*2.1.1.1. NS1 antigen detection*

Omar et al. reported an electrochemical immunosensor based on screen-printed carbon electrodes (SPCE) for the detection of dengue NS1 antigen. Anti-NS1-capturing antibodies were immobilized on BSA-modified working electrode of SPCE. The detection was based on the measurement of electron transfer resistance before and after the NS1 binding. The study demonstrated that the immunosensor successfully detected NS1 antigen with a limit of detection (LOD) of 0.3 ng/mL and the linear range was 1–200 ng/mL [24]. Pirich et al. worked on piezoelectric immunosensor to detect dengue NS1 antigen. For the enhanced binding of anti-NS1 antibodies, sensor surface was coated with a thin film of bacterial cellulose nanocrystals. The formation of antigen antibody complex was then analyzed using quartz crystal microbalance. The study showed that immunochip was able to detect dengue NS1 antigen from serum with a LOD of 0.32 μg/mL [25]. In another study, NS1 was detected using Langmuir–Blodgett and gold nanoparticles (AuNP) composite as a biosensing surface. The anti-NS1 antibodies were immobilized on the biosensing surface and then the sample containing NS1 antigen was pipetted on it. Subsequently, the biorecognition event between anti-NS1 antibody and NS1 antigen was detected through electrochemical impedance spectroscopy. The study showed that developed electrochemical immunosensor was capable to detect dengue with a LOD of 1.19 ng/mL in spiked serum sample [26].
