Sequential detection of vitamin B6 cofactors and nitroaromatics by using albumin-stabilized fluorescent copper nanoclusters

Abstract

Abstract The red-emitting bovine serum albumin (BSA) stabilized copper nanoclusters (BSA-CuNCs) was applied for the cascade detection of vitamin B6 cofactors and nitroaromatics. The fluorescence profile of BSA-CuNCs is perturbed with the addition of cofactors pyridoxal and pyridoxal 5’-phosphate (PLP). The fluorescence intensity at 640 nm of BSA-CuNCs is decreased with the concomitant appearance of a new emission band between 450-460 nm. The –CHO group of pyridoxal/PLP is expected to form an imine linkage with the free –NH2 group available with the functionalized BSA, which altered the conformation of BSA and the fluorescence profile of BSA-CuNCs. Importantly, the BSA-CuNCs showed selective fluorescence response towards pyridoxal at lower concentration among the other examined cofactors. Using BSA-CuNCs as a nanoprobe, the concentration of pyridoxal and PLP can be detected down to 66.3 nM and 1.08 μM, respectively. Subsequently, the pyridoxal and PLP conjugated BSA-CuNCs was applied for the fluorescent detection of nitroaromatics. The fluorescence of pyridoxal and PLP conjugated BSA-CuNCs was selectively quenched with the addition of picric acid and para-nitrophenol due to the energy and electron transfer processes.