Microdevice for plasma separation from whole human blood using bio-physical and geometrical effects

High-Throughput Microfluidic Extraction of Platelet-free Plasma for MicroRNA and Extracellular Vesicle Analysis

Cell-free RNAs and extracellular vesicles (EVs) are valuable biomarkers in liquid biopsies, but they are prone to preanalytical variabilities such as nonstandardized centrifugation or ex vivo blood degradation. Herein, we report a high-throughput and label-free inertial microfluidic device (ExoArc) for isolation of platelet-free plasma from blood for RNA and EV analysis. Unlike conventional inertial microfluidic devices widely used for cell sorting, a submicrometer size cutoff (500 nm) was achieved which completely removed all leukocytes, RBCs, platelets, and cellular debris based on differential lateral migration induced by Dean vortices. The single-step operation also reduced platelet-associated miRNAs (∼2-fold) compared to centrifugation. We clinically validated ExoArc for plasma miRNA profiling (39 samples) and identified a 7-miRNA panel that detects non-small cell lung cancer with ∼90% sensitivity. ExoArc was also coupled with size exclusion chromatography (SEC) to isolate EVs within 50 min with ∼10-fold higher yield than ultracentrifugation. As a proof-of-concept for EV-based transcriptomics analysis, we performed miRNA analysis in healthy and type 2 diabetes mellitus (T2DM) subjects (n = 3 per group) by coupling ExoArc and ExoArc+SEC with quantitative polymerase chain reaction (RT-qPCR) assay. Among 293 miRNAs detected, plasmas and EVs showed distinct differentially expressed miRNAs in T2DM subjects. We further demonstrated automated in-line EV sorting from low volume culture media for continuous EV monitoring. Overall, the developed ExoArc offers a convenient centrifugation-free workflow to automate plasma and EV isolation for point-of-care diagnostics and quality control in EV manufacturing.

Modified polysulfone membrane facilitates rapid separation of plasma from whole blood for an effective anti-SARS-CoV-2-IgM diagnosis

During the outbreak of coronavirus, RT-PCR was the premier gold standard method for severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) diagnosis. However, the sophisticated procedure of RT-PCR persuades researchers to develop sustainable point-of-need immunoassay methods for tracing unwitting carriers of SARSCoV-2. Herein, by fabricating a modified polysulfone (MPSF) membrane, we developed an integrated radial flow immunoassay (IRFIA) platform as a point-of-care system, capable of multiplying the immunoassays at a short run time. The target molecule is the SARSCoV-2 IgM in separated plasma. Although the lateral flow immunoassay kits for the rapid identification of Covid-19 have already been commercially developed but, the proposed method is superior to the conventional lateral flow immunoassay. In the newly designed membrane system, we have combined the five membranes of prevalent lateral flow immunoassay (LFIA) strips in one polymeric membrane. The MPSF membrane is capable of separating plasma from whole blood sample, which will reduce the interference of red colour of hemoglobin with generated signal and enhance the immunoassay precision. The efficiency of plasma separation, reached the mean value of 97.34 v/v% in 5 s. Furthermore, the gel electrophoresis results of the separated plasma contrasted with centrifuged plasma sample, demonstrated more efficient separation by the membrane. Using the MPSF membrane, signal generation time reduced from about 20 min in conventional rapid test strip for Covid-19 to about 7 min in IRFIA platform. The sensitivity and specificity of the membrane platform were determined to be 89% and 90%, respectively and a Kappa coefficient of 0.79 showed reliable agreement between the RT-PCR and the membrane system.

Design and Fabrication of a High Performance Microfluidic Chip for Blood Plasma Separation: Modelling and Prediction of System Behaviour via CFD Method

This paper presents a single-step microfluidic system designed for passive separation of human fresh blood plasma using direct capillary forces. Our microfluidic system is composed of a cylindrical well between upper and lower channel pairs produced by soft photolithography. The microchip was fabricated based on hydrophobicity differences upon suitable cylindrical surfaces using gravitational and capillary forces and lateral migration of plasma and red blood cells. The plasma radiation was applied to attach the polymeric segment (polydimethylsiloxane (PDMS)) to the glass. Meanwhile, Tween 80 was used as a surfactant to increase the hydrophobicity of the lateral channel surfaces. This led to the higher movement of whole blood, including plasma. Fick's law of diffusion was validated for this diffusion transfer, the Navier-Stokes equation was used for the momentum balance, and the Laplace equation was utilized for the dynamics of the mesh. A model with high accuracy using the COMSOL Multiphysics software was created to predict the capillary forces and chip model validation. RBCs (red blood cells) were measured by the H3 cell counter instrument, by which 99% plasma purity was achieved. Practically, 58.3% of the plasma was separated from the blood within 12 min. Correlation between plasma separation results obtained from software and experimental data showed a coefficient of determination equal to 0.9732. This simple, rapid, stable, and reliable microchip can be considered as a promising candidate for providing plasma in point-of-care diagnostics.

