An off-on fluorescence method for acid phosphatase assay based on the inner filter effect of MnO nanosheets on vitamin B.

Fluorescence analysis has attracted much attention due to its rapidity and sensitivity. The present work describes a novel fluorescence detection method for acid phosphatase (ACP) on the basis of inner-filter effect (IFE), where MnO nanosheets (MnO NSs) and vitamin B (VB) are served as absorbers and fluorophores, respectively. In the absence of ACP, the absorption band of MnO NSs overlaps well with the excitation band of VB, resulting in effective IFE and inhibition of VB fluorescence. In the presence of ACP, 2-phospho-L-ascorbic acid trisodium salt (AAP) is hydrolyzed to generate ascorbic acid (AA), which efficiently trigger the reduction of MnO NSs into Mn ions, causing the weakening of the MnO NSs absorption band and the recovery of VB fluorescence. Further investigation indicates that the fluorescence recovery degree of VB increases with the increase of ACP concentration. Under selected experimental conditions, the proposed method can achieve sensitive detection of ACP in the ranges of 0.5-4.0 mU/mL and 4.0-15 mU/mL along with a limit of detection (LOD) as low as 0.14 mU/mL. Finally, this method was successfully applied for the detection of ACP in human serum samples with satisfactory recoveries in the range of 95.0 %-108 %.