Intracellular viscosity is a crucial parameter that determines rates of diffusion of macromolecules and reaction rates within a cell. Unfortunately, measuring viscosity in a microscopic sample, such as a biological cell, is a very challenging task. However, this is possible to achieve with the help of fluorophores that are sensitive to viscosity. The main feature of these sensors is a viscosity-dependent fluorescence lifetime and spectrum. Even though there are quite a few examples of applications of these compounds, they still possess several disadvantages such as undesirable sensitivity to temperature and solvent polarity besides viscosity, and low fluorescence wavelength, which is not ideally compatible with biological samples. The reasons for these disadvantages remain unclear since the photophysical mechanism of fluorescent sensors is not yet fully understood. During this PhD project, the mechanism of fluorescent viscosity sensors will be investigated using both steady-state and ultrafast spectroscopy methods. Additionally, the impact of the molecular structure of the fluorophores on this mechanism will be examined, and then new viscosity sensors that do not have disadvantages of current viscosity probes will be designed. These new probes will be tested by measuring viscosity in biological samples. The work proposed in this project promises to set the foundation for developing fluorescent viscosity sensors of a new generation.
For more information, please contact the theme supervisor A. Vyšniauskas