Cobalt(ii)–curcumin cysteine conjugate as c-MYC promoter G-quadruplex selective switch-on fluorescence probe

Abstract

We have synthesized a metal organic framework comprising a cobalt(II) complex of a curcumin–cysteine conjugate (i.e., Co–CC) as a fluorescent probe for the detection of G-quadruplex DNA sequences. The as-synthesized probe has been characterized using different spectroscopic and microscopic methods. The strong fluorescence emission of the Co–CC probe was noticed upon sequential addition of different guanine-rich DNA sequences without the appearance of any new absorption band. Among the different DNA sequences, the probe showed better selectivity and a significantly lower detection limit for the c-MYC hypersensitivity element Pu-27 (i.e., LOD: 8.61 ± 1.96 nM) and quantification detection limit (28.72 nM). Further, cytotoxicity analysis was performed with A549 human carcinoma lung cancer cells and ATCC CCL-81 Vero cells. This study reveals that the as-synthesized Co–CC has improved cytotoxicity toward A549 lung cells and mild toxicity toward Vero cells when compared to pristine curcumin. Real-world sample analysis also showed an encouraging result, with a recovery range of 101 to 104%. As a result, the current study provides insights for further improving bioavailability through metal–organic ligand complexation and Co–CC could be used for in vivo analysis as well.