Smartphone-powered, ultrasensitive, and selective, portable and stable multi-analyte chemiresistive immunosensing platform with PPY/COOH-MWCNT as bioelectrical transducer: Towards point-of-care TBI diagnosis

Traumatic Brain Injury, one of the significant causes of mortality and morbidity, affects worldwide and continues to be a diagnostic challenge. The most desirable and partially met clinical need is to simultaneously detect the disease-specific-biomarkers in a broad range of readily available body fluids on a single platform with a rapid, low-cost, ultrasensitive and selective device. Towards this, an array of interdigitated microelectrodes was fabricated on commercially existing low-cost single-side copper cladded printed-circuit-board substrate followed by the bioelectrodes preparation through covalent immobilization of brain injury specific biomarkers on carboxylic functionalized multi-walled carbon nanotubes embedded polypyrrole nanocomposite modified interdigitated microelectrodes. Subsequently, the immunological binding events were transduced as the normalized change in bioelectrode resistance with and without the target analyte via current-voltage analysis. As proof of concept, current-voltage responses were primarily recorded using a conventional probe station, and later, a portable handheld-electronic-readout was developed for the point-of-care application. The data compilation and analysis were carried out using the in-house developed android-based mobile app. Notably, the smartphone powered the readout through a PL-2303 serial connector, avoiding integrating power sources with the readout. Further, this technology can be adapted to other point-of-care biosensing applications.

A microfluidic device to separate high-quality plasma from undiluted whole blood sample using an enhanced gravitational sedimentation mechanism

The growing interest in lab-on-a-chip systems for plasma separation has led to the presentation of various devices. Trench-based devices benefiting from gravitational sedimentation are efficient structures with air-locking and low speed-drawbacks. The present study introduces a fast, hemolysis-free, highly efficient blood plasma separation microfluidic device. The proposed device is based on gravitational sedimentation combined with dielectrophoresis force to promote the purity of the separated plasma, reduce the separation process time, and overcome the air-locking problem. The effect of geometrical parameters on the separation process is investigated using finite element analysis to attain optimal design specifications. A drop of whole blood (10 μl) is injected into the fabricated chip at four flow rates of 70 nl/s to 100 nl/s. It takes less than 4 min to obtain 2.2 μl plasma from undiluted blood without losing plasma proteins. Additionally, a porous Melt-Blown Polypropylene (MBPP) layer is used to eliminate the air-locking problem, which in previous trench-based microsystems led to time-consuming device preparation steps. Blood samples with various hematocrits (15%-65%) are tested with the applied voltages of 0-20 V_pp through the optimized structure. A purity of 99.98% ± 0.02% (evaluated by hemocytometry) is achieved using optimized dielectrophoresis force by the applied voltage of 20 V_pp, which is more than the previous studies. The UV-Visible spectroscopy results confirm obtaining a non-hemolyzed sample at a flow rate of 70 nl/s. The proposed device achieves a relative increase in the flow rate compared to similar previous studies while maintaining the high quality of the separated plasma. This achievement lies in using the MBPP layer and combining two separation methods.

Microfluidics geometries involved in effective blood plasma separation

The last two decades witnessed a significant advancement in the field of diluted and whole blood plasma separation. This is one of the common procedures used to diagnose, cure and treat numerous acute and chronic diseases. For this separation purpose, various types of geometries of microfluidic devices, such as T-channel, Y-channel, trifurcation, constriction-expansion, curved/bend/spiral channels, a combination of any of the two geometries, etc., are being exploited, and this is detailed in this review article. The evaluation of the performance of such devices is based on the several parameters such as separation efficiency, flow rate, hematocrits, channel dimensions, etc. Thus, the current extensive review article endeavours to understand how particular geometry influences the separation efficiency for a given hematocrit. Additionally, a comparative analysis of various geometries is presented to demonstrate the less explored geometric configuration for the diluted and whole blood plasma separation. Also, a meta-analysis has been performed to highlight which geometry serves best to give a consistent separation efficiency. This article also presents tabulated data for various geometries with necessary details required from a designer's perspective such as channel dimensions, targeted component, studied range of hematocrit and flow rate, separation efficiency, etc. The maximum separation efficiency that can be achieved for a given hematocrits and geometry has also been plotted. The current review highlights the critical findings relevant to this field, state of the art understanding and the future challenges.

A low-cost, open-source centrifuge adaptor for separating large volume clinical blood samples

Blood plasma separation is a prerequisite in numerous biomedical assays involving low abundance plasma-borne biomarkers and thus is the fundamental step before many bioanalytical steps. High-capacity refrigerated centrifuges, which have the advantage of handling large volumes of blood samples, are widely utilized, but they are bulky, non-transportable, and prohibitively expensive for low-resource settings, with prices starting at $1,500. On the other hand, there are low-cost commercial and open-source micro-centrifuges available, but they are incapable of handling typical clinical amounts of blood samples (2-10mL). There is currently no low-cost CE marked centrifuge that can process large volumes of clinical blood samples on the market. As a solution, we customised the rotor of a commercially available low-cost micro-centrifuge (~$125) using 3D printing to enable centrifugation of large clinical blood samples in resource poor-settings. Our custom adaptor ($15) can hold two 9 mL S-Monovette tubes and achieve the same separation performance (yield, cell count, hemolysis, albumin levels) as the control benchtop refrigerated centrifuge, and even outperformed the control in platelet separation by at least four times. This low-cost open-source centrifugation system capable of processing clinical blood tubes could be valuable to low-resource settings where centrifugation is required immediately after blood withdrawal for further testing.

