Figure 1.

Design and synthesis of SiBiGdNP. (a) Schematic representation of the SiBiGdNP uptake in a tumor and efficacy upon external radiation. (b) (Not to scale) The Gd₂O₃ core and its polysiloxane network are grafted to DOTAGA ligands before being transferred to water to dissolve the core. The final fragmentation into sub-5 nm silica-based gadolinium nanoparticles (SiGdNP) was then performed based on the method from Mignot et al.³⁸ At this stage of the synthesis, the Gd³⁺ atoms were complexed by the DOTAGA ligands. After, DOTA-NHS ligands were grafted to the surface to entrap free Bi³⁺ atoms into the final complex. (c) Dynamic light scattering measurements show a SiBiGdNP size of 4.5 ± 0.9 nm. (d) Elemental characterization by ICP-OES of the nanoparticle composition before and after the grafting of Bi³⁺. (e) Percent release of free Bi³⁺ atoms measured by absorbance (305 nm) at pH = 5 and pH = 7 over 48 h. (f) Toxicity of the SiBiGdNP as a function of the concentration 24 h post-incubation. (g) MRI (relaxivity) and CT (Hounsfield units) linear relation with concentration of nanoparticles (metal) in aqueous solution.