Imaging viscosity
The FRIVIC (Fluorescent rotors for imaging viscosity in cells) project has studied the sensitivity to viscosity of new molecules derived from boron dipyrromethene (BODIPY). These molecular rotors are fluorescent compounds that can re-emit light on input of light energy. The resulting fluorescence lifetime imaging is an excellent way to measure the viscosity in a living system. Concentration independent, it requires only one excitation wavelength/emission interval. Two types of BODIPY derivatives were investigated. The first, involved emission in the near-infrared of the electromagnetic spectrum, a better match with the tissue therapeutic window. Results so far indicate that the molecules under test do not act as molecular rotors but are sensitive to temperature and maybe polarity. The second investigation involved BODIPY derivatives with a double positive charge on the aliphatic chain. Specially designed to stain the plasma membrane or outer membrane of the living cell, both acted as molecular rotors in this domain. In an actual application with HeLa cells, cell division at different stages did not change the viscosity in the plasma membrane significantly. Results of the FRIVIC research have been reported in papers that have been submitted to high-profile peer-reviewed journals including The Journal of Physical Chemistry B and Chemistry – A European Journal. Membrane viscosity has been linked with changes associated with ageing and disease pathogenesis. As such, the research deliverables could be applied in a wide range of diagnostic and therapeutic areas.