High-Resolution 3D Printing Fabrication of a Microfluidic Platform for Blood Plasma Separation

Additive manufacturing technology is an emerging method for rapid prototyping, which enables the creation of complex geometries by one-step fabrication processes through a layer-by-layer approach. The simplified fabrication achieved with this methodology opens the way towards a more efficient industrial production, with applications in a great number of fields such as biomedical devices. In biomedicine, blood is the gold-standard biofluid for clinical analysis. However, blood cells generate analytical interferences in many test procedures; hence, it is important to separate plasma from blood cells before analytical testing of blood samples. In this research, a custom-made resin formulation combined with a high-resolution 3D printing methodology were used to achieve a methodology for the fast prototype optimization of an operative plasma separation modular device. Through an iterative process, 17 different prototypes were designed and fabricated with printing times ranging from 5 to 12 min. The final device was evaluated through colorimetric analysis, validating this fabrication approach for the qualitative assessment of plasma separation from whole blood. The 3D printing method used here demonstrates the great contribution that this microfluidic technology will bring to the plasma separation biomedical devices market.

Geometry effect in multi-step crossflow microfluidic devices for red blood cells separation and deformability assessment

The efficient separation of blood components using microfluidic systems can help to improve the detection and diagnosis of several diseases, such as malaria and diabetes. Therefore, a novel multi-step microfluidic device, based on passive crossflow filters was developed. Three different designs were proposed, fabricated and tested in order to evaluate the most suitable geometry to perform, simultaneously, blood cells separation and cell deformability measurements. All the proposed geometries include a main channel and three sequential separation steps, all comprised of symmetrical crossflow filters, with multiple rows of pillars, to reduce the amount of red blood cells (RBCs) flowing to the outlets of the microfluidic device (MD). Sets of hyperbolic constrictions located at the outlets allow the assessment of cells deformability. Based on the proposed geometries, the three correspondent MD were evaluated and compared, by measuring the RBCs velocities, the cell-free layer (CFL) effect through the microchannels and by quantifying the amount of RBCs at the outlets. The results suggest that the proposed MD 3 configuration was the most effective one for the desired application, due to the formation of a wider CFL. As a result, a minor amount of RBCs flow through the hyperbolic contraction at the third separation level of the device. Nevertheless, for all the proposed geometries, the existence of three separation levels shows that it is possible to achieve a highly efficient cell separation. If needed, such microdevices have the potential for further improvements by increasing the number of separation levels, aiming the total separation of blood cells from plasma.

High-Performance Passive Plasma Separation on OSTE Pillar Forest

Plasma separation is of high interest for lateral flow tests using whole blood as sample liquids. Here, we built a passive microfluidic device for plasma separation with high performance. This device was made by blood filtration membrane and off-stoichiometry thiol-ene (OSTE) pillar forest. OSTE pillar forest was fabricated by double replica moldings of a laser-cut polymethylmethacrylate (PMMA) mold, which has a uniform microstructure. This device utilized a filtration membrane to separate plasma from whole blood samples and used hydrophilic OSTE pillar forest as the capillary pump to propel the plasma. The device can be used to separate blood plasma with high purity for later use in lateral flow tests. The device can process 45 μL of whole blood in 72 s and achieves a plasma separation yield as high as 60.0%. The protein recovery rate of separated plasma is 85.5%, which is on par with state-of-the-art technologies. This device can be further developed into lateral flow tests for biomarker detection in whole blood.

DNA-Modified Plasmonic Sensor for the Direct Detection of Virus Biomarkers from the Blood

The rapid spread of viral infections demands early detection strategies to minimize proliferation of the disease. Here, we demonstrate a plasmonic biosensor to detect Dengue virus, which was chosen as a model, via its nonstructural protein NS1 biomarker. The sensor is functionalized with a synthetic single-stranded DNA oligonucleotide and provides high affinity toward NS1 protein present in the virus genome. We demonstrate the detection of NS1 protein at a concentration of 0.1-10 μg/mL in bovine blood using an on-chip microfluidic plasma separator integrated with the plasmonic sensor which covers the clinical threshold of 0.6 μg/mL of high risk of developing Dengue hemorrhagic fever. The conceptual and practical demonstration shows the translation feasibility of these microfluidic optical biosensors for early detection of a wide range of viral infections, providing a rapid clinical diagnosis of infectious diseases directly from minimally processed biological samples at point of care locations.

Microdevice based on centrifugal effect and bifurcation law for separation of plasma from on-line diluted whole blood

In recent decades, scientific interest in the development of devices capable of performing routine clinical analyses through the application of standardized traditional laboratory protocols in a miniaturized lab-on-a-chip device has increased. In the present work, an innovative microdevice for the on-line whole blood dilution with a phosphate buffer solution (PBS) and separation of plasma was designed, manufactured, and characterized. The microdevice was constructed with a rectangular cross-section and spiral-shaped microchannels by photolithography and soft litography. Also, the widths of the diluted plasma and the remaining blood outlet microchannels were different to create a difference in the outlet flow rates to facilitate and achieve the plasma separation based on the combination of centrifugal effect (Dean drag force) and bifurcation law (Zweifach-Fung effect). The separation purity (α) under the separation conditions (total flow rates between 25 and 100 μL/min, entrance flow rate ratio PBS/whole blood between 4 and 10, and hematocrit (% HCT) between 3 and 8) was around 100% for fresh blood samples, while the separation efficiency (β) was between 8 and 13%. The concentration in the separated diluted plasma was between 0.1 and 0.7% (v/v) with plasma flow rates between 3 and 7 μL/min, respectively. The quality of the diluted and separated plasma from micordevice was corroborated from a blood sample from a patient diagnosed with rheumatoid arthritis through the quantification of anti-cyclic citrullinated peptide (anti-CCP) antibodies employing a microdevice immunoassay. The developed microdevice has a high potential to be coupled with the on-line detection of biomarkers.

