Light-Driven Microrobots for Targeted Drug Delivery

As a new micromanipulation tool with the advantages of small size, flexible movement and easy manipulation, light-driven microrobots have a wide range of prospects in biomedical fields such as drug targeting and cell manipulation. Recently, microrobots have been controlled in various ways, and light field has become a research hotspot by its advantages of noncontact manipulation, precise localization, fast response, and biocompatibility. It utilizes the force or deformation generated by the light field to precisely control the microrobot, and combines with the drug release technology to realize the targeted drug application. Therefore, this paper provides an overview of light-driven microrobots with drug targeting to provide new ideas for the manipulation of microrobots. Here, this paper briefly categorizes the driving mechanisms and materials of light-driven microrobots, which mainly include photothermal, photochemical, and biological. Then, typical designs of light-driven microrobots with different driving mechanisms and control strategies for multiple physical fields are summarized. Finally, the applications of microrobots in the fields of drug targeting and bioimaging are presented as well as the future prospects of light-driven microrobots in the biomedical field are demonstrated.

Laser-Based Selective Material Processing for Next-Generation Additive Manufacturing

The connection between laser-based material processing and additive manufacturing is quite deeply rooted. In fact, the spark that started the field of additive manufacturing is the idea that two intersecting laser beams can selectively solidify a vat of resin. Ever since, laser has been accompanying the field of additive manufacturing, with its repertoire expanded from processing only photopolymer resin to virtually any material, allowing liberating customizability. As a result, additive manufacturing is expected to take an even more prominent role in the global supply chain in years to come. Herein, an overview of laser-based selective material processing is presented from various aspects: the physics of laser-material interactions, the materials currently used in additive manufacturing processes, the system configurations that enable laser-based additive manufacturing, and various functional applications of next-generation additive manufacturing. Additionally, current challenges and prospects of laser-based additive manufacturing are discussed.

Human induced pluripotent stem cell-derived cardiac muscle rings for biohybrid self-beating actuator

Cardiac muscle, a subtype of striated muscle composing our heart, has garnered attention as a source of autonomously driven actuators due to its inherent capability for spontaneous contraction. However, conventional cardiac biohybrid robots have utilized planar (2D) cardiac tissue consisting of a thin monolayer of cardiac myotubes with a thickness of 3-5 μm, which can generate a limited contractile force per unit footprint. In this study, 3D cardiac muscle rings were proposed as robotic actuator units. These units not only exhibit higher contractile force per unit footprint compared to their 2D counterparts due to their increased height, but they can also be integrated into desired 3D configurations. We fabricated cardiac muscle rings from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), evaluated their driving characteristics, and verified the actuation effects by integrating them with artificial components. After the 10th day from culture, the cardiac muscle rings exhibited rhythmic spontaneous contraction and increased contractile force in response to stretching stimuli. Furthermore, after constructing a centimeter-sized biohybrid self-beating actuator with an antagonistic pair structure of cardiac muscle rings, the periodic antagonistic beating motion at its tail portion was confirmed. We believe that 3D cardiac muscle rings, possessing high contractile force and capable of being positioned within limited 3D space, can be used as potent biohybrid robotic actuators.

Fly Me to the Micron: Microtechnologies for Drosophila Research

Multicellular model organisms, such as Drosophila melanogaster (fruit fly), are frequently used in a myriad of biological research studies due to their biological significance and global standardization. However, traditional tools used in these studies generally require manual handling, subjective phenotyping, and bulk treatment of the organisms, resulting in laborious experimental protocols with limited accuracy. Advancements in microtechnology over the course of the last two decades have allowed researchers to develop automated, high-throughput, and multifunctional experimental tools that enable novel experimental paradigms that would not be possible otherwise. We discuss recent advances in microtechnological systems developed for small model organisms using D. melanogaster as an example. We critically analyze the state of the field by comparing the systems produced for different applications. Additionally, we suggest design guidelines, operational tips, and new research directions based on the technical and knowledge gaps in the literature. This review aims to foster interdisciplinary work by helping engineers to familiarize themselves with model organisms while presenting the most recent advances in microengineering strategies to biologists.

Biohybrid microrobots regulate colonic cytokines and the epithelium barrier in inflammatory bowel disease

Cytokines have been identified as key contributors to the development of inflammatory bowel disease (IBD), yet conventional treatments often prove inadequate and carry substantial side effects. Here, we present an innovative biohybrid robotic system, termed "algae-MΦNP-robot," for addressing IBD by actively neutralizing colonic cytokine levels. Our approach combines moving green microalgae with macrophage membrane-coated nanoparticles (MΦNPs) to efficiently capture proinflammatory cytokines "on the fly." The dynamic algae-MΦNP-robots outperformed static counterparts by enhancing cytokine removal through continuous movement, better distribution, and extended retention in the colon. This system is encapsulated in an oral capsule, which shields it from gastric acidity and ensures functionality upon reaching the targeted disease site. The resulting algae-MΦNP-robot capsule effectively regulated cytokine levels, facilitating the healing of damaged epithelial barriers. It showed markedly improved prevention and treatment efficacy in a mouse model of IBD and demonstrated an excellent biosafety profile. Overall, our biohybrid algae-MΦNP-robot system offers a promising and efficient solution for IBD, addressing cytokine-related inflammation effectively.

Intelligent micro/nanorobots based on biotemplates

Intelligent micro/nanorobots based on natural materials as biotemplates are considered to be some of the most promising robots in the future in the microscopic field. Due to the advantages of biotemplates such as unique structure, abundant resources, environmental friendliness, easy removal, low price, easy access, and renewability, intelligent micro/nanorobots based on biotemplates can be endowed with both excellent biomaterial activity and unique structural morphology through biotemplates themselves and specific functions through artificial micro/nanotechnology. Thus, intelligent micro/nanorobots show excellent application potential in various fields from biomedical applications to environmental remediation. In this review, we introduce the advantages of using natural biological materials as biotemplates to build intelligent micro/nanorobots, and then, classify the micro/nanorobots according to different types of biotemplates, systematically detail their preparation strategies and summarize their application prospects. Finally, in order to further advance the development of intelligent micro/nanorobots, we discuss the current challenges and future prospects of biotemplates. Intelligent micro/nanorobots based on biotemplates are a perfect combination of natural biotemplates and micro/nanotechnology, which is an important trend for the future development of micro/nanorobots. We hope this review can provide useful references for developing more intelligent, efficient and safe micro/nanorobots in the future.

