The authors used an environmental air sampling unit to trap particulate material on a membrane, followed by a rapid extraction of the DNA using magnetic beads. After clean-up, the DNA-containing solution was placed into an "on-bead" padlock probe/proximity ligation assay (PLA) catalyzed by Ampligase enzyme. Reacted probes were then subjected to two further rounds of RCA, first on beads and then in solution. Probes were then tagged with fluorescent dye and detected using an optical system with sensitivity down to 30 bacteria or 5 spores. The authors have improved the performance of the system by reducing the time required for the RCA step and are working improve the sensitivity of the process.
The combination of improved RCA and sensitive detection represent a significant improvement over previous methods for pathogen detection. The method can also be adapted to detect proteins.
Göransson, J. et al. (2012). Rapid Identification of Bio-Molecules Applied for Detection of Biosecurity Agents Using Rolling Circle Amplification PLoS ONE, 7 (2) DOI: 10.1371/journal.pone.0031068