Antibody Surface Coverage Drives Matrix Interference in Microfluidic Capillary Immunoassays

The performance of biosensors is often optimized in buffers, which brings inconsistencies during applications with biological samples. Current strategies for minimizing sample (matrix) interference are complex to automate and miniaturize, involving, e.g., sample dilution or recovery of serum/plasma. This study shows the first systematic analysis using hundreds of actual microfluidic immunoassay fluoropolymer strips to understand matrix interference in microflow systems. As many interfering factors are assay-specific, we have explored matrix interference for a range of enzymatic immunoassays, including a direct mIgG/anti-mIgG, a sandwich cancer biomarker PSA, and a sandwich inflammatory cytokine IL-1β. Serum matrix interference was significantly affected by capillary antibody surface coverage, suggesting for the first time that the main cause of the serum matrix effect is low-affinity serum components (e.g., autoantibodies) competing with high-affinity antigens for the immobilized antibody. Additional experiments carried out with different capillary diameters confirmed the importance of antibody surface coverage in managing matrix interference. Building on these findings, we propose a novel analytical approach where antibody surface coverage and sample incubation times are key for eliminating and/or minimizing serum matrix interference, consisting in bioassay optimization carried out in serum instead of buffer, without compromising the performance of the bioassay or adding extra cost or steps. This will help establishing a new route toward faster development of modern point-of-care tests and effective biosensor development.

Enhanced Diamagnetic Repulsion of Blood Cells Enables Versatile Plasma Separation for Biomarker Analysis in Blood

A hemolysis-free and highly efficient plasma separation platform enabled by enhanced diamagnetic repulsion of blood cells in undiluted whole blood is reported. Complete removal of blood cells from blood plasma is achieved by supplementing blood with superparamagnetic iron oxide nanoparticles (SPIONs), which turns the blood plasma into a paramagnetic condition, and thus, all blood cells are repelled by magnets. The blood plasma is successfully collected from 4 mL of blood at flow rates up to 100 µL min^-1 without losing plasma proteins, platelets, or exosomes with 83.3±1.64% of plasma volume recovery, which is superior over the conventional microfluidic methods. The theoretical model elucidates the diamagnetic repulsion of blood cells considering hematocrit-dependent viscosity, which allows to determine a range of optimal flow rates to harvest platelet-rich plasma and platelet-free plasma. For clinical validations, it is demonstrated that the method enables the greater recovery of bacterial DNA from the infected blood than centrifugation and the immunoassay in whole blood without prior plasma separation.

Point-of-care testing detection methods for COVID-19

COVID-19 is an acute respiratory disease caused by SARS-CoV-2, which has high transmissibility. People infected with SARS-CoV-2 can develop symptoms including cough, fever, pneumonia and other complications, which in severe cases could lead to death. In addition, a proportion of people infected with SARS-CoV-2 may be asymptomatic. At present, the primary diagnostic method for COVID-19 is reverse transcription-polymerase chain reaction (RT-PCR), which tests patient samples including nasopharyngeal swabs, sputum and other lower respiratory tract secretions. Other detection methods, e.g., isothermal nucleic acid amplification, CRISPR, immunochromatography, enzyme-linked immunosorbent assay (ELISA) and electrochemical sensors are also in use. As the current testing methods are mostly performed at central hospitals and third-party testing centres, the testing systems used mostly employ large, high-throughput, automated equipment. Given the current situation of the epidemic, point-of-care testing (POCT) is advantageous in terms of its ease of use, greater approachability on the user's end, more timely detection, and comparable accuracy and sensitivity, which could reduce the testing load on central hospitals. POCT is thus conducive to daily epidemic control and achieving early detection and treatment. This paper summarises the latest research advances in POCT-based SARS-CoV-2 detection methods, compares three categories of commercially available products, i.e., nucleic acid tests, immunoassays and novel sensors, and proposes the expectations for the development of POCT-based SARS-CoV-2 detection including greater accessibility, higher sensitivity and lower costs.

Numerical and experimental analysis of a high-throughput blood plasma separator for point-of-care applications

Blood plasma separation from undiluted blood is an essential step in many diagnostic procedures. This study focuses on the numerical optimization of the microfluidic blood plasma separator (BPS) and experimental validation of the results to achieve portable blood plasma separation with high purity and reasonable yield. The proposed design has two parts: a microchannel for blood processing and a tank below the aforementioned main channel for plasma collection. The study uses 3D computational fluid dynamic analysis to investigate the optimal ratio of heights between the top microchannel and the tank and their geometry at various flow rates. Thereafter, the results are compared with the experimental findings of the fabricated devices. These results are contrasted with some recent reported works to verify the proposed device's contribution to the improvement in the quality and quantity of the extracted plasma. The optimized design is capable of achieving a 19% yield with purity of 77.1%, depending on the requirement of the point-of-care (POC) application. These amounts could be tuned, for instance to 100% pure plasma, but the yield would decrease to 9%. In this study, the candidate application is hemostasis; therefore, the BPS is integrated to a biomimetic surface for hemostasis evaluation near the patients.

