Fe(III)-mediated reversible catalytic activity of MoS2 nanozymes for bisphosphonate drug sensing

Peroxidase-like activity of MoS2 quantum dots (QDs) can be reversibly regulated by means of Fe3+/alendronate sodium (ALDS)-induced aggregation/disaggregation of the QDs in solution. Specifically, Fe3+ can selectively aggregate the MoS2 QDs and thus greatly enhance their peroxidase-like activity, while such enhancement can be inhibited in the presence of ALDS owing to the competitive coordination of ALDS with Fe3+. By regulating the enzyme-like activity of MoS2 QDs, different colorimetric signal of a typical substrate of horseradish peroxidase, 3,3΄,5,5΄-tetramethylbenzidine, can be measured in the presence of H2O2. Based on this mechanism, we develop a colorimetric approach for the determination of ALDS and further applied in quality control of pharmaceutical products, utilizing either smartphone or UV–vis spectrometer as a readout. This detection method is rapid and selective, where derivatization of ALDS before detection is not needed. Such a smartphone-based colorimetric detection platform is promising to be applied in point-of-care testing at home, small clinics, or underdeveloped regions.