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Chemotherapy screening plays a crucial role in cancer drug discovery and clinical medicine. Although conventional methods have contributed greatly to macromanipulation of cell populations, profounder insights related to the tumor microenvironment require approaches for completing integrated cell-3D tumor micromanipulation, massive tumor simulation and production, and dynamic and high-throughput tumor analysis. In this study, we introduced an integrated microfluidic platform with multiparallel components for heterotypic 3D tumor reconstruction and antitumor screening. Sequential microfluidic manipulations including sample loading, precise localization, 3D tumor formation, chemical stimulation, on-chip analysis, and tumor recovery for off-chip assessment were permitted and experimentally confirmed in the device on the basis of facile and efficient pneumatic control. Heterotypic 3D tumors with tissue-biomimetic phenotypes can be produced in massive and size-uniform manners. Notably, we accomplished a screening-like chemotherapy assessment involving different heterotypic 3D tumors and antitumor drugs and demonstrated the versatility of the platform in large-scale tumor manipulation and analysis. This advancement in microfluidics has potential applications in the fields of oncology, pharmacology, and tissue engineering and provides insight into the construction of high-performance microsystems for drug development and cancer research.

Micropatterning technologies are emerging as an enabling tool for various microfluidic-based applications in life sciences. However, the high throughput and multiplex localization of multiple bio-components in a microfluidic device has not yet been well established. In this paper, we describe a simple and in situ micropatterning method using an integrated microfluidic device with pneumatic microstructures (PμSs) for highly controllable immobilization of both proteins and cells in a high throughput, geometry-dynamic, and multi-patterning way. The precise Pluronic F127 passivation of a microchamber surface except the PμS-blocked regions was performed and characterized, and the spatial dynamics and consistency of both the PμSs and protein/cell micropatterning were optically evaluated and quantitatively demonstrated too. Furthermore, a systematic investigation of PμS-assisted micropatterning in microfluidics was carried out. The feature of high throughput and spatial control of micropatterning can be simply realized by using the well-designed PμS arrays. Meanwhile, the co-micropatterning of different proteins (bovine serum albumin and chicken egg albumin) and cells (human umbilical vein endothelial cells and human hepatocellular carcinoma cells) in a microfluidic device was successfully accomplished with the orderly serial manipulation of PμS groups. We demonstrate that PμS-assisted micropatterning can be applied as a convenient microfluidic component for large-scale and diversified protein/cell patterning and manipulation, which could be useful for cell-based tissue organization, high-throughput imaging, protein-related interactions and immunoassays.

Recently, microfluidic systems have shown great potential in the study of molecular and cellular biology. With its excellent properties, such as miniaturization, integration and automation, to name just a few, microfluidics creates new opportunities for the spatial and temporal control of cell growth and environmental stimuli in vitro. In the field of neuroscience, microfluidic devices offer precise control of the microenvironment surrounding individual cells, and the delivery of biochemical or physical cues to neural networks or single neurons. The intent of this review is to outline recent advances in microfluidic-based applications in neurobiology, with emphasis on neuron culture, neuron manipulation, neural stem cell differentiation, neuropharmacology, neuroelectrophysiology, and neuron biosensors. It also aims to stimulate development of microfluidic-based applications in neurobiology by involving scientists from various disciplines, especially neurobiology and microtechnology.

In this paper, we introduce a new approach for the in situ electrochemical fabrication of an individually addressable array of conducting polymer nanowires (CPNWs) positioned within an integrated microfluidic device and also demonstrate that such an integrated device can be used as a chemical sensor immediately after its construction.

