Curcumin-based molecular probes for fluorescence imaging of fungi.

Fluorescence imaging is a powerful and widely used method to visualize and study living organisms. However, fungi are notoriously difficult to visualize using fluorescence microscopy, given that their cell wall represents a diffusion barrier, and the synthetic organic dyes available are very limited when compared to molecular probes available for other organisms. Moreover, these dyes are usually available in only one colour, preventing co-staining experiments. To fill this gap, curcumin-based molecular probes were designed based on the rationale that curcumin is fluorescent and has moderate toxicity toward fungi, implying its ability to cross the cell wall to reach targets in the intracellular compartments. A family of boron diketonate complexes was synthesized, based on a curcumin backbone, tuning their emission color from blue to red. These probes did not present noticeable toxicity to filamentous fungus and, when applied to their visualization, readily entered the cells and precisely localized in sub-cellular organelles, enabling their visualization.