Observation of the protein expression level via naked eye: Pt clusters catalyze non-color molecules into brown-colored molecules in cells

α (v) β (3) is overexpressed in various tumor cells and plays a key role in tumor genesis, invasion, and metastasis. Therefore, it is of great significance to precisely detect the α (v) β (3) level in cells via a simple method. For this purpose, we have constructed a peptide-coated platinum (Pt) cluster. Due to its bright fluorescence, well-defined Pt atom numbers, and peroxidase-like catalytic activity, this cluster can be used to evaluate α (v) β (3) levels in cells by fluorescence imaging, inductively coupled plasma mass spectrometry (ICP-MS), and catalytic amplification of visual dyes, respectively. In this report, the expression level of α (v) β (3) in living cells is well-detected by the naked eye under an ordinary light microscope when the Pt cluster binds to αvβ3 in cells and catalyzes non-color 3,3′-diaminobenzidine (DAB) into brown-colored molecules in situ. Moreover, SiHa, HeLa, and 16HBE cell lines with different α (v) β (3) expression levels can be visually distinguished by the peroxidase-like Pt clusters. This research will provide a reliable method for the simple detection of α (v) β (3) levels in cells.