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The advent of single-molecule techniques has spurred rapid advancements in enzymology, revealing the individual behaviors of enzymes that are obscured by ensemble averages. Traditional enzyme evaluation methods, often based on Fluorescence Resonance Energy Transfer (FRET) technology, provide average-level information through platforms like enzyme-linked instruments, which do not allow for single-molecule rate assessments. In this research, we introduce a digital single-molecule enzymatic kinetics evaluation method based on a custom microfluidic biochip. By optimizing the reagent system and conducting kinetic studies at various template concentrations, we can assess the rate changes of individual phi29 DNA polymerases within tens of thousands of microwells using fluorescence intensity variations during Rolling Circle Amplification (RCA) reactions. This method, which also includes statistical distribution analysis, enhances the conformational kinetics research of phi29 DNA polymerase and offers new insights for single-molecule studies of other proteases or nucleases, with potential applications in real-time single-molecule sequencing and drug screening. [ABSTRACT FROM AUTHOR]

Fish bones hold significant potential in the food industry. Investigating the allergenic characteristics of fish bone food products can enhance our understanding of fish allergies. In this study, the allergenic proteins in aqueous extracts from large yellow croaker (Larimichthys crocea) bones boiled for various durations were analyzed and identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and protein database searches. Tryptic products of potential allergens were detected using MALDI-TOF MS and further identified through analysis with Bruker's FlexAnalysis software and the FindMod tool available on the ExPASy proteomics server of the SIB (http://expasy.org/). 25 proteins related to allergy were identified. Two proteins reported as allergens were identified, along with twenty-three (23) proteins that, to the best knowledge of the authors, have not been reported as allergens. At least one aligned tryptic peptide were detected for 17 of the 25 proteins. The 17 potentially allergenic proteins exhibit peptide coverage ranging from 6.72 % to as high as 80 %. The results indicate that boiling the bones for 10 min releases many potentially allergenic proteins. However, the sensitization of most proteins diminishes when the bones are boiled for 30 to 120 min. Despite this, boiling does not completely eliminate the allergenicity of proteins in large yellow croaker bone samples. It is recommended to boil large yellow croaker fish bones for 30 min or longer to reduce most of the protein allergenicity when processing fish bones. Boiling may affect the allergenicity of proteins in fish bones by modifying their structure. These findings provide valuable guidance for monitoring allergens in aquatic food by-products, promisingly assisting to ensure the safety of allergy sufferers. Additionally, this research offers a reference for allergy management and the development of diagnostic reagents derived from aquatic food by-products. • Monitoring aquatic by-product allergens ensures safety and aids allergy management; • Protein allergenicity in aqueous extracts from large yellow croaker bones was studied; • Two allergenic proteins and 23 potentially allergenic proteins were identified; • Boiling large yellow croaker bones for 10 min releases many allergenic protein; • Boiling bones for 30–120 min reduces protein sensitization but doesn't eliminate allergenicity; [ABSTRACT FROM AUTHOR]

• Address application limitations of traditional focus variation microscopy. • Determine the optimal parameters for active illumination mode. • Measurement noise immunity enhanced from 8.7 nm to 1.1 nm (50 × objective). • Reconstruct the surface topography of microchannels through transparent encapsulation layer. Optical measurement methods for surface topography offer the advantages of high accuracy, rapid measurement, and non-destructiveness. Each method has its own suitable application scenarios. Among them, focus variation microscopy is extensively employed in precision manufacturing, aerospace, and medical industries due to its ability to measure rough and large slopes surfaces. However, since the measurement depends on local grayscale differences between focused and blurred images, it cannot measure surfaces with low reflectivity or insufficient texture information. In this work, we propose an active illumination mode for focus variation method that utilizes a digital micromirror device (DMD) to generate a checkerboard pattern. This method introduces additional texture information, resulting in a usable local gradient of image grayscale. Additionally, we analyze the selection criteria for the checkerboard pattern parameters, including the period and light-dark ratio. Furthermore, measurements of two standard steps with different heights demonstrate that the measurement repeatability of the proposed method can reach the nanometer level, rendering it suitable for high-precision measurements. More importantly, the measurement noise results indicate significantly superior performance of active illumination mode compared to the uniform illumination mode. Finally, we reconstruct the surface topography of the microchannels in a microfluidic chip through the encapsulation layer, demonstrating the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Co-culture spheroids mimic tumor architecture more accurately than traditional 2D cell cultures, but non-invasive, long-term tracking of live cells within these 3D models remains a challenge. This study addresses this critical need by developing a novel approach for live cell imaging in U-87/HUF co-culture spheroids. We introduce water-soluble, biocompatible red carbon dots (R-CDs) exhibiting exceptional stability and brightness (21% quantum yield) specifically designed for imaging within these 3D models. Furthermore, we designed a microfluidic chip with ellipsoid-shaped microwells to efficiently generate two distinct co-culture spheroid types: direct mixing and core-shell. R-CDs enabled non-invasive tracking of U-87 cancer cell location within these 3D models demonstrating their efficacy for long-term monitoring of live cells in cancer research. This R-CD and microfluidic technology has the potential to accelerate cancer drug discovery by enabling live cell studies in 3D tumor models. [Display omitted] [ABSTRACT FROM AUTHOR]

