Abstract:
A novel electrochemical immunosensor based on graphene/polyaniline nanocomposite modified electrode is successfully developed for the detection of neutrophil gelatinase-associated lipocalin (NGAL), a biomarker of acute kidney injury (AKI). The modified electrodes are fabricated by electrospraying of graphene/polyaniline (G/PANI) nanocomposite to increase electrode surface area and conductivity followed by electropolymerization of aniline to enhance the amino group (-NH2) on the electrode surface for antibody functionalization. Here, the factors affecting the electrode surface area and electrochemical sensitivity, such as aniline concentration, and scan number of electropolymerization are investigated and optimized. The morphologies of modified electrodes are characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and atomic force microscopy (AFM). The electrochemical characteristics of modified electrode are investigated using cyclic voltammetry (CV). The CV results show the substantial increase of both anodic and cathodic peak currents of [Fe(CN)6]3-/4- on the modified electrode compared to an unmodified electrode indicating the improved electrochemical sensitivity of the system. For immunosensor application, the electrochemical detection of NGAL relies on the increase of oxidation current during the binding between antigen (NGAL) and antibody. In this study, NGAL binds to NGAL antibody attached on electropolymerized aniline on the modified electrode. Under optimum condition, a linear relationship between oxidation current and NGAL concentration is found in a range of 50-500 ng/mL and a limit of detection is found to be 21.13 ng/mL. Eventually, the proposed system is applied for the detection of NGAL in biological fluid (e.g. urine).
