Scanning fluorescence-based ultrasensitive detection of dengue viral DNA on ZnO thin films

In this article, ZnO thin film acts as a matrix to bind with a sequence specific probe strand, which is employed as a recognition element and is involved in sensing the complementary DNA of dengue virus specific serotypes. ZnO thin films possess high surface area, high catalytic efficiency with an isoelectric point of ∼9.5, thus leading to strong electrostatic attraction and strong adsorption capability towards negatively charged DNA having an isoelectric point of 4. ZnO thin film deposition is carried out by ultrasonic spray pyrolysis (USP) at the temperature of 450 °C using dry air as the carrier gas along with 0.1 M of zinc acetate as the precursor to obtain transparent films with a thickness of around 150-200 nm. X-ray diffraction data show the dominant peak corresponding to (100). The morphology of ZnO thin films was analyzed using field emission-scanning electron microscope (FE-SEM) and atomic force microscope (AFM). The optical characteristics of thin films were studied using UV-spectroscopic analysis, which confirms the band gap of the film to be 3.3 eV. Further, sequence specific DNA immobilization is carried out for the bio-functionalization of ZnO thin films to detect 4 DENV serotypes, thus enabling simultaneous detection in an array having sensitivity in the range of 1 × 10^-15 moles of DNA.