A centrifugal microfluidic cross-flow filtration platform to separate serum from whole blood for the detection of amphiphilic biomarkers

The separation of biomarkers from blood is straightforward in most molecular biology laboratories. However, separation in resource-limited settings, allowing for the successful removal of biomarkers for diagnostic applications, is not always possible. The situation is further complicated by the need to separate hydrophobic signatures such as lipids from blood. Herein, we present a microfluidic device capable of centrifugal separation of serum from blood at the point of need with a system that is compatible with biomarkers that are both hydrophilic and hydrophobic. The cross-flow filtration device separates serum from blood as efficiently as traditional methods and retains amphiphilic biomarkers in serum for detection.

Inertial Microfluidics Enabling Clinical Research

Fast and accurate interrogation of complex samples containing diseased cells or pathogens is important to make informed decisions on clinical and public health issues. Inertial microfluidics has been increasingly employed for such investigations to isolate target bioparticles from liquid samples with size and/or deformability-based manipulation. This phenomenon is especially useful for the clinic, owing to its rapid, label-free nature of target enrichment that enables further downstream assays. Inertial microfluidics leverages the principle of inertial focusing, which relies on the balance of inertial and viscous forces on particles to align them into size-dependent laminar streamlines. Several distinct microfluidic channel geometries (e.g., straight, curved, spiral, contraction-expansion array) have been optimized to achieve inertial focusing for a variety of purposes, including particle purification and enrichment, solution exchange, and particle alignment for on-chip assays. In this review, we will discuss how inertial microfluidics technology has contributed to improving accuracy of various assays to provide clinically relevant information. This comprehensive review expands upon studies examining both endogenous and exogenous targets from real-world samples, highlights notable hybrid devices with dual functions, and comments on the evolving outlook of the field.

Amalgamation of diverse hydrodynamic effects with novel triple-sided membrane valves for developing a microfluidic device for filterless and continuous water purification

A microfluidic device displaying multiple hydrodynamic effects was designed to separate suspended impurities (i.e. bacteria and similar length scale particles present in water in the suspension form) from water.

Visualization and Measurements of Blood Cells Flowing in Microfluidic Systems and Blood Rheology: A Personalized Medicine Perspective

Hemorheological alterations in the majority of metabolic diseases are always connected with blood rheology disturbances, such as the increase of blood and plasma viscosity, cell aggregation enhancement, and reduction of the red blood cells (RBCs) deformability. Thus, the visualizations and measurements of blood cells deformability flowing in microfluidic devices (point-of-care devices) can provide vital information to diagnose early symptoms of blood diseases and consequently to be used as a fast clinical tool for early detection of biomarkers. For instance, RBCs rigidity has been correlated with myocardial infarction, diabetes mellitus, hypertension, among other blood diseases. In order to better understand the blood cells behavior in microfluidic devices, rheological properties analysis is gaining interest by the biomedical committee, since it is strongly dependent on the interactions and mechanical cells proprieties. In addition, the development of blood analogue fluids capable of reproducing the rheological properties of blood and mimic the RBCs behavior at in vitro conditions is crucial for the design, performance and optimization of the microfluidic devices frequently used for personalized medicine. By combining the unique features of the hemorheology and microfluidic technology for single-cell analysis, valuable advances in personalized medicine for new treatments and diagnosis approach can be achieved.

A case for measuring both cellular and cell-free mitochondrial DNA as a disease biomarker in human blood

Circulating mitochondrial DNA (mtDNA), widely studied as a disease biomarker, comprises of mtDNA located within mitochondria, indicative of mitochondrial function, and cell-free (cf) mtDNA linked to inflammation. The purpose of this study was to determine the ranges of, and relationship between, cellular and cf mtDNA in human blood. Whole blood from 23 controls (HC) and 20 patients with diabetes was separated into peripheral blood mononuclear cells (PBMCs), plasma, and serum. Total DNA was isolated and mtDNA copy numbers were determined using absolute quantification. Cellular mtDNA content in PBMCs was higher than in peripheral blood and a surprisingly high level of cf mtDNA was present in serum and plasma of HC, with no direct relationship between cellular and cf mtDNA content within individuals. Diabetes patients had similar levels of cellular mtDNA compared to healthy participants but a significantly higher cf mtDNA content. Furthermore, only in patients with diabetes, we observed a correlation between whole blood and plasma mtDNA levels, indicating that the relationship between cellular and cf mtDNA content is affected by disease status. In conclusion, when evaluating mtDNA in human blood as a biomarker of mitochondrial dysfunction, it is important to measure both cellular and cf mtDNA.

Recent advancements in microfluidics that integrate electrical sensors for whole blood analysis

Whole blood analysis reveals crucial information about various physiological and pathological conditions, including cancer metastasis, infection, and immune status, among others. Despite this rich information, the complex composition of whole blood usually required multiple sample preparation steps to purify targeted analytes. Traditionally, whole blood preparation processes, including centrifugation, lysis, dilution, or staining, are usually manually operated by well-trained technicians using bench-top instruments. This preparation can require a large blood volume and cannot be directly integrated with detection systems. Recently, various studies have integrated microfluidics with electrical sensors for whole blood analysis, with a focus on cell-based analysis, such as cell type, number, morphology, phenotype, and secreted molecules. These miniaturized systems require less sample and shorter reaction times. Besides, the sample processing and analysis can be fully integrated and automated with minimal operations. We believe these systems can transfer the current whole blood analysis from hospitals or laboratories into clinics or home settings to enable real-time and continuous health condition monitoring in point-of-care settings.

