Fundamental understanding of the size and surface modification effects on r 1 , the relaxivity of Prussian blue nanocube@ m -SiO 2 : a novel targeted chemo-photodynamic theranostic agent to treat colon cancer.

A targeted multimodal strategy on a single nanoplatform is attractive in the field of nanotheranostics for the complete ablation of cancer. Herein, we have designed mesoporous silica ( m -SiO 2 )-coated Prussian blue nanocubes (PBNCs), functionalized with hyaluronic acid (HA) to construct a multifunctional PBNC@ m -SiO 2 @HA nanoplatform that exhibited good biocompatibility, excellent photodynamic activity, and in vitro T 1 -weighted magnetic resonance imaging ability ( r 1 ∼ 3.91 mM -1 s -1 ). After loading doxorubicin into the as-prepared PBNC@ m -SiO 2 @HA, the developed PBNC@ m -SiO 2 @HA@DOX displayed excellent pH-responsive drug release characteristics. Upon irradiation with 808 nm (1.0 W cm -2 ) laser light, PBNC@ m -SiO 2 @HA@DOX exhibited synergistic photodynamic and chemotherapeutic efficacy (∼78% in 20 minutes) for human colorectal carcinoma (HCT 116) cell line compared to solo photodynamic or chemotherapy. Herein, the chemo-photodynamic therapeutic process was found to follow the apoptotic pathway via ROS-mediated mitochondrion-dependent DNA damage with a very low cellular uptake of PBNC@ m -SiO 2 @HA@DOX for the human embryonic kidney (HEK 293) cell line, illustrating its safety. Hence, it may be stated that the developed nanoplatform can be a potential theranostic agent for future applications. Most interestingly, we have noted variation in r 1 at each step of the functionalization along with size variation that has been the first time modelled on the basis of the Solomon-Bloembergen-Morgan theory considering changes in the defect crystal structure, correlation time, water diffusion rate, etc. , due to varied interactions between PBNC and water molecules.