IR-to-visible upconversion nanoparticles for in vitro fluorescent imaging

Abstract

IR-to-visible upcoversion fluorescent nanoparticles (UCNs) were developed as in vitro imaging probes. NaYF4 upconversion nanoparticles co-doped with Yb/Er (NaYF4:Yb,Er) were coated with silica, modified with amino groups or conjugated with folic acid. After incubated with cells the green-fluorescence nanoparticles were visualized under confocal microscopy. The factors such as cell lines, surface charge and surface modification of UCNs that might affect the cellular uptake were analyzed. No matter what the surface charge of UCNs was, the nanoparticles were small enough to be internalized by several cell lines. The ligand-mediated cellular uptake of UCNs took the least internalization time and processed in the specific cancer cells. This article provided initial insights into the effectiveness and suitability of NaYF 4:Yb,Er upconversion nanoparticles as an imaging probe. © 2008 Springer-Verlag.