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Cell analysis at the single-cell level is of great importance to investigate the inherent heterogeneity of cell populations and to understand the morphology, composition, and function of individual cells. With the continuous innovation of analytical techniques and methods, single-cell analysis on microfluidic chip systems has been extensively applied for its precise single-cell manipulation and sensitive signal response integrated with various detection techniques, such as optical, electrical, and mass spectrometric analyses. In this review, we focus on the specific optical events in single-cell analysis on a microfluidic chip system. First, the four most commonly applied optical technologies, i.e., fluorescence, surface-enhanced Raman spectroscopy, surface plasmon resonance, and interferometry, are briefly introduced. Then, we focus on the recent applications of the abovementioned optical technologies integrated with a microfluidic chip system for single-cell analysis. Finally, future directions of optical technologies for single-cell analysis on microfluidic chip systems are predicted. [ABSTRACT FROM AUTHOR]

Microfluidic technology has shown advantages of low sample consumption, reduced analysis time, high throughput, and potential for integration and automation. Coupling microfluidic chips to mass spectrometry (Chip-MS) can greatly improve the overall analytical performance of MS-based approaches and expand their potential applications. In this article, we review the advances of Chip-MS in the past decade, covering innovations in microchip fabrication, microchips coupled to electrospray ionization (ESI)-MS and matrix-assisted laser desorption/ionization (MALDI)-MS. Development of integrated microfluidic systems for automated MS analysis will be further documented, as well as recent applications of Chip-MS in proteomics, metabolomics, cell analysis, and clinical diagnosis. © 2014 Wiley Periodicals, Inc. Mass Spec Rev 34: 535-557, 2015. [ABSTRACT FROM AUTHOR]

Public health events caused by pathogens have imposed significant economic and societal burdens. However, conventional methods still face challenges including complex operations, the need for trained operators, and sophisticated instruments. Here, we proposed a fully integrated and automated centrifugal microfluidic chip, also termed IACMC, for point-of-care multiplexed molecular diagnostics by harnessing the advantages of active and passive valves. The IACMC incorporates multiple essential components including a pneumatic balance module for sequential release of multiple reagents, a pneumatic centrifugation-assisted module for on-demand solution release, an on-chip silicon membrane module for nucleic acid extraction, a Coriolis force-mediated fluid switching module, and an amplification module. Numerical simulation and visual validation were employed to iterate and optimize the chip's structure. Upon sample loading, the chip automatically executes the entire process of bacterial sample lysis, nucleic acid capture, elution quantification, and isothermal LAMP amplification. By optimizing crucial parameters including centrifugation speed, direction of rotation, and silicone membrane thickness, the chip achieves exceptional sensitivity (twenty-five Salmonella or forty Escherichia coli) and specificity in detecting Escherichia coli and Salmonella within 40 min. The development of IACMC will drive advancements in centrifugal microfluidics for point-of-care testing and holds potential for broader applications in precision medicine including high-throughput biochemical analysis immune diagnostics, and drug susceptibility testing. • A novel fully integrated and automated centrifugal microfluidic chip, also termed IACMC, is proposed for point-of-care multiplexed molecular diagnostics by harnessing the advantages of active and passive valves. • Upon sample loading, the chip automatically executes the entire process of bacterial sample lysis, nucleic acid capture elution quantification, and isothermal LAMP amplification. • The IACMC achieves exceptional sensitivity (twenty-five Salmonella or forty Escherichia coli) and specificity in detecting Escherichia coli and Salmonella within 40 minutes. [ABSTRACT FROM AUTHOR]

