An Impedimetric Immunosensor for Progranulin Detection Using Streptavidin‐Biotin Conjugation on Carbon Screen‐Printed Electrodes

ABSTRACT Glycoprotein 88 (GP88) is a secreted biomarker overexpressed in various cancers, as well as neurological and inflammatory diseases. In this study, we introduce the first disposable electrochemical immunosensor for GP88 detection that is built on a screen‐printed carbon electrode modified with carboxylated multi‐walled carbon nanotubes. Surface carboxyl groups are activated using EDC/NHS chemistry, followed by covalent attachment of streptavidin to facilitate the capture of a biotinylated anti‐GP88 antibody. When exposed to GP88, the sensor shows a 19% increase in charge‐transfer resistance, used as the sensor's response parameter, indicating a binding between GP88 and its biorecognition element. Reproducibility is confirmed with a relative standard deviation (RSD) of 4.05% across multiple trials, demonstrating reliable sensor fabrication. The limit of detection was estimated at 52 ng/mL, with a linear range of 25500 ng/mL. The specificity of the sensor is verified by exposing the bio‐electrode to a human serum albumin control, which causes negligible signal changes. We have also concluded that maintaining streptavidin hydration during bio‐electrode assembly is critical for preserving biotin‐binding activity. To our knowledge, this is the first reported electrochemical platform for direct quantification of GP88, providing groundwork for further optimization of GP88 detection in an electroanalytical manner.