Multiple enzyme-doped thread-based microfluidic system for blood urea nitrogen and glucose detection in human whole blood

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In biological chip systems, urea and glucose are important indicators for detection in human blood. Urea forms in the liver as a waste product of protein metabolism then collects in the bloodstream. The concentration of blood urea nitrogen (BUN) is an important biological indicator used for monitoring the functionality of the kidney. In general, patients with kidney failure have high BUN levels. However, with changing food culture, glucose has also become a identify control factor for diabetes mellitus. Excessive glucose displays a deficiency of insulin. Therefore, developing a microfluidic device for capillary electrophoresis electrochemical (CE-EC) detection of bio-samples is a necessary. This research presents a novel technique for detection in human whole blood which utilizes a novel enzyme-doped thread with a PVC (polyvinylchloride) membrane coating for on-site urea and glucose detection on a thread-based microfluidic device. The enzyme can be directly applied to the thread without delicate pretreatment or a surface modification process. The passing biomolecules are digested by the enzymes and then electrochemically detected downstream. With this approach, CE-EC detection with on-site bio-reaction can be simply achieved. The whole blood sample is first mixed with a RBC lysis buffer to prevent blood coagulation. The lysed RBC and other solid pieces are simultaneously filtered away while electrokinetically flowing through the thread-based microfluidic system. A thin layer of PVC membrane is coated on the enzyme-doped thread to further fix the applied enzyme and to prevent rapid evaporation of the running buffer due to the Joule heating effect. In addition, the PVC coated thread can be operated at a higher separation electric field of 500 V/cm due to the reduction of buffer evaporation. Results also indicate that the developed system exhibits a good linear dynamic range for detecting urea and glucose in concentrations from 0.1 mM – 10.0 mM (R2=0.9850) and 0.1 mM – 13.0 mM (R2=0.9668), which is suitable for adoption in detecting the BUN concentration in serum (1.78~7.12 mM) and the glucose fasting measuring range (3.89~6.11 mM). The whole blood detection shows that the developed thread-based microfluidic system can successfully separate the ions, BUN and glucose in blood. The calculated concentrations for BUN and GLU-AC in the whole blood sample are 3.98 mM and 4.94 mM, respectively.