Abstract: Electrokinetic gating, functioning as a micro-valve, has been widely employed in microfluidic chips for sample injection and flow switch. Investigating its valving performance is fundamentally vital for microfluidics and microfluidics-based chemical analysis. In this paper, electrokinetic gating valve in microchannels was evaluated using optical imaging technique. Microflow profiles at channels junction were examined, revealing that molecular diffusion played a significant role in the valving disable; which could cause analyte leakage in sample injection. Due to diffusion, the analyte crossed the interface of the analyte flow and gating flow, and then formed a cometic tail-like diffusion area at channels junction. From theoretical calculation and some experimental evidences, the size of the area was related to the diffusion coefficient and the velocity of analytes. Additionally, molecular diffusion was also believed to be another reason of sampling bias in gated injection. [Copyright &y& Elsevier]

Due to the ever-increasing challenge of emerging and reemerging infections on global health, the development of POCT tools has been propelled. However, conventional point-of-care testing methods suffer from several limitations, including cumbersome operation, long detection times, and low accuracy, which hamper their widespread application. Compared to traditional disease diagnostic equipment, mobile health platforms offer several advantages, including portability, ease of operation, and automated analysis of detection results through recognition algorithms. Consequently, they hold great promise for the future. Here, we developed a smartphone-based centrifugal mHealth platform implementing daisy-shaped quick response chip for hematocrit measurement. The centrifugal microfluidic chip is combined with a smartphone through a back-clip-on mobile phone adapter whose control circuit is designed with low power consumption to enable the platform to operate without requiring a high-power source that is inconvenient to carry, thereby achieving the goal of portability. Concurrently, we designed a quick response chip featuring a unique hollow daisy structure that is in line with the properties of hematocrit detection. The distinctive configuration of the chip enables adequate centrifugal force to be supplied for hematocrit detection. Additionally, our customized quick response code recognition algorithm is able to recognize this chip, facilitating non-experts in performing hematocrit intelligent recognition with their smartphones. • The proposed mHealth platform highly integrated components, such as a low power motor, and Bluetooth Low Energy circuit, resulting in high portability without the need for a large power source. • The proposed mHealth platform is equipped with a hollow-structured quick response chip tailored to the requirements of the low-power motor for high-speed centrifugation under low power consumption. This chip enables automated high-throughput detection according to the detection protocol stored in the smartphone, with the ability to detect 36 samples simultaneously in a chip within only 5 min, using a small sample volume of about 10 μL. • A customized quick response code recognition algorithm has been specifically designed for the centrifugal microfluidic chip. The algorithm utilizes perspective transformation and star-ray radiating sampling to "decode" the hematocrit value from the quick response chip, enabling non-experts to perform intelligent hematocrit recognition with their smartphones. • The proposed mHealth platform has great potential for POCT with the characteristics of portability and intelligence. [ABSTRACT FROM AUTHOR]

Immune response to environmental pathogen invasion is a complex process to prevent host from further damage. For quantitatively understanding immune responses and revealing the pathogenic environmental information, real-time monitoring of such a whole dynamic process with single-animal resolution in well-defined environments is highly desired. In this work, an integrated microfluidic device coupled with worm-based biosensor was proposed for in vivo studies of dynamic immune responses and antibiotics interference in infected C. elegans . Individual worms housed in chambers were exposed to the various pathogens and discontinuously manipulated for imaging with limited influence on physiological activities. The expression of immune responses gene ( irg-1 ) was time-lapse measured in intact worms during pathogen infection. Results demonstrated that irg-1 gene could be induced in the presence of P. aeruginosa strain PA14 in a dose-dependent manner, and the survival of infected worm could be rescued under gentamicin or erythromycin treatments. We expect it to be a versatile platform to facilitate future studies on pathogenesis researches and rapid drug screen using C. elegans disease model. [ABSTRACT FROM AUTHOR]

