Detection of tomato leaf curl New Delhi virus DNA using U-bent optical fiber-based LSPR probes

The detection of Tomato leaf curl New Delhi virus (ToLCNDV) DNA has been presented using U-bent fiber optic sensor (FOS) by an evanescent wave absorption method in the visible region. The localized surface plasmon resonance (LSPR) based FOS was developed by immobilizing gold nanoparticles on the amine-functionalized surface and the receptor probe was prepared by attaching a short segment of the complementary DNA (cDNA) on this surface. Further, the cDNA attachment was confirmed by monitoring the real-time change in LSPR ab-sorption spectra. The conjugation protocol of single-strand DNA (ssDNA) from the viral genome of ToLCNDV was established like antibody-antigen-based assays by observing the real-time change in absorption kinetics. Consequently, a linear correlation between ssDNA concentration and the conjugation-dependent change in refractive index (RI) has been observed. The limit of detection (LOD) using two different cDNA immobilized FOS probes was determined to be 50 +/- 10 ng/mu L and the change in RI was found 12.5 +/- 1.3x10-4 RIU/Abs. From this systematic binding study, a straightforward target-specific sensor has been constructed using a digital electronic logic gate analogy. This device has significant commercial potential for the development of a portable LSPR sensor for real-time detection of plant pathogens in addition to the possibility of multi-target environments.