The increasing contamination of water with antibiotics presents significant environmental and health hazards, leading to a rise in antibiotic-resistant microorganisms. This work focused on the removal of one common pharmaceutical contaminant, Amoxicillin (AMX) from water. The approach involved enhancing a microfluidic chip by integrating a poly vinylidene fluoride (PVDF) membrane, aiming the highest and most precise adsorption capacity. The designed microfluidic chip included optical pH and dissolved oxygen sensors. The sensors enabled real-time monitoring of the solution to guarantee efficient removal of AMX. To increase the efficiency of a PVDF membrane for AMX elimination, MnFe 2 O 4 nanoparticles with particle size around 25 nm were utilized as modifier adsorbent. The chemical, morphological, and elemental content of the modified porous membrane was determined using FTIR, XRD, FESEM, and EDS characterizations and confirmed the loading of MnFe 2 O 4 nanoparticles on the PVDF membrane. The BET analysis revealed that the structural alteration obtained using the electrospray approach greatly increased the membrane's surface area after adding the nanoparticles approximately from 11.09 to 80.87 m2g−1. The hydrophilicity and thermal stability of the membranes were assessed, showing their applicability for efficient filtering operations. The optical sensors enabled real-time monitoring of pH in the range of 6–8 and dissolved oxygen in the range of 80–120 %, ensuring optimal conditions for amoxicillin adsorption in high flow rates of 100 µl/min, approximately 99 %. The comprehensive design of this system significantly improved the efficiency of removing the AMX by follows the Langmuir's model, and demonstrated the adaptability and effectiveness of microfluidic technology in decreasing pharmaceutical pollution in the water sources. Moreover, it offers a simple and quick approach for users in the membrane industry to assess the manufactured membrane, making the technology accessible and feasible for broad use. [Display omitted] • The microfluidic chip incorporated with electrosprayed MnFe 2 O 4 /PVDF membrane for amoxicillin removal from polluted water. • Optical pH and dissolved oxygen sensors for real-time continuous monitoring have been integrated to microfluidic platform. • MnFe 2 O 4 nanoparticles as an absorbent increased the surface area and porosity of PVDF membranes. • MnFe 2 O 4 /PVDF membrane can filter AMX from polluted water due to its hydrophilicity and thermal stability. [ABSTRACT FROM AUTHOR]

[Display omitted] Vesicants are chemical warfare agents (CWAs) capable of causing severe skin damage and systemic toxicity. Melatonin, known for its anti-inflammatory and antioxidant properties, can mitigate the effects of these agents. Self-nano-emulsifying drug delivery systems (SNEDDS) containing a high melatonin concentration (5 %, 50 mg/g) were optimized using a quality-by-design approach from biocompatible, non-irritant excipients with a particle size of about 100 nm. The melatonin-loaded SNEDDS showed a 43-fold greater permeability than a conventional melatonin cream. Chemical stability at ambient temperature (25 °C) was maintained for one year. The preparation of optimised melatonin-loaded SNEDDS using a simple mixing method was compared to microfluidic micromixers. Mixing was successfully achieved using a 3D-printed (fused deposition modeling or stereolithography) T-shaped toroidal microfluidic chip (with a channel geometry optimized by computational fluid dynamics), resulting in a scalable, continuous process for the first time with a substantial reduction in preparation time compared to other conventional mixing approaches. No statistically significant differences were observed in the key quality attributes, such as particle size and melatonin loading, between mixing method till kinetic equilibrium solubility is reached and mixing using the 3D-printed micromixers. This scalable, continuous, cost-effective approach improves the overall efficiency of SNEDDS production, reduces the cost of quality control for multiple batches, and demonstrates the potential of continuous microfluidic manufacture with readily customizable 3D-printed micromixers at points of care, such as military bases. [ABSTRACT FROM AUTHOR]

