Conventional magnetophoresis techniques for manipulating biocarriers and cells predominantly rely on large‐scale electromagnetic systems, which is a major obstacle to the development of portable and ...miniaturized cell‐on‐chip platforms. Herein, a novel magnetic engineering approach by tailoring a nanoscale notch on a disk micromagnet using two‐step optical and thermal lithography is developed. Versatile manipulations are demonstrated, such as separation and trapping, of carriers and cells by mediating changes in the magnetic domain structure and discontinuous movement of magnetic energy wells around the circumferential edge of the micromagnet caused by a locally fabricated nano‐notch in a low magnetic field system. The motion of the magnetic energy well is regulated by the configuration of the nanoscale notch and the strength and frequency of the magnetic field, accompanying the jump motion of the carriers. The proposed concepts demonstrate that multiple carriers and cells can be manipulated and sorted using optimized nanoscale multi‐notch gates for a portable magnetophoretic system. This highlights the potential for developing cost‐effective point‐of‐care testing and lab‐on‐chip systems for various single‐cell‐level diagnoses and analyses.
A sophisticated engineering approach involving a tailored nano‐micro scale notched micromagnet is a novel gate that efficiently enables versatile cell manipulation, such as separation and capture, with a compact system area and less power for operation. This technique provides a milestone for a simple and effective solution for a portable cell‐on‐chip platform.
Accurate recognition of antigens by specific T cells is crucial for adaptive immunity to work properly. The activation of a T‐cell antigen‐specific response by an antigen‐presenting cell (APC) has ...not been clearly measured at a single T‐cell level. It is also unknown whether the cell‐extrinsic environment alters antigen recognition by a T cell. To measure the activation probability of a single T cell by an APC, we performed a single‐cell live imaging assay and found that the activation probability changes depending not only on the antigens but also on the interactions of other T cells with the APC. We found that the specific reactivity of single naïve T cells was poor. However, their antigen‐specific reactivity increased drastically when attached to an APC interacting with activated T cells. Activation of T cells was suppressed when regulatory T cells interacted with the APC. These findings suggest that although the ability of APCs to activate an antigen‐specific naïve T cell is low at a single‐cell level, the surrounding environment of APCs improves the specificity of the bulk response.
Recent advances in the versatility and sophistication of design, fabrication, and control methods of mobile microrobots could have a transforming impact on future healthcare technologies. ...Self‐propelled or remotely actuated, synthetic, or biohybrid microrobots can navigate to difficult‐to‐reach regions in the human body to deliver therapeutics for microscopically localized medical interventions. Here, recent progress in the design of microrobotic systems concerning therapeutic delivery of drugs, cells, and genetic materials is reported. This perspective prioritizes the design aspects of microrobots for medical cargo loading, navigation in biologically relevant environments, and controlled cargo release. In the final section, future prospects and a discussion on the critical shortcomings for the benchside‐to‐bedside translation of medical microrobots are provided.
Microrobots are emerging as a new generation of active drug‐delivery platforms. These active drug‐delivery platforms, fabricated from synthetic and biohybrid materials, can navigate by self‐propulsion or external guidance and locally deliver therapeutics in hard‐to‐reach, confined body regions. This report focuses on recent microrobotic strategies from a therapeutic delivery perspective while addressing the limitations and potential toward future clinical applications.
Over the past few years, manipulating and analyzing methods based on single-cell level have become frequently adopted to conduct the cell heterogeneity study (e.g., differentiation of stem cells, ...tumor cell heterogeneity). Traditional single-cell analysis techniques exhibit high processing complexity and time-consuming characteristic, and require expensive equipment, considerably limiting their applications in cellular heterogeneity study. Microfluidics-based systems to conduct single-cell study have appeared to be powerful methods as fueled with the advancement of microfluidics techniques. This paper reviews microstructure-based methods for single-cell manipulation and analysis. The methods based on microvalve for single-cell manipulation are also discussed in this paper. Lastly, the challenges required to be addressed in the future are highlighted.
•Introduction of microfluidics for single-cell isolation and analysis.•Summarization and illustration of various microstructure-based technologies for single-cell manipulation and analysis.•The challenges and future perspectives of microstructure-based techniques.
Optical tweezers have provided tremendous opportunities for fundamental studies and applications in the life sciences, chemistry, and physics by offering contact-free manipulation of small objects. ...However, it requires sophisticated real-time imaging and feedback systems for conventional optical tweezers to achieve controlled motion of micro/nanoparticles along textured surfaces, which are required for such applications as high-resolution near-field characterizations of cell membranes with nanoparticles as probes. In addition, most optical tweezers systems are limited to single manipulation modes, restricting their broader applications. Herein, we develop an optothermal platform that enables the multimodal manipulation of micro/nanoparticles along various surfaces. Specifically, we achieve the manipulation of micro/nanoparticles through the synergy between the optical and thermal forces, which arise due to the temperature gradient self-generated by the particles absorbing the light. With a simple control of the laser beam, we achieve five switchable working modes i.e., tweezing, rotating, rolling (toward), rolling (away), and shooting for the versatile manipulation of both synthesized particles and biological cells along various substrates. More interestingly, we realize the manipulation of micro/nanoparticles on rough surfaces of live worms and their embryos for localized control of biological functions. By enabling the three-dimensional control of micro/nano-objects along various surfaces, including topologically uneven biological tissues, our multimodal optothermal platform will become a powerful tool in life sciences, nanotechnology, and colloidal sciences.
