Synthesis of new Schiff’s base copper conjugate for optically and electrochemically tuning of l-cysteine in cancer cells and bovine serum albumin

Abstract

An environmentally benign chemosensor probe-N'1,N'4-bis((E)-2-hydroxy-3,5-diiodobenzylidene)terephthalohydrazide (HDT) is synthesized via Schiff base reaction between the terephthalic acid and dihalo-substituted salicylaldehyde. The turn-off-on fluorescence technique is accomplished for the detection of cysteine (Cys), in which the fluorescence behavior of HDT probe is initially quenched with Cu2+ ions via the chelation effect by the formation of the HDT-Cu2+ conjugate. The quenched fluorescence behavior of HDT in HDT-Cu2+ conjugate is restored with Cys, owing to the formation of a stable Cys-Cu2+ conjugate. Under optimized conditions, the as-developed HDT-Cu2+ conjugate demonstrates the lower detection limit and broad linear range, respectively, of 55 nM and 0–200 μM on Cys sensing. It also accelerates the selective detection of Cys even under the existence of biologically relevant amino acids. The electrochemical detection of as-prepared HDT-Cu2+ conjugate toward Cys is also enunciated from the cyclic voltammetry studies. Furthermore, the as-developed probes (HDT and HDT-Cu2+) comprehend their practical sensing applicability toward Cu2+ ions and Cys detection in cancer cells (A459 cancer cells), opening progressive research avenues towards the scale-up process of developed chemosensor probe in sensitive and selective Cys detection.