The cellular heterogeneity of tumors has played important roles in various tumor-related research areas and applications such as the cellular biology, metastasis and clinical diagnosis of tumors. Although several microfluidics-based single-cell separation and analysis techniques have been used in research into the cellular heterogeneity of tumors, further investigation is still required for studying the effect of the biomechanical (e.g., size and deformability) heterogeneity of cells on their biological characteristics (e.g., drug resistance and tumor-initiating features). Here, we established an integrated microfluidic platform for the construction of single-cell arrays and analysis of drug resistance. Using this device, high-throughput single-cell arrays could be easily obtained according to the biomechanical (size and deformability) heterogeneity of cells. To demonstrate the capability of the microfluidic platform, a proof-of-concept experiment was implemented by determining the vincristine resistance of single glioblastoma cells with different biomechanical properties. The results indicated that the biomechanics of tumor cells had significant implications for cell drug resistance; that is, small and/or more deformable tumor cells had higher drug resistance than large and/or less deformable tumor cells. This device provides a new approach for the isolation of single cells according to the different biomechanical properties of cells. Also, it possesses practical potential for studies of tumors on a single-cell level. [ABSTRACT FROM AUTHOR]

The construction of a micro-platform capable of microscale control for continuous, dynamic, and high-throughput biomimetic tumor manipulation and analysis plays a significant role in biological and clinical research. Here, we introduce a pneumatic microstructure-based microfluidic platform for versatile three-dimensional (3D) tumor cultures. The manipulative potential of pneumatic microstructures in a fabrication-optimized microfluidic device can be stimulated to achieve ultra-repetitive (tens of thousands of times) and persistent (over several months) microfluidic control. We demonstrated that the microfluidic platform is reusable (dozens of times) for stable, reproducible, and high-throughput generation of tumors with uniform size. Various heterotypic and homotypic 3D tumor arrays can be produced successfully in the device based on robust pneumatic control. On-chip monitoring and analysis of tumor phenotypes and responses to different culture conditions and chemotherapies were also achieved in real-time in the microfluidic platform. The results indicate that fibroblasts cocultured with tumor cells positively promote the phenotypical appearance of heterotypic tumors. This microfluidic advancement offers a new methodological approach for the development of high-performance and non-disposable 3D culture systems and for tissue-mimicking cancer research. We believe that it could be valuable for various tumor-related research fields such as oncology, pharmacology, tissue engineering, and bioimaging. [ABSTRACT FROM AUTHOR]

The presence and quantity of rare cells in the bloodstream of cancer patients provide a potentially accessible source for the early detection of invasive cancer and for monitoring the treatment of advanced diseases. The separation of rare cells from peripheral blood, as a “virtual and real-time liquid biopsy”, is expected to replace conventional tissue biopsies of metastatic tumors for therapy guidance. However, technical obstacles, similar to looking for a needle in a haystack, have hindered the broad clinical utility of this method. In this study, we developed a multistage microfluidic device for continuous label-free separation and enrichment of rare cells from blood samples based on cell size and deformability. We successfully separated tumor cells (MCF-7 and HeLa cells) and leukemic (K562) cells spiked in diluted whole blood using a unique complementary combination of inertial microfluidics and steric hindrance in a microfluidic system. The processing parameters of the inertial focusing and steric hindrance regions were optimized to achieve high-throughput and high-efficiency separation, significant advantages compared with existing rare cell isolation technologies. The results from experiments with rare cells spiked in 1% hematocrit blood indicated ＞90% cell recovery at a throughput of 2.24 × 107 cells min−1. The enrichment of rare cells was ＞2.02 × 105-fold. Thus, this microfluidic system driven by purely hydrodynamic forces has practical potential to be applied either alone or as a sample preparation platform for fundamental studies and clinical applications. [ABSTRACT FROM AUTHOR]

Poly(dimethylsiloxane) (PDMS)-based microfluidic systems have been gaining popularity in various applications, particularly for biological analyses because of their non-toxicity, easy fabrication, practical scalability, optical transparency, and low cost. However, because of the inherent hydrophobicity of PDMS-based material, biological samples easily and strongly interact with PDMS surfaces in biological environments, which prevents the immediate use of PDMS-based microfluidics without any surface processing. To date, various surface modification methods and different materials have been utilized to improve the repelling properties of the PDMS surface and to introduce new functional groups. Based on the recent advances in this field, we outline the main strategies utilized in PDMS surface modification in this review. We also present several applications of modified PDMS surfaces in biological analysis, such as biomolecule separation, immunoassay, cell culture, and DNA hybridization. [ABSTRACT FROM AUTHOR]

