Vitamin B6 cofactors conjugated ovalbumin-stabilized gold nanoclusters: Application in alkaline phosphatase activity detection and generating white-light emission

Abstract

The red-emitting ovalbumin-stabilized gold nanoclusters (OVA@AuNCs) was prepared and applied for the selective detection of vitamin B6 cofactors. The addition of pyridoxal 5′-phosphate (PLP) and pyridoxal perturbed the fluorescence profile of OVA@AuNCs, and showed new emission band respectively at 532 nm and 437 nm due to the formation of Schiff base linkage between the aldehyde group of the cofactors and the free amine groups present in the OVA. Using OVA@AuNCs, the cofactors PLP and pyridoxal can be detected down to 6.14 × 10−7 M and 5.47 × 10−7 M, respectively. Also, the OVA@AuNCs can be mixed with optimized amount of pyridoxal to generate pure white-light emission. Further, considering the catalytic role of the alkaline phosphatase (ALP) in dephosphorylation, the PLP conjugated OVA@AuNCs was applied as a probe to detect ALP activity. The yellow-emitting PLP_OVA@AuNCs turned to pale-white emitting nanoclusters due to the ALP directed catalytic conversion of PLP into pyridoxal. With PLP_OVA@AuNCs, the ALP activity can be detected down to 3.9 U/L. In addition, the fluorescent color changes of PLP_OVA@AuNCs in the presence of varying amounts of the ALP were integrated with smartphone to develop a simple and cost-effective approach for the on-site detection of ALP activity. Finally, the practical utilities of both the fluorimetric and smartphone approaches were validated by quantifying ALP in various environmental and biological samples.