Imaging tumor microscopic viscosity in vivo using molecular rotors

Abstract

The microscopic viscosity plays an essential role in cellular biophysics by controlling the rates of diffusion and bimolecular reactions within the cell interior. While several approaches have emerged that have allowed the measurement of viscosity and diffusion on a single cell level in vitro, the in vivo viscosity monitoring has not yet been realized. Here we report the use of fluorescent molecular rotors in combination with Fluorescence Lifetime Imaging Microscopy (FLIM) to image microscopic viscosity in vivo, both on a single cell level and in connecting tissues of subcutaneous tumors in mice. We find that viscosities recorded from single tumor cells in vivo correlate well with the in vitro values from the same cancer cell line. Importantly, our new method allows both imaging and dynamic monitoring of viscosity changes in real time in live animals and thus it is particularly suitable for diagnostics and monitoring of the progress of treatments that might be accompanied by changes in microscopic viscosity.

Molecular rotors report on changes in live cell plasma membrane microviscosity upon interaction with beta-amyloid aggregates

“…This presents significant advantages compared to uncharged BODIPY rotors, which effectively internalise in live cells via endocytosis. 37,39,41 The time resolved fluorescence decays of BODIPY 1 conform to mono-exponential fitting and the fluorescence lifetime (τf) is sensitive to viscosity in the range between 3-1000 cP. The calibration plot of lifetime vs. viscosity recorded in methanolglycerol mixtures (Fig.…”

Exploring viscosity, polarity and temperature sensitivity of BODIPY-based molecular rotors

“…In that respect, and coupled with excellent stability in the biological environment, BODIPY 1 and its derivatives remain the golden standard of cellular imaging of local viscosity. 7,23,39,40…”

Imaging viscosity of intragranular mucin matrix in cystic fibrosis cells

“…BODIPY dyes are among the most versatile fluorophores that have been used as sensors and environmental probes for numerous applications, especially in biological and biomedical fields 14 , 15 . BODIPY-based viscometers proved to be useful in assessing the viscosity of various types of biological media, including membranes, tissues, and cellular environments 16 – 22 . In the course of our studies on developing BODIPY-based viscometers 16 , 17 , we discovered that a simple BODIPY dye (Fig.…”