Nanomonitors: electrical immunoassays for protein biomarker profiling

The objective of this research is to develop a 'point-of-care' device for early disease diagnosis through protein biomarker characterization. Here, we present label-free, high sensitivity detection of proteins with the use of electrical immunoassays that we call nanomonitors.

The basis of the detection principle lies in the formation of an electrical double layer and its perturbations caused by proteins trapped in a nanoporous alumina membrane over a microelectrode array platform.

High sensitivity and rapid detection of study protein biomarkers for cardiovascular diseases, C-reactive protein (CRP) and myeloperoxidase (MPO) in pure and clinical samples through label-free electrical detection were achieved. CRP and MPO were detected in pure solutions with a lower detection limit of 200 pg/ml and 500 pg/ml, respectively. These two study proteins were also detected from multiplexed samples containing a mixture of both proteins as well as human serum samples.

The performance parameters of the nanomonitors, such as speed of detection on the order of minutes, volume of reagents of a few microliters and low cost per assay are comparable to traditional assay methods, such as ELISA. In addition, nanomonitors also provide the advantages of being a label-free technique with large linear dynamic range of detection and a significant reduction in the size of assay, thus making it an ideal candidate for a clinical diagnostic 'lab-on-a-chip' device for protein biomarker profiling and hence early disease diagnosis.