Blood Plasma Microfluidic Device: Aiming for the Detection of COVID-19 Antibodies Using an On-Chip ELISA Platform

COVID-19 is a public health emergency of international concern. Detection of SARS-CoV-2 virus is an important step towards containing the virus spread. Although viral detection using molecular diagnostic methods is quite common and efficient, these methods are prone to errors, laborious and time consuming. There is an urgent need for blood-based tests which are simple to use, accurate, less time consuming, portable and cost-effective. Human blood plasma contains water, proteins, organic and in-organic substances including bacteria and viruses. Blood plasma can be effectively used to detect COVID-19 antibodies. The immune system generates antibodies (IgM/IgG proteins) in response to the virus and identification of these antibodies is related to the presence of the infection in the patient in the past. Therefore, detecting and testing the presence of these antibodies will be extremely useful for monitoring and surveillance of the population (Petherick, Lancet 395:1101-1102, 2020). Herein, we describe and propose a microfluidic ELISA (enzyme-linked immunosorbent assay) system to detect COVID-19 antibodies on a lab-on-chip platform. We propose to first separate plasma from whole human blood using a microfluidic device and subsequently perform the detection of antibodies in the separated plasma using a semi-automated on-chip ELISA.

Plasma Isolation in a Syringe by Conformal Integration of Inertial Microfluidics

A thermoplastic microfluidic substrate is conformally integrated onto the cylindrical barrel of a conventional venipuncture syringe, forming a spiral inertial separation element supporting the isolation of plasma from diluted whole blood. The cylindrical shape of the syringe itself serves to define the flow path required for inertial separation by transforming a linear microchannel to a spiral topology. The hybrid system enables inertial plasma separation by Dean flow focusing within the same syringe used for a patient blood draw, with the seamlessly interconnected microfluidic element operated by automated or manual actuation of the syringe plunger. Plasma isolation is achieved without the need for external instrumentation. Device design and fabrication challenges are discussed, and effective plasma isolation within the system is demonstrated, with a peak separation efficiency above 97% using 25 × diluted blood.

Investigation of Bifurcation Effect on Various Microfluidic Designs for Blood Separation

In this project, a microfluidic device for blood separation will be designed and tested in order to separate plasma from whole blood for diagnostic purposes. The design will be based on previously implemented designs that will be further discussed in the next sections. When designing microfluidic devices, it is essential to consider the different physical phenomena that arise from switching from the macro scale to the micro scale. Parameters such as the Reynolds number and the forces affecting the fluid must be studied in order to produce a suitable and effective design. Finite element methods have been implemented prior to the production of the microfluidic devices. Various geometries/designs have been tested using Fluent ANSYS software. Later on, the successful design was fabricated using micromachining on an acrylic substrate and was tested using simulated blood through of a syringe pump.

Biosensors for Detection of Human Placental Pathologies: A Review of Emerging Technologies and Current Trends

Substantial growth in the biosensor research has enabled novel, sensitive and point-of-care diagnosis of human diseases in the last decade. This paper presents an overview of the research in the field of biosensors that can potentially predict and diagnosis of common placental pathologies. A survey of biomarkers in maternal circulation and their characterization methods is presented, including markers of oxidative stress, angiogenic factors, placental debris, and inflammatory biomarkers that are associated with various pathophysiological processes in the context of pregnancy complications. Novel biosensors enabled by microfluidics technology and nanomaterials is then reviewed. Representative designs of plasmonic and electrochemical biosensors for highly sensitive and multiplexed detection of biomarkers, as well as on-chip sample preparation and sensing for automatic biomarker detection are illustrated. New trends in organ-on-a-chip based placental disease models are highlighted to illustrate the capability of these in vitro disease models in better understanding the complex pathophysiological processes, including mass transfer across the placental barrier, oxidative stress, inflammation, and malaria infection. Biosensor technologies that can be potentially embedded in the placental models for real time, label-free monitoring of these processes and events are suggested. Merger of cell culture in microfluidics and biosensing can provide significant potential for new developments in advanced placental models, and tools for diagnosis, drug screening and efficacy testing.

A passive portable microfluidic blood-plasma separator for simultaneous determination of direct and indirect ABO/Rh blood typing

The blood typing test is mandatory in any transfusion, organ transplant, and pregnancy situation. There is a lack of point-of-care (POC) blood typing that could perform both direct and indirect methods using a single droplet of whole blood. This study presents a new methodology combining a passive microfluidic blood-plasma separator (BPS) and a blood typing detector for the very first time, leading to a stand-alone microchip which is capable of determining the blood group from both direct and indirect methods simultaneously. The proposed design separates blood cells from plasma by applying hydrodynamic forces imposed on them, which overcomes the clogging issue and consequently maximizes the volume of the extracted plasma. An axial migration effect across the main channel is responsible for collecting the plasma in plasma collector channels. The BPS novel design approached 12% yield of plasma with 100% purity in approximately 10 minutes. The portable BPS was designed and fabricated to perform ABO/Rh blood tests based on the detection of agglutination in both antigens of RBCs (direct) and antibodies of plasma (indirect). The differences between agglutinated and non-agglutinated samples were distinguishable by the naked eye and also validated by particle analysis of microscopic pictures. The results of this passive BPS in ABO/Rh blood grouping verified the quality and quantity of the extracted plasma in practical applications.