Cell signaling has been recognized as a highly dynamic process. How to capture such dynamics with changes of chemical microenvironment at single cell resolution among cells population without interfering with adjacent cells has been still an immense challenge. Here, we proposed a precision guided microfluidic chemical perfusion strategy for investigating chemical-activated cell signaling via dynamic imaging with high temporal (∼12 ms), spatial resolutions and precision. Theory for the microfluidic operation was first established and validated by both numerical simulations and experiments. A computer-aided multi-channel pressure control system was constructed to automatically implement chemical perturbations with various microperfusion times, relaxation times and number of cycles. The width and the position of the chemical microflow could also be precisely controlled with high reliability and accuracy. Investigations of intracellular and intercellular calcium signaling were successfully demonstrated using the proposed method. These results revealed that the precision guided microfluidic chemical perfusion strategy provided a versatile means for cell signaling analysis, which is potentially meaningful in chemical biology, cell biology and pharmacology. [ABSTRACT FROM AUTHOR]

C. elegans is a leading model organism for addressing many fundamental biology issues. Sufficient quantities of the worms with specific developmental stage are needed in C. elegans studies due to the size-dependent features shown in C. elegans . In this work, we presented a simple and feasible microfluidic chip to realize simultaneous sorting of C. elegans with different sizes by graduated microfilters. The micro-device was fabricated with PDMS-agarose hybrid layers consisting of 5 arrays of geometrically optimized square columns as microfilters for separating worms of different sizes. Fluid flow and electric field were simultaneously applied to drive the worms to rapidly and directionally pass through the microfilters, resulting in increased sorting efficiency and accuracy. Further, the sorted worms could be easily collected from 4 grooves of the agarose layer by slipping the PDMS layer to the top of grooves. With this sorting strategy, we demonstrated the feasibility of simultaneously sorting different sizes of C. elegans with high efficiency and accuracy (>95%) and throughput of hundreds of worms per minute. Therefore, the micro-device could be a promising tool to C. elegans assays that need a large number of stage-synchronized worms. It could also be useful for body size-based mutant screening and taxis-response studies in C. elegans . [ABSTRACT FROM AUTHOR]

Paper-based microfluidic chips have shown great potential for use in rapid clinical diagnostics. In this work, we present a paper-based device that integrates an electromagnetically actuated valve and an adjustable time controller for the simultaneous detection of multiple tumor biomarkers. The time controller consists of a timing channel and two movable conductive iron bands that function as an electric switch. Once the conductive iron bands are connected by the fluid flow, the circuit would be closed to actuate the magnetic valve, initiating chemiluminiscent immunoassay (CLIA) reactions. Using a HRP- O -phenylenediamine-H 2 O 2 detection system, simultaneous detection of different concentrations of carcinoembryonic antigens (CEA) was demonstrated. The resulting CLIA peak intensity exhibited a good linear relationship with the logarithm of the CEA concentration from 0.1–80 ng mL −1 . Further experiments showed that the developed device was capable of detecting multiple tumor biomarkers simultaneously. We can program different incubation times for the detection of different biomarkers by moving the conductive bands on this paper-based device. In this study, only 16 min was required to complete CEA detection. This strategy greatly shortens detection time compared to the conventional chemiluminiscence technique for CEA detection (nearly 2 h). This paper-based device provides a simple and inexpensive platform for immunoassay-based detection of disease-related biomarkers. [ABSTRACT FROM AUTHOR]

Cell-based biosensor (CBB) has shown potential to provide a rapid and sensitive measurement means for monitoring specific biological substances. However, the detecting frequency and reusability remain a challenge for further application of CBB. In this paper, a microfluidic cell-based biosensor (μCBB) was developed, which consisted of a localized millisecond chemical pulse as sample introduction for pulsing individual cells without interfering with adjacent cells and single HeLa cells expressing endogenous P2Y receptors as the sensing elements. Gated injection of pinched flow was used to generate millisecond ATP pulses with predefined width. By integrating localized ATP pulse with predefined width, multiple sensing elements could be used to detect ATP pulses without impact on their functionality. Thus, the detecting frequency of the developed μCBB is multiplied by the number of available cells in comparison to that reported previously. We expect the developed method to be potentially useful to enhance the usability of CBB for biological and biomedical analysis. [ABSTRACT FROM AUTHOR]

