Proteome Mediated Synthesis of Biocompatible Green Fluorescence Cerium Oxide Quantum Dots with Enhanced Antioxidant Activity

Abstract

Biocompatibility of quantum dots make good candidature for in vivo and in vitro diagnostic applications. In this study biocompatible cerium oxide quantum dots (CeO2 QDs) were synthesized from proteome of Justicia adhatoda leaf using simple aqueous protocol. Synthesized cerium oxide nanoparticle possessed green colored fluorescence under UV light. Quantum yield of CeO2 QDs was found to be 31.13% and were stable for 3 month at 4 °C. The band gap was found to be 3.26 eV which was higher than the band gap of bulk material i.e., 3.19 eV. The concentration of synthesized CeO2 QDs was determined as 165.96 ppm. These quantum dots were also characterized using an UV-Vis spectroscopy, Fourier Transform Infra-red Spectroscopy (FT-IR) and Transmission Electron Microscopy (TEM) respectively. It displayed distinct absorbance peak at 380 nm under UV-Visible spectrum. TEM images showed monodispersity of 2–5 nm spherical shaped CeO2 QDs and higher degree of crystallinity was observed by the pattern of selected area electron diffraction. In FTIR, the stretching observed at 621.65 cm–1 is assigned to Ce-O which confirmed the CeO2QDs formation. In view of biocompability, synthesized CeO2QDs were also characterised in reference to cell toxicity. Generated CeO2QDs has not showed any toxicity to J774A.1, Raw 264.7 and 3T3 cell lines in vitro cell viability assay. Significant enhancement in antioxidant activity of synthesized cerium oxide nanoparticles was observed from bulk material. This process offers plenty of advantages such as simple protocol, mild environment operation, potential for large scale commercial production of biocompatible CeO2QD. These QDs might find potential applications in both in vitro and in vivo diagnostics.