I) irradiation, this motor can generate favorable photothermal heat, and meantime, emit a robust ICG fluorescence in the second near-infrared window (NIR-II). The heat turns the motor into an active photothermal agent able to perform thermophoretic propulsion along the irradiation direction in subcutaneous tissue, while the ICG fluorescence can direct the subcutaneous propulsion of motors toward specific tumor through real-time NIR-II imaging. These functions endow the motor with the ability of moving to tumor after being injected at peritumoral site, enabling an enhanced photothermal therapy (PTT). The results demonstrated herein suggest an integrated nanorobotic tool for the superficial PTT using peritumoral administration, highlighting an NIR-II imaging-directed subcutaneous propulsion.

Urease-powered micro/nanomotors: Current progress and challenges

Enzyme-powered micro/nanomotors (MNMs) (EMNMs) use natural enzymes to facilitate the decomposition of fuels, including hydrogen peroxide (H2O2), glucose, triglycerides, and urea to provide power. EMNMs can achieve self-propulsion through the in situ utilization of biofuels without additional fuels, exhibiting excellent biocompatibility and significant potential for application in the biomedical field. Compared with H2O2, which may cause oxidative damage to the body, urea exhibits superior biosafety characteristics. Presently, urease-powered MNMs (UMNMs) have made notable progress in their applications in the biomedical field and have garnered considerable attention from researchers. In this review, we present the latest advancements in the biomedical field of UMNMs, primarily focusing on: 1) diverse materials used for constructing the fundamental framework of motors; 2) control of motor movement through the regulation of enzymatic reaction rates; and 3) research directions for the clinical application of motors, including in vivo imaging, biomarker detection, cancer treatment, optical therapy, overcoming biological barriers, antibacterial interventions, antithrombotic strategies, and gastric disease management. Despite showing immense potential in biomedical applications, there are still several challenges impeding its practical implementation, such as maintaining activity in the in vivo environment while accurately targeting specific sites to achieve the desired clinical therapeutic effects.

Hybrid Zwitterionic Hydrogels with Encoded Differential Swelling and Programmed Deformation for Small-Scale Robotics

Stimuli-responsive shape-morphing hydrogels with self-healing and tunable physiochemical properties are excellent candidates for functional building blocks of untethered small-scale soft robots. With mechanical properties similar to soft organs and tissues, such robots enable minimally invasive medical procedures, such as cargo/cell transportation. In this work, responsive hydrogels based on zwitterionic/acrylate chemistry with self-healing and stimuli-responsiveness are synthesized. Such hydrogels are then judiciously cut and pasted to form hybrid constructs with predetermined swelling and elastic anisotropy. This method is used to program hydrogel constructs with predetermined 2D-to-3D deformation upon exposure to different environmental ionic strengths. Untethered soft robotic functionalities are demonstrated, such as actuation, magnetic locomotion, and targeted transport of soft and light cargo in flooded media. The proposed hydrogel expands the repertoire of functional materials for fabricating small-scale soft robots.

Dual-driven biodegradable nanomotors for enhanced cellular uptake

Hybrid nano-sized motors with navigation and self-actuation capabilities have emerged as promising nanocarriers for a wide range of delivery, sensing, and diagnostic applications due to their unique ability to achieve controllable locomotion within a complex biological environment such as tissue. However, most current nanomotors typically operate using a single driving mode, whereas propulsion induced by both external and local stimuli could be more beneficial to achieve efficient motility in a biomedical setting. In this work, we present a hybrid nanomotor by functionalizing biodegradable stomatocytes with platinum nanoparticles (Pt NPs). These Pt NPs enable two distinct propulsion mechanisms. First, near-infrared (NIR) laser irradiation causes plasmonic heating, which, due to the asymmetric shape of the stomatocytes, creates a temperature gradient around the nanomotors. Second, the catalytic properties of the Pt NPs allow them to convert hydrogen peroxide into water and oxygen, generating a chemical gradient that serves as an additional driving force. Hydrogen peroxide is thereby locally produced from endogenous glucose by a co-encapsulated enzyme, glucose oxidase. The motile features are employed to achieve enhanced accumulation within tumor cells. This nanomotor design offers a versatile approach for developing dual stimuli-responsive nanomotors that operate more effectively in complex environments.

