Peroxidase-mimicking poly-L-lysine/alginate microspheres with PtS₂ nanoparticles for image-based colorimetric assays

Morphologically controllable ALG@ε-PL water-in-water microspheres were successfully prepared using a two-step method through precise control of the two-phase flow rate. Through further interfacial coagulation, the ALG@ε-PL microspheres possess a dense surface structure and good permeability. The sensor based on PtS₂@ALG@ε-PL microspheres was constructed by encapsulating PtS₂ nanosheets with peroxidase-like properties in ALG@ε-PL water-in-water microspheres. PtS₂ nanosheets catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ to produce blue oxTMB. The strong reducing property of the model analyte dopamine (DA) can reduce oxTMB, thus causing the blue color to fade and successfully achieving colorimetric detection of DA. The linear range of the assay is 2.0-200 μM, and the detection limit is 0.22 μM. The recoveries of DA in serum samples were determined by the spik method, and the results were reproducible.