Tuning Gold Nanoparticle Aggregation through the Inhibition of Acid Phosphatase Bioactivity: A Plasmonic Sensor for Light-Up Visual Detection of Arsenate (AsV)

A plasmonic biosensor for arsenate has been developed which uses gold nanoparticles (AuNPs) as the signal reporter and in which the biocatalytic activity of acid phosphatase (AcP) is modified by the target ion. The enzyme catalyzes the hydrolysis of negatively charged adenosine 5-monophosphate (AMP) to neutral adenosine, causing appreciable aggregation of AuNPs and then visible color change of the solution from red to blue. The presence of arsenate (As-V), as a molecular analogue of phosphate, can effectively interfere with the bioactivity of AcP by competitive inhibition, and so the hydrolysis process is slowed down. This is reflected by the change in the solution color from blue to red with increasing concentrations of As-V. In contrast to AuNP-based sensors for arsenic (basically As-III) that employ the strong interaction between As-III-specific molecules and As-III, this sensor adopts a different sensing principle and is the first visible sensor for specifically As-V specifically using AuNPs. Finally the practical assay of As-V in groundwater and lake water was performed with satisfactory results, suggesting this approach can be used for quantification of As-V levels in real water samples.