Small molecules have been widely developed as drugs, dyes, and research tools. DNA logic system interaction with small molecules as a new analytical method has offered remarkable promise for disease diagnosis and therapy. However, tedious modification process and large sample consumption of traditional DNA logic gates limit the application of this method in bioanalysis. Therefore, developing a simple and less sample consumption platform for DNA logic gates construction is of great importance. Here, we proposed a DNA colorimetric multilevel circuit construction strategy using gold nanoparticles (AuNPs) as an indicator without any modification and labeling step. Two colorimetric logic gates were constructed based on the aggregation of AuNPs mediated by molecular recognition between DNA and protoberberines (palmatine/berberine), including a NIMPLY logic gate and a multi-input NIMPLY + OR logic gate. The logic gate allows the detection of DNA concentrations as low as 0.25 μg/mL by naked eyes within 10 min. More importantly, a microfluidic device was successfully designed to perform the DNA molecular logic gates for reducing reagent consumption and performing precisely and automatically. The working volume of the logic system has been successfully reduced from 0.5 mL in bulk to 22 μL in our designed microfluidic chip, and the DNA solution needed was only 1.1 μL. The method presented here showed great potential in bioanalysis, diagnostics and therapeutics. [ABSTRACT FROM AUTHOR]

Microfluidic chips allow the rapid production of a library of nanoparticles (NPs) with distinct properties by changing the precursors and the flow rates, significantly decreasing the time for screening optimal formulation as carriers for drug delivery compared to conventional methods. The batch-to-batch reproducibility which is essential for clinical translation is achieved by precisely controlling the precursors and the flow rate, regardless of operators. Poly (lactic- co -glycolic acid) (PLGA) is the most widely used Food and Drug Administration (FDA)-approved biodegradable polymers. Researchers often combine PLGA with lipids or amphiphilic molecules to assemble into a core/shell structure to exploit the potential of PLGA-based NPs as powerful carriers for cancer-related drug delivery. In this review, we discuss the advantages associated with microfluidic chips for producing PLGA-based functional nanocomplexes for drug delivery. These laboratory-based methods can readily scale up to provide sufficient amount of PLGA-based NPs in microfluidic chips for clinical studies and industrial-scale production. [ABSTRACT FROM AUTHOR]

Preparation of high internal phase emulsions comes with many challenges. Droplet stability is hardly explored in these systems because they are not transparent, and highly dynamic. There is a clear need for advanced methods that allow elucidation of the mechanism of droplet coalescence in high internal phase emulsions. For this reason, we developed microfluidic chip that allow ultimate control over droplet size and high volume fraction. The chip concentrates emulsions in a concentration section, and subsequently allows coalescence investigation at volume fractions larger than 0.74. To illustrate the effect of surface active components, a systematic study was successfully carried out with β-lactoglobulin and sodium dodecyl sulfate, thus highlighting the versatility of the approach. [Display omitted] • Microfluidic device for high internal phase emulsions successfully developed. • Dispersed volume fraction can be steered through geometry and flow conditions. • Emulsions were stable from 0.1 g L−1 β-lactoglobulin and 0.1 mmol L−1 SDS onward. • Coalescence frequency increased with dispersed phase volume fraction. [ABSTRACT FROM AUTHOR]

Simultaneous, sensitive and quantitative detection of biomarkers in infectious disease is crucial for guiding antimicrobial treatment and predicting prognosis. This work reported an ultrasensitive and quantitative microfluidic immunoassay combined with the streptavidin-biotin-peroxidase (SA-B-HRP) nanocomplex-signal amplification system (MIS) to detect two inflammatory biomarkers, procalcitonin (PCT, for discriminating bacterial infections from nonbacterial infections) and interleukin-6 (IL-6, for monitoring the kinetics of infectious disease) simultaneously. The amplification system was based on the one step self-assembly of SA and B-HRP to form the SA-B-HRP nanocomplex, which effectively amplified the chemiluminescent signals. The linear ranges for PCT and IL-6 detections by MIS were 250–1.28 × 10 5 pg mL −1 and 5–1280 pg mL −1 , and the limit of detection (LOD) were 48.9 pg mL −1 and 1.0 pg mL −1 , respectively, both of which were significantly improved compared with microfluidic immunoassays without amplification system (MI). More importantly, PCT and IL-6 in human serum could be simultaneously detected in the same run by MIS, which could greatly improve the detection efficiency and reduce the cost. Given the advantages of high sensitivity, multiplex and quantitative detection, MIS could be potentially applied for detection of biomarkers at low concentration in clinical diagnosis. [ABSTRACT FROM AUTHOR]

Circulating tumor cells (CTCs) present in the blood of patients with non-hematological cancers are accessible sources for diagnosis and monitoring of cancers. By the aid of the ability of the anti-EpCAM antibody to recognize the epithelial cells, microsystem-based technologies provide robust means for effectively detecting CTCs in vitro . Considering the EpCAM expression is down-regulated during epithelial-mesenchymal transition (EMT) process, the amount of CTCs detected based on anti-EpCAM antibody is underestimated. In our study, the A549 cells targeting peptide (A-1 peptide), as the substitute of anti-EpCAM antibody, was introduced to microfluidic chip to capture A549 cells. Our results showed that both epithelial-like and mesenchymal-like A549 cells could efficiently be captured by the A-1 peptide modified microfluidic chip, and the capture efficiency for epithelial-like cells is comparable to that captured by the EpCAM antibody. Thus, we concluded that the peptide could be a better supplement to the EpCAM antibody for capturing CTCs in microfluidic system with broader spectrum. [ABSTRACT FROM AUTHOR]

