Amperometric Monitoring of Substance-P Levels in Biological Fluids

In this paper, a foil-based microfluidic chip (Fig. 1) for rapid determination of the neuropeptide Substance-P (SP) level in biological fluids is presented. Compared with standard ELISA methods, the miniaturization allows reducing the assay preparation and the measurement time. Due to the high variability levels and the extremely poor stability of SP in blood plasma, such improvement is crucial in point of care diagnostics of SP-induced inflammatory and immune diseases. The measurement is realized by a competitive immunoassay based on the sequenced immobilization of primary and secondary capture antibody into the capillary channel of the sensor (Fig. 2). Subsequent oxidation of hydrogen peroxide generated by the SP-labeled glucose oxidase mixed with the plasma sample resulted in a current signal inversely proportional to SP concentration. The measured 160 pg/ml in human sample (Fig. 3) was repeatable and reproducible by the corresponding optical ELISA kit on microtiter plates. Combined sensitive detection limit of 10 pg/ml and two minutes response demonstrates that this on-chip immunosensing technique is ideally suited for clinical application.