Label Free Quantitative Immunoassay for Hepatitis B

Complementary metal oxide semiconductor (CMOS) technology has already been proven in molecular diagnostics. The present research proved that CMOS image sensor based immunodetection is a suitable diagnostic system for hepatitis B virus antigen (HBV-Ag)-antibody (Ab) interaction. The Ag-Ab was interacted on InNP substrate which was analyzed by a CMOS image sensor by photon number variation. The photon passes through the protein adsorbed substrate and hits the sensor surface. The number of photons attained by the sensor depends on the Ag concentration, nanoparticles size and substrates thickness; therein substrate with higher concentrations of Ag were blocked more photons. The number of photons was detected by the sensor and converted into a digital number with the aid of an analog-to-digital-converter (ADC). A topographical study of AFM and fluorescence images have evaluated the morphological changes, height increment, surface roughness of protein treated and non-treated InNP substrates, to prove the efficiency of CMOS image sensor based immunodetection. Also, the study was compared with conventional ELISA method, to find the sensitivity of CMOS image sensor. Hence, the detection of HBV Ag-Ab interactions by CMOS image sensors is suitable for point-of-care diagnosis.