Magnetic Nanorobots as Maneuverable Immunoassay Probes for Automated and Efficient Enzyme Linked Immunosorbent Assay

Roadmap for Clinical Translation of Mobile Microrobotics

Medical microrobotics is an emerging field to revolutionize clinical applications in diagnostics and therapeutics of various diseases. On the other hand, the mobile microrobotics field has important obstacles to pass before clinical translation. This article focuses on these challenges and provides a roadmap of medical microrobots to enable their clinical use. From the concept of a "magic bullet" to the physicochemical interactions of microrobots in complex biological environments in medical applications, there are several translational steps to consider. Clinical translation of mobile microrobots is only possible with a close collaboration between clinical experts and microrobotics researchers to address the technical challenges in microfabrication, safety, and imaging. The clinical application potential can be materialized by designing microrobots that can solve the current main challenges, such as actuation limitations, material stability, and imaging constraints. The strengths and weaknesses of the current progress in the microrobotics field are discussed and a roadmap for their clinical applications in the near future is outlined.

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.

Multicolor-Assay-on-a-Chip Processed by Robotic Operation (MACpro) with Improved Diagnostic Accuracy for Field-Deployable Detection

The ability to deploy decentralized laboratories with autonomous and reliable disease diagnosis holds the potential to deliver accessible healthcare services for public safety. While microfluidic technologies provide precise manipulation of small fluid volumes with improved assay performance, their limited automation and versatility confine them to laboratories. Herein, we report the utility of multicolor assay-on-a-chip processed by robotic operation (MACpro), to address this unmet need. The MACpro platform comprises a robot-microfluidic interface and an eye-in-hand module that provides flexible yet stable actions to execute tasks in a programmable manner, such as the precise manipulation of the microfluidic chip along with different paths. Notably, MACpro shows improved detection performance by integrating the microbead-based antibody immobilization with enhanced target recognition and multicolor sensing via Cu2+-catalyzed plasmonic etching of gold nanorods for rapid and sensitive analyte quantification. Using interferon-gamma as an example, we demonstrate that MACpro completes a sample-to-answer immunoassay within 30 min and achieves a 10-fold broader dynamic range and a 10-fold lower detection limit compared to standard enzyme-linked immunosorbent assays (0.66 vs 5.2 pg/mL). MACpro extends the applications beyond traditional laboratories and presents an automated solution to expand diagnostic capacity in diverse settings.

Advancements in magnetic nanoparticle-based biosensors for point-of-care testing

The significance of point-of-care testing (POCT) in early clinical diagnosis and personalized patient care is increasingly recognized as a crucial tool in reducing disease outbreaks and improving patient survival rates. Within the realm of POCT, biosensors utilizing magnetic nanoparticles (MNPs) have emerged as a subject of substantial interest. This review aims to provide a comprehensive evaluation of the current landscape of POCT, emphasizing its growing significance within clinical practice. Subsequently, the current status of the combination of MNPs in the Biological detection has been presented. Furthermore, it delves into the specific domain of MNP-based biosensors, assessing their potential impact on POCT. By combining existing research and spotlighting pivotal discoveries, this review enhances our comprehension of the advancements and promising prospects offered by MNP-based biosensors in the context of POCT. It seeks to facilitate informed decision-making among healthcare professionals and researchers while also promoting further exploration in this promising field of study.

Progress in Procalcitonin Detection Based on Immunoassay

Procalcitonin (PCT) serves as a crucial biomarker utilized in diverse clinical contexts, including sepsis diagnosis and emergency departments. Its applications extend to identifying pathogens, assessing infection severity, guiding drug administration, and implementing theranostic strategies. However, current clinical deployed methods cannot meet the needs for accurate or real-time quantitative monitoring of PCT. This review aims to introduce these emerging PCT immunoassay technologies, focusing on analyzing their advantages in improving detection performances, such as easy operation and high precision. The fundamental principles and characteristics of state-of-the-art methods are first introduced, including chemiluminescence, immunofluorescence, latex-enhanced turbidity, enzyme-linked immunosorbent, colloidal gold immunochromatography, and radioimmunoassay. Then, improved methods using new materials and new technologies are briefly described, for instance, the combination with responsive nanomaterials, Raman spectroscopy, and digital microfluidics. Finally, the detection performance parameters of these methods and the clinical importance of PCT detection are also discussed.

