A new visual method of detecting DNA, inspired by the way reactions work in biological systems, has been developed. Roland Krämer and colleagues at the Ruprecht-Karls University, Heidelberg, Germany, have developed a reagent that produces an optical response within seconds of coming into contact with DNA. 

The sensing reagent consists of a strand of DNA bound to a metal ion, and an apoenzyme, a co-factor dependent enzyme which is not bound to its co-factor. When the reagent comes into contact with DNA, the strand of DNA in the reagent releases the metal and binds preferentially to the DNA in the analyte. The free metal then binds to the apoenzyme, activating it. The completed enzyme, carbon anhydrase, is used to catalyse reactions producing the fluorescence.

The researchers have found that strands of complimentary DNA are detected quickly, whereas single-mismatch DNA does not lead to fluorescence. High background activity of the apoenzyme can affect the sensitivity of the assay, and Krämer is investigating different enzymes which could improve the sensitivity of the assay. 

'This research is inspired by biological signal cascades which efficiently enhance molecular signals and rapidly convert them into biochemical response,' said Krämer. 'Artificial signal cascades hold potential as very simple and sensitive assays for the selective detection of molecular targets without the need of dedicated instrumentation,' he said. 

Sethuraman Mahadevan from Boston University Medical School supports this work. 'This is a thoughtful model, which integrates basic functionalities like metal chelation, DNA hybridization and metal ion-cofactor dependent enzyme activity, for signaling cascades,' he said. 

Rebecca Gillan