Construction of bifunctional carbon dots based fluorescent/colorimetric/ smartphone-assisted multi-signal strategy for monitoring alkaline phosphatase activity

In view of the importance of alkaline phosphatase (ALP) as a clinical diagnostic indicator of related diseases and physiological research, developing a reliable measurement assay with high efficiency and accuracy is of tremendous value. In this study, bifunctional carbon dots (CDs) with peroxidase-like and fluorescence properties were synthesized through a readily available solvothermal method. Peroxidase-like CDs could oxidaze colorless 1,4-phenylenediamine (PPD) to the colored oxidized product (oxPPD), which quenched the CDs' fluorescence. A multi-signal sensing system was strategically fabricated for detecting ALP for the first time, taking advantage of CDs' remarkable peroxidase-mimic activity and fluorescence properties. The limits of detection (LOD) and linear ranges for ALP was 0.034 and 0.027 U/L, 0.1 to 1.8 and 0.05 to 1.8 U/L by the colorimetric and fluorescent method, respectively. Besides, the results of hydrogel devices processed by smartphones also exhibited satis-factory results. The multi-signal strategy developed in this study provides a new impetus for designing different biosensors with bifunctional nanomaterials.

Automated summary

This study synthesized bifunctional carbon dots with peroxidase-like and fluorescence properties, and developed a multi-signal sensing system for the detection of alkaline phosphatase (ALP). The detection limits and linear ranges of ALP were determined using colorimetric and fluorescent methods. The results showed that the strategy developed in this study has great potential for designing biosensors with bifunctional nanomaterials.