Magnetic Lateral Ladder for Unidirectional Transport of Microrobots: Design Principles and Potential Applications of Cells-on-Chip

Functionalized microrobots, which are directionally manipulated in a controlled and precise manner for specific tasks, face challenges. However, magnetic field-based controls constrain all microrobots to move in a coordinated manner, limiting their functions and independent behaviors. This article presents a design principle for achieving unidirectional microrobot transport using an asymmetric magnetic texture in the shape of a lateral ladder, which the authors call the "railway track." An asymmetric magnetic energy distribution along the axis allows for the continuous movement of microrobots in a fixed direction regardless of the direction of the magnetic field rotation. The authors demonstrated precise control and simple utilization of this method. Specifically, by placing magnetic textures with different directionalities, an integrated cell/particle collector can collect microrobots distributed in a large area and move them along a complex trajectory to a predetermined location.  The authors can leverage the versatile capabilities offered by this texture concept, including hierarchical isolation, switchable collection, programmable pairing, selective drug-response test, and local fluid mixing for target objects. The results demonstrate the importance of microrobot directionality in achieving complex individual control. This novel concept represents significant advancement over conventional magnetic field-based control technology and paves the way for further research in biofunctionalized microrobotics.

Advanced Nanomaterials in Medical 3D Printing

3D printing is now recognized as a significant tool for medical research and clinical practice, leading to the emergence of medical 3D printing technology. It is essential to improve the properties of 3D-printed products to meet the demand for medical use. The core of generating qualified 3D printing products is to develop advanced materials and processes. Taking advantage of nanomaterials with tunable and distinct physical, chemical, and biological properties, integrating nanotechnology into 3D printing creates new opportunities for advancing medical 3D printing field. Recently, some attempts are made to improve medical 3D printing through nanotechnology, providing new insights into developing advanced medical 3D printing technology. With high-resolution 3D printing technology, nano-structures can be directly fabricated for medical applications. Incorporating nanomaterials into the 3D printing material system can improve the properties of the 3D-printed medical products. At the same time, nanomaterials can be used to expand novel medical 3D printing technologies. This review introduced the strategies and progresses of improving medical 3D printing through nanotechnology and discussed challenges in clinical translation.

Innovations in chemical degradation technologies for the removal of micro/nano-plastics in water: A comprehensive review

Micro/nanoplastics (M/NPs) in water have raised global concern due to their potential environmental risks. To reestablish a M/NPs free world, enormous attempts have been made toward employing chemical technologies for their removal in water. This review comprehensively summarizes the advances in chemical degradation approaches for M/NPs elimination. It details and discusses promising techniques, including photo-based technologies, Fenton-based reaction, electrochemical oxidation, and novel micro/nanomotors approaches. Subsequently, critical influence factors, such as properties of M/NPs and operating factors, are analyzed in this review specifically. Finally, it concludes by addressing the current challenges and future perspectives in chemical degradation. This review will provide guidance for scientists to further explore novel strategies and develop feasible chemical methods for the improved control and remediation of M/NPs in the future.

Application of micro/nanorobot in medicine

The development of micro/nanorobots and their application in medical treatment holds the promise of revolutionizing disease diagnosis and treatment. In comparison to conventional diagnostic and treatment methods, micro/nanorobots exhibit immense potential due to their small size and the ability to penetrate deep tissues. However, the transition of this technology from the laboratory to clinical applications presents significant challenges. This paper provides a comprehensive review of the research progress in micro/nanorobotics, encompassing biosensors, diagnostics, targeted drug delivery, and minimally invasive surgery. It also addresses the key issues and challenges facing this technology. The fusion of micro/nanorobots with medical treatments is poised to have a profound impact on the future of medicine.

Label-Free Biochemical Sensing Using Processed Optical Fiber Interferometry: A Review

