Dopamine functionalized CuO nanoparticles: A high valued "turn on" colorimetric biosensor for detecting cysteine in human serum and urine samples.

An attempt has been made to design one step synthesis of dopamine coated copper oxide nanoparticles (CuO@DOP NPs) by using microwave radiation method. The luminescent properties of CuO@DOP NPs have been explored for making colorimetric and visual biosensor for L-cys. Natural occurring dopamine has used as a precursor for the coating of CuO NPs that provides stability and generates functionality for the sensing of L-Cysteine (L-Cys). Being one of the important amino acid, L-cys has shown a fundamental role in living species due to the existence of sulfhydryl bonding which further affect the process of protein synthesis in living system. Therefore sensing of L-cys by using CuO@DOP NPs deserves higher consideration. Further, morphological and size parameters have been analyzed by using FESEM and HRTEM techniques. Surface interaction and coating of dopamine over CuO NPs has been examined through FTIR and TGA analysis. The non-toxicity and bio-compatibility of CuO@DOP NPs has been evaluated against L929 cell lines and on bacterial species. A computational study using DFT has been performed to check the possible mechanism of interaction between the CuO@DOP NPs and L-Cys. The higher value of detection limit (35 nM) has further shown its potential scope in sensing L-cys. The interference studies in presence of other amino acids have also taken into consideration for checking the selectivity and sensitivity of designed sensor. The applicability of prepared sensor has further been tested for real human blood serum and urine samples for detecting the presence of L-Cys. The as developed sensor of CuO@DOP NPs has provided rapid and selective sensing ability towards L-Cys over a wide range of concentration and bio-compatibility towards living entity. NOVELTY STATEMENT: Herein, the application of unique chemical and photo-luminescent properties of CuO NPs have been chosen for the fabrication of new type of fluorophore to complement conventional types of biosensor for L-Cys. The synthesis of CuO based biosensor has been achieved via an economically viable microwave assisted method. The article has not been published in any language anywhere and that it is not under simultaneous consideration by another journal. The current work is novel.