Amperometric micro-immunosensor for rapid Substance-P quantification in biological fluids

A capillary immunosensor-chip has been developed for fast determination of substance-p (SP) levels in biological fluids. The microdevice approach combines the advantages of the microfluidic capillary for implementation of a competitive immunoassay retaining sensitivity and specificity, with the highly sensitive electrochemical detection of GOD-tracer by flow-injection analysis. The assay exhibits a detection limit of 10 pg/mL. The immunosensor has been successfully used for SP quantification in blood plasma and saliva of healthy human volunteers: 110 pg/mL in plasma and 200 pg/mL in saliva were measured. The developed miniaturized immunoassay showed good precision, high sensitivity, acceptable stability and reproducibility with consistent results comparable to those obtained by the commercial assay kit. According to this, the proposed on-chip immunosensing method may have a potential applicability in medical diagnostics of major diseases.