Over the last 20 years, optical fiber-based devices have been exploited extensively in the field of biochemical sensing, with applications in many specific areas such as the food processing industry, environmental monitoring, health diagnosis, bioengineering, disease diagnosis, and the drug industry due to their compact, label-free, and highly sensitive detection. The selective and accurate detection of biochemicals is an essential part of biosensing devices, which is to be done through effective functionalization of highly specific recognition agents, such as enzymes, DNA, receptors, etc., over the transducing surface. Among many optical fiber-based sensing technologies, optical fiber interferometry-based biosensors are one of the broadly used methods with the advantages of biocompatibility, compact size, high sensitivity, high-resolution sensing, lower detection limits, operating wavelength tunability, etc. This Review provides a comprehensive review of the fundamentals as well as the current advances in developing optical fiber interferometry-based biochemical sensors. In the beginning, a generic biosensor and its several components are introduced, followed by the fundamentals and state-of-art technology behind developing a variety of interferometry-based fiber optic sensors. These include the Mach-Zehnder interferometer, the Michelson interferometer, the Fabry-Perot interferometer, the Sagnac interferometer, and biolayer interferometry (BLI). Further, several technical reports are comprehensively reviewed and compared in a tabulated form for better comparison along with their advantages and disadvantages. Further, the limitations and possible solutions for these sensors are discussed to transform these in-lab devices into commercial industry applications. At the end, in conclusion, comments on the prospects of field development toward the commercialization of sensor technology are also provided. The Review targets a broad range of audiences including beginners and also motivates the experts helping to solve the real issues for developing an industry-oriented sensing device.

Dual Functional Ultrasensitive Point-of-Care Clinical Diagnosis Using Metal-Organic Frameworks-Based Immunobeads

Sepsis is an acute systemic infectious syndrome with high fatality. Fast and accurate diagnosis, monitoring, and medication of sepsis are essential. We exploited the fluorescent metal-AIEgen frameworks (MAFs) and demonstrated the dual functions of protein detection and bacteria identification: (i) ultrasensitive point-of-care (POC) detection of sepsis biomarkers (100 times enhanced sensitivity); (ii) rapid POC identification of Gram-negative/positive bacteria (selective aggregation within 20 min). Fluorescent lateral flow immunoassays (LFAs) are convenient and inexpensive for POC tests. MAFs possess a large surface area, excellent photostability, high quantum yield (∼80%), and multiple active sites serving as protein binding domains for ultrasensitive detection of sepsis biomarkers (IL-6/PCT) on LFAs. The limit of detection (LOD) for IL-6/PCT is 0.252/0.333 pg/mL. Rapid appraisal of infectious bacteria is vital to guide the use of medicines. The dual-functional fluorescent MAFs have great potential in POC tests for the clinical diagnosis of bacterial infections.

Intelligent sensing based on active micro/nanomotors

In the microscopic world, synthetic micro/nanomotors (MNMs) can convert a variety of energy sources into driving forces to help humans perform a number of complex tasks with greater ease and efficiency. These tiny machines have attracted tremendous attention in the field of drug delivery, minimally invasive surgery, in vivo sampling, and environmental management. By modifying their surface materials and functionalizing them with bioactive agents, these MNMs can also be transformed into dynamic micro/nano-biosensors that can detect biomolecules in real-time with high sensitivity. The extensive range of operations and uses combined with their minuscule size have opened up new avenues for tackling intricate analytical difficulties. Here, in this review, various driving methods are briefly introduced, followed by a focus on intelligent detection techniques based on MNMs. And we discuss the distinctive advantages, current issues, and challenges associated with MNM-based intelligent detection. It is believed that the future advancements of MNMs will greatly impact the diagnosis, treatment, and prevention of diseases.

Micro-/nanoscale robotics for chemical and biological sensing

The field of micro-/nanorobotics has attracted extensive interest from a variety of research communities and witnessed enormous progress in a broad array of applications ranging from basic research to global healthcare and to environmental remediation and protection. In particular, micro-/nanoscale robots provide an enabling platform for the development of next-generation chemical and biological sensing modalities, owing to their unique advantages as programmable, self-sustainable, and/or autonomous mobile carriers to accommodate and promote physical and chemical processes. In this review, we intend to provide an overview of the state-of-the-art development in this area and share our perspective in the future trend. This review starts with a general introduction of micro-/nanorobotics and the commonly used methods for propulsion of micro-/nanorobots in solution, along with the commonly used methods in their fabrication. Next, we comprehensively summarize the current status of the micro/nanorobotic research in relevance to chemical and biological sensing (e.g., motion-based sensing, optical sensing, and electrochemical sensing). Following that, we provide an overview of the primary challenges currently faced in the micro-/nanorobotic research. Finally, we conclude this review by providing our perspective detailing the future application of soft robotics in chemical and biological sensing.

