Pd(II)-based coordination polymer nanosheets for ratiometric colorimetric and photothermal dual-mode assay of serum alkaline phosphatase.

Fabrication of a multi-signal readout assay with high sensitivity and selectivity is highly desirable for clinical and biochemical analysis, but remains a challenge due to laborious procedures, large-scale instruments, and inadequate accuracy. Herein, a straightforward, rapid, and portable detection platform based on palladium(II) methylene blue (MB) coordination polymer nanosheets (PdMBCP NSs) was unveiled for the ratiometric dual-mode detection of alkaline phosphatase (ALP) with temperature and colorimetric signal readout properties. The sensing mechanism is the ALP-catalyzed generation of ascorbic acid for competitive binding and etching PdMBCP NSs to release free MB in a quantitive means for detection. Specifically, ALP addition led to the decrease of temperature signal readout from the decomposed PdMBCP NSs under 808 nm laser excitation, and simultaneous increase of the temperature from the generated MB with a 660 nm laser, together with the corresponding absorbance changes at both wavelengths. Notably, this ratiometric nanosensor exhibited a detection limit of 0.013 U/L (colorimetric) and 0.095 U/L (photothermal) within 10 min, respectively. The reliability and satisfactory sensing performance of the developed method were further confirmed by clinic serum samples. Therefore, this study provides a new insight for the development of dual-signal sensing platforms for convenient, universal, and accurate detection of ALP.