A microfluidic approach for the integration of multiple biochemical concentration gradients in a single microfluidic device is presented in article number 1800434, by Wenming Liu, Jinyi Wang, and co‐workers. The employment of multidirectional hydrogel barriers permits a facile, stable, and long‐term microfluidic production of shear‐free single and double biochemical gradients. Multi‐gradient microfluidics provides a prototypical platform to perform on‐chip biomimetic neuronal manipulation and analysis for the exploration of neurogenesis and development as well as neuro‐regeneration. [ABSTRACT FROM AUTHOR]

Axon guidance is a fundamental process during neural development and regeneration. The combinatorial impacts of guidance cues on neuronal axons remain largely unexplored, owing to the lack of micromanipulation methods to conduct such studies. Herein, a microfluidic platform is reported for simultaneously establishing multi‐biochemical cue gradients to investigate attractive and repulsive response integration of axons. The employment of multidirectional hydrogel barriers permits a facile, stable, and long‐term production of shear‐free single linear and double radial biochemical gradients in the device. On‐chip cultivation of primary cortical neurons is favorably performed with microscale control while preserving their high viability, typical neuronal phenotype, and neurite growth and orientation. The applicability of the established platform in studying the complex integration of netrin‐1 and slit‐2 cue gradients by axons and their corresponding responses is experimentally demonstrated. The results indicate that axon guidance in a complex neural microenvironment is strongly associated with the concentration and guiding duration of biochemical signals, providing composite insight into the guidance mechanism underlying the combinatorial effects of netrin‐1 and slit‐2 on neuronal axons. This platform, which has the capability of multiple biochemical gradient control in time and space, holds great potential for applications in neurobiology, oncology, inflammation, and precision medicine. Synchronous on‐chip construction of multiple biochemical cue gradients and its applicability in studying complex integration of attractive and repulsive signals by neuronal axons and their corresponding responses are demonstrated. This microfluidic multigradient approach may pave the way to perform on‐chip establishment and micromanipulation of biomimetic tissue microenvironment for research on neurodevelopment, tissue repair, and tumor metastasis. [ABSTRACT FROM AUTHOR]

• A microfluidic system for simultaneous and large scale multi-size 3D tumor manipulation and analysis was developed. • Controllable and massive production of biomimetic multi-size tumors was established in the single microfluidic device. • The system allows highly efficient multi-size tumor formation with quantitative-uniformity. • Orthogonal drug resistance determination of multi-size tumors was accomplished in throughput in the single device. The establishment of a miniaturized platform capable of microscale control for sequential, coordinated, and throughput biomimetic tumor manipulation and analysis offer a high degree of biological and clinical relevance to cancer therapy and pharmaceutical research. In this study, we developed a microfluidic system with well-established microwell arrays and simple double-layer composition that allows massive fabrication of biomimetic multi-size 3D tumors and their simultaneous manipulation and orthogonal analysis. Serial manipulations including cell localization, array-like self-assembly/cultivation, and dynamic analysis of different types of 3D tumors, were accomplished in the microfluidic device. We demonstrated that the microfluidic platform is stable and throughput cell trapping and tumor generation with quantity uniform. Furthermore, on-chip monitoring and throughput analysis of tumor phenotypes and responses to culture and different chemotherapies were also achieved in the device. The microfluidic advancement offers a new methodological approach for the development of high-performance and multifunctional 3D tumor systems and for tissue-mimicking cancer research and therapy evaluation. This microfluidic platform, which has the capability of multiple control in time and space, holds great potential for applications in the fields of tumor biology, tissue engineering, and clinical medicine. [ABSTRACT FROM AUTHOR]

