Separation and detection of urinary proteins by two-dimensional electrophoresis on the microfluidic chip

A novel separating and detecting method of urinary proteins by non-gel sieving electrophoresis–free flow electrophoresis on the microfluidic chip was proposed in this article. Human serum albumin and human transferrin labeled by fluorescein isothiocyanate were mixed and taken as the synthesized urinary protein samples. Factors affected on separation, such as the rate of electric fields applied in two dimension, the addition in the buffer, the concentration, and pH of buffer, were optimized, that is, 10% (w/v) dextran, 0.5% ethanediamine, 0.2 mol L⁻¹ Tris–boric acid, pH 9.3, the ratio of the applied electric field in two dimensions 1:4.8, respectively. Fluorescein isothiocyanate–human serum albumin and fluorescein isothiocyanate–transferrin were efficiently separated in 2 min, and the resolution of two proteins achieved was 2.2 by the designed microfluidic chip. Then, the urine samples of nephropathy patient were analyzed by the proposed non-gel sieving electrophoresis–free flow electrophoresis on the microfluidic chip. The results matched well with those detected by common clinical methods.