Enhancing the stability of nanotheranostic systems

Author(s): Seda Demirel Topel

Theranostics is new term which defined as a combination of therapy and diagnosis to establish a targeted drug delivery and monitoring of treatment into a single nanosystem. The most important parameter in the theranostic platforms is their stability to be able to increase the crossing some biological barriers and avoid the aggregation in the circulatory system. Therefore, polymeric nanoparticles are highly desirable to design novel nanotheranostics due to their improved pharmacokinetic properties, stability in physiological conditions, biocompatibility, and biodegradability. In our studies, we designed and synthesized some polymeric nanocapsules and one part of these nanocapsules utilized as a pH responsive nanosystem which includes Doxorubicin (Dox), a chemotherapeutic drug, and upconversion nanoparticles (UCNPs) as a luminescent probe and the other part of the nanocapsules were used for the photodynamic therapy (PDT) by loading the capsules with photosensitizer molecules, a derivative of Bodipy. Both studies exhibited excellent stability in phosphate buffered solutions (pH:7.4) which is proved by Zeta-sizer measurements, dynamic light scattering studies and stability tests. The size of the nanocapsules were dramatically decreased by increasing the stirring rate. In the first study, the nanocapsules were loaded with Dox up to ~63 % efficiency and acid-induced release (~47 %) obtained at pH 3.6 and 5.5. It was found that encapsulation decreased toxicity of UCNPs as confirmed in a cellular assay (L-929 and MCF-7 cell lines). In the second study, a higher encapsulation efficiency of Bodipy has been observed. The singlet oxygen measurements of the Bodipy encapsulated nanocapsules have been done in the presence of a trap molecule, resulted in a promising PDT activity. As a result, for both studies, a less soluble drug molecules in solution become highly soluble via encapsulation technology using a polysaccharide nanocapsule. Further studies, such as biological experiments are ongoing.