Surface engineering of organic nanoparticles for highly improved bioimaging.

Surface properties of nanoparticles (NPs) have a huge influence on their biological activities. In this work, we report to use mesoporous silica nanoshell surface to regulate the cellular internalization rate and intracellular fate of fluorescent organic NPs for highly improved cellular imaging. We systematically studied the internalization of the NPs into cells, the intracellular transport pathways, the excretion from cells, and very importantly, compared the results with those from various NPs with different surface properties. It was found that the silica nanoshell coating allow the NPs to achieve strikingly improved brightness in imaging (over ten-fold enhancement) and much higher delivery efficiency than other NPs. This was attributed to their unique non-clathrin- and non-caveolae-mediated pathways which enable them to enter cells very efficiently and quickly in the cellular internalization, as well as their low cellular excretion rate. This highly effective cellular imaging effect caused by silica surface coating is much desirable for applications in sensitive imaging and long-term tracking of cells.