Medical procedures are poised to become safer, thanks to chemists who have developed a tool to monitor heparin, an anticoagulant used widely in the clinic.

Young-Tae Chang, National University of Singapore, and colleague Shenliang Wang have developed two dye molecules that fluoresce in response to heparin. A naturally occurring polysaccharide, heparin has been used during surgery for almost a century to prevent thrombosis - blocked blood vessels caused by unwanted clotting. However, applying too much heparin risks side-effects that include haemorrhage, so the ability to more quickly and accurately monitor heparin levels would be an important tool, said Chang.

To identify sensors that fluoresce at clinically-relevant heparin concentrations, Chang screened a library of potential dyes. 'While demand for useful fluorescent sensors is acute, the conventional target-oriented approach is limited for rapid sensor discovery,' said Chang. 'The diversity-oriented approach had intrigued us as a novel way to discover sensors.'

Heparin orange shows a variable colour change depending on the heparin concentration (increasing from left to right)

The two dyes Chang's combinatorial approach uncovered, which the team called Heparin orange and Heparin blue based on their colour changes, were tested against heparin in human blood plasma under a range of conditions. 'The fluorescence response is so obvious that the colour change could be distinguished even by the naked eye,' said Chang.

'The discovery of Heparin orange and Heparin blue is an important step towards the development of rapid, point-of-care heparin detection,' said Dallas Rabenstein, a heparin expert at the University of California, Riverside, US. 'However, further research needs to be done.  For example, do these chemosensors detect the total heparin in plasma, or just that which is free and not bound to plasma proteins and other constituents of plasma?'

The broader assessment of the two sensors for analysing clinical samples is ongoing, said Chang.

James Mitchell Crow