Fabrication and testing of microfluidic devices for blood cell separation

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Blood separation is a strategic preliminary step in preparation to on-chip biological analysis. Two microfluidic devices for on-chip blood separation are presented. Both devices will be integrated to form the separation module of a Lab on Chip for non-invasive prenatal diagnosis. In the first device, a blood plasma separator, the separation of blood cells from plasma is made possible in microchannels by bio-physical effects such as an axial migration effect and Zweifach-Fung bifurcation law. Behaviour of mussel and human blood suspensions were studied alongside the effect of different geometries. The second device aims to separate fetal nucleated red blood cells based on their magnetic susceptibility. Biocompatible materials are used in the manufacturing of both devices.The authors acknowledge the financial support of the Engineering and Physical Science Research Council (EPSRC) through the funding of the Grand Challenge Project ‘3DMintegration’, reference EP/C534212/1. This work has also been supported by the EPSRC through a Doctoral Training Account (DTA) and has been performed at the Microsystems Engineering Centre (MISEC), Heriot-Watt University, Edinburgh. We thank Tim Ryan and Phil Summersgill, Epigem Ltd. for the fabrication of the blood plasma chips. The fabrication work was carried out in the Fluence Microfluidics Application Centre supported by the DTI and the OneNE Regional Development Agency as part of the UK's MNT Network

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

This review weights the advantages and limits of miniaturised blood plasma separation and highlights interesting advances in direct biomarker capture.</p

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 remarka-ble 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

Laser ablation of polylactic acid sheets for the rapid prototyping of sustainable, single-use, disposable medical micro-components

The employment of single-use, disposable medical equipment has increased the amount of medical waste produced and the advent of point-of-care diagnostics in lab-on-chip format is likely to add further volume. Current materials used for the manufacture of these devices are derived from petroleum sources and are, therefore, unsustainable. In addition, disposal of these plastics necessitates combustion to reduce infection risk, which has, depending on material composition, an undesirable environmental impact. To address these issues, we have developed a general approach for the rapid prototyping of single-use point-of-care cartridges prepared from poly­(lactic acid), a sustainable material which can be milled and laser-cut as well as molded for translation to mass-market products. Here, the laser workability of poly­(lactic acid) sheets is reported together with examples of microfluidic components. Furthermore, the low molecular adsorption in laser-ablated poly­(lactic acid) channels and the compatibility of poly­(lactic acid) for common on-chip bioassays, such as polymerase chain reaction (PCR), are demonstrated. This innovative prototyping technique can be easily translated to high volume manufacturing and presents exciting opportunities for future sustainable microfluidic laboratories as well as potential for sustainable disposable single-use microcomponents for clinical applications

Polylactic is a Sustainable, Low Absorption, Low Autofluorescence Alternative to Other Plastics for Microfluidic and Organ-on-Chip Applications

Organ-on-chip (OOC) devices are miniaturized devices replacing animal models in drug discovery and toxicology studies. The majority of OOC devices are made from polydimethylsiloxane (PDMS), an elastomer widely used in microfluidic prototyping, but posing a number of challenges to experimentalists, including leaching of uncured oligomers and uncontrolled absorption of small compounds. Here we assess the suitability of polylactic acid (PLA) as a replacement material to PDMS for microfluidic cell culture and OOC applications. We changed the wettability of PLA substrates and demonstrated the functionalization method to be stable over a time period of at least 9 months. We successfully cultured human cells on PLA substrates and devices, without coating. We demonstrated that PLA does not absorb small molecules, is transparent (92% transparency), and has low autofluorescence. As a proof of concept of its manufacturability, biocompatibility, and transparency, we performed a cell tracking experiment of prostate cancer cells in a PLA device for advanced cell culture

Integrated acoustic immunoaffinity-capture (IAI) platform for detection of PSA from whole blood samples.

On-chip detection of low abundant protein biomarkers is of interest to enable point-of-care diagnostics. Using a simple form of integration, we have realized an integrated microfluidic platform for the detection of prostate specific antigen (PSA), directly in anti-coagulated whole blood. We combine acoustophoresis-based separation of plasma from undiluted whole blood with a miniaturized immunoassay system in a polymer manifold, demonstrating improved assay speed on our Integrated Acoustic Immunoaffinity-capture (IAI) platform. The IAI platform separates plasma from undiluted whole blood by means of acoustophoresis and provides cell free plasma of clinical quality at a rate of 10 uL/min for an online immunoaffinity-capture of PSA on a porous silicon antibody microarray. The whole blood input (hematocrit 38-40%) rate was 50 μl min(-1) giving a plasma volume fraction yield of ≈33%. PSA was immunoaffinity-captured directly from spiked female whole blood samples at clinically significant levels of 1.7-100 ng ml(-1) within 15 min and was subsequently detected via fluorescence readout, showing a linear response over the entire range with a coefficient of variation of 13%