The advent of chemical sensors and biosensors has drawn tremendous attention particularly in the inspection of food quality. Array-based sensors take advantage of the integration of multiple recognition elements on a single microdetector, and the ability to recognize a myriad of molecular targets from complex samples. With the continuous advancement in lab-on-a-chip technology, microfluidic-based techniques have enabled rapid and portable monitoring of multiple nutritional or harmful substances that provide high sensitivity, high throughput, and low sample consumption. In this article, the latest progress in array-based chemical sensors and biosensors is carefully reviewed. Several major chemometric methods for handling high-dimensional data, including hierarchical cluster analysis, principal component analysis, and support vector machine, are introduced and commented of reference to their use primarily in the detection of foodborne hazardous species or contaminants. Finally, special insights are given into the development of miniaturized, sensitive, and selective sensors as the next generation of point-of-care tools. [Display omitted] • Array-based chemical or biological sensors are able to recognize multiple targets from complex samples. • Microfluidic chip is a powerful platform for the construction of sensor arrays with microscale components. • Chemometrics enhance the performance of sensor arrays through the analysis of high dimensional data. • Array-based sensors display great potentials in food safety screening and quality control. [ABSTRACT FROM AUTHOR]

The large-scale use of antibiotics and the resulting drug residues poses a significant threat to global human health. Waste discharge and biological chain transmission are closely linked to residual antibiotic pollution in the fields of medicine, environmental monitoring, and food safety. Monitoring drug dosage in medicines and the detection of trace antibiotic residues in environmental and food matrices is therefore especially important. Microfluidic technology allows manipulation and flexible design of micro/nanofluids and is thus an essential means of antibiotic detection and analysis. Herein, we review recent progress in the design and applications of microfluidic chips as biosensors for the analysis of antibiotic residue analysis over the past five years. The types of chip materials and combination of microfluidic chips with essential technologies involving optics, electrochemistry, and mass spectrometry are introduced, and the critical principles of antibiotic microfluidic analysis and its application in the three aforementioned fields are summarized. [Display omitted] • The types of microfluidic chips used for analysis of antibiotics were described. • Described and summarized the important principles applied by microfluidic biosensors in antibiotic assays. • Described the progress of detection techniques for antibiotic microfluidic biosensing analysis in the last five years. • Summarized the application of microfluidic biosensing analysis of antibiotic detection in three major fields. [ABSTRACT FROM AUTHOR]

The Coronavirus disease 2019 (COVID-19) outbreak has urged the establishment of a global-wide rapid diagnostic system. Current widely-used tests for COVID-19 include nucleic acid assays, immunoassays, and radiological imaging. Immunoassays play an irreplaceable role in rapidly diagnosing COVID-19 and monitoring the patients for the assessment of their severity, risks of the immune storm, and prediction of treatment outcomes. Despite of the enormous needs for immunoassays, the widespread use of traditional immunoassay platforms is still limited by high cost and low automation, which are currently not suitable for point-of-care tests (POCTs). Microfluidic chips with the features of low consumption, high throughput, and integration, provide the potential to enable immunoassays for POCTs, especially in remote areas. Meanwhile, luminescence detection can be merged with immunoassays on microfluidic platforms for their good performance in quantification, sensitivity, and specificity. This review introduces both homogenous and heterogenous luminescence immunoassays with various microfluidic platforms. We also summarize the strengths and weaknesses of the categorized methods, highlighting their recent typical progress. Additionally, different microfluidic platforms are described for comparison. The latest advances in combining luminescence immunoassays with microfluidic platforms for POCTs of COVID-19 are further explained with antigens, antibodies, and related cytokines. Finally, challenges and future perspectives were discussed. • Immunological signatures of the life cycles of COVID-19 are introduced. • Luminescence immunoassays on microfluidic chips for point-of-care (POC) diagnosis of COVID-19 are well detailed. • Existent challenges and future perspectives for POC immunoassays are further discussed. [ABSTRACT FROM AUTHOR]

Solvent bonding represents a joining method for thermoplastic materials that results in high bond strength, with short process times. However, there is a challenge in bonding micro-channeled substrates for microfluidic devices due to excessive channel clogging and distortion. In this work, a simple design method to fuse poly(methyl methacrylate) microfluidic chips with solvents without micro-channel clogging is demonstrated. The joining process is improvised improved by subjecting the chip to a vacuum during the bonding process, whereby the undesired excess solvent between the microfluidic chip and cover can be removed. The microfluidic devices that were bonded using this method exceeded the application requirements, in particular transparency and internal back pressure requirements. [ABSTRACT FROM AUTHOR]