C. elegans was widely used as a prominent model organism in the study of physiological response to gaseous environment, thanks to its suitability for in vivo optical imaging of neuronal sensing. Immobilization of the active worms is a key procedure to obtain high-resolution imaging and gas stimulations. In this work, we presented a novel microfluidic approach for immobilizing C. elegans due to the fact that its movement could be eliminated under the condition of gentle surface-dehydration. Nitrogen gas was directly injected into the microfluidic chip to dehydrate the surface of worm appropriately, resulting in rapid and repetitive immobilization of C. elegans . The imaging analysis of subcellular distribution of DAF-16, a well-known transcription factor regulating different stress responses, indicated that this dehydration-based immobilization method would not induce obvious stress response of the worm within 20 min. Furthermore, this microfluidic device could generate gas stimulation to the immobilized worm without the interference resulted from the switch of liquid-gas. Finally, the developed micro-device clearly demonstrated that URX neuronal responses were induced by oxygen gas with increasing levels of 0–20%, indicating that this method could be used for imaging analysis of gas-evoked neuronal sensing, especially to the pressure-change sensitive neurons in C. elegans . [ABSTRACT FROM AUTHOR]

In this work, we propose a microfluidic in-gel loop-mediated isothermal amplification (gLAMP) containing preloaded reagents as a self-contained microdevice for simultaneous detection of multiple pathogenic bacterial DNA in near point of care settings. The microchip consists of multiple channels with reaction chambers accommodating low-melting-point agarose and all LAMP reagents except the DNA samples, which can be kept at 4 °C for long-term storage. The current microchip enables simultaneous tests of four different bacterial DNA targets. After DNA samples were introduced into the microchip, gLAMP reactions were carried out on a hot plate at 65 °C. The gLAMP reaction conditions including the concentrations of the fluorescence indicator, Bst DNA polymerase, primers, and Mg 2+ ions were further optimized. Under the optimized conditions, detection of foodborne bacteria in serum samples, including Escherichia coli, Proteus hauseri, Vibrio parahaemolyticus, and Salmonella subsp. Enterica were demonstrated with high selectivity and sensitivity (as low as 3 copies/μL). The gLAMP microchip provides a simple and easy-to-operate platform for LAMP-based pathogen detection, which holds high potential for future applications in point-of-care settings. [ABSTRACT FROM AUTHOR]

Random compartmentalization of cells by common droplet formation methods, i.e., T-junction and flow-focusing, results in low occupancy of droplets by single cells. To resolve this issue, a fluorescence-activated droplet formation method was developed for the on-command generation of droplets and encapsulation of single cells. In this method, droplets containing one cell were generated by switching on/off a two-phase hydrodynamic gating valve upon optical detection of single cells. To evaluate the developed method, flow visualization experiments were conducted with fluorescein. Results indicated that picoliter droplets of uniform sizes (RSD<4.9%) could be generated. Encapsulation of single fluorescent polystyrene beads demonstrated an average of 94.3% droplets contained one bead. Further application of the developed methods to the compartmentalization of individual HeLa cells indicated 82.5% occupancy of droplets by single cells, representing a 3 fold increase in comparison to random compartmentalization. [ABSTRACT FROM AUTHOR]

A rotate & react SlipChip (RnR-SlipChip) was developed for simultaneous visual detection of multiple bacterial pathogens by loop-mediated isothermal amplification (LAMP). The SlipChip system consists of two round PDMS-glass hybrid chips that are assembled coaxially by a plastic screw-nut suite. After sample loading, one-step rotation allowed immediate mixing and reaction of multiple bacteria samples with LAMP reagents on the chip. A home-built peltier heating device was used to implement the isothermal control by an advanced RISC machines (ARM) processor. Under the optimized LAMP conditions, a fluorescent signal-to-noise ratio of about 5-fold and a detection limit of 7.2 copies/μL genomic DNA were achieved. Furthermore, five common digestive bacterial pathogens including Bacillus cereus, Escherichia coli, Salmonella enterica, Vibrio fluvialis and Vibrio parahaemolyticus , were visually identified using the established method in 60 min with a success rate of 100%. The developed RnR-SlipChip provided a rapid, simple-to-use and cost-effective solution for pathogenic bacteria detection, which holds high potential for clinical diagnosis especially in resource-limited areas. [ABSTRACT FROM AUTHOR]

