Photodegradable and pH responsive nanocapsules encapsulated with upconversion nanoparticles for diagnosis and treatment

Multifunctional composite nanoparticles with monodispersity and uniform particle size can be synthesized by distillation precipitation polymerization. The rare-earth upconversion nanoparticles were used as the core–shell structure and emit visible light under 980 nm near-infrared light for developing imaging. A layer of template SiO₂ was coated by reverse microemulsion method, and the surface of SiO₂ was coated with reactive polymer (ONB/PMAA) by distillation precipitation polymerization. The composite nanoparticles with a certain hollow structure were formed under after etch of HF. DOX was loaded into the particles, the drug loading rate was 6.23 %. Under acidic conditions, the PMAA layer shrinked and released the drug. Under the stimulation of UV light, the ONB (5-methylallyloxy-2-nitrobenzyl methacrylate) will photocleavage and release the internal drug. Under the stimulation of pH = 4 and UV light, the release rate could reach up to 85.13 %. Human breast cancer cells (MCF-7) were used as experimental subjects to investigate the drug release behavior in living cells by cytotoxicity assay and cellular uptake. The composite nanoparticles were found to have lower cytotoxicity and stable drug release behavior.