Microfluidic systems have important application value in biology and medicine research. However, a major challenge in Microfluidic based cell analysis is to automatically segment touching cells in the microscopic images. In this paper, we propose a novel automatic cell segment method based on concave point detection and matching. On the basis of high-quality image deblurring, we adopt a UNet++ based deep neural network to accurately extract cell contours by taking as input both bright and dark-field images, and trained with a Dice loss based objective function. Then, we propose a method that extracts concave points from the contours by detecting the convex hull defects, and the issue of missing concave points is addressed by considering the distance between the starting and the ending point of defect. Finally, to overcome the limitation of existing methods that the accuracy of segmentation is highly dependent on the accuracy of concave point detection, we propose a concave points matching condition based on compactness to obtain the concave point pairs for segmentation. Experimental results show that our method can effectively segment touching cells with high accuracy, and is robust to different cell concentration levels. • Propose a novel deep learning based cell segmentation method for microfluidic chips. • Both the bright and dark field information is used in contour extraction. • Novel concave point detection and matching algorithms are proposed. • Achieve over 90% accuracy on most experiments of different concentration levels. [ABSTRACT FROM AUTHOR]

Detection of the droplet contents is a key function for droplet-based microfluidic systems. This paper presents a polystyrene microfluidic device integrated with droplet generator and micro film electrodes for direct amperometric detection of droplet contents without droplet desegmentation and phase separation. The method for fabrication of the full polystyrene micro chip was presented, and the behaviors of the developed polystyrene chip for generation and stabilization of water in n-octanol droplets, and detection of H2O2 in droplets were examined. The influences of electrode architecture and flow conditions on the electrochemical signals were studied in detail. With the developed chip, a sensitivity of 0.12Amol-1Lcm-2 and a detection limit of 10.0μmolL-1 were observed for the determination of droplet contained H2O2. The achieved precision for the detection of 21 droplets containing 250μmolL-1 H2O2 was 3.8% in relative standard deviation. The way for the aqueous droplets encapsulated by the oil-carrier to contact sensing electrodes was discussed based on the experimental observations, and the potential approaches for further improving the analytical performance were suggested. [ABSTRACT FROM AUTHOR]

Abstract: Background: Conventional immunoassays are labor intensive, time consuming, expensive and require large pieces of equipment for detection. In an effort to overcome these shortcomings, this study established an immunoassay method of alpha fetoprotein (AFP) in serum in combination with the microfluidic chip technology. Methods: A sandwich immunoassay approach was applied to detect AFP based on microfluidic chips and the chemiluminescence as detection signal. The chip used in this method was composed of a polydimethylsiloxane (PDMS) microchannel layer over a PDMS base layer. Result: AFP concentration and chemiluminescence intensity were linearly correlated over the concentration ranging from 12.5 to 200ng/ml, and a detection limit as low as 1.5ng/ml using this method. The coefficients of variation were 9.91% and 11.4% for the within- and between-run assays, respectively. More than 50 clinical samples were tested and the results obtained for this method strongly correlated with Roche's electrochemiluminescence (ECL) kit. Conclusions: The proposed method offers a reliable, simple, reagent safe and inexpensive analytical platform for the determination of AFP in serum, and promotes the development of high throughput screening and point-of-care testing (POCT) diagnostics in clinical practice. [Copyright &y& Elsevier]

Abstract: A novel microfluidic chip coupled with near-infrared (NIR) fluorescence detection set-up was established for specific analysis of trace Hg2+. Based on the NIR fluorescence changes caused by Hg2+-induced dissolution and aggregation of label-free single-strand DNA (ssDNA) wrapped single-walled carbon nanotubes (SWNTs), Hg2+ in aqueous solution were detected sensitively and specifically in the microfluidic chips system. Due to the small device dimension effect as well as the high efficiency of microfluidic chips, the reagent volume reduced from 500μL to 9μL and the minimum reaction time reaching the plateau was shortened from 60min to 30min, while the detection limit for Hg2+ decreased from 10.5nM to 1.5nM, compared with that of measured in regular Eppendorf tube. The idea of detecting NIR fluorescence spectra in microfluidic systems opens new avenues to optical analysis and bioassays in probing trace species. [Copyright &y& Elsevier]

