Suitability of PEG capped carboxylic acid terminated fluorescent ZnS nanoparticles for NDV peptide binding

Abstract

Newcastle disease, an economically important endemic OIE (World Organisation for Animal Health) listed viral disease remains a major impediment to the vibrant status of the poultry industry. The outbreak of the disease leads to huge economic loss posing a major threat to the Country’s economy. To detect the disease outbreak, an effective tool is required. The present study is a first step in forming a peptide nanoparticle conjugate as an attempt to develop a biosensor for NDV outbreak detection. ZnS due to its emission properties and photo stability, it was used as fluorescent labels in immunoassays. ZnS is widely used as the shell material in most luminescent core–shell nanoparticles. In this study, ZnS was used as the core material and the ZnS–PEG modified with the carboxylic acid group functionalized nanoparticles were prepared by a simple wet chemical method. To the ZnS–PEG–COOH nanoparticle, Newcastle disease virus peptide was attached using EDC/NHS coupling and analyzed. Structural properties of the ZnS, ZnS–PEG and ZnS–PEG–COOH nanoparticles were analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and dynamic light scattering (DLS). FTIR peak at 2364 cm⁻¹ indicates the formation of S–H bond which confirms the attachment of PEG to ZnS surface by S–H bond formation. The XRD, FTIR, DLS and optical study such as UV–Vis results support the particle size reduction upon capping ZnS with PEG and dicarboxylic-terminated PEG. The optical properties were studied using Photoluminescence (PL) and UV–visible Spectra. PL result shows upon capping ZnS with PEG-COOH, the fluorescence intensity increased by ≈ 5 times more than that of the bare ZnS nanoparticles. ZnS–PEG–COOH found to have superior photo luminescent property. NDV peptides were tagged by means of EDC/NHS activation to ZnS–PEG–COOH. The peptide conjugation was confirmed by UV–Vis spectral analysis and the peak was found to be shifted by 4 nm which confirms the attachment of NDV peptide on the surface of ZnS–PEG–COOH nanoparticle. Hence ZnS–PEG–COOH nanoparticle is found to be suitable option for attaching biomolecule which can be further extended for bio sensing application of NDV detection.