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.