Electrical signaling of enzyme-linked immunosorbent assays with an ion-sensitive field-effect transistor

Optical laboratory-based immunoassays, such as enzyme-linked immunosorbent assay (ELISA) give a high sensitivity and specificity of various fatal diseases. However, these assays are no longer efficient in on-spot diagnostics of wide-spreading and contagious infections. At this point in time, portable and handhold devices play a pivotal role in infectious diseases with quick diagnostics at or near the site of the disease propagation. In this paper, we demonstrated a novel electrical immunoassay of ELISA that was not based on optical signaling but on electrical signaling. This was done by combining an ion-sensitive field-effect transistor (ISFET) with ELISA. By harnessing the catalytic reaction of alkaline phosphatase that precipitated silver particles, we effectively overcame the chronic Debye screening length issue of the ISFET. Ultimately, small signal ranging from 1pg/mL to 10ng/mL was immensely amplified with the ALP label, regardless of buffer conditions. The sensor platform herein surpassed a sensing capability of conventional ELISA that is considered to have a LOD on the order of ~1ng/mL. The results were compared with those of horseradish peroxidase label, which is generally used for optical analyses in ELISA. Our newly developed ISFET-based portable sensor holds a large potential for point-of-care tools in a variety of diseases, without being limited by the need for expensive equipment such as spectrophotometers. •A reliable electrical immunosensor was developed by combining the ELISA and the ISFET platform.•The highly amplified electrical signal was achieved by harnessing alkaline phosphatase (ALP) on the surface of the ISFET platform.•The electrical immunosensor overcame the chronic Debye screening length issue of the ISFET.•The developed platform was evaluated by comparing with the conventional platform using horseradish peroxidase (HRP).