Synthesis, Characterization, and Evaluation of Silica-Nanosphere-Based Contrast Agents for Biomedical Application

Abstract

Following cytotoxicity studies, MRI contrast agents were ultimately introduced into the silica nanospheres for dual functionality. Gd-DTPA, a commonly used MRI contrast agent, was chosen as an appropriate candidate for initial study. Through an in vivo experiment using tadpoles, we demonstrated and evaluated dual functionality of Gd-DTPA loaded silica spheres for MRI, integrated OCT/MPM, and CT using the same biological sample. The results confirmed that when ingested by the tadpole, dual functional spheres improved MRI contrast in areas around the brain and spine. Core/shell type of dual modality nanospheres were developed using superparamagnetic iron oxide particles. The agglomeration problems of iron oxide nanoparticles were resolved with an ultrasonication process and then ultimately settled by encapsulating within a silica shell. The surface of silica shells were further modified with --NH2 functional groups. The magnetization curve measured by MPMS indicated that these spheres show excellent magnetization values and high T2 relaxation time for MRI measurements, making them suitable as dual modality contrast agents and further applications for cell-labeling/tracking when they are conjugated with other bio-molecules such as proteins, enzymes, and DNA.