Abstract: An immunoassay based on the enrichment of antibodies by magnetic beads (MB) and their subsequent detection of antigens in a microfluidic chip (MFC)–quartz crystal microbalance (QCM) was developed and investigated. The MB conjugated to goat anti-human-immunoglobulin G (MB-anti-h-IgG) were concentrated within microchannels by the application of a magnetic field, which also functioned as a separation switch outside the MFC. The conjugation of the MB and the anti-h-IgG antibody in the MFC was completed in 1min. Removal of the magnetic field allowed the resulting tributary buffer solution to flush the MB-anti-h-IgG out of the MFC and onto a QCM chip. The combination of the MB-anti-h-IgG and the QCM chip amplified the detection sensitivity of antigen(s) to 10−1 ng/ml. By controlling the enrichment velocity and sample injection mode in the MFC, a linear response ranging from 10−1 to 103 ng/ml was obtained. This technique establishes a simple, rapid MFC method for the amplification of a QCM-based immunoassay. [Copyright &y& Elsevier]

Abstract: This review, covering reports published from 2002 to August 2010, shows how aptamers have made significant contributions in the improvements of microfluidic chips for affinity extraction, separations and detections. Furthermore, microfluidic chip methods for studying aptamer-target interactions and performing aptamer selections have also been summarized. Accordingly, research vacancies and future development trends in these areas are discussed. [ABSTRACT FROM AUTHOR]

It has been reported that more than 90% of cancer patients are died from cancer metastasis. Circulating tumor cells (CTCs) could detach from solid tumors to form new lesions via blood transport and play an important role in cancer metastasis and progression. As part of the liquid biopsy, the investigation and analysis toward CTCs are of great importance for prognosis assessment and tumor precision medical treatment. Unfortunately, the enrichment of circulating tumor cells has been a huge challenge due to the fact that CTCs are very rare and vulnerable. Thus, a number of effective strategies have been developed for the enrichment of CTCs. This paper discusses the advantages and disadvantages of label-free and label-based methods commonly used in the isolation of CTCs. In particular, we systematically review the most recent advances in the combination of microfluidic chips and biosensing for the enrichment of circulating tumor cells. Finally, we put forward the current barriers that need to be overcome and developmental trends in the CTCs research. [ABSTRACT FROM AUTHOR]

Abstract: A micro flow injection wetting film liquid–liquid extraction system has been developed for trace analyte concentration and on-chip detection. A hydrophobic channel fabricated on a polycarbonate chip was used to support the wetting film, and hydrostatic pressure generated by the difference in liquid levels was employed to drive the fluids. Sequential injection of segments of aqueous sample solution and organic solvent was conducted by switching the sample- or solvent-containing vials to an on-chip sampling probe, and detection was performed by a co-focused, laser induced fluorescence detector. Using butyl rhodamine B as a model analyte and butanol as the solvent for both film-coating and elution, various experimental conditions such as hydrostatic pressure, coating time, channel length, sampling volume, and sample acidity were investigated. Under optimized conditions, a 24-fold enrichment factor was obtained with the consumption of about 3μL sample solution, and a detection limit (3σ) of 6.0×10−9 M butyl rhodamine B was achieved at the sampling rate of 19h−1. Eleven consecutive runs of a 1.0×10−5 M butyl rhodamine B solution produced a relative standard deviation of 1.5% for the detected fluorescence signals. [Copyright &y& Elsevier]

Abstract: Human cancer is inherently heterogeneous, so the ability to monitor individual cancer cells at every clinic visit would be a valuable tool. This work describes the first step towards developing handheld and automated devices for molecular and phenotypic analysis of cancer cells. Here, we show that use of capillary electrophoresis to detect PCR product amplified from either transcripts (high abundance template) or genomic DNA (low abundance template) encoding clonotypic immunoglobulin heavy chain VDJ of plasma cells from patients with multiple myeloma. High abundance IgH VDJ transcripts amplified in conventional systems or by capillary electrophoresis through channels on microfluidic chips or, alternatively, PCR product amplified from individual myeloma plasma cells in a single stage RT-PCR reaction was readily detectable on microfluidic chips. For low abundance templates, a nested PCR strategy was needed to detect PCR product by any method. Using microfluidic chips, PCR products amplified from genomic IgH VDJ DNA were detected in six out of eight plasma cells. Comparison of the ABI3100 and the microfluidic chip indicates that approximately 20 times more sample is injected into the ABI 3100 capillary than for the microfluidics chip. Overall, for high and low abundance template in individual cells, the microfluidic separation/detection system is at least as sensitive as the ABI 3100. In the future, integrated microfluidic platforms that incorporate both PCR cycling and product detection on the same chip are likely to exceed conventional systems in sensitivity and speed of genetic analysis by RT-PCR or PCR. [Copyright &y& Elsevier]

