A Novel Microfluidic Device for Blood Plasma Filtration

Abstract

The use of whole blood and some biological specimens, such as urine, saliva, and seminal fluid are limited in clinical laboratory analysis due to the interference of proteins with other small molecules in the matrix and blood cells with optical detection methods. Previously, we developed a microfluidic device featuring an electrokinetic size and mobility trap (SMT) for on-chip extract, concentrate, and separate small molecules from a biological sample like whole blood. The device was used to on-chip filtrate the whole blood from the blood cells and plasma proteins and then on-chip extract and separate the aminoglycoside antibiotic drugs within 3 min. Herein, a novel microfluidic device featuring a nano-junction similar to those reported in the previous work formed by dielectric breakdown was developed for on-chip filtration and out-chip collection of blood plasma with a high extraction yield of 62% within less than 5 min. The filtered plasma was analyzed using our previous device to show the ability of this new device to remove blood cells and plasma proteins. The filtration device shows a high yield of plasma allowing it to detect a low concentration of analytes from the whole blood.

Keywords: blood molecules; blood plasma filtration; chip extract; microfluidics.

Figure 1

(A) An AutoCAD design of the filtration device (B) photograph image of the negative 3D printed portable device using an Eden 3D printer (C) Photograph image of the hot embossed filtration poly (methyl methacrylate) (PMMA)/adhesive tape device filled with green food dye. Scale bar = 10 mm. (D) Zoomed-in image of the V channel and the filtration channel (white box in panel C) filled with green food dye. Scale Bar = 200 µm. (E) Schematic of the microfluidic device (dimension not to scale) indicating terminating current and voltages used for generation of the nano-junction Sample (S), and Sample Waste (SW).

Figure 2

(A) Schematic of the operation of the microfluidic device (dimension not to scale) indicating the filtration process and (B) illustration of the filtration device concept. Nanochannel was formed by controlled dielectric breakdown of the tip of the V-channel and the filtration channel. Large molecules are blocked (Cells and Proteins) while small molecules pass the filtration channel.

Figure 3

Screenshots presenting the restriction (left column) and passing (right column) of different molecules through nano-junctions formed under different conditions. (A) shows the use of 5 μA to create nanochannels which transported Bovine Serum Albumin (BSA) (blue, right) and restricted Blood Cells (left); (B) shows the use of 5 μA to create nanochannels which restricted BSA (blue, left) and transported fluorescein (green, right). The nanochannels formed using a breakdown electrolyte of 10 mM phosphate buffer, pH = 11, and terminating currents of 5 and 1 μA. Images on the left show blocked transport, while those on the right show the permeability of different molecules. Scale Bar = 200 μm.

Figure 4

Electropherograms show the analysis of filtered blood spiked with 5 ppm gentamicin and BSA after labeling with fluorescamine in size and mobility trap (SMT) device after using a current limit of 5 uA (red trace) and 1uA current limit (black trace). The background electrolyte (BGE) in the separation channel, was 100 mM phosphate buffer, pH 11.5, with 0.5% HPMC, while V-sample waste channel was 10 mM phosphate buffer, pH 11.5. Applied voltages used in SMT device for extraction and concentration were −200, −850, −600, and +650 V for 60s, and separation process were −250, +250, +2200, and −500 V at reservoirs B, S, BW, and SW, respectively.

Figure 5

The linear calibration curve for Gentamicin from whole blood.