Proper Sample Preparation for Characterization of Drug Delivery Carriers in TEM

TEM has been most frequently used for the evaluation of morphology, size, composition and ultrastructure of colloidal delivery carriers, such as nanoparticles (NPs), liposomes, lipoproteins and polymer-based colloids [1, 2]. Increasingly complex systems have been developed for targeted delivery, sustained release formulations and even drug tracing after administration [3], leading to more challenging sample preparation of these colloidal systems for their study under the TEM. The combination of different sample preparation methods, such as staining, labeling, freeze-fracture and plunge freezing etc., and the corresponding TEM imaging techniques have seen an increase in demand.