Emerging Microfluidic Devices for Sample Preparation of Undiluted Whole Blood to Enable the Detection of Biomarkers

Finger-actuated microfluidic chip integrated with visual immunoassay for ultrasensitive detection of PSA in whole blood

Cumbersome preprocessing and specialized manual operations in clinical blood samples remain a significant challenge for achieving high sensitivity and accurate quantification in point-of-care testing. In this paper, a finger-driven integrated microfluidic chip based on visualization of single nanoparticle scattering was proposed for the detection of prostate-specific antigen (PSA) in the whole blood. To control on-chip fluid, a finger-driven module based on a Tesla valve was designed to unidirectionally regulate fluid mixing and separation in the microchannel. In addition, a membrane separation unit was designed to efficiently separate blood cells and serum, reducing interference from blood cells in the detection process. For quantitative PSA concentration detection, a Multi-functional core-satellite magnetic probe was constructed by using the principle of complementary base pairing of ligands on the surface of gold nanoparticles and magnetic beads. In the presence of target PSA, the constructed core-satellite nanostructure was decomposed, producing a characteristic fluorescence signal and releasing gold nanoparticles with green scattering spots under dark-field microscopy. By correlating the concentration with the number of green scattering spots, cancer risk levels were displayed intuitively using a traffic light system. This biosensor achieves an ultra-low detection limit of 0.5 pg/mL for PSA. Due to the ultra-sensitive ability in detection, the monitoring of PSA concentrations for patients during treatment was also demonstrated. Compared with other methods, this proposed microfluidic assay technology has the advantages of small sample volume, minimal operation, high sensitivity and accuracy. Overall, this biosensor provides a new approach for cancer recurrence monitoring and early diagnosis.

MIP-Chip: Integrated Microfluidic Plasma Separation and Redox-Enhanced Molecularly Imprinted Polymer Succinate Sensor for Whole Blood Metabolite Analysis

The precise quantification of metabolites in bodily fluids is essential for advancing digital health monitoring and clinical diagnostics. Among these fluids, whole blood stands out as a valuable source of predictive metabolite biomarkers, providing critical insights into disease diagnosis and progression. However, traditional blood testing methods often require expensive instrumentation and specialized training, primarily due to the need for plasma extraction to remove interfering blood cells. This study addresses these limitations by introducing a novel, sensitive, rapid, reagent-free, and cost-effective capillary microfluidic-integrated molecularly imprinted polymer (MIP) sensor (MIP-Chip) designed for metabolite detection in whole blood. The MIP-Chip integrates two key components: (1) a highly efficient plasma separation module capable of extracting plasma from whole blood (∼95% efficiency) without requiring sample pretreatment or external active forces and (2) an electrochemical MIP sensor employing an ultrasensitive electrode with on-electrode Prussian Blue nanoparticles (PB NPs) as embedded redox probes for sensitive and specific metabolite detection in the extracted plasma. Using this platform, we successfully quantified succinate, a critical metabolite, across a wide linear concentration range (50 nM-250 μM) with a limit of detection of 5 nM. The device processed 120 μL of whole blood, delivering 8 μL of plasma, and completed the entire workflow-from sample introduction to biomarker detection within 25 min. The MIP-Chip demonstrated exceptional performance, including self-powered assay automation, high specificity for succinate quantification in whole blood, excellent reproducibility, and long-term stability of the MIP-based sensor. These features establish the MIP-Chip as a powerful analytical platform for point-of-care diagnostics, offering a significant step forward in clinical metabolite detection and digital health monitoring.

Continuous High-Throughput Plasma Separation for Blood Biomarker Sensing Using a Hydrodynamic Microfluidic Device

Continuous, cost-effective, high-throughput with admissible yield and purity of blood plasma separation is widely needed for biomarker detection in the clinic. The existing gold standard technique (centrifugation) and microfluidic technologies fall short of meeting these criteria. In this study, a microfluidic device design is demonstrated based on passive hydrodynamic principles to achieve admissible yield and purity plasma samples. Through computational and experimental assessments, it is shown that side channels with varying lengths are required to improve the plasma extraction rate. The optimized side channels in this device design use the formed cell-free layer regions in the expanded areas to extract plasma consistently and efficiently. These Hydrodynamic Continuous, High-Throughput Plasma Separator (HCHPS) microfluidic devices achieve a purity in the range of 47% to 64% with whole blood and maintaining a yield of 10% to 18%, with half hemolysis compared to gold standard centrifugation. These devices also separate the plasma from diluted blood with a purity in the range of 62% to 97% with a similar yield range. Additionally, whole human blood spiked with lactate was processed through the HCHPS device, and the separated plasma is collected and analyzed using two biosensing approaches, a bead-based fluorescence, and an electrochemical aptamer biosensing, confirming the quality of plasma for downstream biomarker detection.

