The detection of specific DNA sequences has facilitated the diagnosis and targeted treatment of several human diseases. Although great advances have been made in the last few years, the detection of certain pathogenic bacteria is still based on bacterial culture and colony counts or on the polymerase chain reaction (PCR) . In this work we demonstrate detection of DNA coils formed from a Vibrio Cholerae DNA target at pM concentrations using a novel opto-magnetic approach exploiting the dynamic collective behavior of magnetic nanobeads. The technique relies on measurements of the light transmission modulation caused by the AC magnetic field-stimulated reversible formation and disruption of elongated MNB supra-structures during a cycle of the uniaxial applied magnetic field. As a specific clinically relevant diagnostic case, we detect DNA coils formed via padlock probe recognition and isothermal rolling circle amplification from Vibrio cholerae DNA. The detection method is shown in Figure 1. MNBs which specifically bind to the micrometric sized DNA coil cannot rotate under the field action as free beads and form chains; this results in a strongly modified opto-magnetic signal. As a core result, summarized in Figure 2, we show that the method can be used to detect target analyte down to a concentrations of 5 pM with a linear range up to few hundred pM. We characterize the dependence to MNB size, concentration and we benchmark the results with commercial equipment. We also realized a miniaturized version of the readout system based on the use of a commercial Blu-Ray pickup head used as a single and unique optomagnetic component. Figure 3 shows measurements on Bacillus Globigii spores detected using this novel setup. The data demonstrate fast and low-cost implementation of bacterial DNA in a miniaturized and low-cost platform, where the read-out requires only a transparent window and inexpensive optical components. Strömberg, M.; Göransson, J.; Gunnarsson, K.; Nilsson, M.; Svedlindh, P; Strømme, M Nano Lett. 2008, 8 (3), 816-821. Zardán Gómez de la Torre, T.; Ke, R.; Mezger, A.; Svedlindh, P.; Strømme, M.; Nilsson, M. Small 2012, 8, 2174–2177.
Proceedings of the 10th International Conference on the Scientific and Clinical Applications of Magnetic Carriers, 2014
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10th International Conference on the Scientific and Clinical Applications of Magnetic Carriers, 2014