Cellulose acetate encapsulated upconversion nanoparticles – A novel theranostic platform

Luminescent upconversion nanoparticles (UCNPs) are of great interest in a wide range of nanotechnological applications, particularly in the biomedical area like imaging and therapy but their biocompatibility and stability pose major challenges hampering progression towards further pharmaceutical applications. Herein, we present a biocompatible theranostic platform enabling simultaneous diagnosis and drug delivery consisting of UCNPs encapsulated with cellulose acetate (CA), a biocompatible polymer. Luminescence properties of UCNPs in the developed theranostic platform remain stable even after encapsulation. The size of the CA capsules, ranging from micro- to nano-sized particles, can easily be tuned by adjusting the stirring rate during encapsulation. Doxorubicin, a well-known chemotherapeutic drug, onto the CA nanocapsules containing UCNPs (UCNP-CA nanocapsules) was loaded with 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). Taken together, the developed UCNP-CA nanocapsules serve as a highly interesting novel theranostic platform, combining the biocompatible optical properties of UCNP, with reduced cell toxicity and drug encapsulating properties of CA. The proposed system could be subject for further refinement and exploration.