Bovine serum albumin-coated quantum dots as a cytoplasmic viscosity probe in a single living cell

We report that bovine serum albumin (BSA)-coated quantum dots can be used as a fluorescent probe for measuring the cytoplasmic viscosity of a single living cell: fluorescence correlation spectroscopy measurements for a HeLa cell incorporating BSA-quantum dots show that the viscosity of cytoplasm is 4.7 times greater than that of water.