Microchip-based plasma separation from whole blood via axial migration of blood cells

An Automated Centrifugal Microfluidic Platform for Efficient Multistep Blood Sample Preparation and Clean-Up towards Small Ion-Molecule Analysis

Sample preparation for mass spectroscopy typically involves several liquid and solid phase clean-ups, extractions, and other unit operations, which are labour-intensive and error-prone. We demonstrate a centrifugal microfluidic platform that automates the whole blood sample's preparation and clean-up by combining traditional liquid-phase and multiple solid-phase extractions for applications in mass spectroscopy (MS)-based small molecule detection. Liquid phase extraction was performed using methanol to precipitate proteins in plasma separated from a blood sample under centrifugal force. The preloaded solid phase composed of C18 beads then removed lipids with a combination of silica particles, which further cleaned up any remaining proteins. We further integrated the application of this sample prep disc with matrix-assisted laser desorption/ionization (MALDI) MS by using glancing angle deposition films, which further cleaned up the processed sample by segregating the electrolyte background from the sample salts. Additionally, hydrophilic interaction liquid chromatography (HILIC) MS was employed for detecting targeted free amino acids. Therefore, several representative ionic metabolites, including several amino acids and organic acids from blood samples, were analysed by both MALDI-MS and HILIC-MS to demonstrate the performance of this sample preparation disc. The fully automated blood sample preparation procedure only took 35 mins, with a throughput of three parallel units.

Micro-Volume Blood Separation Membrane for In-Situ Biosensing

In this paper, we report a point-of-care (POCT) testing strip based on a porous membrane structure for whole blood separation and colorimetric analysis without external supporting equipment. Conventional blood tests rely on large instruments for blood pretreatment and separation to improve measurement accuracy. Cellulose acetate (CA) membranes with different pore diameters and structures were prepared via a non-solvent method for the separation of whole blood. Among them, CA@PEG-2000 membranes with nano-pores on the surface and micro-pores in the interior facilitated the capture of blood cells on the surface, as well as the free diffusion of plasma through the porous interior structure. The fluid flow of blood in the asymmetric porous structure can be theoretically estimated using the Lucas-Washburn equation. Compared with the conventional paper strips and other porous membranes, the CA@PEG-2000 membrane with an immobilized sensing layer exhibited efficient blood separation, a short response time (less than 2 min), an ultralow dosage volume (5 μL), and high sensitivity. The fabricated blood separation membranes can be further used for the detection of various biomarkers in whole blood, providing additional options for rapid quantitative POCT tests.

A simple and rapid method for blood plasma separation driven by capillary force with an application in protein detection

Blood plasma separation is a vital sample pre-treatment procedure for microfluidic devices in blood diagnostics, and it requires reliability and speediness. In this work, we propose a novel and simple method for microvolume blood plasma separation driven by capillary force. Flat-shaped filter membranes combined with hydrophilic narrow capillaries are introduced into devices, in order to reduce the residual volumes of blood plasma. An interference fit is used to ensure no leakage of blood or cells. There is desired trapping efficiency of blood cells in the devices. The method provides high efficiency with a plasma extraction yield of 71.7% within 6 min, using 60 μL of undiluted whole human blood with 45% haematocrit. The influence from structural parameters on the separation kinetics and the dependence of the haematocrit levels on the separation efficiency are also investigated. The total protein detection shows considerable protein recovery of 82.3% in the extracted plasma. Thus, the plasma separation unit with a very simple structure is suitable for integrating into microfluidic devices, presenting promising prospects for clinical diagnostics as well as for point-of-care testing applications.

Real-time CRP detection from whole blood using micropost-embedded microfluidic chip incorporated with label-free biosensor

We demonstrate the detection of C-creative protein (CRP) from whole blood samples without sample pretreatment by using a lab-on-a-chip system consisting of a microfluidic chip and a label-free biosensor.

Characterization of thermoplastic microfiltration chip for the separation of blood plasma from human blood

