Polymers that are normally used in optoelectronic devices could be modified for use in biosensors, say UK scientists.

Conjugated polymers can act as electronic conductors, which means they can be used in optoelectronic devices such as light-emitting diodes, solar cells and field-effect transistors. 

These polymers also have useful fluorescence properties that have led to the use of their water soluble derivatives, known as conjugated polyelectrolytes, as chemical sensors.  These can be used to track the activity of enzymes or detect glucose derivatives, for example.

But to monitor enzymatic activity in biological media such as blood, urine and saliva, the polymers must be able to operate at biologically relevant temperature, pH and ionic strength. Previously, polymers tended to lose their sensitivity in these media due to the high levels of dissolved salts. 

Now, Joachim Steinke at Imperial College London and colleagues say they have solved the problem. The team made a cationic derivative of a conjugated polymer. In a proof-of-principle test, using buffer solutions, and with the addition of a non-ionic surfactant, the team found that the new biosensor retained excellent sensitivity in the high ionic strength media.

Steinke plans to use real biological samples next. 'I'm sure their use in blood and urine will throw up all sorts of challenges and difficulties we hadn't anticipated!' he said.

Elinor Richards