An Integrating Microfluidic System for Concentration Gradient Generation of Exosomes and Exosome-Assisted Single-Cell-Derived Tumor-Sphere Formation

To enhance exploration on tumor stem-like cells (TSCs) without altering their cellular biological characteristics, researchers advocate for application of single-cell-derived tumor-spheres (STSs). TSCs are regulated by their surrounding microenvironment, making it crucial to simulate a tumor microenvironment to facilitate STS formation. Recently, exosomes that originated from the tumor microenvironment have emerged as a promising approach for mimicking the tumor microenvironment. In the tumor microenvironment, various associated cells (such as fibroblasts, endothelial cells, and immune cells) play crucial roles. Utilizing exosomes derived from these cells enabled us to simulate the tumor microenvironment and promote STS formation. Herein, we have developed an integrated microfluidic platform to generate serial concentration gradients and evaluate the effects of multiple exosomes on STS formation. To demonstrate the feasibility of our approach, we generated serial concentration gradients of exosomes derived from two different cell types (HUVEC and NIH/3T3 cells) and assessed their effects on STS formation. Subsequently, we investigated the drug resistance of STSs treated with free doxorubicin and doxorubicin-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles. Our findings revealed that the serial concentration gradients of mixed exosomes could be successfully generated, leading to an enhanced formation rate and size of STSs. Compared to exosomes derived from one cell type, the mixed exosomes exhibited superior promotion of STS formation. Additionally, nanomedicines demonstrated a reduction in the drug resistance of TSCs compared to free drug treatment, particularly in smaller and/or more deformable TSCs. This platform provides an innovative approach for STS formation enhancement and tumor microenvironment simulation.

A Droplet Microfluidic Sensor for Point-of-Care Measurement of Plasma/Serum Total Free Thiol Concentrations

Total free thiols are an important marker of the whole-body redox state, which has been shown to be associated with clinical outcome in health and disease. Recent investigations have suggested that increased insight may be gained by monitoring alterations of redox state in response to exercise and hypoxia and to monitor redox trajectories in disease settings. However, conducting such studies is challenging due to the requirement for repeated venous blood sampling and intensive lab work. Droplet microfluidic sensors offer an alternative platform for developing a point-of-care testing approach using small sample volumes and automated systems to complement or ultimately replace laboratory testing. Here we developed a small, portable droplet microfluidic sensor that can measure total free thiol concentrations in 20 μL human plasma (or serum) samples, providing a reading in less than 10 min. This system features a novel method to enhance the mixing of reagent and analyte in droplets containing viscous biological fluids. The results in a range of real-world human plasma samples showed equivalence with current standard laboratory assays while reducing sample volume requirements 9-fold and fully automating the process. Micro hematocrit capillaries allowed testing of capillary blood samples collected by fingerprick lancing. The system was used to monitor total free thiols using fingerprick samples in healthy volunteers and revealed significant changes in total free thiols in response to food intake and exercise. This device has the potential to improve our ability to conduct physiological studies of total free thiol level changes and improve our understanding of redox physiology, which may ultimately be applied in redox medicine to improve patient care.

A microfluidic chip with integrated plasma separation for sample-to-answer detection of multiple chronic disease biomarkers in whole blood

Point-of-care testing of multiple chronic disease biomarkers is crucial for timely intervention and management of chronic diseases. Here, a "sample-to-answer" microfluidic chip was developed for simultaneous detection of multiple chronic disease biomarkers in whole blood by integrating a plasma separation module. The whole detection process is very convenient, i.e., just add whole blood and get the results. The chip successfully achieved the simultaneous detection of total cholesterol, triglycerides, uric acid, and glucose in undiluted whole blood within 21 min, including 6 min for plasma separation and 15 min for enzymatic chromogenic reactions. Moreover, the sensitivity levels of on-chip detection of chronic disease biomarkers can also meet clinically relevant thresholds. The chip is easy to use and has significant potential to improve home self-management of chronic diseases and enhance healthcare outcomes.