Biohybrid microrobots locally and actively deliver drug-loaded nanoparticles to inhibit the progression of lung metastasis

Lung metastasis poses a formidable challenge in the realm of cancer treatment, with conventional chemotherapy often falling short due to limited targeting and low accumulation in the lungs. Here, we show a microrobot approach using motile algae for localized delivery of drug-loaded nanoparticles to address lung metastasis challenges. The biohybrid microrobot [denoted "algae-NP(DOX)-robot"] combines green microalgae with red blood cell membrane-coated nanoparticles containing doxorubicin, a representative chemotherapeutic drug. Microalgae provide autonomous propulsion in the lungs, leveraging controlled drug release and enhanced drug dispersion to exert antimetastatic effects. Upon intratracheal administration, algae-NP(DOX)-robots efficiently transport their drug payload deep into the lungs while maintaining continuous motility. This strategy leads to rapid drug distribution, improved tissue accumulation, and prolonged retention compared to passive drug-loaded nanoparticles and free drug controls. In a melanoma lung metastasis model, algae-NP(DOX)-robots exhibit substantial improvement in therapeutic efficacy, reducing metastatic burden and extending survival compared to control groups.

Steering Muscle-Based Bio-Syncretic Robot Through Bionic Optimized Biped Mechanical Design

Bio-syncretic robots consisting of artificial structures and living muscle cells have attracted much attention owing to their potential advantages, such as high drive efficiency, miniaturization, and compatibility. Motion controllability, as an important factor related to the main performance of bio-syncretic robots, has been explored in numerous studies. However, most of the existing bio-syncretic robots still face challenges related to the further development of steerable kinematic dexterity. In this study, a bionic optimized biped fully soft bio-syncretic robot actuated by two muscle tissues and steered with a direction-controllable electric field generated by external circularly distributed multiple electrodes has been developed. The developed bio-syncretic robot could realize wirelessly steerable motion and effective transportation of microparticle cargo on artificial polystyrene and biological pork tripe surfaces. This study may provide an effective strategy for the development of bio-syncretic robots and other related studies, such as nonliving soft robot design and muscle tissue engineering.

Recent advances in micro/nanomotors for antibacterial applications

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

Pillar electrodes embedded in the skeletal muscle tissue for selective stimulation of biohybrid actuators with increased contractile distance

Electrodes are crucial for controlling the movements of biohybrid robots, but their external placement outside muscle tissue often leads to inefficient and non-selective stimulation of nearby biohybrid actuators. To address this, we propose embedding pillar electrodes within the skeletal muscle tissue, resulting in enhanced contraction of the target muscle without affecting the neighbor tissue with a 4 mm distance. We use finite element method simulations to establish a selectivity model, correlating the VIE(volume integration of electric field intensity within muscle tissue) with actual contractile distances under different amplitudes of electrical pulses. The simulated selective index closely aligns with experimental results, showing the potential of pillar electrodes for effective and selective biohybrid actuator stimulation. In experiments, we validated that the contractile distance and selectivity achieved with these pillar electrodes exceed conventional Au rod electrodes. This innovation has promising implications for building biohybrid robots with densely arranged muscle tissue, ultimately achieving more human-like movements. Additionally, our selectivity model offers valuable predictive tools for assessing electrical stimulation effects with different electrode designs.

Heterogeneous Sensor-Carrier Microswarms for Collaborative Precise Drug Delivery toward Unknown Targets with Localized Acidosis

Micro/nanorobots hold the potential to revolutionize biomedicine by executing diverse tasks in hard-to-reach biological environments. Nevertheless, achieving precise drug delivery to unknown disease sites using swarming micro/nanorobots remains a significant challenge. Here we develop a heterogeneous swarm comprising sensing microrobots (sensor-bots) and drug-carrying microrobots (carrier-bots) with collaborative tasking capabilities for precise drug delivery toward unknown sites. Leveraging robust interspecific hydrodynamic interactions, the sensor-bots and carrier-bots spontaneously synchronize and self-organize into stable heterogeneous microswarms. Given that the sensor-bots can create real-time pH maps employing pH-responsive structural-color changes and the doxorubicin-loaded carrier-bots exhibit selective adhesion to acidic targets via pH-responsive charge reversal, the sensor-carrier microswarm, when exploring unknown environments, can detect and localize uncharted acidic targets, guide itself to cover the area, and finally deploy therapeutic carrier-bots precisely there. This versatile platform holds promise for treating diseases with localized acidosis and inspires future theranostic microsystems with expandability, task flexibility, and high efficiency.

Nano revolution: pioneering the future of water reclamation with micro-/nano-robots

Earth's freshwater reserves are alarmingly limited, with less than 1% readily available. Factors such as industrialisation, population expansion, and climate change are compounding the scarcity of clean water. In this context, self-driven, programmable micro- and nano-scale synthetic robots offer a potential solution for enhancing water monitoring and remediation. With the aid of these innovative robots, diffusion-limited reactions can be overcome, allowing for active engagement with target pollutants, such as heavy metals, dyes, nano- and micro-plastics, oils, pathogenic microorganisms, and persistent organic pollutants. Herein, we introduced and reviewed recent influential and advanced studies on micro-/nano-robots (MNR) carried out over the past decade. Typical works are categorized by propulsion modes, analyzing their advantages and drawbacks in detail and looking at specific applications. Moreover, this review provides a concise overview of the contemporary advancements and applications of micro-/nano-robots in water-cleaning applications.

Nanoarchitectonic Engineering of Thermal-Responsive Magnetic Nanorobot Collectives for Intracranial Aneurysm Therapy

Stent-assisted coiling is a main treatment modality for intracranial aneurysms (IAs) in clinics, but critical challenges remain to be overcome, such as exogenous implant-induced stenosis and reliance on antiplatelet agents. Herein, an endovascular approach is reported for IA therapy without stent grafting or microcatheter shaping, enabled by active delivery of thrombin (Th) to target aneurysms using innovative phase-change material (PCM)-coated magnetite-thrombin (Fe3O4-Th@PCM) FTP nanorobots. The nanorobots are controlled by an integrated actuation system of dynamic torque-force hybrid magnetic fields. With robust intravascular navigation guided by real-time ultrasound imaging, nanorobotic collectives can effectively accumulate and retain in model aneurysms constructed in vivo, followed by controlled release of the encapsulated Th for rapid occlusion of the aneurysm upon melting the protective PCM (thermally responsive in a tunable manner) through focused magnetic hyperthermia. Complete and stable aneurysm embolization is confirmed by postoperative examination and 2-week postembolization follow-up using digital subtraction angiography (DSA), contrast-enhanced ultrasound (CEUS), and histological analysis. The safety of the embolization therapy is assessed through biocompatibility evaluation and histopathology assays. This strategy, seamlessly integrating secure drug packaging, agile magnetic actuation, and clinical interventional imaging, avoids possible exogenous implant rejection, circumvents cumbersome microcatheter shaping, and offers a promising option for IA therapy.

