title: Turn-on optomagnetic bacterial DNA sequence detection using volume-amplified magnetic nanobeads.
abstract: Detection of a Vibrio cholerae DNA-sequence using an optomagnetic read-out exploiting the dynamic behavior of magnetic nanobeads along with two turn-on data analysis approaches is demonstrated. The optomagnetic method uses a weak uniaxial AC magnetic field of varying frequency applied perpendicular to the optical path and measures the modulation of laser light passing through a cuvette containing the sample with oligonucleotide-tagged magnetic beads and macromolecular coils of single-stranded DNA. The DNA coils are formed upon a padlock probe ligation followed by rolling circle amplification (RCA). The presence of target gives rise to a change of the 2nd harmonic component, V2=V2(')+iV2(''), of the transmitted light. We demonstrate that by using the phase angle ξ defined as ξ=arctanV2(')/V2('') in the low-frequency region we obtain a limit of detection of 10pM for an RCA time of only 20min corresponding to a total assay time of 60min. Moreover, we show that the approach based on ξ is significantly more robust than the analysis based on a turn-off of the signal due to free magnetic nanobeads used in previous work (Donolato et al., submitted for publication), where a limit of detection of 10pM was obtained for an RCA time of 60min. The increased robustness and the reduction in total assay time constitute significant steps towards the realization of a low-cost, rapid and sensitive biosensor platform suitable for pathogen detection in both human and veterinary medicine settings.
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Bejhed
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: Teresa Zardán Gómez
authors.initials: TZ
authors.lastname: de la Torre
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Marco
authors.initials: M
authors.lastname: Donolato
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Mikkel F
authors.initials: MF
authors.lastname: Hansen
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Svedlindh
authors.affiliation: Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden. Electronic address: mattias.stromberg@angstrom.uu.se.
authors.forename: Mattias
authors.initials: M
authors.lastname: Strömberg
mesh_terms: D015374:Biosensing Techniques / Q000379:methods; D002771:Cholera / Q000175:diagnosis / Q000382:microbiology*; D004269:DNA, Bacterial / Q000032:analysis*; D006801:Humans; D057230:Limit of Detection; D008280:Magnetics / Q000379:methods; D059346:Magnets / Q000737:chemistry; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D015345:Oligonucleotide Probes / Q000737:chemistry*; D014734:Vibrio cholerae / Q000302:isolation & purification*
chemical_list: D004269:DNA, Bacterial; D015345:Oligonucleotide Probes
keywords: Brownian relaxation; Oligonucleotide-tagged magnetic beads; Optomagnetic system; Padlock probes; Phase angle spectra.; Rolling circle amplification