Phototoxicity and luminescence of the upconversion nanoparticles embedded in the cells

The present work demonstrates the visualization of the intracellular distribution of upconversion nanoparticles (UCNPs) by microscopy with excitation in the NIR spectral range and detection of upconversion luminescence in the VIS range. The cell viability is scored for cytotoxic effects of UCNPs at dark and light exposed conditions. Non-functionalized UCNPs incubated with the cells are found to be endocytosed by cells. The obtained results confirm a high sensitivity of the luminescent UCNPs to the concentration variations within cells. UCNPs are promising alternatives to traditional fluorescent labels for cell imaging and possess prominent potentials in biological and clinical applications