High-Efficiency Capillary-Driven Plasma Separation with Porous Filter Materials for Point-of-Care Plasma Sampling

This work presents the first capillary driven microfluidic device that separates a specific volume of plasma from a blood sample of unknown volume. We demonstrate high plasma extraction efficiency from whole blood using capillary forces, where approximately 20µL of plasma can be extracted from 50µL of whole blood.

Blood plasma-based tests are the gold standard for analytical laboratory analysis, owing to their ability to derive a large range of information pertaining to patient health. However, contemporary tests require collection of venous whole blood samples in milliliter volumes, where they are fractionated via centrifugation to obtain plasma. The disadvantages associated with this method include invasiveness, costliness, collection of large volumes of blood, slow processing times, and inability to be performed in varied settings. To alleviate these issues, an autonomous microfluidic device was developed to extract blood plasma. This functionality was achieved by combining a porous filtration membrane with a hydrophilic microchannel. Using such a device, various commercially available filtration membranes were characterized for their extraction capability, efficiency, and extraction kinetics.

Of the 7 commercial membrane filters tested, 4 were successful in extracting plasma from untreated whole blood while 3 filters demonstrated massive leakage of blood cells and hemoglobin. Filtration rates and filtration efficiencies were measured to determine the most effective filtration membrane. We found that the Vivid Plasma Separation membrane, model GR was most suitable, yielding 75% plasma extraction efficiency within 10 minutes. Additionally, we found that membrane filters with coatings, used to minimize cell lysis by osmotic effects, yielded higher plasma extraction volumes compared to the uncoated filter; however the increased volume may be due to dilution of plasma. This potential source for bias has to be considered when capillary extracted plasma is used for quantitative downstream analysis. Future work to be completed is to fit the extracted plasma volume to the channel dimensions and dissolvable valve characteristics, as well as to optimize the timing of deviceâ??s functional sequence.