A three-layer poly(dimethylsiloxane) (PDMS)/glass microfluidic system for performing on-chip solid-phase enzymatic reaction and chemiluminescence (CL) reaction was used for the determination of glucose as a model analyte. A novel method for the immobilization of controlled-pore-glass based reactive particles on PDMS microreactor beds was developed, producing an on-chip solid-phase reactor that featured large reactive surface and low flow impedance. Efficient mixing of reagent/sample/carrier streams was achieved by incorporating chaotic mixer structures in the microfluidic channels. A conventional sequential injection (SI) system was adapted for direct coupling with the microfluidic system, and combined with hydrostatic delivery of reagents to achieve efficient and reproducible sample introduction at 10 μl levels. A detection limit of 10 μM glucose (3σ), and a precision of 3.1% RSD (n=7, 0.2 mM glucose) were obtained using the SI-microfluidic-CL system integrated with a glucose oxidase (GOD) reactor. Carryover was <5% at a throughput of 20 samples/h. [Copyright &y& Elsevier]

Rapid, efficient, and accurate detection of foodborne bacteria is important for public health and food safety; however, point-of-care testing remains a limiting factor in the field. Compared with traditional methods, the use of microfluidic chips in monitoring foodborne bacteria has the advantages of miniaturization, automation, integration, high throughput, and low consumption. Notably, the combination of nanomaterials with microfluidics further provides an improved method of pathogen detection with superior, rapid, and sensitive detection efficiencies. This review presents a broad overview of a wide range of microfluidic chips, including the magnetic nanomaterial-based assay, metal nanomaterial-based assay, carbon nanomaterial-based assay, quantum dot-based assay, and upconversion nanoparticle-based assay, for the detection of foodborne bacteria using different nanomaterials. Additionally, the main challenges that exist for translation of scientific research into product development are discussed. On this basis, we provide perspectives on both future technological directions and potential applications, which will guide researchers in identifying the most promising areas of development in this field. • covers recent advances in microfluidic platforms at foodborne bacteria detection field. • summarizes the utilization of nanomaterials on microfluidic chips. • highlights the advantage and disadvantage of nanomaterial-based microfluidic devices. • discusses the current status and further prospective of nanomaterial-based microfluidic systems. [ABSTRACT FROM AUTHOR]

In the replication of polymeric micro/nano structures, adhesion and friction between mould tool and polymer cause significant feature failure. For the first time, this work developed a novel strategy for the fabrication of high-hardness and self-lubricating 2D material-reinforced nickel mould tools using electroforming to achieve high precision replication of polymeric micro structures. In this study, layered 2D material, including graphene oxide (GO), molybdenum disulfate (MoS 2), and tungsten disulfide (WS 2), for the fabrication of self-lubricating mould tools, were systematically studied. Our results demonstrated that nickel/WS 2 mould tools, followed by nickel/GO and nickel/MoS 2 mould tools, presented the most significant microhardness improvement. A maximum microhardness of ∼660 HV together with a minimum crystallite size of 12 nm was achieved from 0.5 g/L WS 2 , indicating a 3.67 times microhardness increase and 3 times crystallite size reduction relative to the pure nickel mould tool. The enhanced microhardness can be attributed to the 2D material-induced crystal refinement, and inherent hardness and incorporation content of 2D material. Additionally, friction and wear tests revealed that a low concentration of WS 2 at 0.14 g/L achieved the lowest coefficient of friction (COF) and superior wear resistance. The COFs in the initial stage and steady state stage were 0.08 and 0.18, respectively, implying decreases of 42.8% and 72.3%, respectively, and a 27-fold increase in lifetime compared with those of the pure nickel mould tool. Such a significant improvement in tribological properties was due to the formation of self-lubricating transfer film by the interlayer shear effect of few-layered 2D material nanosheets. Finally, defect-free polymeric microfluidic chips were micro hot embossed using an optimal self-lubricating nickel/WS 2 mould tool for validation. This work provides significant insight into the fabrication of potential self-lubricating micro/nano mould tools for microfluidics applications. [Display omitted] • Novel 2D material-reinforced nickel composite mould tools were fabricated by the electroforming process. • Nickel/WS 2 mould tools presented optimal hardness and friction coefficient of 660 HV and 0.18, respectively. • The reduction of friction coefficient was related to the self-lubricating properties of 2D material. • Nickel/WS 2 mould tool achieved high-quality replication of microfluidic chips. [ABSTRACT FROM AUTHOR]

Benefiting from emerging miniaturized and equipment-free nucleic acid testing (NAT) technologies, fully integrated NAT devices at point of care (POC) with the capability of "sample-in-answer-out" are proceeding at a break-neck speed to eliminate complex operations and reduce the risk of contamination. Like the development of polymerase chain reaction (PCR) technology (the standard technique for NAT), the detection signal of fully integrated NAT devices has evolved from qualitative to quantitative and recently to digital readout, aiming at expanding their extensive applications through gradually improving detection sensitivity and accuracy. This review firstly introduces the existing commercial products, and then illustrates recent fully integrated microfluidic devices for NAT at POC from the aspect of detection signals (i.e. , qualitative, quantitative and digital). Importantly, the key issues of existing commercial products and the main challenges between scientific research and product development are discussed. On this basis, we envision that the MARCHED (m iniaturized, a utomatic, r eagent-preloaded, c ommercializable, h igh-throughput, e nvironment-independent and d isposable) NAT devices are expected to be realized in the near future. • The key issues of existing commercial products and the main challenges for product development were discussed. • Advances in fully integrated NAT devices from qualitative to quantitative to digital readout were introduced. • The MARCHED NAT devices were proposed as prospective development tendency. [ABSTRACT FROM AUTHOR]