Putting Hybrid Nanomaterials to Work for Biomedical Applications

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

4D Printed Soft Microactuator for Particle Manipulation via Surrounding Medium Variation

Soft actuators have assumed vital roles in a diverse number of research and application fields, driving innovation and transformative advancements. Using 3D molding of smart materials and combining these materials through structural design strategies, a single soft actuator can achieve multiple functions. However, it is still challenging to realize soft actuators that possess high environmental adaptability while capable of different tasks. Here, the response threshold of a soft actuator is modulated by precisely tuning the ratio of stimulus-responsive groups in hydrogels. By combining a heterogeneous bilayer membrane structure and in situ multimaterial printing, the obtained soft actuator deformed in response to changes in the surrounding medium. The response medium is suitable for both biotic and abiotic environments, and the response rate is fast. By changing the surrounding medium, the precise capture, manipulation, and release of micron-sized particles of different diameters in 3D are realized. In addition, static capture of a single red blood cell is realized using biologically responsive medium changes. Finally, the experimental results are well predicted using finite element analysis. It is believed that with further optimization of the structure size and autonomous navigation platform, the proposed soft microactuator has significant potential to function as an easy-to-manipulate multifunctional robot.

4D printing for biomedical applications

While three-dimensional (3D) printing excels at fabricating static constructs, it fails to emulate the dynamic behavior of native tissues or the temporal programmability desired for medical devices. Four-dimensional (4D) printing is an advanced additive manufacturing technology capable of fabricating constructs that can undergo pre-programmed changes in shape, property, or functionality when exposed to specific stimuli. In this Perspective, we summarize the advances in materials chemistry, 3D printing strategies, and post-printing methodologies that collectively facilitate the realization of temporal dynamics within 4D-printed soft materials (hydrogels, shape-memory polymers, liquid crystalline elastomers), ceramics, and metals. We also discuss and present insights about the diverse biomedical applications of 4D printing, including tissue engineering and regenerative medicine, drug delivery, in vitro models, and medical devices. Finally, we discuss the current challenges and emphasize the importance of an application-driven design approach to enable the clinical translation and widespread adoption of 4D printing.

Cargo Size Limits and Forces of Cell-Driven Microtransport

The integration of motile cells into biohybrid microrobots offers unique properties such as sensitive responses to external stimuli, resilience, and intrinsic energy supply. Here, biohybrid cell-cargo systems that are driven by amoeboid Dictyostelium discoideum cells are studied and how the cargo speed and the resulting viscous drag force scales with increasing radius of the spherical cargo particle are explored. Using a simplified geometrical model of the cell-cargo interaction, the findings toward larger cargo sizes, which are not accessible with the experimental setup, are extrapolated and a maximal cargo size is predicted beyond which active cell-driven movements will stall. The active forces exerted by the cells to move a cargo show mechanoresponsive adaptation and increase dramatically when challenged by an external pulling force, a mechanism that may become relevant when navigating cargo through complex heterogeneous environments.

Macrophages-Based Biohybrid Microrobots for Breast Cancer Photothermal Immunotherapy by Inducing Pyroptosis

Pyroptosis-based immunotherapy can escape drug resistance as well as inhibit metastasis. It is urgently required to develop a delivery platform to induce targeted tumor-specific pyroptosis for cancer immunotherapy. Herein, macrophages-based biohybrid microrobots (IDN@MC) are constructed with IR-macrophage and decitabine-loaded Metal-organic frameworks (DZNPs). The integration of fluorescence photosensitizers and pH-sensitive DZNPs endow the microrobots properties such as photothermal conversion, fluorescent navigation, targeted drug delivery, and controlled drug release. In light of the inherent tumor targeting, tumor accumulation of IDN@MC is facilitated. Due to the sustained release of decitabine from packaged DZNPs, the host macrophages are differentiated into M1 phenotypes to exert the tumor phagocytosis at the tumor site, directly transporting the therapeutic agents into cancer cells. With laser control, the rapid and durable caspase 3-cleaved gasdermin E (GSDME)-related tumor pyroptosis is achieved with combined photothermal-chemotherapy, releasing inflammatory factors such as lactate dehydrogenase and interleukin-18. Subsequently, the robust and adaptive immune response is primed with dendritic cell maturation to initiate T-cell clone expansion and modulation of the immune suppressive microenvironment, thus enhancing the tumor immunotherapy to inhibit tumor proliferation and metastasis. This macrophages-based biohybrid microrobot is an efficient strategy for breast cancer treatment to trigger photo-induced pyroptosis and augment the immune response.

Human Motor System-Based Biohybrid Robot-On-a-Chip for Drug Evaluation of Neurodegenerative Disease

Biohybrid robots have been developed for biomedical applications and industrial robotics. However, the biohybrid robots have limitations to be applied in neurodegenerative disease research due to the absence of a central nervous system. In addition, the organoids-on-a-chip has not yet been able to replicate the physiological function of muscle movement in the human motor system, which is essential for evaluating the accuracy of the drugs used for treating neurodegenerative diseases. Here, a human motor system-based biohybrid robot-on-a-chip composed of a brain organoid, multi-motor neuron spheroids, and muscle bundle on solid substrateis proposed to evaluate the drug effect on neurodegenerative diseases for the first time. The electrophysiological signals from the cerebral organoid induced the muscle bundle movement through motor neuron spheroids. To evaluate the drug effect on Parkinson's disease (PD), a patient-derived midbrain organoid is generated and incorporated into a biohybrid robot-on-a-chip. The drug effect on PD is successfully evaluated by measuring muscle bundle movement. The muscle bundle movement of PD patient-derived midbrain organoid-based biohybrid robot-on-a-chip is increased from 4.5 ± 0.99 µm to 18.67 ± 2.25 µm in response to levodopa. The proposed human motor system-based biohybrid robot-on-a-chip can serve as a standard biohybrid robot model for drug evaluation.

Biohybrid Microalgae Robots: Design, Fabrication, Materials, and Applications

The integration of microorganisms and engineered artificial components has shown considerable promise for creating biohybrid microrobots. The unique features of microalgae make them attractive candidates as natural actuation materials for the design of biohybrid microrobotic systems. In this review, microalgae-based biohybrid microrobots are introduced for diverse biomedical and environmental applications. The distinct propulsion and phototaxis behaviors of green microalgae, as well as important properties from other photosynthetic microalga systems (blue-green algae and diatom) that are crucial to constructing powerful biohybrid microrobots, will be described first. Then the focus is on chemical and physical routes for functionalizing the algae surface with diverse reactive materials toward the fabrication of advanced biohybrid microalgae robots. Finally, representative applications of such algae-driven microrobots are presented, including drug delivery, imaging, and water decontamination, highlighting the distinct advantages of these active biohybrid robots, along with future prospects and challenges.

