Versatile fluorophores

Bodipy dyes have proved advantageous for biology, medicine and environmental chemistry applications. They can be modified in numerous ways to detect various chemical properties of the surrounding medium, yet remain unaffected by those not under investigation. They have large absorption coefficients, high quantum yields, high photostability compared with that of fluorescein and narrow emission spectra. Additionally, many Bodipy dyes are commercially available. Researchers from Université Louis Pasteur in Strasbourg, France, and from the University of Newcastle in Newcastle-upon-Tyne, UK, have reviewed the chemistry of these fluorophores.

The authors note that many organic fluorophores exhibit an undesirably small Stokes shift for flow cytometry and for fluorescence microscopy. However, a fluorophore with a large Stokes shift can be created by covalently attaching a light-absorbing compound to a Bodipy emitter. The efficiency of the energy transfer from the absorber to the Bodipy dye almost always is greater than 90 percent.

Bodipy dyes often are modified so that they are quenched until something in the chemical environment triggers them to fluoresce, or vice versa. They have been modified with crown ethers for sensing various cations and with aniline to detect nitric oxide, an important biochemical messenger. Bodipy dyes conjugated to pyrene can sense DNA molecules because the fluorescence becomes quenched when the conjugate binds the nucleic acids.

Near-IR emitters and singlet-oxygen sensitizers also have been made from Bodipy fluorophores. The authors give examples of water-soluble dyes that could be used for photodynamic therapy, because they have desirable permeability and tumor-targeting ability. The authors also state that Bodipy dyes are being developed for determining magnetic spin. (Angewandte Chemie International Edition, Jan. 25, 2008, pp. 1184-1201.)