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| Hauptseite > Publikationsdatenbank > Frequency Mixing Magnetic Detection of Superparamagnetic Nanoparticles as Markers for Immunoassays |
| Hauptseite > Publikationsdatenbank > Frequency Mixing Magnetic Detection of Superparamagnetic Nanoparticles as Markers for Immunoassays |
| Talk (non-conference) (Invited) | FZJ-2023-05289 |
2023
Abstract: Superparamagnetic Nanoparticles exhibit a nonlinear magnetization. Upon magnetic excitation at two distinct frequencies f1 and f2, the nonlinearity gives rise to the generation of response signals at intermodulation frequencies m×f1 ± n×f2 which are picked up by a detection coil and demodulated in a magnetic reader device. The appearance of the mixing components is highly specific to the nonlinearity of the magnetization curve of the particles. Preferably, the response signal at frequency f1 + 2×f2 is detected as it gives the strongest response. The method yields a very large dynamic range of detection, extending to more than 4 orders of magnitude in the number of particles. Analysis of the phase of the response gives information on the magnetic relaxation of the particles, and thus on their hydrodynamic size and binding state. Variation of excitation amplitudes or a static magnetic offset field enables determining the size distribution of the particles’ magnetic cores. Magnetic immunoassays for various biomolecular targets such as Cholera toxin B in water, antibiotics in milk, and SARS-CoV-2-specific antibodies in blood have been successfully realized. The magnetic reader enables portable immunodetection at point-of-care, with improved detection limits as compared to conventional lab-based enzyme linked immuno sorbent assays (ELISA).
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