Organisms as sensors in biohybrid entities as a novel tool for in-field aquatic monitoring

Rapidly intensifying global warming and water pollution calls for more efficient and continuous environmental monitoring methods. Biohybrid systems connect mechatronic components to living organisms and this approach can be used to extract data from the organisms. Compared to conventional monitoring methods, they allow for a broader data collection over long periods, minimizing the need for sampling processes and human labour. We aim to develop a methodology for creating various bioinspired entities, here referred to as 'biohybrids', designed for long-term aquatic monitoring. Here, we test several aspects of the development of the biohybrid entity: autonomous power source, lifeform integration and partial biodegradability. An autonomous power source was supplied by microbial fuel cells which exploit electron flows from microbial metabolic processes in the sediments. Here, we show that by stacking multiple cells, sufficient power can be supplied. We integrated lifeforms into the developed bioinspired entity which includes organisms such as the zebra musselDreissena polymorphaand water fleaDaphniaspp. The setups developed allowed for observing their stress behaviours. Through this, we can monitor changes in the environment in a continuous manner. The further development of this approach will allow for extensive, long-term aquatic data collection and create an early-warning monitoring system.

Skeletal muscle cells opto-stimulation by intramembrane molecular transducers

Optical stimulation and control of muscle cell contraction opens up a number of interesting applications in hybrid robotic and medicine. Here we show that recently designed molecular phototransducer can be used to stimulate C2C12 skeletal muscle cells, properly grown to exhibit collective behaviour. C2C12 is a skeletal muscle cell line that does not require animal sacrifice Furthermore, it is an ideal cell model for evaluating the phototransducer pacing ability due to its negligible spontaneous activity. We study the stimulation process and analyse the distribution of responses in multinuclear cells, in particular looking at the consistency between stimulus and contraction. Contractions are detected by using an imaging software for object recognition. We find a deterministic response to light stimuli, yet with a certain distribution of erratic behaviour that is quantified and correlated to light intensity or stimulation frequency. Finally, we compare our optical stimulation with electrical stimulation showing advantages of the optical approach, like the reduced cell stress.

Conductive 3D nano-biohybrid systems based on densified carbon nanotube forests and living cells

Conductive biohybrid cell-material systems have applications in bioelectronics and biorobotics. To date, conductive scaffolds are limited to those with low electrical conductivity or 2D sheets. Here, 3D biohybrid conductive systems are developed using fibroblasts or cardiomyocytes integrated with carbon nanotube (CNT) forests that are densified due to interactions with a gelatin coating. CNT forest scaffolds with a height range of 120-240 µm and an average electrical conductivity of 0.6 S/cm are developed and shown to be cytocompatible as evidenced from greater than 89% viability measured by live-dead assay on both cells on day 1. The cells spread on top and along the height of the CNT forest scaffolds. Finally, the scaffolds have no adverse effects on the expression of genes related to cardiomyocyte maturation and functionality, or fibroblast migration, adhesion, and spreading. The results show that the scaffold could be used in applications ranging from organ-on-a-chip systems to muscle actuators.

Graphical abstract

Bioinspired superhydrophobic SERS substrates for machine learning assisted miRNA detection in complex biomatrix below femtomolar limit

Surface-enhanced Raman spectroscopy (SERS) is an analytical method with high potential in the field of medicine. The design of SERS substrates, based on specific morphology and/or chemical modification, allow the recognition of the presence of specific analytes with precision close to a single-molecule detection limit. However, the SERS analysis of real samples is significantly complicated by the presence of a large number of "minor" molecules that can shield the signal from the target analyte and make it impossible to determine it in practice. In this work, an advanced SERS approach was used for the detection of cancer-related miRNA-21 in blood plasma, used as a molecular model background. The approach was based on the combination of the biomimetic plasmon-active SERS substrate, its tuned surface chemistry and advanced SERS data analysis, making use of artificial machine learning. In the first step, biomimetic SERS substrates were created using a butterfly wing as a starting template. The substrates were covered by thin Au layer and covalently grafted with hydrophobic chemical moieties to introduce superhydrophobic and water-adhesive properties. The self-concentration of the analyte on the substrates was achieved by minimizing the contact area between the analyte drop and the substrate, which is facilitated by surface superhydrophobicity and additionally enhanced by drop evaporation on the flipped over substrate. Due to the presence of cancer miRNA and blood plasma background, the measured SERS spectra represent a complex of interfering peaks. Thus, their interpretation was carried out using a specially trained machine learning model. As a result, reliable and repeatable quantitative detection of miRNAs below the femtomolar level (up to 10-16 M) on the background of human blood plasma becomes possible.

A potential paradigm in CRISPR/Cas systems delivery: at the crossroad of microalgal gene editing and algal-mediated nanoparticles

Microalgae as the photosynthetic organisms offer enormous promise in a variety of industries, such as the generation of high-value byproducts, biofuels, pharmaceuticals, environmental remediation, and others. With the rapid advancement of gene editing technology, CRISPR/Cas system has evolved into an effective tool that revolutionised the genetic engineering of microalgae due to its robustness, high target specificity, and programmability. However, due to the lack of robust delivery system, the efficacy of gene editing is significantly impaired, limiting its application in microalgae. Nanomaterials have become a potential delivery platform for CRISPR/Cas systems due to their advantages of precise targeting, high stability, safety, and improved immune system. Notably, algal-mediated nanoparticles (AMNPs), especially the microalgae-derived nanoparticles, are appealing as a sustainable delivery platform because of their biocompatibility and low toxicity in a homologous relationship. In addition, living microalgae demonstrated effective and regulated distribution into specified areas as the biohybrid microrobots. This review extensively summarised the uses of CRISPR/Cas systems in microalgae and the recent developments of nanoparticle-based CRISPR/Cas delivery systems. A systematic description of the properties and uses of AMNPs, microalgae-derived nanoparticles, and microalgae microrobots has also been discussed. Finally, this review highlights the challenges and future research directions for the development of gene-edited microalgae.

Towards multifunctional robotic pills

Robotic pills leverage the advantages of oral pharmaceutical formulations-in particular, convenient encapsulation, high loading capacity, ease of manufacturing and high patient compliance-as well as the multifunctionality, increasing miniaturization and sophistication of microrobotic systems. In this Perspective, we provide an overview of major innovations in the development of robotic pills-specifically, oral pills embedded with robotic capabilities based on microneedles, microinjectors, microstirrers or microrockets-summarize current progress and applicational gaps of the technology, and discuss its prospects. We argue that the integration of multiple microrobotic functions within oral delivery systems alongside accurate control of the release characteristics of their payload provides a basis for realizing sophisticated multifunctional robotic pills that operate as closed-loop systems.

