Characterization of binding of magnetic nanoparticles to rolling circle amplification products by turn-on magnetic assay
Journal article, 2019

The specific binding of oligonucleotide-tagged 100 nm magnetic nanoparticles (MNPs) to rolling circle products (RCPs) is investigated using our newly developed differential homogenous magnetic assay (DHMA). The DHMA measures ac magnetic susceptibility from a test and a control samples simultaneously and eliminates magnetic background signal. Therefore, the DHMA can reveal details of binding kinetics of magnetic nanoparticles at very low concentrations of RCPs. From the analysis of the imaginary part of the DHMA signal, we find that smaller MNPs in the particle ensemble bind first to the RCPs. When the RCP concentration increases, we observe the formation of agglomerates, which leads to lower number of MNPs per RCP at higher concentrations of RCPs. The results thus indicate that a full frequency range of ac susceptibility observation is necessary to detect low concentrations of target RCPs and a long amplification time is not required as it does not significantly increase the number of MNPs per RCP. The findings are critical for understanding the underlying microscopic binding process for improving the assay performance. They furthermore suggest DHMA is a powerful technique for dynamically characterizing the binding interactions between MNPs and biomolecules in fluid volumes.

binding kinetics

differential homogenous magnetic assay

rolling circle amplification product


magnetic nanoparticle

biomolecular dynamics



Sobhan Sepehri

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Björn Agnarsson

Chalmers, Physics, Biological Physics

Teresa Zardán Gómez De La Torre

Uppsala University

Justin Schneiderman

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Jakob Blomgren

RISE Research Institutes of Sweden

Aldo Jesorka

Chalmers, Chemistry and Chemical Engineering, Chemistry and Biochemistry

Christer Johansson

Chalmers, Microtechnology and Nanoscience (MC2)

Mats Nilsson

Stockholm University

Jan Albert

Karolinska Institutet

Maria Strømme

Uppsala University

Dag Winkler

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Alexei Kalaboukhov

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics


2079-6374 (ISSN)

Vol. 9 3 109

Point-of care Influenza Diagnostics FLU-ID

Swedish Foundation for Strategic Research (SSF), 2014-06-01 -- 2019-05-31.

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Subject Categories

Biochemistry and Molecular Biology

Materials Chemistry


Nanofabrication Laboratory





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