Organ-on-a-chip (OOC) systems were developed by combining microfluidic technologies and tissue engineering to mimic physiological conditions in the body. OOC systems can recreate key aspects of the complex human physiological microenvironment, such as critical tissue interfaces; spatiotemporal cell–cell/extracellular matrix interactions; and concentration gradients involving nutrients, metabolic waste, and cytokines. Faithful reconstruction of in vitro systems can facilitate further studies of the fundamental mechanisms involved in physiology and pathology and the development of applications for biomimetic cell analysis. In this review, we summarize OOC development from the perspective of microfluidic technologies, focusing on multilayer microfluidics, parallel microchannels, cell spheroids, cell patterning, paper microfluidics, microfluidic spinning, and three-dimensional bioprinting-involved microfluidics. Their key features, limitations, and the challenges associated with constructing in vivo -like tissue environments are discussed. Then, body-on-a-chip systems are described in detail. Finally, the challenges that need to be overcome for OOC systems in the future are highlighted. • Introduction of microfluidics for organ-on-a-chip (OOC). • Summarization and illustration of various microfluidic technologies for developing OOC systems. • Presentation and discussion of body-on-a-chip systems. • The challenges and future perspectives of OOC. [ABSTRACT FROM AUTHOR]

Microfluidic mixings create considerable opportunities for microscale exploration of biomacromolecule function and local reaction kinetics. However, a robust and efficient way for localized mixing performance is not yet well established. In this study, we describe a simple and reliable method for rapid, stable, and controllable in situ mixing using a single-layer acoustofluidic system with a microneedle. We developed the single microstructure for region-confined mixing, which can be controlled dynamically by intentional acoustic activation. Various acoustofluidic impacts including driving frequency, microstructure design, driving voltage, and flow control on homogeneous mixing were systematically investigated. The microneedle-based device allows a fast (∼ 85 ms) mixing operation. Robust and high reusability of acoustofluidic system was experimentally demonstrated with up to 200 times of repetitive mixing and 100 min of continuous mixing. Furthermore, the proof-of-concept applications including real-time characterization of fluorescein quenching and β -glucuronidase-catalyzed hydrolysis of 4-methyl-umbelliferyl- β - d -glucuronide were successfully accomplished in the in situ mixing platform. We believe this microfluidic system could be suitable for investigation of different instantaneous chemical/biochemical events associated with various molecular interactions and reactions. Also, the acoustofluidic approach is potentially valuable to the development of mixing-based integrated microfluidic systems for applications in molecular science and life science. [ABSTRACT FROM AUTHOR]

Large-scale single-cell arrays are urgently required for current high-throughput screening of cell function and heterogeneity. However, the rapid and convenient generation of large-scale single-cell array in a multiplex and universal manner is not yet well established. In this paper, we report a simple and reliable method for the generation of a single-cell array by combining pneumatic microvalve arrays (PμVAs) and hydrodynamic single-cell trapping sites in a single microfluidic device. The PμVAs, which can be precisely controlled by actuated pressures, were designed to guide multiple types of cells being trapped in the corresponding single-cell trapping sites located in the fluidic channel. According to the theoretical demonstration and computational simulation, we successfully realized a multiplex single-cell array with three different types of cells by a step-by-step protocol. Furthermore, the analysis of cellular esterase heterogeneity of the three types of cells was concurrently implemented in the device as a proof-of-concept experiment. All the results demonstrated that the method developed in the current study could be applied for the generation of large-scale single-cell array with multiple cell types, which would be also promising and helpful for single-cell-based high-throughput drug test, multipurpose immunosensor and clinical diagnosis. [ABSTRACT FROM AUTHOR]

