Dual-aptamer assay for C-reactive protein detection by using field-effect transistors on an integrated microfluidic system

Rapid and accurate diagnosis of C-reactive protein (CRP) is crucial for monitoring cardiovascular diseases because it is a well-known biomarker for evaluating risks of cardiovascular diseases. This study presents a dual-aptamer assay for detection of CRP by using field-effect transistors (FET). This is the first time that two aptamers, which are specific to CRP, were used to form a sandwich assay such that the CRP concentration could be detected by FET devices. Furthermore, a microfluidic system was used to automate the dual-aptamer sandwich assay such that the entire diagnosis process could be automated. In addition to electric signals from the FET device, fluorescent signals were also used to confirm this assay. Experimental results revealed that the first aptamer (1
^st
aptamer) and the second aptamer (c aptamer) could be specifically binded with target CRP. Furthermore, the microfluidic chip integrated with FET can be re-used if the binded CRP and 2
^nd
aptamer was eluted. Besides, in order to prevent the interference materials like proteins, cells and any nonspecific molecules from adhering onto the gate region of the FET device even after immobilization of 1
^st
aptamer, we used ethanolamine as the blocking agent to prevent nonspecific adhesion. The experimental results confirmed that blocking using ethanolamine could successfully prevent nonspecific binding.