Apoferritin-templated yttrium phosphate nanoparticle conjugates for radioimmunotherapy of cancers.

We report a templated-synthetic approach based on protein-cage of apoferritin to prepare radionuclide nanoparticle (NP) conjugates. Non-radioactive yttrium (89Y) was used as a model target and surrogate for radioyttrium (90Y) to prepare the nanoparticle conjugate. The center cavity and multiple channel structure of apoferritin offer a fast and facile method to precipitate yttrium phosphate by diffusing yttrium and phosphate ions into the cavity of apoferritin, resulting a core-shell nanoparticle. The yttrium phosphate/apoferritin nanoparticle was functionalized with biotin for further application. The synthesized nanoparticle was characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). We found that the resulting nanoparticles were uniform in size, with a diameter of around 8 nm. We tested the pre-targeting capability of the biotin-modified yttrium phosphate/apoferritin nanoparticle conjugate with streptavidin-modified magnetic beads and with aid of streptavidin-modified fluorescein isothiocyanate (FITC) tracer. This work shows that an yttrium phosphate NP conjugate provides a fast, simple and efficient method to prepare radioactive yttrium conjugate for potential applications in radioimmunotherapy of cancer.