Exploring BODIPY-Based Sensor for Imaging of Intracellular Microviscosity in Cancer Cells

What is it about?

BODIPY-based molecular rotors are highly attractive imaging tools for imaging intracellular microviscosity in living cells. In our study, we investigated the ability to detect the microviscosity of biological objects by using BDP-NO2 and BDP-H molecular rotors. We describe in detail the optical properties of BDP-NO2 and BDP-H molecular rotors in aqueous media with and without proteins, together with their accumulation dynamics and localization in live and fixed human breast cancer cells. Furthermore, we investigate the applicability of these molecules to monitor microviscosity in the organelles of human breast cancer cells by fluorescence lifetime imaging microscopy (FLIM). We demonstrate that the BDP-NO2 molecular rotor aggregates in aqueous media and is incompatible with live cell imaging. The opposite effect is observed with BDP-H which preserves its stability in aqueous media, diffuses through the plasma membrane and accumulates in lipid droplets (LDs) and the cytosol of both live and fixed MCF-7 and MDA-MB-231 cancer cells. Finally, by utilizing BDP-H we demonstrate that LD microviscosity is significantly elevated in more malignant MDA-MB-231 human breast cancer cells, as compared to MCF-7 breast cancer cells. Our findings demonstrate that BDP-H is a water-compatible probe that can be successfully applied to measure microviscosity in the LDs of living cells

Featured Image

Why is it important?

we highlight the importance of conducting a photophysical characterization of novel molecular rotors in aqueous media with or without proteins before their application in live biological models. Our work has led us to conclude that BDP-NO2 molecules form aggregates in aqueous media. Thus, the molecular rotor is unsuitable for biological systems. In contrast, the BDP-H molecular rotor exhibits better solubility in aqueous media and is more applicable for microviscosity measurements in live cells. Furthermore, our study delivers evidence that despite the interaction between BDP-H and protein molecules, the intracellular accumulation of the fluorophore is unaffected. It diffuses through the plasma membrane of both live and fixed human breast cancer cells and mainly accumulates in LDs. Furthermore, slight accumulation is visible in cytosol. Finally, we successfully utilize the BDP-H molecular rotor for the measurement of LD microviscosity in human breast cancer cells lines of different malignancy. For the first time, we demonstrate a significant difference between LD microviscosity in MCF-7 and MDA-MB-231 cancer cells. We anticipate that LD microviscosity will become a novel biomarker for the identification of the malignancy of cancer cells, and that the BDP-H molecular rotor could be used for this purpose.

Perspectives