The increase of antimicrobial resistance and the outbreak of new diseases have brought unprecedented challenges with antibiotic therapy, and discovering and developing effective compounds to fight against infections or diseases have become a challenge. Conventionally, natural antibiotics or active compounds can be obtained from microorganisms with a long time span, complex screening, and cumbersome operations. In this work, we developed a droplet-based microfluidic platform combined with liquid chromatography tandem mass spectrometry for rapid screening of chemically induced mutant strains and analyzing their metabolites. Using this microfluidic method, N-methyl-N-nitro-N-nitrosoguanidine-induced mutants of two Streptomyces strains, two Salinicoccus strains, a Halomonas strain, and a Planomicrobium strain were screened, and their metabolites were analyzed. Multivariate and heatmap analysis showed that the mutant strains screened by the microfluidic method and traditional method (flasks and agar plates) were clustered and separated evidently from the wild-type strains. The top 20 differential characteristic peaks of all samples were annotated with the HMDB database, and the significant differences of the characteristic peaks indicated that the mutant strains screened by the microfluidic method and traditional method had highly similar metabolic compositions. Results demonstrated that this microfluidic screening method was suitable not only for actinomycete mutant screening, but also for bacterial mutant screening with wide applicability and reliability. Furthermore, this method can reduce screening timescales and simplify cumbersome operations compared with the traditional screening method. [Display omitted] A droplet-based microfluidic platform combined with HPLC-MS/MS was developed for screening chemically induced mutant strains and analyzing their metabolites. • A microfluidic platform was developed for screening chemically induced mutant strains. • The microfluidic platform achieved rapid screening of microbial mutant strains in 4 h. • This method was suitable not only for actinomycete mutant screening, but also for bacterial mutant screening. [ABSTRACT FROM AUTHOR]

Abstract: The present study presents a new microfluidic device integrated with pneumatic microvalves and a membrane mixer for enzyme-based immunoassay of acute myocardial infarction (AMI) biomarkers, namely, myoglobin, and heart-type fatty acid binding protein (H-FABP). Superparamagnetic microspheres with carboxyl groups on their surfaces were used as antibody solid carriers. A membrane mixer consisting of four ψ-type membrane valves was assembled under the reaction chamber for on-chip performing microsphere trapping and reagent mixing. The entire immunoassay process, including microsphere capture, reagent input, mixing, and subsequent reaction, was accomplished on the device either automatically or manually. The post-reaction substrate resultant was analyzed using a microplate reader. The results show that the average absorbance value is correlated with the concentration of cardiac markers, in agreement with the results obtained using a conventional microsphere-based immunoassay; this indicated that the proposed on-chip immunoassay protocol could be used to detect both myoglobin and H-FABP. The minimum detectable concentration is 5ng/mL for myoglobin and 1ng/mL for H-FABP. [Copyright &y& Elsevier]

Abstract: In this study, a high-throughput microfluidic system is presented. The system is comprised of seven parallel channels. Each channel contains 32 square-shaped microchambers. After simulation studies on samples loaded into the microchambers, and the solute exchange between the microchambers and channels, the long-term culture of Escherichia coli (E. coli) HB101 in the microchambers is realized. Using the principle that l-arabinose (l-Ara) can induce recombinant E. coli HB101 pGLO to synthesize green fluorescent protein (GFP), the real-time analysis of GFP expression in different initial bacterial densities is performed. The results demonstrate that higher initial loading densities of the bacterial colony cause bacterial cell to enter log-phase proliferation sooner. High or low initial loading densities of the bacterial cell suspension induce the same maximum growth rates during the log-phase. Quantitative on-chip analysis of tetracycline and erythromycin inhibition on bacterial cell growth is also conducted. Bacterial morphology changes during antibiotic treatment are observed. The results show that tetracycline and erythromycin exhibit different inhibition activities in E. coli cells. Concentrations of 3μg/mL tetracycline can facilitate the formation of long filamentous bacteria with the average length of more than 50μm. This study provides an on-chip framework for bacteriological research in a high-throughput manner and the development of recombinant bacteria-based biosensors for the detection of specific substances. [ABSTRACT FROM AUTHOR]