(6e) Fluorescence and Magnetic Resonance Enabled Silica Nanoparticles for Bio Imaging Applications

Optical imaging is a sensitive, non-invasive, non-ionizing (clinically safe) and relatively inexpensive procedure as compared to imaging techniques that are routinely used for the diagnosis of tumors such as Computed Tomography, Positron Emission Tomography, and Magnetic Resonance etc. Moreover CT, MRI, PET, do not permit the real time and gross visualization of tumor tissue and particularly the tissue boundary during intraoperative surgical procedure. Hence there is a need for multimodal contrast agent that combines radio opaque, optical and magnetic properties in a single nanoparticle. Our group has recently engineered multifunctional, core shell, novel tris(2,2'-bipyridyl)dichlororuthenium(II)hexahydrate (Rubpy) and gadolinium(III) doped silica nanoparticles. The core of the silica contains the optical component i.e. Rubpy, an organomettalic dye. The Gd(III) ions chelated to the silica shell through a silane ligand provide the magnetic character and the Ru(II) and Gd(III) electron dense metal ions impart the radio opaque nature. The silica shell performs multiple functions e.g. it prevents the rapid photo bleaching of the Rubpy dye, prevents direct contact between the paramagnetic ions and the media solution (resulting in possible degradation of complexed metal ions) and in addition has surface reactive groups that can be modified to attach both ligands and antibodies, allowing for the detection of cellular events in vivo.