Multidrug resistance analysis represents a great challenge in cancer chemotherapy, drug development and pathological study. In this paper, multifunctional gradients-customizing microfluidic devices were developed for high-throughput single-cell multidrug resistance (MDR) analysis. The gradient profile was determined by the lengths of the distribution microchannels regardless of flow rates and pressure, which provided good stability and remarkably reduced redundancy of microfluidic architecture. The drug of gradient concentrations consecutively stimulate upon the cells in the downstreaming cell cultivation chamber. Time-dependent drug efflux kinetics of HepG2 cells were firstly investigated on our device using both the different-single-cell and the same-single-cell strategies. Furthermore, hepatic polarized HepG2 cells, which collected the secreted cholephilic substances in the apical vacuoles, were used as model to investigate the inhibition of MDR-associated protein with secretion inhibitor cyclosporine A of varied concentrations on single organelle level. Finally, a high-throughput drug screening experiment was conducted to examine both the chemo-sensitizing effect and the cytotoxity of the potential chemo-sensitizing agents. Conclusively, the results confirmed that our method was a highly efficient way to analyze multidrug resistance (MDR) at single-cell or even single-organelle level with advantages of high-throughput, flexibility, stability and low sample consumption. [ABSTRACT FROM AUTHOR]

Rapid mixing of highly viscous solutions is a great challenge, which helps to analyze the reaction kinetics in viscous liquid phase, particularly to discover the folding kinetics of macromolecules under molecular crowding conditions mimicking the conditions inside cells. Here, we demonstrated a novel microfluidic mixer based on Dean flows with three-dimensional (3D) microchannel configuration for fast mixing of high-viscosity fluids. The main structure contained three consecutive subunits, each consisting of a “U”-type channel followed by a chamber with different width and height. Thus, the two solutions injected from the two inlets would undergo a mixing in the first “U”-type channel due to the Dean flow effect, and simultaneous vortices expansions in both horizontal and vertical directions in the following chamber. Numerical simulations and experimental characterizations confirmed that the micromixer could achieve a mixing time of 122.4 μs for solutions with viscosities about 33.6 times that of pure water. It was the fastest micromixer for high viscosity solutions compared with previous reports. With this highly efficient 3D microfluidic mixer, we further characterized the early folding kinetics of human telomere G-quadruplex under molecular crowding conditions, and unravelled a new folding process within 550 μs. [ABSTRACT FROM AUTHOR]

It is a challenging task to realize gaseous stimulations on Caenorhabibditis elegans for in vivo neuronal analysis of chemo-sensing, due to the difficulties in gas control and worm manipulation. Here, we demonstrated an integrated microfluidic system that could accurately deliver the gaseous stimuli to the worms’ noses and track the in vivo neuronal activities simultaneously. The microfluidic chip consisted of a comb-shaped micro-valve for worm immobilization and a T-junction structure for precise gas delivery. Neuronal responses of C. elegans to polar and non-polar gases were both investigated. The microfluidic device clearly demonstrated that oxygen with increasing levels of 0–10% and 0–21% induced URX neuronal responses. BAG neuronal activities were inhibited by carbon dioxide, showing the symptom of anesthesia. The vapor of polar odorant 1-octonal evoked significant calcium transients in ASH neurons in the wild-type animals but weak signals in tph-1 and Ce-grk-2 mutants. These results indicated that the developed device could be useful to identify various odor-evoked neuronal activities. [ABSTRACT FROM AUTHOR]

