Tissue and cellular localization of nanoparticles using ³⁵S labeling and light microscopic autoradiography

Microscopical visualization of nanoparticles in tissues is essential for assessing their distribution in whole organisms and their interaction with the cellular microenvironment, including possible toxic effects. However, labeling of nanoparticles with fluorescent dyes may affect their physicochemical properties. Moreover, the detection of organic nanoparticles in their tissue context often poses a particular challenge due to their closer similarities with biomolecules. As part of a biodistribution and toxicity study on organic anti-inflammatory nanoscaled dendritic polyglycerol sulfate amine (dPGS amine) we have established light microscopic autoradiography (LMA) for the tracking of (35)S labeled dPGS in standard histopathological tissue samples following intravenous injection in mice. The dPG(35)S amine was specifically localized in hepatic Kupffer cells with no histopathologic evidence of toxic, degenerate or inflammatory side effects. The combination of radiolabeling of organic nanoparticles with LMA offers a novel approach for their localization in microscopical slides, also allowing for a simultaneous standard toxicopathology analysis.

In this study, a novel light microscopic autoradiography utilizing (35)S isotope demonstrates a combined approach to visualize nanoparticle locations in microscopic slides with no obvious toxicity to the studied cells and with minimal external hazard.