In this study, we developed a fully thermoplastic microfiltration chip for the separation of blood plasma from human blood. Spiral microchannels were manufactured on a PMMA substrate using a micromilling machine, and a commercial polycarbonate membrane was bonded between two thermoplastic substrates. To achieve an excellent bonding between the commercial membrane and the thermoplastic substrates, we used a two-step injection and curing procedure of UV adhesive into a ring-shaped structure around the microchannel to efficiently prevent leakage during blood filtration. We performed multiple filtration experiments using human blood to compare the influence of three factors on separation efficiency: hematocrit level (40%, 23.2%, and 10.9%), membrane pore size (5 μm, 2 μm, and 1 μm), and flow rate (0.02 ml/min, 0.06 ml/min, 0.1 ml/min). To prevent hemolysis, the pressure within the microchannel was kept below 0.5 bars throughout all filtration experiments. The experimental results clearly demonstrated the following: (1) The proposed microfiltration chip is able to separate white blood cells and red blood cells from whole human blood with a separation efficiency that exceeds 95%; (2) no leakage occurred during any of the experiments, thereby demonstrating the effectiveness of bonding a commercial membrane with a thermoplastic substrate using UV adhesive in a ring-shaped structure; (3) separation efficiency can be increased by using a membrane with smaller pore size, by using diluted blood with lower hematocrit, or by injecting blood into the microfiltration chip at a lower flow rate.

Sorting of human mesenchymal stem cells by applying optimally designed microfluidic chip filtration

Human bone marrow-derived mesenchymal stem cells (hMSCs) consist of heterogeneous subpopulations with different multipotent properties: small and large cells with high and low multipotency, respectively. Accordingly, sorting out a target subpopulation from the others is very important to increase the effectiveness of cell-based therapy. We performed flow-based sorting of hMSCs by using optimally designed microfluidic chips based on the hydrodynamic filtration (HDF) principle. The chip was designed with the parameters rigorously determined by the complete analysis of laminar flow for flow fraction and complicated networks of main and multi-branched channels for hMSCs sorting into three subpopulations: small (<25 μm), medium (25-40 μm), and large (>40 μm) cells. By focusing with a proper ratio between main and side flows, cells migrate toward the sidewall due to a virtual boundary of fluid layers and enter the branch channels. This opens the possibility of sorting stem cells rapidly without damage. Over 86% recovery was achieved for each population of cells with complete purity in small cells, but the sorting efficiency of cells is slightly lower than that of rigid model particles, due to the effect of cell deformation. Finally, we confirmed that our method could successfully fractionate the three subpopulations of hMSCs by analyzing the surface marker expressions of cells from each outlet.

Self-driven filter-based blood plasma separator microfluidic chip for point-of-care testing

There is currently a growing need for lab-on-a-chip devices for use in clinical analysis and diagnostics, especially in the area of patient care. The first step in most blood assays is plasma extraction from whole blood. This paper presents a novel, self-driven blood plasma separation microfluidic chip, which can extract more than 0.1 μl plasma from a single droplet of undiluted fresh human blood (~5 μl). This volume of blood plasma is extracted from whole blood with high purity (more than 98%) in a reasonable time frame (3 to 5 min), and without the need for any external force. This would be the first step towards the realization of a single-use, self-blood test that does not require any external force or power source to deliver and analyze a fresh whole-blood sample, in contrast to the existing time-consuming conventional blood analysis. The prototypes are manufactured in polydimethylsiloxane that has been modified with a strong nonionic surfactant (Silwet L-77) to achieve hydrophilic behavior. The main advantage of this microfluidic chip design is the clogging delay in the filtration area, which results in an increased amount of extracted plasma (0.1 μl). Moreover, the plasma can be collected in one or more 10 μm-deep channels to facilitate the detection and readout of multiple blood assays. This high volume of extracted plasma is achieved thanks to a novel design that combines maximum pumping efficiency without disturbing the red blood cells' trajectory through the use of different hydrodynamic principles, such as a constriction effect and a symmetrical filtration mode. To demonstrate the microfluidic chip's functionality, we designed and fabricated a novel hybrid microdevice that exhibits the benefits of both microfluidics and lateral flow immunochromatographic tests. The performance of the presented hybrid microdevice is validated using rapid detection of thyroid stimulating hormone within a single droplet of whole blood.

Micro-scale blood plasma separation: from acoustophoresis to egg-beaters

Plasma is a rich mine of various biomarkers including proteins, metabolites and circulating nucleic acids. The diagnostic and therapeutic potential of these analytes has been quite recently uncovered, and the number of plasma biomarkers will still be growing in the coming years. A significant part of the blood plasma preparation is still handled manually, off-chip, via centrifugation or filtration. These batch methods have variable waiting times, and are often performed under non-reproducible conditions that may impair the collection of analytes of interest, with variable degradation. The development of miniaturised modules capable of automated and reproducible blood plasma separation would aid in the translation of lab-on-a-chip devices to the clinical market. Here we propose a systematic review of major plasma analytes and target applications, alongside existing solutions for micro-scale blood plasma extraction, focusing on the approaches that have been biologically validated for specific applications.