Abstract

Integrating multiple functionalities into individual nanoscale materials is of tremendous importance in biomedicine, since this would expand the capabilities of nanoscale materials to perform multiple tasks. Here, fluorescence optical imaging and magnetic resonance imaging (MRI) are combined within the same nanoparticle based material. NaYF4: Tm3+, Yb3+, showed NIR to NIR upconversion, giving deep tissue penetration, which is an advantage in medical imaging. Their lanthanide ions (Tm3+/Yb3+) derived optical properties in the near infrared region of the spectrum, where tissue is maximally transparent. Multimodal properties may be imparted to NaYF4: Tm3+, Yb3+ via the functionalization of gadonium-tetraazacyclododecanetetraacetic acid (Gd-DOTA), a commercially available MRI contrast agent. Gd-DOTA was covalently bonded to the surface of the silica coated UCNPs using the click reaction. This imaging probe may be used for both MRI and fluorescent imaging.
Another approach to achieve bimodalities is by doping Gd3+ ions into the systems of UCNPs, which provides both magnetic and optical properties. Ultra-small NaGdF4, Tm3+, Yb3+ of 5 nm was chosen since it is an excellent T1 contrast agent. The surface chemistry of nanoparticles has direct impact on its physiochemical properties. Therefore, it is aimed to design nanoparticle based blood pool contrast agent for disease diagnostics, which involved the functionalization the polyethylene glycol (PEG) polymer on the ultra-small UCNPs. Here we report the design and characterization of bimodal contrast agent, PEG coated ultra-small NaGdF4, Tm3+, Yb3+.