Microwave-Responsive Engineered Platelet Microneedle Patch for Deep Tumor Penetration and Precision Therapy

Controllable and precise delivery of therapeutic agents is critical for effective tumor therapy. However, tumor targeting and the deep penetration of drugs remain among the most challenging issues in achieving controlled delivery. Herein, a novel engineered platelet microneedle patch with a microwave-responsive magnetic biometal-organic framework is proposed to facilitate the combination of the engineered platelet and microwave hyperthermia, enhancing deep drug penetration into tumors and enabling precision therapy. The prepared magnetic biometal-organic framework as nanomedicine exhibits excellent microwave thermal effects. The engineered platelets could be activated in the tumor microenvironment to release PMPs and nanomedicines combined with microwave hyperthermia for enhancing both cell uptake and deep drug penetration into tumors. The developed separable microneedle patch system allows the microneedle tip to be quickly detached from the backing layer and retained within the target tissue for repeated local cancer hyperthermia treatments. By integration of engineered platelets into the microneedle patch, the transdermal deep delivery of drugs could be effectively enhanced for local microwave thermochemotherapy of tumors. This work represents the first attempt to graft microwave-responsive inorganic nanomedicines onto platelets as cell drugs, offering a novel strategy for precise drug delivery activated by microwave thermal therapy.

Advancements in Micro/Nanorobots in Medicine: Design, Actuation, and Transformative Application

In light of the ongoing technological transformation, embracing advancements that foster shared benefits is essential. Nanorobots, a breakthrough within nanotechnology, have demonstrated significant potential in fields such as medicine, where diagnostic and therapeutic applications are the primary focus areas. This review provides a comprehensive overview of nanotechnology, robots, and their evolving role in medical applications, particularly highlighting the use of nanorobots. Various design strategies and operational principles, including sensors, actuators, and nanocontrollers, are discussed based on prior research. Key nanorobot medical applications include biomedical imaging, biosensing, minimally invasive surgery, and targeted drug delivery, each utilizing advanced actuation technologies to enhance precision. The paper further examines recent progress in micro/nanorobot actuation and addresses important considerations for the future, including biocompatibility, control, navigation, delivery, targeting, safety, and ethical implications. This review offers a holistic perspective on how nanorobots can reshape medical practices, paving the way for precision medicine and improved patient outcomes.

Translational nanorobotics breaking through biological membranes

In the dynamic realm of translational nanorobotics, the endeavor to develop nanorobots carrying therapeutics in rational in vivo applications necessitates a profound understanding of the biological landscape of the human body and its complexity. Within this landscape, biological membranes stand as critical barriers to the successful delivery of therapeutic cargo to the target site. Their crossing is not only a challenge for nanorobotics but also a pivotal criterion for the clinical success of therapeutic-carrying nanorobots. Nevertheless, despite their urgency, strategies for membrane crossing in translational nanorobotics remain relatively underrepresented in the scientific literature, signaling an opportunity for further research and innovation. This review focuses on nanorobots with various propulsion mechanisms from chemical and physical to hybrid mechanisms, and it identifies and describes four essential biological membranes that represent the barriers needed to be crossed in the therapeutic journey of nanorobots in in vivo applications. First is the entry point into the blood stream, which is the skin or mucosa or intravenous injection; next is the exit from the bloodstream across the endothelium to the target site; further is the entry to the cell through the plasma membrane and, finally, the escape from the lysosome, which otherwise destroys the cargo. The review also discusses design challenges inherent in translating nanorobot technologies to real-world applications and provides a critical overview of documented membrane crossings. The aim is to underscore the need for further interdisciplinary collaborations between chemists, materials scientists and chemical biologists in this vital domain of translational nanorobotics that has the potential to revolutionize the field of precision medicine.

