| Nanotechnology is more and more present in our world today and different fields are taking advantage of its possibilities. Among others, microscopists have been interested in using nanoparticles in combination with available techniques, one of which is fluorescence microscopy. Lanthanide-doped nanoparticles for example have been studied for many years now for their interesting luminescence and upconversion characteristics. This research presents the development of upconverting biolabels operating in the near-infrared (NIR) to eventually allow scientists to probe deeper into tissues using fluorescence microscopy. Two distinct types of nanoparticles were fabricated using the lanthanide ions Yb3+ and Tm3+ for their upconversion capabilities (from 980 to 800 nm) within the biological window (700 to 1000 nm). The first one, an annealed silica-coated LaF3:Yb,Tm nanoparticle, could not be used as a biolabel due to its lack of dispersibility in aqueous environment. However, the second type, a silica-coated NaYF4:Yb,Tm nanoparticles proved to be very promising. Two surface modifications of these particles were successfully performed. The first introduced NH2 groups while the second incorporated polyethyleneglycol (PEG). The latter was achieved using two distinct methods: one through a reaction with the amino groups and one through a second silica coating involving PEGsilanes. Stable dispersions of these PEGylated nanoparticles were obtained and imaging of ovarian cancer cells grown in their presence showed that they interact with the cells although the nature of this interaction is still to be determined. |
