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03.10.2023CCiTUB Cryo-electron microscopy aids in the design of complex nanomaterials for drug delivery
The Electron Cryomicroscopy Laboratory of the CCiTUB has collaborated with researchers from the IBEC, the IQAQ-CSIC and the Eindhoven University of Technology in a characterization study of the intracellular trafficking of nanoparticles by Correlative Light and Electron Microscopy (CLEM), which has been published in the journal Nanoscale.
The study has combined the fluorescence technique of stochastic optical reconstruction microscopy (dSTORM) with transmission electron microscopy on samples prepared using cryomethods: high-pressure freezing (HPF), cryosubstitution and cryoinclusion in acrylic resins. The correlation of these techniques has made it possible to locate with great precision the location of the nanoparticles in the context of the preserved cellular ultrastructure, in conditions very close to how the cells would be in natural conditions, thanks to the advantages that cryotechniques provide to structural preservation.
Nanoparticles are used to encapsulate therapeutic cargos for release at a specific or target location. Intracellular trafficking governs the distribution of nanoparticles and their charge throughout the different cellular compartments and therefore determines their efficiency and safety. Therefore, research in this area is very important both to understand the biological fate of nanoparticles and to improve their design to facilitate the delivery of the drug to its target.
Individual fluorescently labeled poly(lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) nanoparticles were visualized directly by dSTORM and assigned to cellular compartments by transmission electron microscopy. They first tracked the nanoparticles along the endolysosomal pathway at different time points, then demonstrated the effect of chloroquine on their intracellular distribution (i.e., endosomal escape).
The proposed protocol can apply to fluorescent nanoparticles and/or cargo, including those that cannot be detected by TEM alone. This study is of great relevance to obtain important insights into nanoparticle trafficking and crucial for the design of more complex nanomaterials for cytoplasmic/nucleic drug delivery.