Application of Organic Fluorophores in the Development of Drug Delivery Systems Based on Synthetic and Natural Polymers

The application of fluorescent markers in the study of nanoparticle interaction with living matter has proven to be a highly effective method. Numerous studies have demonstrated the rapid and efficient uptake of nanoparticles by the cells, with the use of fluorescent markers in microscopic observations playing a pivotal role. These methods facilitate not only the observation of qualitative changes in fluorescence intensity but also the quantitative assessment of changes occurring during delivery system components influx into the body. Synthetic dyes can be integrated into the structure of a polymer (polylactide or modified hyaluronic acid) during the production of nanoparticles with a fluorescent marker, without the formation of new chemical bonds between the fluorophore and the nanoparticle. However, the tracking of such systems is often inefficient due to poor solubility and diffusion of the components in the biological environment. Conversely, the incorporation of fluorescent tags via chemical modification of the functional groups of polymers with dyes appears to be a far more promising alternative, as it allows the production of strong conjugates that serve as markers of the system itself. Furthermore, the covalent binding of fluorophores to the polymer addresses problems such as the inaccuracy of localization associated with the release of the tag from the nanoparticle and its further penetration into non-target cells and organelles. This review presents a detailed critical evaluation of the methods of introduction and the classes of fluorescent markers used to modify polymers, based on lactic, glycolic and hyaluronic acids, for drug delivery.