Label free thrombin detection in presence of high concentration of albumin using an aptamer-functionalized nanoporous membrane

Nanoporous alumina membranes have become a ubiquitous biosensing platform for a variety of applications and aptamers are being increasingly utilized as recognition elements in protein sensing devices. Combining the advantages of the two, we report label-free sensitive detection of human alpha-thrombin by an aptamer-functionalized nanoporous alumina membrane using a four-electrode electrochemical cell. The sensor response to alpha-thrombin was determined in the presence of a high concentration (500 mu M) of human serum albumin (HSA) as an interfering protein in the background. The sensor sensitivity was also characterized against gamma-thrombin, which is a modified alpha-thrombin lacking the aptamer binding epitope. The detection limit, within an appreciable signal/noise ratio, was 10 pM of alpha-thrombin in presence of 500 mu M HSA. The proposed scheme involves the use of minimum reagents/sample preparation steps, has appreciable response in presence of high concentrations of interfering molecules and is readily amenable to miniaturization by association with existing-chip based electrical systems for application in point-of-care diagnostic devices.