Microgrippers are used in cell manipulation, micro-assembly, and material characterization. However, rarely a systematic approach is presented for microgripper design. The current research presents a ...methodology for single-cell manipulation design and fabricating a MEMS electrothermal microgripper. The result is a list of constraints required for microgripper design. The jaw thickness is defined by simulating oocyte gripping and injecting quantitatively; a genuine approach is presented here. Due to the long list of extracted constraints, a genetic algorithm (GA) is employed to optimize the design to satisfy all constraints. To do so, the required analytical models are developed to be used in the GA. UV- LIGA is employed to fabricate the device with nickel as the structural layer and copper as the sacrificial layer. The microgripper has a compliant structure with a thin layer of titanium and SU8 coated on jaws. The simulation and experimental results shows that the designed structure provides the jaw displacement of 52 µm at the voltage of 0.172 V and a maximum temperature of 75 ºC, with activation and cooling time of 0.3 s (jaw opening and closing). The procedure developed in this research is a systematic approach and can be adopted to design other types of microgrippers for different applications.
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•A systematic design approach is presented for a MEMS electrothermal microgripper based on an analytical model, finite element simulation, and GA optimization in single-cell manipulation.•Satisfied 10 challenges, including biological, performance, and microfabrication constraints for the design of the microgripper.•Considered physic of oocyte on design overall shape and thickness of the jaw in the cell manipulating and injection time.•Present a novel mechanism for electrothermal microgripper that enables a proper gripping force and makes it suitable for cell handling.•Implementation of copper as the sacrificial layer and nickel as the structural layer can reduce one lithographic step from the fabrication process.
In a forest of a hundred thousand trees, no two leaves are alike. Similarly, no two cells in a genetically identical group are the same. This heterogeneity at the single-cell level has been ...recognized to be vital for the correct interpretation of diagnostic and therapeutic results of diseases, but has been masked for a long time by studying average responses from a population. To comprehensively understand cell heterogeneity, diverse manipulation and comprehensive analysis of cells at the single-cell level are demanded. However, using traditional biological tools, such as petri-dishes and well-plates, is technically challengeable for manipulating and analyzing single-cells with small size and low concentration of target biomolecules. With the development of microfluidics, which is a technology of manipulating and controlling fluids in the range of micro- to pico-liters in networks of channels with dimensions from tens to hundreds of microns, single-cell study has been blooming for almost two decades. Comparing to conventional petri-dish or well-plate experiments, microfluidic single-cell analysis offers advantages of higher throughput, smaller sample volume, automatic sample processing, and lower contamination risk, etc., which made microfluidics an ideal technology for conducting statically meaningful single-cell research. In this review, we will summarize the advances of microfluidics for single-cell manipulation and analysis from the aspects of methods and applications. First, various methods, such as hydrodynamic and electrical approaches, for microfluidic single-cell manipulation will be summarized. Second, single-cell analysis ranging from cellular to genetic level by using microfluidic technology is summarized. Last, we will also discuss the advantages and disadvantages of various microfluidic methods for single-cell manipulation, and then outlook the trend of microfluidic single-cell analysis.
Micropipette-based methods have been widely used for the manipulation of cells and characterization of the mechanical properties at the cell or tissue level. Here, we introduce the glass ...micropipette-based mechanical assays for the stability of cell-cell adhesion. A probing microbead coated with specific adhesion ligands, captured by a glass micropipette, is manipulated to form the adhesion complexes with the corresponding receptors on a single cell. Once the cell is moving away from the micropipette, forces are generated from 20 pN to 100 nN to the adhesion complexes, which are quantified in real-time based on the bending of the glass micropipette. We specifically emphasize the principle and method to probe the rupturing forces of the adhesion complexes at controlled force loading rates, the ligand coating on the probe microbeads, the force calibration of the glass micropipette, and the applications of the method to probe the E-cadherin-based cell-cell adhesions. The principles can be broadly applied to other cell adhesions such as cell-matrix adhesions, neuronal synapses, and bacterial-cell adhesions.
Optical manipulation of tiny objects has benefited many research areas ranging from physics to biology to micro/nanorobotics. However, limited manipulation modes, intense lasers with complex optics, ...and applicability to limited materials and geometries of objects restrict the broader uses of conventional optical tweezers. Herein, we develop an optothermal platform that enables the versatile manipulation of synthetic micro/nanoparticles and live cells using an ultralow-power laser beam and a simple optical setup. Five working modes (i.e., printing, tweezing, rotating, rolling, and shooting) have been achieved and can be switched on demand through computer programming. By incorporating a feedback control system into the platform, we realize programmable multimodal control of micro/nanoparticles, enabling autonomous micro/nanorobots in complex environments. Moreover, we demonstrate in situ three-dimensional single-cell surface characterizations through the multimodal optothermal manipulation of live cells. This programmable multimodal optothermal platform will contribute to diverse fundamental studies and applications in cellular biology, nanotechnology, robotics, and photonics.
Fluidic force microscopy (FluidFM), which combines atomic force microscopy (AFM) with microchanneled cantilevers connected to a pressure controller, is a technique allowing the realization of ...force-sensitive nanopipette under aqueous conditions. FluidFM has unique advantages in simultaneous three-dimensional manipulations and mechanical measurements of biological specimens at the micro-/nanoscale. Over the past decade, FluidFM has shown its potential in biophysical assays particularly in the investigations at single-cell level, offering novel possibilities for discovering the underlying mechanisms guiding life activities. Here, we review the utilization of FluidFM to address biomechanical and biophysical issues in the life sciences. Firstly, the fundamentals of FluidFM are represented. Subsequently, the applications of FluidFM for biophysics at single-cell level are surveyed from several facets, including single-cell manipulations, single-cell force spectroscopy, and single-cell electrophysiology. Finally, the challenges and perspectives for future progressions are provided.
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