Abstract: The propagation of intercellular calcium wave (ICW) is essential for coordinating cellular activities in multicellular organisms. However, the limitations of existing analytical methods hamper the studies of this biological process in live animals. In this paper, we demonstrated for the first time a novel microfluidic system with an open chamber for on-chip microinjection of C. elegans and investigation of ICW propagations in vivo. Worms were long-term immobilized on the side wall of the open chamber by suction. Using an external micro-manipulator, localized chemical stimulation was delivered to single intestinal cells of the immobilized worms by microinjection. The calcium dynamics in the intestinal cells expressing Ca2+ indicator YC2.12 was simultaneously monitored by fluorescence imaging. As a result, thapsigargin injection induced ICW was observed in the intestinal cells of C. elegans. Further analysis of the ICW propagation was realized in the presence of heparin (an inhibitor for IP3 receptor), which allowed us to investigate the mechanism underlying intercellular calcium signaling. We expect this novel microfluidic platform to be a useful tool for studying cell–cell communication in multicellular organisms in vivo. [Copyright &y& Elsevier]

Abstract: Conventional macro-scale methods are not appropriate for in vivo neuronal analysis at a single neuron level when experimental subject is small model organism Caenorhabditis elegans. In this paper, we demonstrate a powerful microfluidic device that allowed investigating in vivo chemo-sensing of intact C. elegans by integrating functions of automated manipulation of worms, effective immobilization without damages and well-controllable stimulations. Live C. elegans were effectively immobilized in microfluidic channels by a comb-shaped microvalve without physiological damages. A well-controlled sample introduction system was used to deliver chemicals to the chemosensory cilia at the worm''s nose tip. In vivo neuronal responses of the animal to the chemical stimulations were monitored using calcium fluorescence imaging. Dynamic calcium signals related to varying concentrations and durations of stimuli were investigated using this integrated microfluidic device. We anticipate this immobilization approaches can have an impact in a variety of applications, such as neuron responses investigation before and after laser ablation upstream or downstream neurons for studying olfactory or gustatory neural circuits in individual healthy worms, in this high-throughput system. [Copyright &y& Elsevier]

Abstract: The propagation of intercellular calcium signals provides a mechanism to coordinate cell population activity, which is essential for regulating cell behavior and organ development. However, existing analytical methods are difficult to realize localized chemical stimulation of a single cell among a population of cells that are in close contact with one another for studying the propagation of calcium wave. In this work, a microfluidic method is presented for the analysis of contact-dependent propagation of intercellular calcium wave induced by extracellular ATP using multiple laminar flows. Adjacent cells were seeded ∼300μm downstream the intersection of a Y-shaped microchannel with negative pressure pulses. Consequently, the lateral diffusion distance of the chemical at cell locations was limited to ∼26μm with a total flow rate of 20μLmin−1, which prevented the interference of diffusion-induced cellular responses. Localized stimulation of the target cell with ATP induced the propagation of intercellular calcium wave among the cell population. In addition, studies on the spread of intercellular calcium wave under octanol inhibition allowed us to characterize the gap junction mediated cell–cell communication. Thus, this novel device will provide a versatile platform for intercellular signal transduction studies and high throughput drug screening. [Copyright &y& Elsevier]

Abstract: Conventional neuronal analysis at the single neuron level usually involves culturing of neurons in vitro and analysis of neuronal activities by electrophysiological or pharmacological methods. However, the extracellular environments of in vitro neuronal analysis cannot mimic the exact surroundings of the neurons. Here, we report a microfluidic worm-chip for in vivo analysis of neuronal activities upon dynamic chemical stimulations. A comb-shaped microvalve was developed to immobilize whole animal for high-resolution imaging of neuronal activities. Using a sequential sample introduction system, multiple chemical stimuli were delivered to an individual Caenorhabditis elegans nose tip based on programmed interface shifting of laminar flows. ASH sensory neuron responses to various stimuli in individual C. elegans were quantitatively evaluated, and mutants were significantly defective in neuronal responses to certain stimulus in comparison to others. Sensory reduction in the magnitude of the response to repetitive chemical stimulation with different durations was also found. Our study explored the possibility of real-time detection of neuronal activities in individual animals upon multiple stimulations. [Copyright &y& Elsevier]