Construction of micro-nano robots: living cells and functionalized biological cell membranes

Micro-nano robots have emerged as a promising research field with vast potential applications in biomedicine. The motor is the key component of micro-nano robot research, and the design of the motor is crucial. Among the most commonly used motors are those derived from living cells such as bacteria with flagella, sperm, and algal cells. Additionally, scientists have developed numerous self-adaptive biomimetic motors with biological functions, primarily cell membrane functionalized micromotors. This novel type of motor exhibits remarkable performance in complex media. This paper provides a comprehensive review of the structure and performance of micro-nano robots that utilize living cells and functionalized biological cell membranes. We also discuss potential practical applications of these mirco-nano robots as well as potential challenges that may arise in future development.

Biological Robots: Perspectives on an Emerging Interdisciplinary Field

Advances in science and engineering often reveal the limitations of classical approaches initially used to understand, predict, and control phenomena. With progress, conceptual categories must often be re-evaluated to better track recently discovered invariants across disciplines. It is essential to refine frameworks and resolve conflicting boundaries between disciplines such that they better facilitate, not restrict, experimental approaches and capabilities. In this essay, we address specific questions and critiques which have arisen in response to our research program, which lies at the intersection of developmental biology, computer science, and robotics. In the context of biological machines and robots, we explore changes across concepts and previously distinct fields that are driven by recent advances in materials, information, and life sciences. Herein, each author provides their own perspective on the subject, framed by their own disciplinary training. We argue that as with computation, certain aspects of developmental biology and robotics are not tied to specific materials; rather, the consilience of these fields can help to shed light on issues of multiscale control, self-assembly, and relationships between form and function. We hope new fields can emerge as boundaries arising from technological limitations are overcome, furthering practical applications from regenerative medicine to useful synthetic living machines.

Light-triggered cardiac microphysiological model

Light is recognized as an accurate and noninvasive tool for stimulating excitable cells. Here, we report on a non-genetic approach based on organic molecular phototransducers that allows wiring- and electrode-free tissue modulation. As a proof of concept, we show photostimulation of an in vitro cardiac microphysiological model mediated by an amphiphilic azobenzene compound that preferentially dwells in the cell membrane. Exploiting this optical based stimulation technology could be a disruptive approach for highly resolved cardiac tissue stimulation.

Artificial Muscles and Soft Robotic Devices for Treatment of End-Stage Heart Failure

Medical soft robotics constitutes a rapidly developing field in the treatment of cardiovascular diseases, with a promising future for millions of patients suffering from heart failure worldwide. Herein, the present state and future direction of artificial muscle-based soft robotic biomedical devices in supporting the inotropic function of the heart are reviewed, focusing on the emerging electrothermally artificial heart muscles (AHMs). Artificial muscle powered soft robotic devices can mimic the action of complex biological systems such as heart compression and twisting. These artificial muscles possess the ability to undergo complex deformations, aiding cardiac function while maintaining a limited weight and use of space. Two very promising candidates for artificial muscles are electrothermally actuated AHMs and biohybrid actuators using living cells or tissue embedded with artificial structures. Electrothermally actuated AHMs have demonstrated superior force generation while creating the prospect for fully soft robotic actuated ventricular assist devices. This review will critically analyze the limitations of currently available devices and discuss opportunities and directions for future research. Last, the properties of the cardiac muscle are reviewed and compared with those of different materials suitable for mechanical cardiac compression.

Drug-Free Antimicrobial Nanomotor for Precise Treatment of Multidrug-Resistant Bacterial Infections

Manufacturing heteronanostructures with specific physicochemical characteristics and tightly controllable designs is very appealing. Herein, we reported NIR-II light-driven dual plasmonic (AuNR-SiO₂-Cu₇S₄) antimicrobial nanomotors with an intended Janus configuration through the overgrowth of copper-rich Cu₇S₄ nanocrystals at only one high-curvature site of Au nanorods (Au NRs). These nanomotors were applied for photoacoustic imaging (PAI)-guided synergistic photothermal and photocatalytic treatment of bacterial infections. Both the photothermal performance and photocatalytic activity of the nanomotors are dramatically improved owing to the strong plasmon coupling between Au NRs and the Cu₇S₄ component and enhanced energy transfer. The motion behavior of nanomotors promotes transdermal penetration and enhances the matter-bacteria interaction. More importantly, the directional navigation and synergistic antimicrobial activity of the nanomotors could be synchronously driven by NIR-II light. The marriage of active motion and enhanced antibacterial activity resulted in the expected good antibacterial effects in an abscess infection mouse model.

Reconfigurable scaffolds for adaptive tissue regeneration

Tissue engineering and regenerative medicine have offered promising alternatives for clinical treatment of body tissue traumas, losses, dysfunctions, or diseases, where scaffold-based strategies are particularly popular and effective. Over the decades, scaffolds for tissue regeneration have been remarkably evolving. Nevertheless, conventional scaffolds still confront grand challenges in bio-adaptions in terms of both tissue-scaffold and cell-scaffold interplays, for example complying with complicated three-dimensional (3D) shapes of biological tissues and recapitulating the ordered cell regulation effects of native cell microenvironments. Benefiting from the recent advances in "intelligent" biomaterials, reconfigurable scaffolds have been emerging, demonstrating great promise in addressing the bio-adaption challenges through altering their macro-shapes and/or micro-structures. This mini-review article presents a brief overview of the cutting-edge research on reconfigurable scaffolds, summarizing the materials for forming reconfigurable scaffolds and highlighting their applications for adaptive tissue regeneration. Finally, the challenges and prospects of reconfigurable scaffolds are also discussed, shedding light on the bright future of next-generation reconfigurable scaffolds with upgrading adaptability.

Improving the Accuracy of a Biohybrid for Environmental Monitoring

Environmental monitoring should be minimally disruptive to the ecosystems that it is embedded in. Therefore, the project Robocoenosis suggests using biohybrids that blend into ecosystems and use life forms as sensors. However, such a biohybrid has limitations regarding memory-as well as power-capacities, and can only sample a limited number of organisms. We model the biohybrid and study the degree of accuracy that can be achieved by using a limited sample. Importantly, we consider potential misclassification errors (false positives and false negatives) that lower accuracy. We suggest the method of using two algorithms and pooling their estimations as a possible way of increasing the accuracy of the biohybrid. We show in simulation that a biohybrid could improve the accuracy of its diagnosis by doing so. The model suggests that for the estimation of the population rate of spinning Daphnia, two suboptimal algorithms for spinning detection outperform one qualitatively better algorithm. Further, the method of combining two estimations reduces the number of false negatives reported by the biohybrid, which we consider important in the context of detecting environmental catastrophes. Our method could improve environmental modeling in and outside of projects such as Robocoenosis and may find use in other fields.