Advancements in artificial micro/nanomotors for nucleic acid biosensing: a review of recent progress

Artificial micro/nanomotors represent a class of well-designed tools that exhibit dynamic motion and remote-control capabilities, endowing them with the capacity to perform complex tasks at the micro/nanoscale. Their utilization in nucleic acid biosensing has been paid significant attention, owing to their ability to facilitate targeted delivery of detection probes to designated sites and enhance hybridization between detection probes and target nucleic acids, thereby improving the sensitivity and specificity of biosensing. Within this comprehensive overview, we elucidate the advancement of nucleic acid biosensing through the integration of micro/nanomotors over the past decade. In particular, we provide an in-depth exploration of the diverse applications of micro/nanomotors in nucleic acid biosensing, including fluorescence recovery-based biosensing, velocity change-based biosensing, and aggregation-enhanced biosensing. Additionally, we outline the remaining challenges that impede the practical application of artificial micro/nanomotors in nucleic acid detection, and offer personal insights into prospective avenues for future development. By overcoming these obstacles, we anticipate that artificial micro/nanomotors will revolutionize conventional nucleic acid detection methodologies, providing enhanced sensitivity and reduced diagnostic timeframes, thereby facilitating more effective disease diagnosis.

Biocompatible smart micro/nanorobots for active gastrointestinal tract drug delivery

INTRODUCTION

Oral delivery is the most commonly used route of drug administration owing to good patient compliance. However, the gastrointestinal (GI) tract contains multiple physiological barriers that limit the absorption efficiency of conventional passive delivery systems resulting in a low drug concentration reaching the diseased sites. Micro/nanorobots can convert energy to self-propulsive force, providing a novel platform to actively overcome GI tract barriers for noninvasive drug delivery and treatment.

AREAS COVERED

In this review, we first describe the microenvironments and barriers in the different compartments of the GI tract. Afterward, the applications of micro/nanorobots to overcome GI tract barriers for active drug delivery are highlighted and discussed. Finally, we summarize and discuss the challenges and future prospects of micro/nanorobots for further clinical applications.

EXPERT OPINION

Micro/nanorobots with the ability to autonomously propel themselves and to load, transport, and release payloads on demand are ideal carriers for active oral drug delivery. Although there are many challenges to be addressed, micro/nanorobots have great potential to introduce a new era of drug delivery for precision therapy.

Magnetic nanoprobe-enabled lateral flow assays: recent advances

In recent years, magnetic nanoparticle sensor technologies have attracted considerable interest in the point-of-care-testing (POCT) field, especially in lateral flow immunoassays (LFIAs). Although the visual signal of magnetic nanoparticles is reduced during an inspection, it can be compensated for by magnetic induction, and detection results can be quantified by magnetic sensors. Sensors that use magnetic nanoparticles (MNPs) as markers can overcome the high background noise of complex samples. In this study, MNP signal detection strategies are described from the perspectives of magnetoresistance, magnetic flux, frequency mixing technology, and magnetic permeability, and the principles and development of each technology are introduced in detail. Typical applications of magnetic nanoparticle sensor technologies are introduced. By describing the advantages and limitations of different sensing strategies, we highlight the development and improvement directions of different sensing strategies. In general, the future development of magnetic nanoparticle sensor technologies will be toward intelligent, convenient, and mobile high-performance detection equipment.

Responsive Magnetic Nanocomposites for Intelligent Shape-Morphing Microrobots

With the development of advanced biomedical theragnosis and bioengineering tools, smart and soft responsive microstructures and nanostructures have emerged. These structures can transform their body shape on demand and convert external power into mechanical actions. Here, we survey the key advances in the design of responsive polymer-particle nanocomposites that led to the development of smart shape-morphing microscale robotic devices. We overview the technological roadmap of the field and highlight the emerging opportunities in programming magnetically responsive nanomaterials in polymeric matrixes, as magnetic materials offer a rich spectrum of properties that can be encoded with various magnetization information. The use of magnetic fields as a tether-free control can easily penetrate biological tissues. With the advances in nanotechnology and manufacturing techniques, microrobotic devices can be realized with the desired magnetic reconfigurability. We emphasize that future fabrication techniques will be the key to bridging the gaps between integrating sophisticated functionalities of nanoscale materials and reducing the complexity and footprints of microscale intelligent robots.

