Platinum Nanozyme Probes for Cellular Imaging by Electron Microscopy.

The highly efficient peroxidase-like activity of platinum nanozymes (3-20 nm size) is exploited within the complex cellular environment to catalyze the oxidation of the DAB substrate, producing an electron-dense signal around the nanozyme surface, upon osmium staining. It is proved that such nanozyme amplification can achieve a catalytic signal enhancement up to 10-fold, enabling the quick detection of the Pt particles (even of 3 nm size) by transmission electron microscopy (TEM) also at low magnification and across wide fields of view in the intricate intracellular milieu. The developed procedure is ideally suited to overcome standard amplification strategies currently used in TEM analysis, such as gold or silver enhancements. Furthermore, the wide versatility of the Pt-nanozyme probes in TEM imaging is demonstrated in immuno-EM and protein trafficking studies, showing their potential to track the subcellular localization of target biomolecules at both low and high magnifications. These results suggest that the use of nanozymes might represent a paradigm shift in the conventional amplification systems currently employed in electron microscopy for cellular analyses, offering enhanced imaging capabilities.