Novel Upconversion Nanoparticles for Biomedical Imaging Applications

With the confluence of biology, chemistry, and physics now being a reality in many hot topics of research, nanoparticles are being translated into the realm of biomedicine as novel biomarkers, sensors, and therapeutic agents. In particular, rare-earth ions doped into fluoride, oxide, and oxysulfide nanocrystals exhibit extraordinary optical properties which are useful for biomedical applications including sharp absorption and emission lines in the visible and near-infrared (NIR) and long fluorescent lifetimes. Rare-earth based nanomaterials are advantageous as biomarkers because they do not photobleach like organic fluorophores, require lower power excitation sources, and do not blink such as quantum dots. Here, we present the optical characterization and upconversion quantum yield of KYb2F7:Er, Tm. The strong NIR to NIR upconversion emission is ideal for bio-imaging since light in the NIR regime is not strongly scattered or absorbed by most soft tissues. Finally, the nanoparticles are incubated with monkey retinal endothelial cells in order to determine toxicity, and nonspecific cell uptake is imaged using multiphoton microscopy.