Clustering based magnetic assays for SARS-CoV-2 detection with scFv-functionalized magnetic nanoparticles

Abstract

Magnetic nanoparticles (MNP) can be used in magnetic immunoassays (MIA) by functionalizing them with antibodies. In homogeneous assays that follow a "mix-and-measure" approach, it is then sufficient to add the sample in question and evaluate the response of the MNPs using a magnetic measurement method. Magnetic Particle Spectroscopy (MPS) is a fast and sensitive method for this purpose, capable of determining the binding state by measuring changes in Brownian relaxation. For further analysis, alternating current susceptometry (ACS) is considered, although it is significantly more time-consuming and therefore no option for applications interested in point of care detection. In this study, we aim to further improve the approach of MIA evaluated by MPS. To this end, we use self-synthesized scFv fragments instead of whole IgG antibodies during functionalization in order to keep the size of the BNF-Dextran MNP with 80 nm nominal diameter as small as possible, which allows for greater relative size changes upon binding to an analyte. Virus-like particles (VLP) and the N protein of SARS-CoV-2, which were also produced in-house, are used as analytes. Due to multiple binding sites, these form cluster structures, which, in the case of VLP, were investigated in greater depth ACS to assess their field dependence. In addition, the sensitivity of the assays was analyzed as a function of MNP concentration, and the detection limit for both analytes was estimated. We found that, using scFv-functionalized MNPs, we were able to detect low concentrations of just 490 fM of SARS-CoV-2 VLP and 1.7 nM of the N protein. However, the slightly above-proportional increase in sensitivity as the MNP concentration decreases does not automatically imply a better detection limit.

Reduced vortex descriptors linking polycrystallinity in magnetic nanoparticles with polarized magnetic small-angle neutron scattering
Michael P. Adams, Jonathan Leliaert, Andreas Michels +1
Physical Review Research23 Oct 2026Peer-reviewedPublisher termsAtomic, molecular & optical physicsCrossrefAPS
Artificial intelligence and machine learning for magnetic nanoparticles and nanocarriers in cancer imaging, drug delivery, and magnetic control: a systematic review
Yier Yao, Wanis Nafo
Beilstein Journal of Nanotechnology1 Oct 2026Peer-reviewedCC BYFull textGeneral physicsDOAJ
Magnetic Particle Magnetometer Based on Langevin Response of Superparamagnetic Nanoparticles for Remote Magnetic Field Sensing
M. Jurj, C. McDonough, C. Bastajian +1
arXiv19 Sep 2026PreprintCC BY 4.0Full textApplied physics & instrumentationarXiv
Optimizing the magnetic hyperthermia efficiency from the structural dependence of dipolar interactions in magnetic nanoparticles assemblies
Abdelhamid Morjane, François Vernay, Vincent Russier
arXiv2 Oct 2026PreprintCC BY 4.0Full textCondensed matterarXiv
A Hybrid Brownian Dynamics-kinetic Monte Carlo Framework for Coupled Magnetic and Rotational Dynamics of Nanoparticles
Siraj Ul Haq, Iago López-Vázquez, Kazuya Okada +6
arXiv26 Oct 2026PreprintCC BY 4.0Full textCondensed matterarXiv

Cite

BibTeX RIS

BibTeX

@misc{wolgast2026clustering,
  title = {{Clustering based magnetic assays for SARS-CoV-2 detection with scFv-functionalized magnetic nanoparticles}},
  author = {F. T. Wolgast and N. Lehmler and S. Westerhoff and S. Demiral and J. Lohmann and R. Amin and R. Sack and A. Lak and M. Schilling and M. Schubert and T. Viereck},
  howpublished = {arXiv},
  year = {2026},
  month = aug,
  doi = {10.48550/arxiv.2608.30772},
  eprint = {2608.30772},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.30772},
}

RIS

TY  - UNPB
TI  - Clustering based magnetic assays for SARS-CoV-2 detection with scFv-functionalized magnetic nanoparticles
AU  - F. T. Wolgast
AU  - N. Lehmler
AU  - S. Westerhoff
AU  - S. Demiral
AU  - J. Lohmann
AU  - R. Amin
AU  - R. Sack
AU  - A. Lak
AU  - M. Schilling
AU  - M. Schubert
AU  - T. Viereck
PY  - 2026
DA  - 2026/08/31
PB  - arXiv
DO  - 10.48550/arxiv.2608.30772
UR  - https://arxiv.org/abs/2608.30772
AB  - Magnetic nanoparticles (MNP) can be used in magnetic immunoassays (MIA) by functionalizing them with antibodies. In homogeneous assays that follow a "mix-and-measure" approach, it is then sufficient to add the sample in question and evaluate the response of the MNPs using a magnetic measurement method. Magnetic Particle Spectroscopy (MPS) is a fast and sensitive method for this purpose, capable of determining the binding state by measuring changes in Brownian relaxation. For further analysis, alternating current susceptometry (ACS) is considered, although it is significantly more time-consuming and therefore no option for applications interested in point of care detection. In this study, we aim to further improve the approach of MIA evaluated by MPS. To this end, we use self-synthesized scFv fragments instead of whole IgG antibodies during functionalization in order to keep the size of the BNF-Dextran MNP with 80 nm nominal diameter as small as possible, which allows for greater relative size changes upon binding to an analyte. Virus-like particles (VLP) and the N protein of SARS-CoV-2, which were also produced in-house, are used as analytes. Due to multiple binding sites, these form cluster structures, which, in the case of VLP, were investigated in greater depth ACS to assess their field dependence. In addition, the sensitivity of the assays was analyzed as a function of MNP concentration, and the detection limit for both analytes was estimated. We found that, using scFv-functionalized MNPs, we were able to detect low concentrations of just 490 fM of SARS-CoV-2 VLP and 1.7 nM of the N protein. However, the slightly above-proportional increase in sensitivity as the MNP concentration decreases does not automatically imply a better detection limit.
ER  -

Abstract

Related

Cite