Programmable assemblies of photothermal anisotropic micromotors for multimodal motion

Light-driven micromotors with multiple motion modes offer significantly greater application potential than single-mode micromotors. However, achieving such versatility often requires complex structural designs and precise light focusing on specific micromotor regions, presenting challenges for dynamic operations and microscale precisions. This study introduces programmable assemblies of anisotropic micromotors driven by the photothermal Marangoni effect, produced in bulk via microfluidic technology. Under full-area near-infrared (NIR) irradiation, the micromotor exhibits multiple motion modes, including translation and revolution, while micromotor assemblies display additional rotational motion. Self-assembly of these micromotors is highly controllable and programmable, enabling easy customization of assembled structures to achieve desired motion modes. These features are expected to advance the development of various intelligent self-propelling systems, using multimodal individual micromotors as foundational building blocks.

Advances in micro-/nanorobots for cancer diagnosis and treatment: propulsion mechanisms, early detection, and cancer therapy

In recent years, medical micro-/nanorobots (MNRs) have emerged as a promising technology for diagnosing and treating malignant tumors. MNRs enable precise, targeted actions at the cellular level, addressing several limitations of conventional cancer diagnosis and treatment, such as insufficient early diagnosis, nonspecific drug delivery, and chemoresistance. This review provides an in-depth discussion of the propulsion mechanisms of MNRs, including chemical fuels, external fields (light, ultrasound, magnetism), biological propulsion, and hybrid methods, highlighting their respective advantages and limitations. Additionally, we discuss novel approaches for tumor diagnosis, precision surgery, and drug delivery, emphasizing their potential clinical applications. Despite significant advancements, challenges such as biocompatibility, propulsion efficiency, and clinical translation persist. This review examines the current state of MNR applications and outlines future directions for their development, with the aim of enhancing their diagnostic and therapeutic efficacy and facilitating their integration into clinical practice.

Magnetically driven bionic nanorobots enhance chemotherapeutic efficacy and the tumor immune response via precise targeting

We developed magnetically driven bionic drug-loaded nanorobots (MDNs) to accurately target tumors and deliver chemotherapy agents using a customized three-dimensional (3D) magnetic manipulation platform (MMP) system to precisely control their movement mode. MDNs were based on polyethylene glycol-modified homogeneous ultrasmall iron oxide nanoparticles (7.02 ± 0.18 nm). Doxorubicin (12% ± 2% [w/w]) was encapsulated in MDNs by an imide bond. MDNs could imitate the movement mode of a school of wild herrings (e.g., re-dispersion/arrangement/vortex/directional movement) to adapt to the changing and complex physiological environment through the 3D MMP system. MDNs overcame blood flow resistance and biological barriers using optimized magnetic driving properties according to in vivo imaging (magnetic resonance imaging and fluorescence) and histopathology. The performance of fabricated MDNs was verified through cells and tumor-bearing mouse models. The MDNs showed high efficiency of drug delivery and targeting at the tumor site (>10-fold), lower toxicity than free doxorubicin (5 mg/kg body weight), activated immune response in the tumor site, and significantly lengthened survival for mice. The synergistic interaction between MDNs and the 3D MMP system underscores the immense potential of this drug delivery system, indicating a potential revolution in the field of tumor chemotherapy.

