Probe for intracellular imaging: Let’s tame it!

11 Jul 2016. NUS chemists have developed a model for designing cell-permeable fluorescent probes with little background interference for bioimaging of living cells.

Cells are highly complex and organised entities which are composed of various biological events. Labelling a biomolecule inside the cells with fluorescent dyes to understand the biomolecule’s roles and functions has been around for a long time. However, organic dyes are often sticky and leave high background noise in the biological system which could disrupt observation of the biomolecule. Some probes are also unable to cross plasma membranes in their native environment, making probe delivery into live cells challenging.

A team led by Prof Young-Tae CHANG from the Department of Chemistry at NUS has developed a predictive model for designing cell-permeable probes which can label intracellular specific organelles and engineered proteins with little background interference. These probes which can cross cell membranes without creating background noise in the cells are referred to as being “tamed” in character.

Prof Chang together with Dr Samira Husen ALAMUDI and other team members developed the model by using phenotypic high throughput screening in combination with cheminformatics and feature selection analysis. Their findings showed that a probe can be “tamed” by adjusting three key parameters: lipophilicity, water solubility and charged van der Waals surface area.

The research team has demonstrated the effectiveness of their model. Experimental results showed that these probes are able to specifically label various organelles such as mitochondria, lysosome and golgi apparatus. The probes can also label intracellular proteins such as tubulin and nuclear histones H2B.

This tool can allow users to develop “tamed” probes for intracellular labelling in native living cells. The research findings can be further enhanced to develop other smart probes with various functional groups and colours which can target more than one cellular organelle.

Figure shows a schematic illustration of a “tamed” probe. (a) The model can predict if a probe has affinity to any organelles or biomolecules in cells. When a target is present at a specific site in the cells, the probe could attach to it only at this specific site, while unreacted probes are washed out of the cells, leaving no fluorescence background. (b) Covalent labelling of azide-tagged organelles and engineered proteins using cyclooctyne CO-1 in live cells. [Image credit: Samira Husen Alamudi].

Reference

Alamudi, S.H.et al. “Development of background-free tame fluorescent probes for intracellular live cell imaging”.Nat. Commun.7:11964 doi: 10.1038/ncomms11964 (2016).