Multifunctional yolk-in-shell nanoparticles for pH-triggered drug release and imaging

Multifunctional nanoparticles are synthesized for both pH-triggered drug release and imaging with radioluminescence, upconversion luminescent, and magnetic resonance imaging (MRI). The particles have a yolk-in-shell morphology, with a radioluminescent core, an upconverting shell, and a hollow region between the core and shell for loading drugs. They are synthesized by controlled encapsulation of a radioluminescent nanophosphor yolk in a silica shell, partial etching of the yolk in acid, and encapsulation of the silica with an upconverting luminescent shell. Metroxantrone, a chemotherapy drug, was loaded into the hollow space between X-ray phosphor yolk and up-conversion phosphor shell through pores in the shell. To encapsulate the drug and control the release rate, the nanoparticles are coated with pH-responsive biocompatible polyelectrolyte layers of charged hyaluronic acid sodium salt and chitosan. The nanophosphors display bright luminescence under X-ray, blue light (480 nm), and near infrared light (980 nm). They also served as T₁ and T ₂ MRI contrast agents with relaxivities of 3.5 mM^-1 s ^-1 (r₁) and 64 mM^-1s^-1 (r ₂). These multifunctional nanocapsules have applications in controlled drug delivery and multimodal imaging. Multifunctional nanoparticles are synthesized for pH-triggered drug release and imaging with radioluminescence, upconversion luminescence, and magnetic resonance imaging (MRI). The particles have a yolk-in-shell morphology, with a radioluminescent core, an upconverting shell, and a hollow region between the core and shell for loading drugs. The nanophosphors display bright luminescence under X-ray, blue light (480 nm), and near infrared light (980 nm).