Preconcentration of Cardiac Troponins in Whole Serum By Isotachophoresis

Microchip isotachophoresis is used to concentrate phosphorylated and unphosphorylated forms of the very low-abundance cardiac troponins (cTnI's) in whole serum while removing many of the high abundance proteins that might interfere with downstream detection. This separation is performed in a "cascade" PMMA microchip that contains a 10x width reduction followed by a 20x depth reduction so that, when ITP is performed with the troponins running in "peak" mode, they may concentrate an additional 200x beyond the ~100x contribution from ITP alone expected for our channel design. We were able to obtain concentration factors as high as 8200 in our experiments and to baseline separate the cTnIs with different phosphorylation states into distinct ITP zones between the leading and terminating electrolytes.