Microfluidic In-Flow Decantation Technique Using Stepped Pillar Arrays and Hydraulic Resistance Tuners

Separating the particles from the liquid component of sample solutions is important for several microfluidic-based sample preparations and/or sample handling techniques, such as plasma separation from whole blood, sheath-free flow focusing, particle enrichment etc. This paper presents a microfluidic in-flow decantation technique that provides the separation of particles from particle-free fluid while in-flow. The design involves the expansion of sample fluid channel in lateral and depth directions, thereby producing a particle-free layer towards the walls of the channel, followed by gradual extraction of this particle-free fluid through a series of tiny openings located towards one-end of the depth-direction. The latter part of this design is quite crucial in the functionality of this decantation technique and is based on the principle called wee-extraction. The design, theory, and simulations were presented to explain the principle-of-operation. To demonstrate the proof-of-principle, the experimental characterization was performed on beads, platelets, and blood samples at various hematocrits (2.5%–45%). The experiments revealed clog-free separation of particle-free fluid for at least an hour of operation of the device and demonstrated purities close to 100% and yields as high as 14%. The avenues to improve the yield are discussed along with several potential applications.

Thermopneumatic suction integrated microfluidic blood analysis system

Blood tests provide crucial diagnostic information regarding several diseases. A key factor that affects the precision and accuracy of blood tests is the interference of red blood cells; however, the conventional methods of blood separation are often complicated and time consuming. In this study, we devised a simple but high-efficiency blood separation system on a self-strained microfluidic device that separates 99.7 ± 0.3% of the plasma in only 6 min. Parameters, such as flow rate, design of the filter trench, and the relative positions of the filter trench and channel, were optimized through microscopic monitoring. Moreover, this air-difference-driven device uses a cost-effective and easy-to-use heater device that creates a low-pressure environment in the microchannel within minutes. With the aforementioned advantages, this blood separation device could be another platform choice for point-of-care testing.

Betaine Combined with Membrane Stabilizers Enables Solvent-Free Whole Blood Cryopreservation and One-Step Cryoprotectant Removal

Cryopreservation of red blood cells (RBCs) is fundamentally important to modern transfusion medicine. Currently, organic solvent glycerol is utilized as the state-of-the-art cryoprotectant (CPA) for RBC cryopreservation. However, glycerol must be removed before RBC transfusion to avoid intravascular hemolysis via a time-consuming deglycerolization process with specialized equipment (e.g., ACP 215), thus limiting the clinical use of frozen RBCs. Herein, we report novel biocompatible CPA formulations combining betaine with membrane stabilizers (disaccharides or amino acids), which can achieve outstanding efficiency for RBC cryopreservation directly using whole blood without any separation process. Most importantly, because of the osmotic regulation capacity of betaine, a simple and fast one-step method can be used for CPA removal, which is significantly superior to the current multistep deglycerolization process. This work offers a promising solution for highly efficient and solvent-free RBC cryopreservation and holds great potential for improving the long-term storage and long-distance distribution of RBCs.

Enzyme-Free Plasmonic Biosensor for Direct Detection of Neurotransmitter Dopamine from Whole Blood

Complex biological fluids without pretreatment, separation, or purification impose stringent limitations on the practical deployment of label-free plasmonic biosensors for advanced assays needed in point of care applications. In this work, we present an enzyme-free plasmonic neurotransmitter dopamine biosensor integrated with a microfluidic plasma separator. This integrated device allows the in-line separation of plasma directly from the bloodstream and channels it to the active detection area, where inorganic cerium oxide nanoparticles function as local selective dopamine binding sites through strong surface redox reaction. A thorough understanding and engineering of the nanoparticles is carried out to maximize its dopamine sensitivity and selectivity. We obtain detection of dopamine at 100 fM concentration in simulated body fluid and 1 nM directly from blood without any prior sample preparation. The detection selectivity is found to be at least five-times higher compared to the common interfering species. This demonstration shows the feasibility of the practical implementation of the proposed plasmonic system in detection of variety of biomarkers directly from the complex biological fluids.

In-line whole blood fractionation for Raman analysis of blood plasma

Raman studies of dynamically expanded cell-free plasma domains in microfluidic blood flow.

Early diagnosis of colorectal cancer via plasma proteomic analysis of CRC and advanced adenomatous polyp

AIM

This paper aimed to identify new candidate biomarkers in blood for early diagnosis of CRC.

BACKGROUND

Colorectal cancer (CRC) is the third most widespread malignancies increasing globally. The high mortality rate associated with colorectal cancer is due to the delayed diagnosis in an advanced stage while the metastasis has occurred. For better clinical management and subsequently to reduce mortality of CRC, early detection biomarkers are in high demand.

METHODS

A 2D-PAGE separation of proteins was performed followed by tandem mass Spectrometry (MALDI-TOF-TOF) to discover potential plasma protein markers for CRC and AA (advanced adenomas). Furthermore, western blot method was used to confirm a part of the results in colorectal tissue samples.

RESULTS

The significantly altered proteins including HPR, HP, ALB, KRT1, APOA1, FGB, IGJ and C4A were down-regulated in polyp relative to normal, and CRC compare to polyp surprisingly, and inversely, ORM2 was up-regulated with the fold change ≥ 2 and p-value ≤ 0.05. We also surveyed APOA1, FGB, and C4A for further confirmation of their expression changes by western blotting. All three of them showed a decreasing trend from normal toward CRC tissue samples as it mentioned before, but just changes of FGB and C4A were significant.

