A novel colorimetric/fluorescence dual-channel sensor based on NBD for the rapid and highly sensitive detection of cysteine and homocysteine in living cells

Abstract

A novel and simple turn-on fluorescent probe bearing 7-nitrobenz-2-oxa-1,3-diazole and benzaldehyde fragments for the rapid optical sensing of cysteine and homocysteine has been designed and synthesized. The probe has almost no background fluorescence (Φ_f < 0.0001) in aqueous solutions; however, it displayed fluorescence turn-on response to cysteine and homocysteine and exhibited a large bathochromic-shift (106 nm) in absorption wavelength accompanied by color changes which could be distinguished by the naked-eye. There is a good linearity with cysteine in the range of 0 to 1.37 × 10⁻⁴ M, with a detection limit of 98 nM (S/N = 3). In addition, the optical responses of the probe were investigated by density function theory (DFT) calculations. Moreover, it can be used to detect biological thiols in living cells.