Mesoscale blood cell sedimentation for processing millilitre sample volumes

Simple Bioparticle Filtration Device Based on an Ultralow-Fouling Zwitterionic Polyurethane Membrane for Rapid Large-Volume Separation of Plasma and Viruses from Whole Blood

Plasma separation from whole blood is oftent required as an essential first step when performing blood tests with a viral assay. However, developing a point-of-care plasma extraction device with a large output and high virus recovery remains a significant obstacle to the success of on-site viral load tests. Here, we report a portable, easy-to-use, cost-efficient, membrane-filtration-based plasma separation device that enables rapid large-volume plasma extraction from whole blood, designed for point-of-care virus assays. The plasma separation is realized by a low-fouling zwitterionic polyurethane-modified cellulose acetate (PCBU-CA) membrane. The zwitterionic coating on the cellulose acetate membrane can decrease surface protein adsorption by 60% and increase plasma permeation by 46% compared with a pristine membrane. The PCBU-CA membrane, with its ultralow-fouling properties, enables rapid plasma separation. The device can yield a total of 1.33 mL plasma from 10 mL whole blood in 10 min. The extracted plasma is cell-free and exhibits a low hemoglobin level. In addition, our device demonstrated a 57.8% T7 phage recovery in the separated plasma. The results of real-time polymerase chain reaction analysis confirmed that the nucleic acid amplification curve of the plasma extracted by our device is comparable to that obtained by centrifugation. With its high plasma yield and good phage recovery, our plasma separation device provides an excellent replacement for traditional plasma separation protocols for point-of-care virus assays and a broad spectrum of clinical tests.

Engineered Membranes for Residual Cell Trapping on Microfluidic Blood Plasma Separation Systems: A Comparison between Porous and Nanofibrous Membranes

Blood-based clinical diagnostics require challenging limit-of-detection for low abundance, circulating molecules in plasma. Micro-scale blood plasma separation (BPS) has achieved remarkable results in terms of plasma yield or purity, but rarely achieving both at the same time. Here, we proposed the first use of electrospun polylactic-acid (PLA) membranes as filters to remove residual cell population from continuous hydrodynamic-BPS devices. The membranes hydrophilicity was improved by adopting a wet chemistry approach via surface aminolysis as demonstrated through Fourier Transform Infrared Spectroscopy and Water Contact Angle analysis. The usability of PLA-membranes was assessed through degradation measurements at extreme pH values. Plasma purity and hemolysis were evaluated on plasma samples with residual red blood cell content (1, 3, 5% hematocrit) corresponding to output from existing hydrodynamic BPS systems. Commercially available membranes for BPS were used as benchmark. Results highlighted that the electrospun membranes are suitable for downstream residual cell removal from blood, permitting the collection of up to 2 mL of pure and low-hemolyzed plasma. Fluorometric DNA quantification revealed that electrospun membranes did not significantly affect the concentration of circulating DNA. PLA-based electrospun membranes can be combined with hydrodynamic BPS in order to achieve high volume plasma separation at over 99% plasma purity.

Ultralow-Fouling Zwitterionic Polyurethane-Modified Membranes for Rapid Separation of Plasma from Whole Blood

The separation of plasma from blood cells in whole blood is an essential step for many diagnostic and therapeutic applications. However, the current point-of-care plasma separation approaches have not yet satisfied the need for a rapid, high-flux, and low-cost process. Here, we report a portable, low-cost, disposable membrane-based plasma separation device that enables rapid plasma extraction from whole blood. Rapid separation of plasma can be obtained with a simple three-step operation: blood injection, separation, and plasma collection. Our device benefits from the zwitterionic polyurethane-modified cellulose acetate (PCBU-CA) membrane, which can greatly inhibit the surface fouling of blood cells and membrane flux decline. The zwitterionic coating is stable on the membrane surface during blood filtration and leads to a 60% decrease in surface fibrinogen adsorption than a nonmodified membrane surface. The ultralow-blood-fouling properties of the PCBU-CA membrane enable rapid, continuous separation of plasma: within 10 min, the device can yield 0.5-0.7 mL of plasma from 10 mL of whole blood. The extracted plasma is verified as cell-free, exhibits a low hemoglobin level, and has a high protein recovery. Our PCBU-CA membrane provides a pathway for developing a high-efficiency portable plasma separation device that can reduce the time to diagnosis, allow effective patient care, and eventually reduce hospital costs.

Irregular dynamics of cellular blood flow in a model microvessel

The flow of red blood cells within cylindrical vessels is complex and irregular, so long as the vessel diameter is somewhat larger than the nominal cell size. Long-time-series simulations, in which cells flow 10^{5} vessel diameters, are used to characterize the chaotic kinematics, particularly to inform reduced-order models. The simulation model used includes full coupling between the elastic red blood cell membranes and surrounding viscous fluid, providing a faithful representation of the cell-scale dynamics. Results show that the flow has neither classifiable recurrent features nor a dominant frequency. Instead, its kinematics are sensitive to the initial flow configuration in a way consistent with chaos and Lagrangian turbulence. Phase-space reconstructions show that a low-dimensional attractor does not exist, so the observed long-time dynamics are effectively stochastic. Based on this, a simple Markov chain model for the dynamics is introduced and shown to reproduce the statistics of the cell positions.

Low-power, low-cost urinalysis system with integrated dipstick evaluation and microscopic analysis

We introduce a coupled dipstick and microscopy device for analyzing urine samples. The device is capable of accurately assessing urine dipstick results while simultaneously imaging the microscopic contents within the sample. We introduce a long working distance, cellphone-based microscope in combination with an oblique illumination scheme to accurately visualize and quantify particles within the urine sample. To facilitate accurate quantification, we couple the imaging set-up with a power-free filtration system. The proposed device is reusable, low-cost, and requires very little power. We show that results obtained with the proposed device and custom-built app are consistent with those obtained with the standard clinical protocol, suggesting the potential clinical utility of the device.

Microfluidic blood plasma separation for medical diagnostics: is it worth it?

Circulating biomarkers are on the verge of becoming powerful diagnostic tools for various human diseases. However, the complex sample composition makes it difficult to detect biomarkers directly from blood at the bench or at the point-of-care. Blood cells are often a source of variability of the biomarker signal. While the interference of hemoglobin is a long known source of variability, the release of nucleic acids and other cellular components from hemocytes is a new concern for measurement and detection of circulating extracellular markers. Research into miniaturised blood plasma separation has been thriving in the last 10 years (2006-2016). Most point-of-care systems need microscale blood plasma separation, but developed solutions differ in complexity and sample volume range. But could blood plasma separation be avoided completely? This focused review weights the advantages and limits of miniaturised blood plasma separation and highlights the most interesting advances in direct capture as well as smart blood plasma separation.