Functionalization of upconverted luminescent NaYF₄:Yb/Er nanocrystals by folic acid–chitosan conjugates for targeted lung cancer cell imaging

We demonstrate a robust approach to functionalize the upconverted luminescent NaYF₄:Yb/Er nanocrystals with folic acid (FA)–chitosan conjugates for specific targeting and imaging of lung cancer cells. In this approach, the amine groups of FA–chitosan conjugates covalently reacted with the carboxyl groups located on the surface of dimercaptosuccinic acid (DMSA)-modified NaYF₄:Yb/Er nanoparticles. The produced FA–chitosan-coated NaYF₄:Yb/Er nanoparticles were characterized by means of transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy. Additionally, a cell viability assay showed that those FA–chitosan-coated fluorescence nanocrystals were fully biocompatible. Moreover, confocal fluorescence images illustrated that the functionalized-NaYF₄:Yb/Er nanoparticles with FA–chitosan conjugates were specific in targeting lung cancer cell lines (H460) rather than human lung fibroblast (HLF) cells. Consequently, the surface chemistry and functional design of the upconverted luminescence nanocrystals using biocompatible FA–chitosan conjugates might provide a powerful nanoplatform for the detection and molecular diagnosis of lung cancer.