A ratio fluorescence assay for acid phosphatase based on 4-mercaptobenzoic acid templated copper nanoclusters

Copper nanoclusters were synthesized based on 4-mercaptobenzoic acid (P-MBA) as template. • The addition of small molecule terephthalic acid (PTA) can enhance the fluorescence intensity. • The reaction between PTA and ascorbic acid can produce a blue fluorescent substance PTA-OH. • Acid phosphatase can catalyze the hydrolysis of l -ascorbic acid-2-phosphate to AA. • A ratiometric fluorescence assay for acid phosphatase was developed. Copper nanoclusters were synthesized based on 4-mercaptobenzoic acid (P-MBA) as template (P-MBA-CuNCs). Small molecule terephthalic acid (PTA) was then utilized to modify P-MBA-CuNCs and enhance the fluorescence intensity. Individual P-MBA-CuNCs were self-assembled into nanosheet aggregates in aqueous solution due to π-π stacking and hydrogen bonding interactions. These inter-cluster interactions accelerated the nonradiative process, resulting in quenching of the fluorescence. However, there is strong interaction between PTA and P-MBA, which blocks the inter-cluster interaction of CuNCs and enhances the fluorescence emission. In addition, the reaction between PTA and ascorbic acid (AA) can produce a blue fluorescent substance PTA-OH. Acid phosphatase (ACP) can catalyze the hydrolysis of l -ascorbic acid-2-phosphate (AAP) to AA. Therefore, a ratiometric fluorescence assay for ACP was constructed based on the CuNCs/PTA system with fluorescence intensity of CuNCs unchanged and fluorescence intensity of PTA-OH increased. The assay has linear response to ACP in the concentration range of 0.01–15 U/L, with detection limit as low as 0.003 U/L. The method was successfully applied to determination of the ACP in the human serum samples. Ratio fluorescence assay for acid phosphatase based on 4-mercaptobenzoic acid templated copper nanoclusters. Download: Download high-res image (111KB) Download: Download full-size image