Abstract: The use of cell-based biosensors is usually limited by agonist-induced desensitization of cell-surface receptors. In this work, a microfluidic cell-based biosensor (μCBB) was developed for the detection of ATP in liquid environments. It consists of a millisecond chemical pulse generator for sample introduction in a pulsatile manner and a single NIH-3T3 cell expressing endogenous P2Y receptors as the sensing element. ATP solutions were used to simulate input signals for investigating the μCBB. By controlling negative pressures on two outlets of a cross-shaped microfluidic chip, pulses of ATP solutions were generated based on hydrodynamic gated injection. With ATP pulses of 100ms every 50s, the amplitude of the resulting calcium spikes maintained at a similar level, suggesting that the receptor desensitization was minimized. Consequently, the developed μCBB could be used for detecting pulsatile samples with extended use times. The sensitivity of the μCBB for detecting ATP was further determined and the cellular responses to millisecond ATP pulses were investigated in comparison to long-term stimulations. [Copyright &y& Elsevier]

Abstract: Membrane proteins play essential roles in regulating various fundamental cellular functions. To investigate membrane proteins, extraction and purification are usually prerequisite steps. Here, we demonstrated a microfluidic aqueous PEG/detergent two-phase system for the purification of membrane proteins from crude cell extract, which replaced the conventional discontinuous agitation method with continuous extraction in laminar flows, resulting in significantly increased extraction speed and efficiency. To evaluate this system, different separation and detection methods were used to identify the purified proteins, such as capillary electrophoresis, SDS-PAGE and nano-HPLC–MS/MS. Swiss-Prot database with Mascot search engine was used to search for membrane proteins from random selected bands of SDS-PAGE. Results indicated that efficient purification of membrane proteins can be achieved within 5–7s and approximately 90% of the purified proteins were membrane proteins (the highest extraction efficiency reported up to date), including membrane-associated proteins and integral membrane proteins with multiple transmembrane domains. Compared to conventional approaches, this new method had advantages of greater specific surface area, minimal emulsification, reduced sample consumption and analysis time. We expect the developed method to be potentially useful in membrane protein purifications, facilitating the investigation of membrane proteomics. [Copyright &y& Elsevier]

Abstract: Microfluidic cell sorter allows efficient separation of small number of cells, which is beneficial in handling cells, especially primary cells that cannot be expanded to large populations. Here, we demonstrate a microfluidic fluorescence-activated cell sorter (μFACS) with a novel sorting mechanism, in which automatic on-chip sorting is realized by turning on/off the hydrodynamic gating valve when a fluorescent target is detected. Formation of the hydrodynamic gating valve was investigated by both numerical simulation and flow visualization experiment. Separation of fluorescent polystyrene beads was then conducted to evaluate this sorting mechanism and to optimize the separation conditions. Isolation of fluorescent HeLa-DsRed cells was further demonstrated with high purity and recovery rate. Viability of the sorted cells was also examined, suggesting a survival rate of more than 90%. We expect this sorting approach to find widespread applications in bioanalysis. [Copyright &y& Elsevier]

Abstract: Systems biology advocates the understanding of biology at the systems-level, which requires massive information of correlations among individual components in complex biological systems. Such comprehensive investigation entails the use of high-throughput analytical tools. Microfluidic technology holds high promise to facilitate the progress of biology by enabling miniaturization and upgrading of current biological research tools due to its advantages such as low sample consumption, reduced analysis time, high-throughput and compatible sizes with most biological samples. In this article, we documented the recent applications of microfluidic chips in biological researches at the molecular level, cellular level and organism level, serving the purpose for systems-level understanding of biology. [Copyright &y& Elsevier]