Sensitive, rapid and quantitative detection of substance P in serum samples using an integrated microfluidic immunochip

Miniaturized diagnostic devices hold the promise of accelerate the specific and sensitive detection of various biomarkers, which can translate into many areas of medicine - from cheaper clinical trials, to early diagnosis and treatment of complex diseases. Therefore, we report on a disposable integrated chip-based capillary immunoassay featuring a microfluidic ELISA format combining electrochemical detection and low-cost fabrication employing a dry film photoresist, Vacrel® 8100. The readily accessible carboxylate groups on the material surface allow fast and high yield immobilization of biomolecules using amine-specific coupling via reactive esters requiring no laborious surface pretreatment. The integrated microfluidic system provides a convenient platform for a flow-through immunoassay. Capillary force is used for easy reagent delivery and loading the chip channel. We performed rapid quantification of serum level of substance P, a potential biomarker of acute neuroinflammation, using the developed microfluidic immunochip. Our miniaturized assay demonstrated a sensitive electrochemical detection of the antigen at 15.4 pg ml−1 (11.5 pM) using only 5 µl of the biological fluid while cutting the total assay preparation time in half and the read-out time to 10 min. Combining microfluidics and fabrication suitable for mass production with the capability of testing clinically relevant samples creates conditions for the construction of low-cost and portable point of care diagnostic devices with minimal auxiliary electronics.