A diatom-based biohybrid microrobot with a high drug-loading capacity and pH-sensitive drug release for target therapy

Targeted delivery is a promising mean for various biomedical applications, and various micro/nano robots have been created for drug delivery. Mesoporous silica has been shown to be successful as a drug delivery carrier in numerous studies. However, mesoporous silica preparation usually requires expensive and toxic chemicals, which limits its biomedical applications. Diatoms, as the naturally porous silica structure, are promising substitutes for the artificial mesoporous silica preparation. However, the current studies utilizing intact diatom frustules as drug delivery packets lack flexible and controllable locomotion. Herein, we propose a biohybrid magnetic microrobot based on Thalassiosira weissflogii frustules (TWFs) as a cargo packet for targeted drug delivery using a simple preparation method. Biohybrid microrobots are fabricated in large quantities by attaching magnetic nanoparticles (Fe₃O₄) to the surface of diatoms via electrostatic adsorption. Biohybrid microrobots are agile and controllable under the influence of external magnetic fields. They could be precisely controlled to follow specific trajectories or to move as swarms. The cooperation of the two motion modes of the biohybrid microrobots increased microrobots' environmental adaptability. Microrobots have a high drug-loading capacity and pH-sensitive drug release. In vitro cancer cell experiments further demonstrated the controllability of diatom microrobots for targeted drug delivery. The biohybrid microrobots reported in this paper convert natural diatoms into cargo packets for biomedical applications, which possess active and controllable properties and show huge potential for targeted anticancer therapy. STATEMENT OF SIGNIFICANCE: In this study, diatoms with good biocompatibility were used to prepare biohybrid magnetic microrobots. Compared with the current diatom-based systems for drug delivery, the microrobots prepared in this study for targeted drug delivery have more flexible motion characteristics and exhibit certain swarming behaviors. Under the same magnetic field strength, by changing the magnetic field frequency, the movement state of the diatoms can be changed to pass through the narrow channel, so that it has better environmental adaptability.

Biohybrid robots: recent progress, challenges, and perspectives

The past ten years have seen the rapid expansion of the field of biohybrid robotics. By combining engineered, synthetic components with living biological materials, new robotics solutions have been developed that harness the adaptability of living muscles, the sensitivity of living sensory cells, and even the computational abilities of living neurons. Biohybrid robotics has taken the popular and scientific media by storm with advances in the field, moving biohybrid robotics out of science fiction and into real science and engineering. So how did we get here, and where should the field of biohybrid robotics go next? In this perspective, we first provide the historical context of crucial subareas of biohybrid robotics by reviewing the past 10+ years of advances in microorganism-bots and sperm-bots, cyborgs, and tissue-based robots. We then present critical challenges facing the field and provide our perspectives on the vital future steps toward creating autonomous living machines.

MSCs-laden injectable self-healing hydrogel for systemic sclerosis treatment

As a novel cellular therapy, the anti-inflammatory and immunomodulatory virtues of mesenchymal stem cells (MSCs) make them promising candidates for systemic sclerosis (SSc) treatment. However, the clinical efficacy of this stratagem is limited because of the short persistence time, poor survival, and engraftment of MSCs after injection in vivo. Herein, we develop a novel MSCs-laden injectable self-healing hydrogel for SSc treatment. The hydrogel is prepared using N, O-carboxymethyl chitosan (CS-CM) and 4-armed benzaldehyde-terminated polyethylene glycol (PEG-BA) as the main components, imparting with self-healing capacity via the reversible Schiff-base connection between the amino and benzaldehyde groups. We demonstrate that the hydrogel laden with MSCs not only promoted the proliferation of MSCs and increased the cellular half-life in vivo, but also improve their immune-modulating functions. The tube formation assay indicates that the MSCs could significantly promote angiopoiesis. Moreover, the MSCs-laden hydrogel could inhibit fibrosis by modulating the synthesis of collagen and ameliorate disease progression in SSc disease model mice after subcutaneous injection of bleomycin. All these results highlight this novel MSCs-laden hydrogel and its distinctive functions in treatment of chronic SSc, indicating the additional potential to be used widely in the clinic.

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We proposed novel MSCs-laden injectable self-healing hydrogel for SSc treatment.

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The hydrogel was constructed by PEG-BA and CS-CM.

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MSCs-laden hydrogel promotes angiopoiesis and inhibit fibrosis.

Nanoparticle-modified microrobots for in vivo antibiotic delivery to treat acute bacterial pneumonia

Bioinspired microrobots capable of actively moving in biological fluids have attracted considerable attention for biomedical applications because of their unique dynamic features that are otherwise difficult to achieve by their static counterparts. Here we use click chemistry to attach antibiotic-loaded neutrophil membrane-coated polymeric nanoparticles to natural microalgae, thus creating hybrid microrobots for the active delivery of antibiotics in the lungs in vivo. The microrobots show fast speed (>110 µm s^-1) in simulated lung fluid and uniform distribution into deep lung tissues, low clearance by alveolar macrophages and superb tissue retention time (>2 days) after intratracheal administration to test animals. In a mouse model of acute Pseudomonas aeruginosa pneumonia, the microrobots effectively reduce bacterial burden and substantially lessen animal mortality, with negligible toxicity. Overall, these findings highlight the attractive functions of algae-nanoparticle hybrid microrobots for the active in vivo delivery of therapeutics to the lungs in intensive care unit settings.

Multicomponent and multifunctional integrated miniature soft robots

Miniature soft robots with elaborate structures and programmable physical properties could conduct micromanipulation with high precision as well as access confined and tortuous spaces, which promise benefits in medical tasks and environmental monitoring. To improve the functionalities and adaptability of miniature soft robots, a variety of integrated design and fabrication strategies have been proposed for the development of miniaturized soft robotic systems integrated with multicomponents and multifunctionalities. Combining the latest advancement in fabrication technologies, intelligent materials and active control methods enable these integrated robotic systems to adapt to increasingly complex application scenarios including precision medicine, intelligent electronics, and environmental and proprioceptive sensing. Herein, this review delivers an overview of various integration strategies applicable for miniature soft robotic systems, including semiconductor and microelectronic techniques, modular assembly based on self-healing and welding, modular assembly based on bonding agents, laser machining techniques, template assisted methods with modular material design, and 3D printing techniques. Emerging applications of the integrated miniature soft robots and perspectives for the future design of small-scale intelligent robots are discussed.

“Motile-targeting” drug delivery platforms based on micro/nanorobots for tumor therapy

Traditional drug delivery systems opened the gate for tumor-targeted therapy, but they generally took advantage of enhanced permeability and retention or ligand-receptor mediated interaction, and thus suffered from limited recognition range (<0.5 nm) and low targeting efficiency (0.7%, median). Alternatively, micro/nanorobots (MNRs) may act as emerging “motile-targeting” drug delivery platforms to deliver therapeutic payloads, thereby making a giant step toward effective and safe cancer treatment due to their autonomous movement and navigation in biological media. This review focuses on the most recent developments of MNRs in “motile-targeting” drug delivery. After a brief introduction to traditional tumor-targeted drug delivery strategies and various MNRs, the representative applications of MNRs in “motile-targeting” drug delivery are systematically streamlined in terms of the propelling mechanisms. Following a discussion of the current challenges of each type of MNR in biomedical applications, as well as future prospects, several promising designs for MNRs that could benefit in “motile-targeting” drug delivery are proposed. This work is expected to attract and motivate researchers from different communities to advance the creation and practical application of the “motile-targeting” drug delivery platforms.

