Fundamental understanding of the size and surface modification effects on r1, the relaxivity of Prussian blue nanocube@m-SiO2: a novel targeted chemo-photodynamic theranostic agent to treat colon cancer

Abstract

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-SiO₂)-coated Prussian blue nanocubes (PBNCs), functionalized with hyaluronic acid (HA) to construct a multifunctional PBNC@m-SiO₂@HA nanoplatform that exhibited good biocompatibility, excellent photodynamic activity, and in vitro T₁-weighted magnetic resonance imaging ability (r₁ ∼ 3.91 mM⁻¹ s⁻¹). After loading doxorubicin into the as-prepared PBNC@m-SiO₂@HA, the developed PBNC@m-SiO₂@HA@DOX displayed excellent pH-responsive drug release characteristics. Upon irradiation with 808 nm (1.0 W cm⁻²) laser light, PBNC@m-SiO₂@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-SiO₂@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 r₁ 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.