Transdermal Minimally Invasive Optical Multiplex Detection of Protein Biomarkers by Nanopillars Array-Embedded Microneedles

Biomarkers detection has become essential in medical diagnostics and early detection of life-threatening diseases. Modern-day medicine relies heavily on painful and invasive tests, with the extraction of large volumes of venous blood being the most common tool of biomarker detection. These tests are time-consuming, complex, expensive and require multiple sample manipulations and trained staff. The application of "intradermal" biosensors utilizing microneedles as minimally invasive sensing elements for capillary blood biomarkers detection has gained extensive interest in the past few years as a central point-of-care (POC) detection platform. Herein, we present a diagnosis paradigm based on vertically aligned nanopillar array-embedded microneedles sampling-and-detection elements for the direct optical detection and quantification of biomarkers in capillary blood. We present here a demonstration of the simple fabrication route for the creation of a multidetection-zone silicon nanopillar array, embedded in microneedle elements, followed by their area-selective chemical modification, toward the multiplex intradermal biomarkers detection. The utilization of the rapid and specific antibody-antigen binding, combined with the intrinsically large sensing area created by the nanopillar array, enables the simultaneous efficient ultrafast and highly sensitive intradermal capillary blood sampling and detection of protein biomarkers of clinical relevance, without requiring the extraction of blood samples for the ex vivo biomarkers analysis. Through preliminary in vitro and in vivo experiments, the direct intradermal in-skin blood extraction-free platform has demonstrated excellent sensitivity (low pM) and specificity for the accurate multiplex detection of protein biomarkers in capillary blood.

Recent progress on media for biological sample preparation

The analysis of biological samples is highly valuable for disease diagnosis and treatment, forensic examination, and public safety. However, the serious matrix interference effect generated by biological samples severely affects the analysis of trace analytes. Sample preparation methods are introduced to address the limitation by extracting, separating, enriching, purifying trace target analytes from biological samples. With the raising demand of biological sample analysis, a review focuses on media for biological sample preparation and analysis over the last 5 years is presented. High-performance media in biological sample preparation are first reviewed, including porous organic frameworks, imprinted polymers, hydrogels, ionic liquids, and bioactive media. Then, application of media for different biological sample preparation and analysis is briefly introduced, including liquid samples of body fluids, solid samples (hair, feces, and tissues), and gas samples of exhale breath gas. Finally, conclusions and outlooks on media promoting biological sample preparation are presented.

Stabilizing and Accelerating Secondary Flow in Ultralong Spiral Channel for High-Throughput Cell Manipulation

Efficient cell manipulation is essential for numerous applications in bioanalysis and medical diagnosis. However, the lack of stability and strength in the secondary flow, coupled with the narrow range of practical throughput, severely restricts the diverse applications. Herein, we present an innovative inertial microfluidic device that employs a spiral channel for high-throughput cell manipulation. Our investigation demonstrates that the regulation of Dean-like secondary flow in the microchannel can be achieved through geometric confinement. Introducing ordered microstructures into the ultralong spiral channel (>90 cm) stabilizes and accelerates the secondary flow among different loops. Consequently, effective manipulation of blood cells within a wide cell throughput range (1.73 × 108 to 1.16 × 109 cells/min) and cancer cells across a broad throughput range (0.5 × 106 to 5 × 107 cells/min) can be achieved. In comparison to previously reported technologies, our engineering approach of stabilizing and accelerating secondary flow offers specific performance for cell manipulation under a wide range of high-throughput manner. This engineered spiral channel would be promising in biomedical analysis, especially when cells need to be focused efficiently on large-volume liquid samples.

Revolutionizing agriculture with nanotechnology: Innovative approaches in fungal disease management and plant health monitoring

Nanotechnology has emerged as a transformative force in modern agriculture, offering innovative solutions to address challenges related to fungal plant diseases and overall agricultural productivity. Specifically, the antifungal activities of metal, metal oxide, bio-nanoparticles, and polymer nanoparticles were examined, highlighting their unique mechanisms of action against fungal pathogens. Nanoparticles can be used as carriers for fungicides, offering advantages in controlled release, targeted delivery, and reduced environmental toxicity. Nano-pesticides and nano-fertilizers can enhance nutrient uptake, plant health, and disease resistance were explored. The development of nanosensors, especially those utilizing quantum dots and plasmonic nanoparticles, promises early and accurate detection of fungal pathogens, a crucial step in timely disease management. However, concerns about their potential toxic effects on non-target organisms, environmental impacts, and regulatory hurdles underscore the importance of rigorous research and impact assessments. The review concludes by emphasizing the significant prospects of nanotechnology in reshaping the future of agriculture but advocates for a balanced approach that prioritizes safety, sustainability, and environmental stewardship.