Magnetic Non-Spherical Particles Inducing Vortices in Microchannel for Effective Mixing

Mixing in microfluidic channels is dominated by diffusion owing to the absence of chaotic flow. However, high-efficiency microscale mixing over short distances is desired for the development of lab-on-chip systems. Here, enhanced mixing in microchannels achieved using magnetic nonspherical particles (MNSPs), is reported. Benefiting from the nonspherical shape of the MNSPs, secondary vortices exhibiting cyclical characteristics appear in microchannels when the MNSPs rotate under an external magnetic field. Increasing the rotation rate enlarges the secondary vortices, expanding the mixing zone and enhancing the mixing, resulting in a mixing efficiency exceeding 0.9 at Re of 0.069-0.69. Complementary micro-particle image velocimetry (µPIV) for flow field analysis clarifies the mixing mechanism. In addition, a chaotic vortex area is generated in the presence of two MNSPs, which shortens the distance required for achieving an appropriate mixing efficiency. This study demonstrates the potential of employing MNSPs as efficient mixers in lab-on-chip devices.

Design of Raman reporter-embedded magnetic/plasmonic hybrid nanostirrers for reliable microfluidic SERS biosensors

Magnetic-based microfluidic SERS biosensors hold great potential in various biological analyses due to their integrated advantages including easy manipulation, miniaturization and ultrasensitivity. However, it remains challenging to collect reliable SERS nanoprobe signals for quantitative analysis due to the irregular aggregation of magnetic carriers in a microfluidic chamber. Here, magnetic/plasmonic hybrid nanostirrers embedded with a Raman reporter are developed as capture carriers to improve the reliability of microfluidic SERS biosensors. Experimental results revealed that SERS signals from magnetic hybrid nanostirrers could serve as microenvironment beacons of their irregular aggregation, and a signal filtering method was proposed through exploring the relationship between the intensity range of beacons and the signal reproducibility of SERS nanoprobes using interleukin 6 as a model target analyte. Using the signal filtering method, reliable SERS nanoprobe signals with high reproducibility could be picked out from similar microenvironments according to their beacon intensity, and then the influence of irregular aggregation of magnetic carriers on the SERS nanoprobe could be eliminated. The filtered SERS nanoprobe signals also exhibited excellent repeatability from independent tests, which lay a solid foundation for a reliable working curve and subsequent accurate bioassay. This study provides a simple but promising route for reliable microfluidic SERS biosensors, which will further promote their practical application in biological analysis.

MnO4--Triggered Immediate-Stable Real-Time Fluorescence Immunosensor with High Response Speed and Low Steady-State Error

Real-time chemical and biological sensing in vitro is important for application in health and environmental monitoring. Thus, a more rapid and stable detection method is urgently needed. Herein, an immediate-stable real-time fluorescent immunosensor with a high response speed (∼100%, <1 s) and approximately zero steady-state error is constructed. The developed sensor is based on the MnO₄^--triggered in situ immediate-stable fluorogenic reaction between dopamine and orcinol monohydrate to produce azamonardine (DMTM). The obtained DMTM is identified and characterized by high-resolution mass spectrometry, ¹H NMR spectroscopy, ¹³C NMR spectroscopy, and theoretical calculations. The present sensor achieves a highly sensitive detection of dopamine (DA) with a limit of detection (LOD) of 10 nM as well as alkaline phosphates (ALP) with an LOD of 0.1 mU/mL by using orcinol monohydrate phosphate sodium salt as a substrate. As a proof of concept, ALP-triggered fluorescence ELISA using cardiac troponin I (cTnI) as a model antigen target is further constructed. The developed real-time sensor achieves the detection of cTnI with an LOD of 0.05 ng/mL. Moreover, the sensor proposed by us is successfully applied to assess the cTnI level in clinical serum specimens and yields results consistent with those obtained by the commercial ELISA method. The immediate-stable real-time fluorescence immunosensor provides a promising and powerful platform for the trace detection of biomolecules in clinical diagnosis.

Mobile mechanical signal generator for macrophage polarization

The importance of mechanical signals in regulating the fate of macrophages is gaining increased attention recently. However, the recently used mechanical signals normally rely on the physical characteristics of matrix with non-specificity and instability or mechanical loading devices with uncontrollability and complexity. Herein, we demonstrate the successful fabrication of self-assembled microrobots (SMRs) based on magnetic nanoparticles as local mechanical signal generators for precise macrophage polarization. Under a rotating magnetic field (RMF), the propulsion of SMRs occurs due to the elastic deformation via magnetic force and hydrodynamics. SMRs perform wireless navigation toward the targeted macrophage in a controllable manner and subsequently rotate around the cell for mechanical signal generation. Macrophages are eventually polarized from M0 to anti-inflammatory related M2 phenotypes by blocking the Piezo1-activating protein-1 (AP-1）-CCL2 signaling pathway. The as-developed microrobot system provides a new platform of mechanical signal loading for macrophage polarization, which holds great potential for precise regulation of cell fate.