Reciprocity of Cell Mechanics with Extracellular Stimuli: Emerging Opportunities for Translational Medicine

Human cells encounter dynamic mechanical cues in healthy and diseased tissues, which regulate their molecular and biophysical phenotype, including intracellular mechanics as well as force generation. Recent developments in bio/nanomaterials and microfluidics permit exquisitely sensitive measurements of cell mechanics, as well as spatiotemporal control over external mechanical stimuli to regulate cell behavior. In this review, the mechanobiology of cells interacting bidirectionally with their surrounding microenvironment, and the potential relevance for translational medicine are considered. Key fundamental concepts underlying the mechanics of living cells as well as the extracelluar matrix are first introduced. Then the authors consider case studies based on 1) microfluidic measurements of nonadherent cell deformability, 2) cell migration on micro/nano-topographies, 3) traction measurements of cells in three-dimensional (3D) matrix, 4) mechanical programming of organoid morphogenesis, as well as 5) active mechanical stimuli for potential therapeutics. These examples highlight the promise of disease diagnosis using mechanical measurements, a systems-level understanding linking molecular with biophysical phenotype, as well as therapies based on mechanical perturbations. This review concludes with a critical discussion of these emerging technologies and future directions at the interface of engineering, biology, and medicine.

Three-dimensional bioprinting: A cutting-edge tool for designing and fabricating engineered living materials

The design of engineered living materials (ELMs) is an emerging field developed from synthetic biology and materials science principles. ELMs are multi-scale bulk materials that combine the properties of self-healing and organism adaptability with the designed physicochemical or mechanical properties for functional applications in various fields, including therapy, electronics, and architecture. Among the many ELM design and manufacturing methods, three-dimensional (3D) bioprinting stands out for its precise control over the structure of the fabricated constructs and the spatial distribution of cells. In this review, we summarize the progress in the field, cell type and material selection, and the latest applications of 3D bioprinting to manufacture ELMs, as well as their advantages and limitations, hoping to deepen our understanding and provide new insights into ELM design. We believe that 3D bioprinting will become an important development direction and provide more contributions to this field.

Smart Film Actuators for Biomedical Applications

Taking inspiration from the extremely flexible motion abilities in natural organisms, soft actuators have emerged in the past few decades. Particularly, smart film actuators (SFAs) demonstrate unique superiority in easy fabrication, tailorable geometric configurations, and programmable 3D deformations. Thus, they are promising in many biomedical applications, such as soft robotics, tissue engineering, delivery system, and organ-on-a-chip. In this review, the latest achievements of SFAs applied in biomedical fields are summarized. The authors start by introducing the fabrication techniques of SFAs, then shift to the topology design of SFAs, followed by their material selections and distinct actuating mechanisms. After that, their biomedical applications are categorized in practical aspects. The challenges and prospects of this field are finally discussed. The authors believe that this review can boost the development of soft robotics, biomimetics, and human healthcare.

In situ integrated microrobots driven by artificial muscles built from biomolecular motors

Microrobots have been developed for applications in the submillimeter domain such as the manipulation of micro-objects and microsurgery. Rapid progress has been achieved in developing miniaturized components for microrobotic systems, resulting in a variety of functional microactuators and soft components for creating untethered microrobots. Nevertheless, the integration of microcomponents, especially the assembly of actuators and mechanical components, is still time-consuming and has inherent restrictions, thus limiting efficient fabrications of microrobots and their potential applications. Here, we propose a method for fabricating microrobots in situ inspired by the construction of microsystems in living organisms. In a microfluidic chip, hydrogel mechanical components and artificial muscle actuators are successively photopatterned from hydrogel prepolymer and biomolecular motors, respectively, and integrated in situ into functional microrobots. The proposed method allows the fast fabrication of microrobots through simple operations and affordable materials while providing versatile functions through the precise spatiotemporal control of in situ integration and reconfiguration of artificial muscles. To validate the method, we fabricated microrobots to elicit different motions and on-chip robots with unique characteristics for microfluidic applications. This study may establish a new paradigm for microrobot integration and lead to the production of unique biohybrid microrobots with various advantages.

Acoustic Fabrication of Living Cardiomyocyte-based Hybrid Biorobots

Organized assemblies of cells have demonstrated promise as bioinspired actuators and devices; still, the fabrication of such "biorobots" has predominantly relied on passive assembly methods that reduce design capabilities. To address this, we have developed a strategy for the rapid formation of functional biorobots composed of live cardiomyocytes. We employ tunable acoustic fields to facilitate the efficient aggregation of millions of cells into high-density macroscopic architectures with directed cell orientation and enhanced cell-cell interaction. These biorobots can perform actuation functions both through naturally occurring contraction-relaxation cycles and through external control with chemical and electrical stimuli. We demonstrate that these biorobots can be used to achieve controlled actuation of a soft skeleton and pumping of microparticles. The biocompatible acoustic assembly strategy described here should prove generally useful for cellular manipulation in the context of tissue engineering, soft robotics, and other applications.

Highly robust and soft biohybrid mechanoluminescence for optical signaling and illumination

Biohybrid is a newly emerging and promising approach to construct soft robotics and soft machines with novel functions, high energy efficiency, great adaptivity and intelligence. Despite many unique advantages of biohybrid systems, it is well known that most biohybrid systems have a relatively short lifetime, require complex fabrication process, and only remain functional with careful maintenance. Herein, we introduce a simple method to create a highly robust and power-free soft biohybrid mechanoluminescence, by encapsulating dinoflagellates, bioluminescent unicellular marine algae, into soft elastomeric chambers. The dinoflagellates retain their intrinsic bioluminescence, which is a near-instantaneous light response to mechanical forces. We demonstrate the robustness of various geometries of biohybrid mechanoluminescent devices, as well as potential applications such as visualizing external mechanical perturbations, deformation-induced illumination, and optical signaling in a dark environment. Our biohybrid mechanoluminescent devices are ultra-sensitive with fast response time and can maintain their light emission capability for weeks without special maintenance.

