1 Department of Micro- and Nanotechnology, Technical University of Denmark2 Silicon Microtechnology, Department of Micro- and Nanotechnology, Technical University of Denmark3 Magnetic Systems, Department of Micro- and Nanotechnology, Technical University of Denmark4 Uppsala University5 Stockholm University6 Stockholm University
For the first time DNA coils formed by rolling circle amplification are quantified on-chip by Brownian relaxation measurements on magnetic nanobeads using a magnetoresistive sensor. No external magnetic fields are required besides the magnetic field arising from the current through the sensor, which makes the setup very compact. Limits of detection down to 500 Bacillus globigii spores and 2 pM of Vibrio cholerae are demonstrated, which are on the same order of magnitude or lower than those achieved previously using a commercial macro-scale AC susceptometer. The chipbased readout is an important step towards the realization of field tests based on rolling circle amplification molecular analyses.