CONCLUSION

The results demonstrated that plasma proteins can be less invasive markers for the detection of CRC. FGB and C4A can be considered as plasma potential biomarkers to early diagnosis of CRC patients and understanding the underlying procedures in tumorigenesis. Undoubtedly, the additional study must be conducted on large scale cohorts to verify the results.

A Microfluidic Device for Simultaneous Extraction of Plasma, Red Blood Cells, and On-Chip White Blood Cell Trapping

This study reports a microfluidic device for whole blood processing. The device uses the bifurcation law, cross-flow method, and hydrodynamic flow for simultaneous extraction of plasma, red blood cells, and on-chip white blood cell trapping. The results demonstrate successful plasma and red blood cell collection with a minimum dilution factor (0.76x) and low haemolysis effect. The extracted red blood cells can also be applied for blood type tests. Moreover, the device can trap up to ~1,800 white blood cells in 20 minutes. The three components can be collected simultaneously using only 6 μL of whole blood without any sample preparation processes. Based on these features, the microfluidic device enables low-cost, rapid, and efficient whole blood processing functionality that could potentially be applied for blood analysis in resource-limited environments or point-of-care settings.

Separation of blood microsamples by exploiting sedimentation at the microscale

Microsample analysis is highly beneficial in blood-based testing where cutting-edge bioanalytical technologies enable the analysis of volumes down to a few tens of microliters. Despite the availability of analytical methods, the difficulty in obtaining high-quality and standardized microsamples at the point of collection remains a major limitation of the process. Here, we detail and model a blood separation principle which exploits discrete viscosity differences caused by blood particle sedimentation in a laminar flow. Based on this phenomenon, we developed a portable capillary-driven microfluidic device that separates blood microsamples collected from finger-pricks and delivers 2 µL of metered serum for bench-top analysis. Flow cytometric analysis demonstrated the high purity of generated microsamples. Proteomic and metabolomic analyses of the microsamples of 283 proteins and 1351 metabolite features was consistent with samples generated via a conventional centrifugation method. These results were confirmed by a clinical study scrutinising 8 blood markers in obese patients.

Elastomeric microvalve geometry affects haemocompatibility

This paper reports on the parameters that determine the haemocompatibility of elastomeric microvalves for blood handling in microfluidic systems. Using a comprehensive investigation of blood function, we describe a hierarchy of haemocompatibility as a function of microvalve geometry and identify a "normally-closed" v-gate pneumatic microvalve design that minimally affects blood plasma fibrinogen and von Willebrand factor composition, minimises effects on erythrocyte structure and function, and limits effects on platelet activation and aggregation, while facilitating rapid switching control for blood sample delivery. We propose that the haemodynamic profile of valve gate geometries is a significant determinant of platelet-dependent biofouling and haemocompatibility. Overall our findings suggest that modification of microvalve gate geometry and consequently haemodynamic profile can improve haemocompatibility, while minimising the requirement for chemical or protein modification of microfluidic surfaces. This biological insight and approach may be harnessed to inform future haemocompatible microfluidic valve and component design, and is an advance towards lab-on-chip automation for blood based diagnostic systems.

Microfluidic Cell Retention Device for Perfusion of Mammalian Suspension Culture

Continuous production of biologics, a growing trend in the biopharmaceutical industry, requires a reliable and efficient cell retention device that also maintains cell viability. Current filtration methods, such as tangential flow filtration using hollow-fiber membranes, suffer from membrane fouling, leading to significant reliability and productivity issues such as low cell viability, product retention, and an increased contamination risk associated with filter replacement. We introduce a novel cell retention device based on inertial sorting for perfusion culture of suspended mammalian cells. The device was characterized in terms of cell retention capacity, biocompatibility, scalability, and long-term reliability. This technology was demonstrated using a high concentration (>20 million cells/mL) perfusion culture of an IgG1-producing Chinese hamster ovary (CHO) cell line for 18-25 days. The device demonstrated reliable and clog-free cell retention, high IgG1 recovery (>99%) and cell viability (>97%). Lab-scale perfusion cultures (350 mL) were used to demonstrate the technology, which can be scaled-out with parallel devices to enable larger scale operation. The new cell retention device is thus ideal for rapid perfusion process development in a biomanufacturing workflow.

Micropatterned macroporous structures in microfluidic devices for viral separation from whole blood

Separation and enrichment of bio-nanoparticles from cell suspensions and blood are critical steps in many chemical and biomedical practices. We demonstrate here the design and fabrication of a microfluidic immunochromatographic device incorporating regular and multiscale monolithic structures to capture viruses from blood. The device contains micropatterned arrays of macroporous materials to perform size-exclusion and affinity chromatography in a simple flow-through process. The microscale gaps in the array allow the passage of cells while the macroporous matrices promote viral capture. Computational analyses reveal that fluid permeation into the porous matrices is controllable by the micropattern shape, separation distance and dimensions. Experimental analyses using blood samples containing human immunodeficiency viruses (HIV) as a model system further prove significantly improved viral capture efficiency using devices incorporating multiscale structures than those containing solid micropatterns. Such microfluidic devices with regular and multiscale structures have a potential for the separation and concentration of a wide range of bio-nanoparticles as well as macromolecules from complex mixtures containing both nano- and micro-sized species.