Customizable Microfluidic Devices: Progress, Constraints, and Future Advances

The field of microfluidics encompasses the study of fluid behavior within micro-channels and the development of miniature systems featuring internal compartments or passageways tailored for fluid control and manipulation. Microfluidic devices capitalize on the unique chemical and physical properties exhibited by fluids at the microscopic scale. In contrast to their larger counterparts, microfluidic systems offer a multitude of advantages. Their implementation facilitates the investigation and utilization of reduced sample, solvent, and reagent volumes, thus yielding decreased operational expenses. Owing to their compact dimensions, these devices allow for the concurrent execution of multiple procedures, leading to expedited experimental timelines. Over the past two decades, microfluidics has undergone remarkable advancements, evolving into a multifaceted discipline. Subfields such as organ-on-a-chip and paper-based microfluidics have matured into distinct fields of study. Nonetheless, while scientific progress within the microfluidics realm has been notable, its translation into autonomous end-user applications remains a frontier to be fully explored. This paper sets forth the central objective of scrutinizing the present research paradigm, prevailing limitations, and potential prospects of customizable microfluidic devices. Our inquiry revolves around the latest strides achieved, prevailing constraints, and conceivable trajectories for adaptable microfluidic technologies. We meticulously delineate existing iterations of microfluidic systems, elucidate their operational principles, deliberate upon encountered limitations, and provide a visionary outlook toward the future trajectory of microfluidic advancements. In summation, this work endeavors to shed light on the current state of microfluidic systems, underscore their operative intricacies, address incumbent challenges, and unveil promising pathways that chart the course toward the next frontier of microfluidic innovation.

Flow-Rate-Insensitive Plasma Extraction by the Stabilization and Acceleration of Secondary Flow in the Ultralow Aspect Ratio Spiral Channel

Although microfluidic devices have made remarkable strides in blood cell separation, there is still a need for further development and improvement in this area. Herein, we present a novel ultralow aspect ratio (H/W = 1:36) spiral channel microfluidic device with ordered micro-obstacles for sheathless and flow-rate-insensitive blood cell separation. By introducing ordered micro-obstacles into the spiral microchannels, reduced magnitude fluctuations in secondary flow across different loops can be obtained through geometric confinement. As a result, the unique Dean-like secondary flow can effectively enhance the separation efficiency of particles in different sizes ranging from 3 to 15 μm. Compared to most existing microfluidic devices, our system offers several advantages of easy manufacturing, convenient operation, long-term stability, highly efficient performance (up to 99.70% rejection efficiency, including platelets), and most importantly, insensitivity to cell sizes as well as flow rates (allowing for efficient separation of different-sized blood cells in a wide flow rate from 1.00 to 2.50 mL/min). The unique characteristics, such as ultralow aspect ratio, sequential micro-obstacles, and controlled secondary flow, make our device a promising solution for practical plasma extraction in biomedical research and clinical applications.

High-Throughput Blood Plasma Extraction in a Dimension-Confined Double-Spiral Channel

Microfluidic technologies enabling the control of secondary flow are essential for the successful separation of blood cells, a process that is beneficial for a wide range of medical research and clinical diagnostics. Herein, we introduce a dimension-confined microfluidic device featuring a double-spiral channel designed to regulate secondary flows, thereby enabling high-throughput isolation of blood for plasma extraction. By integrating a sequence of micro-obstacles within the double-spiral microchannels, the stable and enhanced Dean-like secondary flow across each loop can be generated. This setup consequently prompts particles of varying diameters (3, 7, 10, and 15 μm) to form different focusing states. Crucially, this system is capable of effectively separating blood cells of different sizes with a cell throughput of (2.63-3.36) × 108 cells/min. The concentration of blood cells in outlet 2 increased 3-fold, from 1.46 × 108 to 4.37 × 108, while the number of cells, including platelets, exported from outlets 1 and 3 decreased by a factor of 608. The engineering approach manipulating secondary flow for plasma extraction points to simplicity in fabrication, ease of operation, insensitivity to cell size, high throughput, and separation efficiency, which has potential utility in propelling the development of miniaturized diagnostic devices in the field of biomedical science.

Music Box-Inspired Semi-Automatic Hematocrit Validation Device

A high hematocrit (HCT) level is strongly associated with the risk of cardiovascular disease. For early diagnosis of cardiovascular disease, it is vital to regularly measure the HCT, which is typically achieved by centrifuging a blood sample to measure the percentage of red blood cells. However, the centrifugal modalities are usually bulky, expensive, and require a stable electric input, which restrict the availability. This research develops a semi-automatic and portable centrifugal device for HCT measurement. This torque-actuated semi-automatic centrifuge, which we call the tFuge, is inspired by a music box, allowing different operators to generate the same rhythm. It is electricity-free and can be controlled based on a constant torque mechanism. Repeatable test results can be received from among different users regardless of their age, sex, and activity. With the assistance of the Boycott effect on the tFuge, we proved that the HCT level is in high linearity to the length of the sedimentation of the blood cells in a tube (R2 = 0.99, sample HCT range 10-60%). The tFuge takes less than 4 min and requires no more than 10 μL of blood that can be obtained by a less-invasive finger prick to complete the testing procedure. Calibrated gradient numbers are printed onto the rotation disc for instant HCT results that can be read by the naked eye. We expect this proposed point-of-care testing device possesses the potential to replace the microhematocrit centrifuge in the regions with limited resources.