Viscosity is one of the main factors which influence diffusion in condensed media. In a cell viscosity can play a role in several diffusion mediated processes, such as drug delivery, signalling and mass transport. Previously, alterations in viscosity in cells and organs have been linked to malfunction; however, mapping viscosity on a single-cell scale remains a challenge.

We have imaged viscosity first inside lipid mono- and bi-layers and in cells using fluorescent probes, called molecular rotors [1]. In molecular rotors the speed of rotation about a sterically hindered bond is viscosity-dependent [2-5]. This approach enabled us to demonstrate that viscosity distribution in a cell is highly heterogeneous and that the local microviscosity in hydrophobic cell domains can be up to 100 times higher than that of water.

References

[1]           M. K. Kuimova, Phys Chem Chem Phys, 2012, 14, 12671

[2]           M. K. Kuimova, G. Yahioglu, J. A. Levitt, K. Suhling, J. Amer. Chem. Soc., 2008, 130, 6672

[3]           M. K. Kuimova, S. W. Botchway, A. W. Parker, M. Balaz, H. A. Collins, H. L. Anderson, K. Suhling, P. R. Ogilby, Nature Chem., 2009, 1, 69-73

[4]           N. A. Hosny, G. Mohamedi, P. Rademeyer, J. Owen, Y. Wu, M-X. Tang, R. J. Eckersley, E. Stride and M. K. Kuimova, Proc. Nat. Acad. Sci. USA, 2013, 110, 9225–9230

[5]           I. Lopez-Duarte, T. T. Vu, M. A. Izquierdo, J. A. Bull, M. K. Kuimova. Chem. Commun., 2014, DOI: 10.1039/C3CC47530A