Red light activated fluorescent probes for biological imaging, which are less destructive and more efficient than those controlled by green or blue light, have been developed.

Donal O'Shea and colleagues at University College Dublin, Ireland, have made a series of fluorescent molecules based on boron difluorides that can be used in biosensors and activated by red light. Target substrates such as carbohydrates or peptides are detected by a receptor and quantified by a fluorophore on the same molecule. These two components are separated from one another by a methylene spacer. The receptors can be further modified depending on the substrate being monitored.

High sensitivity fluorescence detection and imaging is a common tool for studying molecular processes in vitro and for monitoring cells in vivo for diagnostic purposes. Most existing probes operate with light wavelengths of 300-550nm, the blue/green range of the spectrum. This leads to interference problems caused by background absorbance and even spontaneous fluorescence by the biomolecules themselves. Light of wavelengths greater than 650nm, the visible red and near infrared region, does not cause these problems and has the additional bonus of being less destructive to cells, says O'Shea.

'Advances in this field of molecular sensing and imaging will provide future tools to assist in the continuing drive to understand biological processes at the molecular level,' said O'Shea. Future work to optimise in vivo fluorescence sensors and to improve their specificity towards various target substrates is underway by O'Shea's group.

Suzanne Abbott