Ultrasensitive Homogeneous Detection of PCSK9 and Efficacy Monitoring of the PCSK9 Inhibitor Based on Proximity Hybridization-Dependent Chemiluminescence Imaging Immunoassay

Accurate quantification of proprotein convertase subtilisin/kexin type 9 (PCSK9) in serum before and after the medication is helpful in grasping the evolution of PCSK9-related disease and evaluating the efficacy of PCSK9 inhibitors. Conventional approaches for PCSK9 quantification suffered from complicated operations and low sensitivity. By integrating stimuli-responsive mesoporous silica nanoparticles, dual-recognition proximity hybridization, and T7 exonuclease-assisted recycling amplification, a novel homogeneous chemiluminescence (CL) imaging approach was proposed for ultrasensitive and convenient immunoassay of PCSK9. Owing to the intelligent design and signal amplification property, the whole assay was conducted without separation and rinsing, significantly simplifying the procedure and eliminating the errors associated with the professional operation; meanwhile, it showed linear ranges over 5 orders of magnitude and detection limit as low as 0.7 pg mL^-1. Parallel testing was allowed due to the imaging readout, which brought a maximum throughput of 26 tests h^-1. The proposed CL approach was applied to analyze PCSK9 from hyperlipidemia mice before and after the intervention of the PCSK9 inhibitor. Serum PCSK9 levels in the model group and the intervention group could be distinguished efficiently. The results were reliable compared to commercial immunoassay results and histopathologic findings. Thus, it could facilitate the monitoring of the serum PCSK9 level and the lipid-lowering effect of the PCSK9 inhibitor, showing promising potential in bioanalysis and pharmaceuticals.

Medical micro- and nanomotors in the body

Attributed to the miniaturized body size and active mobility, micro- and nanomotors (MNMs) have demonstrated tremendous potential for medical applications. However, from bench to bedside, massive efforts are needed to address critical issues, such as cost-effective fabrication, on-demand integration of multiple functions, biocompatibility, biodegradability, controlled propulsion and in vivo navigation. Herein, we summarize the advances of biomedical MNMs reported in the past two decades, with particular emphasis on the design, fabrication, propulsion, navigation, and the abilities of biological barriers penetration, biosensing, diagnosis, minimally invasive surgery and targeted cargo delivery. Future perspectives and challenges are discussed as well. This review can lay the foundation for the future direction of medical MNMs, pushing one step forward on the road to achieving practical theranostics using MNMs.

Magnetic micromixing for highly sensitive detection of glyphosate in tap water by colorimetric immunosensor

Glyphosate is the most widely used herbicide in the world and, in view of its toxicity, there is a quest for easy-to-use, but reliable methods to detect it in water. To address this issue, we realized a simple, rapid, and highly sensitive immunosensor based on gold coated magnetic nanoparticles (MNPs@Au) to detect glyphosate in tap water. Not only the gold shell provided a sensitive optical transduction of the biological signal - through the shift of the local surface plasmon resonance (LSPR) entailed by the nanoparticle aggregation -, but it also allowed us to use an effective photochemical immobilization technique to tether oriented antibodies straight on the nanoparticles surface. While such a feature led to aggregates in which the nanoparticles were at close proximity each other, the magnetic properties of the core offered us an efficient tool to steer the nanoparticles by a rotating magnetic field. As a result, the nanoparticle aggregation in presence of the target could take place at higher rate (enhanced diffusion) with significant improvement in sensitivity. As a matter of fact, the combination of plasmonic and magnetic properties within the same nanoparticles allowed us to realize a colorimetric biosensor with a limit of detection (LOD) of 20 ng∙L^-1.