Hybrid Membrane Biomimetic Photothermal Nanorobots for Enhanced Chemodynamic-Chemotherapy-Immunotherapy

Glioblastoma multiforme (GBM) is a highly invasive and fatal brain tumor with a grim prognosis, where current treatment modalities, including postoperative radiotherapy and temozolomide chemotherapy, yield a median survival of only 15 months. The challenges of tumor heterogeneity, drug resistance, and the blood-brain barrier necessitate innovative therapeutic approaches. This study introduces a strategy employing biomimetic magnetic nanorobots encapsulated with hybrid membranes derived from platelets and M1 macrophages to enhance blood-brain barrier penetration and target GBM. The nanorobots encapsulate a polypyrrole/Fe3O4 nanocomplex (PPy@F) for photothermal therapy (PTT) and promote the Fenton reaction of Fe3O4 to generate chemodynamic therapy (CDT). Additionally, temozolomide and PD-L1 antibody (SNTSESF) act as chemotherapy drug and immune checkpoint inhibitor, respectively. The biomimetic design leverages the functional properties of cell membranes to improve the blood residence time and tumor targeting. The integration of PTT and CDT aims to transform "cold" tumors into "hot" tumors, thereby enhancing immunotherapeutic efficacy. This multifaceted approach, PTT, CT, CDT, and immune checkpoint blockade therapy, offers a promising strategy for the treatment of GBM.

Robotic Microcapsule Assemblies with Adaptive Mobility for Targeted Treatment of Rugged Biological Microenvironments

Microrobots are poised to transform biomedicine by enabling precise, noninvasive procedures. However, current magnetic microrobots, composed of solid monolithic particles, present fundamental challenges in engineering intersubunit interactions, limiting their collective effectiveness in navigating irregular biological terrains and confined spaces. To address this, we design hierarchically assembled microrobots with multiaxis mobility and collective adaptability by engineering the potential magnetic interaction energy between subunits to create stable, self-reconfigurable structures capable of carrying and protecting cargo internally. Using double emulsion templates and magnetic control techniques, we confine 10 nm iron oxide and 15 nm silica nanoparticles within the shell of 100 μm microcapsules that form multiunit robotic collectives. Unexpectedly, we find that asymmetric localization of iron oxide nanoparticles in the microcapsules enhances the intercapsule potential energy, creating stable connections under rotating magnetic fields without altering the magnetic susceptibility. These robotic microcapsule collectives exhibit emergent behaviors, self-reconfiguring into kinematic chain-like structures to traverse complex obstacles, arched confinements, and adhesive, rugged biological tissues that typically impede microscale systems. By harnessing these functions, we demonstrate targeted antifungal delivery using a localized biofilm model on mucosal tissues, showing effective killing ofCandida without binding or causing physical damage to host cells. Our findings show how hierarchical assembly can produce cargo-carrying microrobots with collective, self-adaptive mobility for traversing complex biological environments, advancing targeted delivery for biomedical applications.

Light-Programmable g-C3N4 Microrobots with Negative Photogravitaxis for Photocatalytic Antibiotic Degradation

Microrobots enhance contact with pollutants through their movement and flow-induced mixing, substantially improving wastewater treatment efficiency beyond traditional diffusion-limited methods. g-C3N4 is an affordable and environmentally friendly photocatalyst that has been extensively researched in various fields such as biomedicine and environmental remediation. However, compared to other photocatalytic materials like TiO2 and ZnO, which are widely used in the fabrication of micro- and nanorobots, research on g-C3N4 for these applications is still in its early stages. This work presents microrobots entirely based on g-C3N4 microtubes, which can initiate autonomous movement when exposed to ultraviolet and visible light. We observed distinct motion behaviors of the microrobots under light irradiation of different wavelengths. Specifically, under ultraviolet light, the microrobots exhibit negative photogravitaxis, while under visible light, they demonstrate a combination of 3-dimensional motion and 2-dimensional motion. Therefore, the wavelength of the light can be used for programming the motion style of the microrobots and subsequently their application. We show that the microrobots can effectively degrade the antibiotic tetracycline, displaying their potential for antibiotic removal. This exploration of autonomous motion behaviors under different wavelength conditions helps to expand research on g-C3N4-based microrobots and their potential for environmental remediation.

