Simplified microchip electrophoresis for rapid separation of urine proteins

Urine protein test has been widely used in clinics, but to determine the type of proteinuria is usually difficult due to technical limitations.

In the current study, a rapid and simple method to separate and determine urine proteins by a microchip electrophoresis (ME) system has been developed in which only 4 min are required.

Optimal separation conditions have been established by using 15 s injection time at 500 and 1,500 V separation voltage in 75 mmol/l borate buffer containing 0.8 mmol/l calcium lactate and 1% ϕ ethylamine (pH 10.55). Relative standard deviation (RSD) of migration time with purified human albumin and human transferring was 2.68% and 2.24%, and RSD of the peak area was 5.85% and 4.96%, respectively. The linear detection range was 1.0-15.0 g/l for purified human albumin and 1.0-10.0 g/l for human transferrin, with the same detection limit (S/N = 3) of 0.4 g/l. Finally, comparing to conventional agarose gel electrophoresis, the same results were obtained by using ME by testing clinical samples including 60 selective proteinuria, 105 nonselective proteinuria, and 6 overflow proteinuria.

This newly established ME could have broad applications to determine the type of proteinuria in clinics.