Active therapy based on the byproducts of micro/nanomotors

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

Recent Advances in One-Dimensional Micro/Nanomotors: Fabrication, Propulsion and Application

Due to their tiny size, autonomous motion and functionalize modifications, micro/nanomotors have shown great potential for environmental remediation, biomedicine and micro/nano-engineering. One-dimensional (1D) micro/nanomotors combine the characteristics of anisotropy and large aspect ratio of 1D materials with the advantages of functionalization and autonomous motion of micro/nanomotors for revolutionary applications. In this review, we discuss current research progress on 1D micro/nanomotors, including the fabrication methods, driving mechanisms, and recent advances in environmental remediation and biomedical applications, as well as discuss current challenges and possible solutions. With continuous attention and innovation, the advancement of 1D micro/nanomotors will pave the way for the continued development of the micro/nanomotor field.

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.

Biocompatible micromotors for biosensing

Micro/nanomotors are nanoscale devices that have been explored in various fields, such as drug delivery, environmental remediation, or biosensing and diagnosis. The use of micro/nanomotors has grown considerably over the past few years, partially because of the advantages that they offer in the development of new conceptual avenues in biosensing. This is due to their propulsion and intermixing in solution compared with their respective static forms, which enables motion-based detection methods and/or decreases bioassay time. This review focuses on the impacts of micro/nanomotors on biosensing research in the last 2 years. An overview of designs for bioreceptor attachment to micro/nanomotors is given. Recent developments have focused on chemically propelled micromotors using external fuels, commonly hydrogen peroxide. However, the associated fuel toxicity and inconvenience of use in relevant biological samples such as blood have prompted researchers to explore new micro/nanomotor biosensing approaches based on biocompatible propulsion sources such as magnetic or ultrasound fields. The main advances in biocompatible propulsion sources for micro/nanomotors as novel biosensing platforms are discussed and grouped by their propulsion-driven forces. The relevant analytical applications are discussed and representatively illustrated. Moreover, envisioning future biosensing applications, the principal advantages of micro/nanomotor synthesis using biocompatible and biodegradable materials are given. The review concludes with a realistic drawing on the present and future perspectives.

Photoelectron Storages in Functionalized Carbon Nitrides for Colorimetric Sensing of Oxygen

Colorimetric sensors have been widely used for centuries across diverse fields, thanks to their easy operation and uncompromisingly high sensitivity with no need for electricity. However, it is still a great challenge for conventional chromogenic systems to perform multiple measurements meanwhile maintaining high robustness. Here, we reported that carbon nitrides (CNs), the raw materials that are abundant, structure-tunable, and stable semiconductors with photoelectron storage capability, can be developed as a chromogenic system for colorimetric sensors. Beyond conventional metal oxides that only demonstrated a single blue-color switch after photoelectron storage, CN exhibited a multicolor switch under identical conditions owing to the unusual multiple photoelectron storage pathways. Mechanism studies revealed cyano and carbonyl groups in CN crucially elongated the centroid distance of electrons/holes, which exclusively stabilized the specific excited states that have different light absorption; meanwhile, the counter cations strengthened these processes. As a result, O₂, a proof-of-concept analyte, was quantitatively detected by the CN-derived colorimetric sensor, showing high reversibility in hundreds of cycles and adaptable sensitivity/detection range, outperforming most reported and commercial oxygen sensors. These intriguing features of CN are highly envisioned for the next generation of colorimetric sensors, especially in developing countries or fieldworks, to improve the detection reliability and lower the sensing cost.

Colloidal silver-based lateral flow immunoassay for detection of profenofos pesticide residue in vegetables

A colloidal silver nanoparticle (AgNP)-based lateral flow immunoassay (LFIA) was evaluated in terms of the rapid detection of profenofos (PEO) pesticide residue in vegetables. Colloidal AgNPs, of a diameter of approximately 20 nm, were surface-modified with trisodium citrate dehydrate (TSC) in order to improve their stability and dispersion. An anti-profenofos polyclonal antibody (pAb) was successfully immobilized on the surface of the AgNPs by ionic interaction and characterized using UV-vis, SEM, TEM, FTIR and XPS analyses. Surface modification of Ag-pAb conjugates of varying pH, pAb content and cross-reactivity was employed to design and prepare labels for use in an LFIA to examine whether these factors affect the performance of the assay. The visible detection limit and optical detection limit of the PEO test strip were 0.20 and 0.01 ppm, respectively, in PEO standard solution. This assay showed no cross-reaction with omethoate, methamidophos or pyraclofos. Finally, the PEO test strip was effectively applied for the detection of PEO in liquid vegetables A and B, with optical detection limits of 0.09 and 0.075 ppm, respectively.