Comparison of optomagnetic and AC susceptibility readouts in a magnetic nanoparticle agglutination assay for detection of C-reactive protein

Jeppe Fock, Mattias Parmvi, Mattias Strömberg, Peter Svedlindh, Marco Donolato, Mikkel Fougt Hansen

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    There is an increasing need to develop biosensor methods that are highly sensitive and that can be combined with low-cost consumables. The use of magnetic nanoparticles (MNPs) is attractive because their detection is compatible with low-cost disposables and because application of a magnetic field can be used to accelerate assay kinetics. We present the first study and comparison of the performance of magnetic susceptibility measurements and a newly proposed optomagnetic method. For the comparison we use the C-reactive protein (CRP) induced agglutination of identical samples of 100 nm MNPs conjugated with CRP antibodies. Both methods detect agglutination as a shift to lower frequencies in measurements of the dynamics in response to an applied oscillating magnetic field. The magnetic susceptibility method probes the magnetic response whereas the optomagnetic technique probes the modulation of laser light transmitted through the sample. The two techniques provided highly correlated results upon agglutination when they measure the decrease of the signal from the individual MNPs (turn-off detection strategy), whereas the techniques provided different results, strongly depending on the read-out frequency, when detecting the signal due to MNP agglomerates (turn-on detection strategy). These observations are considered to be caused by differences in the volumedependence of the magnetic and optical signals from agglomerates. The highest signal from agglomerates was found in the optomagnetic signal at low frequencies.
    Original languageEnglish
    JournalBiosensors and Bioelectronics
    Pages (from-to)94–100
    Number of pages19
    Publication statusPublished - 2017
    EventBiosensors 2016: 26th Anniversary World Congress on Biosensors - Swedish Exhibition and Congress Centre, Gothenburg, Sweden
    Duration: 25 May 201627 May 2016
    Conference number: 26


    ConferenceBiosensors 2016
    LocationSwedish Exhibition and Congress Centre
    Internet address


    • Brownian relaxation
    • CRP
    • Agglutination assay
    • Magnetic beads
    • Biosensor

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