Cell co-culture serves as a standard method to study intercellular communication. However, random diffusion of signal molecules during co-culture may arouse crosstalk among different types of cells and hide directive signal-target responses. Here, a microfluidic chip is proposed to study unidirectional intercellular communication by spatially controlling the flow of the signal molecules. The chip contains two separated chambers connected by two channels where the culture media flows oppositely. A zigzag signal-blocking channel is designed to study the function of a specific signal. The chip is applied to study the unidirectional communication between tumor cells and stromal cells. It shows that the expression of α-smooth muscle actin (a marker of cancer-associated fibroblast (CAF)) of both MRC-5 fibroblasts and mesenchymal stem cells can be up-regulated only by the secreta from invasive MDA-MB-231 cells, but not from non-invasive MCF-7 cells. The proliferation of the tumor cells can be improved by the stromal cells. Moreover, transforming growth factor beta 1 is found as one of the main factors for CAF transformation via the signal-blocking function. The chip achieves unidirectional cell communication along X-axis, signal concentration gradient along Y-axis and 3D cell culture along Z-axis, which provides a useful tool for cell communication studies. • A microfluidic chip was developed to study unidirectional intercellular communication. • Under unidirectional communication, different tumor cells showed distinct stimuli on the myofibroblastic transformation of stromal cells. • TGF-β1 was the key driven force for myofibroblastic transformation revealed via the signal-blocking design. • Stromal cells improved the proliferation of tumor cells. [ABSTRACT FROM AUTHOR]

Despite significant efforts in the study of cardiovascular diseases (CVDs), they persist as the leading cause of mortality worldwide. Considerable research into human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) has highlighted their immense potential in the development of in vitro human cardiac tissues for broad mechanistic, therapeutic, and patient-specific disease modeling studies in the pursuit of CVD research. However, the relatively immature state of hPSC-CMs remains an obstacle in enhancing clinical relevance ofengineered cardiac tissue models. In this study, we describe development of a microfluidic platform for 3D modeling of cardiac tissues, derived from both rat cells and hPSC-CMs, to better recapitulate the native myocardium through co-culture with interstitial cells (specifically cardiac fibroblasts), biomimetic collagen hydrogel encapsulation, and induction of highly anisotropic tissue architecture. The presented platform is precisely engineered through incorporation of surface topography in the form of staggered microposts to enable long-term culture and maturation of cardiac cells, resulting in formation of physiologically relevant cardiac tissues with anisotropy that mimics native myocardium. After two weeks of culture, hPSC-derived cardiac tissues exhibited well-defined sarcomeric striations, highly synchronous contractions, and upregulation of several maturation genes, including HCN1, KCNQ1, CAV1.2, CAV3.1, PLN, and RYR2. These findings demonstrate the ability of the proposed engineered platform to mature animal- as well as human stem cell-derived cardiac tissues over an extended period of culture, providing a novel microfluidic chip with the capability for cardiac disease modeling and therapeutic testing. [ABSTRACT FROM AUTHOR]

Clinical application of direct sampling electrospray ionization mass spectrometry (ESI-MS) remains limited due to problems associated with very "dirty" sample matrices. Herein we report on a microfluidic platform that allows direct mass spectrometric analysis of serum samples of microliter sizes. The platform integrates in-line paper adsorption-based sample clean-up and voltage assisted liquid desorption ESI-MS/MS (VAL DESI-MS/MS) to detect multiple targeted compounds of clinical interest. Adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP) were selected as model analytes. Simultaneous quantification of these compounds in human serum samples was demonstrated. For all the three compounds, linear calibration curves were obtained in a concentration range from 0.20 to 20.0 μmol/L with r2 values ≥ 0.996. Limits of detection were 0.019, 0.015, and 0.011 μmol/L for AMP, ADP, and ATP, respectively. Recovery was found in the range from 96.5% to 103.5% at spiking concentrations of 0.25 and 2.50 μmol/L. The results indicate that the proposed microfluidic mass spectrometric platform is robust and effective. It may have a potential in clinical analysis. Image 1 • This is the first microfluidic platform of its kind. • Direct mass spectrometric analysis of human serum to simultaneously quantify compounds of clinical interests is achieved. • ATP and its metabolites in serum are simultaneously determined with fast sample throughput. • The new assay strategy may have a potential for POC test applications. [ABSTRACT FROM AUTHOR]