Ultrasensitive detection alkaline phosphatase activity using 3-aminophenylboronic acid functionalized gold nanoclusters

Herein, a fluorescent bi-enzyme sensing platform for ultrasensitive detection of alkaline phosphatase activity was developed based on 3-aminophenylboronic acid functionalized gold nanoclusters (APBA-Au NCs). Alkaline phosphatase (ALP) can catalyze hydrolysis of phenyl phosphate to phenol, which can be subsequently hydroxylated to generate catechol in the presence of tyrosinase (TYR). Due to the special covalent combination between the catechol and boric acid group, the five-membered cyclic esters can be formed on the ligands of APBA-Au NCs, leading to the fluorescence quenching of the Au NCs. Thus, according to the change of fluorescence signal, the proposed biosensor can be utilized to ultrasensitive detection ALP. Under the optimal condition, there exhibited good linear relationships between fluorescence intensity change of APBA-Au NCs and the concentration of ALP in the range of 0.02–2.0 U/L. The detection limits reached 0.005 U/L. The developed strategy was employed to monitor enzyme activity in real samples with satisfactory results obtained, illustrating the potential application of this biosensor.