A Manta Ray-Inspired Biosyncretic Robot with Stable Controllability by Dynamic Electric Stimulation

Biosyncretic robots, which are new nature-based robots in addition to bionic robots, that utilize biological materials to realize their core function, have been supposed to further promote the progress in robotics. Actuation as the main operation mechanism relates to the robotic overall performance. Therefore, biosyncretic robots actuated by living biological actuators have attracted increasing attention. However, innovative propelling modes and control methods are still necessary for the further development of controllable motion performance of biosyncretic robots. In this work, a muscle tissue-based biosyncretic swimmer with a manta ray-inspired propelling mode has been developed. What is more, to improve the stable controllability of the biosyncretic swimmer, a dynamic control method based on circularly distributed multiple electrodes (CDME) has been proposed. In this method, the direction of the electric field generated by the CDME could be real-time controlled to be parallel with the actuation tissue of the dynamic swimmer. Therefore, the instability of the tissue actuation induced by the dynamic included angle between the tissue axis and electric field direction could be eliminated. Finally, the biosyncretic robot has demonstrated stable, controllable, and effective swimming, by adjusting the electric stimulation pulse direction, amplitude, and frequency. This work may be beneficial for not only the development of biosyncretic robots but also other related studies including bionic design of soft robots and muscle tissue engineering.

Electroconductive and Anisotropic Structural Color Hydrogels for Visual Heart-on-a-Chip Construction

Heart-on-a-chip plays an important role in revealing the biological mechanism and developing new drugs for cardiomyopathy. Tremendous efforts have been devoted to developing heart-on-a-chip systems featuring simplified fabrication, accurate imitation and microphysiological visuality. In this paper, the authors present a novel electroconductive and anisotropic structural color hydrogel by simply polymerizing non-close-packed colloidal arrays on super aligned carbon nanotube sheets (SACNTs) for visualized and accurate heart-on-a-chip construction. The generated anisotropic hydrogel consists of a colloidal array-locked hydrogel layer with brilliant structural color on one surface and a conductive methacrylated gelatin (GelMA)/SACNTs film on the other surface. It is demonstrated that the anisotropic morphology of the SACNTs could effectively induce the alignment of cardiomyocytes, and the conductivity of SACNTs could contribute to the synchronous beating of cardiomyocytes. Such consistent beating rhythm caused the deformation of the hydrogel substrates and dynamic shifts in structural color and reflection spectra of the whole hybrid hydrogels. More attractively, with the integration of such cardiomyocyte-driven living structural color hydrogels and microfluidics, a visualized heart-on-a-chip system with more consistent beating frequency has been established for dynamic cardiomyocyte sensing and drug screening. The results indicate that the electroconductive and anisotropic structural color hydrogels are potential for various biomedical applications.

Soft pneumatic actuators for mimicking multi-axial femoropopliteal artery mechanobiology

Tissue biomanufacturing aims to produce lab-grown stem cell grafts and biomimetic drug testing platforms but remains limited in its ability to recapitulate native tissue mechanics. The emerging field of soft robotics aims to emulate dynamic physiological locomotion, representing an ideal approach to recapitulate physiologically complex mechanical stimuli and enhance patient-specific tissue maturation. The kneecap's femoropopliteal artery (FPA) represents a highly flexible tissue across multiple axes during blood flow, walking, standing, and crouching positions, and these complex biomechanics are implicated in the FPA's frequent presentation of peripheral artery disease. We developed a soft pneumatically actuated (SPA) cell culture platform to investigate how patient-specific FPA mechanics affect lab-grown arterial tissues. Silicone hyperelastomers were screened for flexibility and biocompatibility, then additively manufactured into SPAs using a simulation-based design workflow to mimic normal and diseased FPA extensions in radial, angular, and longitudinal dimensions. SPA culture platforms were seeded with mesenchymal stem cells, connected to a pneumatic controller, and provided with 24-hour multi-axial exercise schedules to demonstrate the effect of dynamic conditioning on cell alignment, collagen production, and muscle differentiation without additional growth factors. Soft robotic bioreactors are promising platforms for recapitulating patient-, disease-, and lifestyle-specific mechanobiology for understanding disease, treatment simulations, and lab-grown tissue grafts.

Cell alignment modulated by surface nano-topography - Roles of cell-matrix and cell-cell interactions

The propensity of cells to align in particular directions is relevant to a number of areas, including tissue engineering and biohybrid robotics. Cell alignment is modulated through various extracellular conditions including surface topographies, mechanical cues from cell-matrix interactions, and cell-cell interactions. Understanding of these conditions provides guidance for desirable cellular structure constructions. In this study, we examine the roles of surface topographies and cell-cell interactions in inducing cell alignment. We employed wavy surface topographies at the nanometer scale as a model extracellular environment for cell culture. The results show that, within a certain range of wavelengths and amplitudes of the surface topographies, cell alignment is dependent on cell confluency. This dependence on both topology and confluency suggests interplay between cell-cell and cell-matrix interactions in inducing cell alignment. Images of sparsely distributed and confluent cells also demonstrated clear differences in the structures of their focal adhesion complexes. To understand this effect, we introduced anti-N-cadherin to cell culture to inhibit cell-cell interactions. The results show that, when anti-N-cadherin was applied, cells on wavy surfaces required greater confluency to achieve the same alignment compared to that in the absence of anti-N-cadherin. The understanding of the cell alignment mechanisms will be important in numerous potential applications such as scaffold design, tissue repair, and development of biohybrid robotic systems. STATEMENT OF SIGNIFICANCE: Cell alignment plays a critical role in numerous biological functions. Advances in tissue engineering utilizes cell alignment to restore, maintain, or even replace different types of biological tissues. The clinical impact that tissue engineering has made is facilitated by advancements in the understanding of interactions between scaffolds, biological factors, and cells. This work further elucidates the role of cell-cell interactions in promoting the organization of biological tissues.

Actuation-Augmented Biohybrid Robot by Hyaluronic Acid-Modified Au Nanoparticles in Muscle Bundles to Evaluate Drug Effects

Biohybrid robots, which comprise soft materials with biological components, have the potential to sense, respond, and adapt to changing environmental loads dynamically. Instead of humans and other living things, biohybrid robots can be used in various fields such as drug screening and toxicity assessment. In the actuation part, however, since a muscle cell-based biohybrid robot is limited in that the driving force is weak, it is difficult to evaluate drug and toxicological effects by distinguishing changes in the biohybrid robot's motion. To overcome this limitation, we introduced hyaluronic acid-modified gold nanoparticles (HA-AuNPs) into a muscle bundle-based biohybrid robot that moves forward in response to electrical stimulation. To enhance the actuation of muscle bundles, HA-AuNPs were embedded into the muscle bundles. The motion of the fabricated biohybrid robot was improved due to the enhanced differentiation and the improved electrical conductivity of muscle bundles by HA-AuNPs. In addition, the fabricated biohybrid robot exhibited huge changes in motion with respect to the addition of positive and negative inotropic drugs. The proposed biohybrid robot has the potential for neuromuscular disease drug screening by incorporating nervous tissues such as motor neuron organoids and brain organoids.