Viscometric real-time monitoring of the rolling circle amplification with a micromachined cantilever

DNA amplification reactions are often used for nucleic acid analysis on lab-on-chip devices. In view of point of care testing e.g. for pathogen detection in emergency stations, such an analysis must be fast and simple to be performed. As an alternative to fluorescence based measurements the method presented here is based on detecting the change in the rheological properties of the assay. For the first time, on chip DNA amplification with real time viscometric detection is shown, with first results already being available after less than 20 min. The change of the sample's viscosity during the polymerization employing the rolling circle amplification (RCA) is detected using a micromachined vibrating cantilever. The RCA was chosen, as it is isothermal and produces very long strands resulting in a high change of the fluid's rheological properties. As the reaction proceeds, an increase of the cantilever's damping and required excitation power to keep its amplitude constant is observed in real-time. Evaluating the slope of these two parameters e.g. 27 min after starting the reaction, samples where polymerization takes place and samples without reaction can perfectly be distinguished. The described approach works without explicit functionalization of the sensor surface or labeling of reaction components.