Iodide-Enhanced Perovskite Nanozyme-Based Colorimetric Platform for Detection of Urinary Nuclear Matrix Protein 22

In the last decade, perovskite nanocrystals (PNCs) have brought extensive thinking owing to their excellent optical properties. Recently, we have uncovered the peroxidase-like activity of PNCs and used this for detecting many small molecules; however, the low enzymatic activity makes them unsuitable for fluorescence analysis, which is easily disturbed by the autofluorescence of biological media. This greatly limits their application in bioanalysis. Thus, the development of a method to facilely modulate the activity of PNCs for the instrument-free colorimetric detection is highly desirable. Herein, we demonstrated an iodide-enhanced perovskite nanozyme-based colorimetric platform for the visual assay of urinary nuclear matrix protein 22 (NMP22), a typical biomarker for the diagnosis of bladder cancer. We discovered that halogen could regulate the activity of perovskite nanozymes through a simple anion replacement reaction. Experimental analysis suggested that CsPbI₃ nanocrystals (NCs) displayed 24-fold higher catalytic efficiency than classical CsPbBr₃ NCs. As a proof-of-concept assay, the CsPbI₃ NCs could be explored into an immunoassay for the detection of NMP22 in clinical urine specimens, resulting in a low detection limit of 0.03 U/mL. This iodide-enhanced immunoassay deepens our understanding of perovskite nanozymes and also provides great potential for bioanalysis.