Inhalable biohybrid microrobots: a non-invasive approach for lung treatment

Amidst the rising prevalence of respiratory diseases, the importance of effective lung treatment modalities is more critical than ever. However, current drug delivery systems face significant limitations that impede their efficacy and therapeutic outcome. Biohybrid microrobots have shown considerable promise for active in vivo drug delivery, especially for pulmonary applications via intratracheal routes. However, the invasive nature of intratracheal administration poses barriers to its clinical translation. Herein, we report on an efficient non-invasive inhalation-based method of delivering microrobots to the lungs. A nebulizer is employed to encapsulate picoeukaryote algae microrobots within small aerosol particles, enabling them to reach the lower respiratory tract. Post nebulization, the microrobots retain their motility (~55 μm s-1) to help achieve a homogeneous lung distribution and long-term retention exceeding five days in the lungs. Therapeutic efficacy is demonstrated in a mouse model of acute methicillin-resistant Staphylococcus aureus pneumonia using this pulmonary inhalation approach to deliver microrobots functionalized with platelet membrane-coated polymeric nanoparticles loaded with vancomycin. These promising findings underscore the benefits of inhalable biohybrid microrobots in a setting that does not require anesthesia, highlighting the substantial translational potential of this delivery system for routine clinical applications.

Enhanced rotational diffusion and spontaneous rotation of an active Janus disk in a complex fluid

Active colloids and self-propelled particles moving through microstructured fluids can display different behavior compared to what is observed in simple fluids. As they are driven out of equilibrium in complex fluids they can experience enhanced translational and rotational diffusion as well as instabilities. In this work, we study the deterministic and the Brownian rotational dynamics of an active Janus disk propelling at a constant speed through a complex fluid. The interactions between the Janus disk and the complex fluid are modeled using a fluctuating advection-diffusion equation, which we solve using the finite element method. Motivated by experiments, we focus on the case of a complex fluid comprising molecules that are much smaller than the size of the active disk but much bigger than the solvent. Using numerical simulations, we elucidate the interplay between active motion and fluid microstructure that leads to enhanced rotational diffusion and spontaneous rotation observed in experiments employing Janus colloids in polymer solutions. By increasing the propulsion speed of the Janus disk, the simulations predict the onset of a spontaneous rotation and an increase of the rotational diffusion coefficient by orders of magnitude compared to its equilibrium value. These phenomena depend strongly on the number density of the constituents of the complex fluid and their interactions with the two sides of the Janus disk. Given the simplicity of our model, we expect that our findings will apply to a wide range of active systems propelling through complex media.

Living Therapeutics for Synergistic Hydrogen-Photothermal Cancer Treatment by Photosynthetic Bacteria

Hydrogen gas (H2) therapy, recognized for its inherent biosafety, holds significant promise as an anti-cancer strategy. However, the efficacy of H2 treatment modalities is compromised by their reliance on systemic gas administration or chemical reactions generation, which suffers from low efficiency, poor targeting, and suboptimal utilization. In this study, living therapeutics are employed using photosynthetic bacteria Rhodobacter sphaeroides for in situ H2 production combined with near-infrared (NIR) mediated photothermal therapy. Living R. sphaeroides exhibits strong absorption in the NIR spectrum, effectively converting light energy into thermal energy while concurrently generating H2. This dual functionality facilitates the targeted induction of tumor cell death and substantially reduces collateral damage to adjacent normal tissues. The findings reveal that integrating hydrogen therapy with photothermal effects, mediated through photosynthetic bacteria, provides a robust, dual-modality approach that enhances the overall efficacy of tumor treatments. This living therapeutic strategy not only leverages the therapeutic potential of both hydrogen and photothermal therapeutic modalities but also protects healthy tissues, marking a significant advancement in cancer therapy techniques.

