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.

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

“…Although measurements of the magnetic signal have continued to be of interest (Dieckhoff et al, 2014;Engström et al, 2013;Strömberg et al, 2014;Zardán Gómez de la Torre et al, 2011), optomagnetic readout strategies have attracted significant focus (Antunes et al, 2015;Bejhed et al, 2015;Donolato et al, 2015aDonolato et al, , 2015bMezger et al, 2015;Ranzoni et al, 2012;Tian et al, 2016;Yang et al, 2016).…”

Structural and magnetic properties of multi-core nanoparticles analysed using a generalised numerical inversion method

“…Of the many proposed uses of iron oxide nanoparticles the most promising examples are cancer treatment by magnetic hyperthermia567891011, magnetic resonance1213 and particle imaging1415, magnetic biosensing1617 as well as magnetic drug targeting111213. The required magnetic response of the nanoparticles is typically determined by the application, and is in turn intrinsically dependent on the structural properties of the particle system.…”

Characterization of fine particles using optomagnetic measurements

“…Optical measurements on magnetically actuated nanoparticles have been used extensively for biodetection assays [9][10][11][12][13][14][15][16] as well as for the characterization of the hydrodynamic size of magnetic nanorods. 10,17,18 We have previously introduced a simple optical method that measures the modulation of light transmitted through an MNP suspension in response to an applied axial oscillating magnetic field, and demonstrated this method for biodetection.…”

“…10,17,18 We have previously introduced a simple optical method that measures the modulation of light transmitted through an MNP suspension in response to an applied axial oscillating magnetic field, and demonstrated this method for biodetection. [12][13][14][15][16] The basis for the method is measurements of the magnetic-fieldinduced modulation of the optical extinction of the MNP suspension. To distinguish the method from measurements of traditional magnetooptical effects, it was termed optomagnetic (OM).…”

“…To distinguish the method from measurements of traditional magnetooptical effects, it was termed optomagnetic (OM). For a sinusoidal magnetic field variation, it was hypothesized that the complex OM signal is related to the complex ACS signal as 13,14…”