Blood separation on microfluidic paper-based analytical devices

A microfluidic paper-based analytical device (mu PAD) for the separation of blood plasma from whole blood is described. The device can separate plasma from whole blood and quantify plasma proteins in a single step. The mu PAD was fabricated using the wax dipping method, and the final device was composed of a blood separation membrane combined with patterned Whatman No. 1 paper. Blood separation membranes, LF1, MF1, VF1 and VF2 were tested for blood separation on the mu PAD. The LF1 membrane was found to be the most suitable for blood separations when fabricating the mu PAD by wax dipping. For blood separation, the blood cells (both red and white) were trapped on blood separation membrane allowing pure plasma to flow to the detection zone by capillary force. The LF1-mu PAD was shown to be functional with human whole blood of 24-55% hematocrit without dilution, and effectively separated blood cells from plasma within 2 min when blood volumes of between 15-22 mu L were added to the device. Microscopy was used to confirm that the device isolated plasma with high purity with no blood cells or cell hemolysis in the detection zone. The efficiency of blood separation on the mu PAD was studied by plasma protein detection using the bromocresol green (BCG) colorimetric assay. The results revealed that protein detection on the mu PAD was not significantly different from the conventional method (p > 0.05, pair t-test). The colorimetric measurement reproducibility on the mu PAD was 2.62% (n = 10) and 5.84% (n = 30) for within-day and between day precision, respectively. Our proposed blood separation on mu PAD has the potential for reducing turnaround time, sample volume, sample preparation and detection processes for clinical diagnosis and point-of care testing.