Recent Advances in 4D Printing: A Review of Current Smart Materials, Technologies, and Drug Delivery Systems

Research on shape memory materials (SMM) or smart materials, along with advancements in printing technology, has transformed three-dimensional (3D) printing into what we now refer to as 4D printing. In this context, the addition of time as a fourth dimension enhances 3D printing. 4D printing involves the creation of 3D-printed objects that can change their shapes into complex geometries when influenced by external stimuli such as temperature, light, or pH over time. Currently, the use of smart materials in 4D printing is being explored extensively across various fields, including automotive, wearable electronics, soft robotics, food, mechatronics, textiles, biomedicine, and pharmaceuticals. A particular focus is on designing and fabricating smart drug delivery systems (DDS). This review discusses the evolution of 3D printing into 4D printing, highlighting the differences between the two. It covers the history and fundamentals of 4D printing, the integration of machine learning in 4D printing, and the types of materials used, such as stimuli-responsive materials (SRMs), hydrogels, liquid crystal elastomers, and active composites. Moreover, it presents various 4D printing techniques. Additionally, the review highlights several smart DDS that have been fabricated using 4D printing techniques. These include tablets, capsules, grippers, scaffolds, robots, hydrogels, microneedles, stents, bandages, dressings, and other devices aimed at esophageal retention, gastro-retention, and intravesical DDS. Lastly, it elucidates the current limitations and future directions of 4D printing.

A Lifetime of Catalytic Micro-/Nanomotors

Microscopic and nanoscopic motors, often referred to as micro-/nanomotors, are autonomous devices capable of converting chemical energy from their surroundings into mechanical motion or forces necessary for propulsion. These devices draw inspiration from natural biomolecular motor proteins, and in recent years, synthetic micro-/nanomotors have attracted significant attention. Among these, catalytic micro-/nanomotors have emerged as a prominent area of research. Despite considerable progress in their design and functionality, several obstacles remain, especially regarding the development of biocompatible materials and fuels, the integration of intelligent control systems, and the translation of these motors into practical applications. Thus, a comprehensive understanding of the current advancements in catalytic micro-/nanomotors is critical. This review aims to provide an in-depth overview of their fabrication techniques, propulsion mechanisms, key influencing factors, control methodologies, and potential applications. Furthermore, we examine their physical and hydrodynamic properties in fluidic environments to optimize propulsion efficiency. Lastly, we evaluate their biosafety and biocompatibility to facilitate their use in biological systems. The review also addresses key challenges and proposes potential solutions to advance their practical deployment.

Positive Chemotactic Flasklike Colloidal Motors Propelled by Rotary FoF1-ATP Synthases

Living microorganisms can perform directed migration for foraging in response to a chemoattractant gradient. We report a biomimetic strategy that rotary FoF1-ATPase (adenosine triphosphatase)-propelled flasklike colloidal motors exhibit positive chemotaxis resembling the chemotactic behavior of bacteria. The streamlined flasklike colloidal particles are fabricated through polymerization, expansion, surface rupture, and re-polymerizing nanoemulsions composed of triblock copolymers and ribose. The as-synthesized particles enable the incorporation of thylakoid vesicles into the cavity, ensuring a geometric asymmetric nanoarchitecture. The chemical gradient in the neck channel across flasklike colloidal motors facilitates autonomous movement at a speed of 1.19 μm/s in a ΔpH value of 4. Computer simulations reveal the self-actuated flasklike colloidal motors driven by self-diffusiophoretic force. These flasklike colloidal motors display positive directional motion along an adenosine diphosphate (ADP) concentration gradient during adenosine triphosphate (ATP) synthesis. The positive chemotaxis is ascribed that the phosphorylation reaction occurring inside colloidal motors generates 2 distinct phoretic torques at the bottom and the opening owing to the diffusion of ADP, thereby a continuous reorientation motion. Such a biophysical strategy that nanosized rotary protein molecular motors propel the directional movement of a flasklike colloidal motor holds promise for designing new types of biomedical swimming nanobots.