Silver Staining Technology for Metal Nanoparticles and Their Biological Applications

With the expanding biomedical applications of metal nanoparticles (MNPs), the accurate and intuitive detection of their in vivo behavior in complex biological systems has become an urgent research priority. Silver staining, a label-free and highly sensitive histochemical technology, addresses this challenge by amplifying ultrasmall MNPs to a size detectable by optical or electron microscopy. This allows reliable detection of their microstructural distribution and furnishes essential technical support for MNP-related biomedical research. In this study, we review the research progress of silver staining technology and its applications in investigating in vivo behaviors. We first summarize the development history of silver staining technology, with a focus on silver staining protocols for ultrasmall MNPs (< 2 nm). We then systematically discuss the application of silver staining either alone or combined with other staining techniques for bright-field and electron microscopy for visualizing the distribution of MNPs at the sub-organ, cellular, and organellar levels. Finally, we comprehensively analyze the technical merits and intrinsic limitations of silver staining, and future directions. This review clarifies the critical value of silver staining for elucidating the in vivo behaviors of nanoparticles, and aims to provide technical support for the high-quality advancement of MNPs in nanomedicine.