Electron spin resonance spectroscopy for immunoassay using iron oxide nanoparticles as probe
With the help of iron oxide nanoparticles, electron spin resonance spectroscopy (ESR) was applied to immunoassay. Iron oxide nanoparticles were used as the ESR probe in order to achieve an amplification of the signal resulting from the large amount of Fe3+ ion enclosed in each nanoparticle. Rabbit IgG was used as antigen to test this method. Polyclonal antibody of rabbit IgG was used as antibody to detect the antigen. Iron oxide nanoparticle with a diameter of either 10 or 30 nm was labeled to the antibody, and Fe3+ in the nanoparticle was probed for ESR signal. The sepharose beads were used as solid phase to which rabbit IgG was conjugated. The nanoparticle-labeled antibody was first added in the sample containing antigen, and the antigen-conjugated sepharose beads were then added into the sample. The nanoparticle-labeled antibody bound to the antigen on sepharose beads was separated from the sample by centrifugation and measured. We found that the detection ranges of the antigen obtained with nanoparticles of different sizes were different because the amount of antibody on nanoparticles of 10 nm was about one order of magnitude higher than that on nanoparticles of 30 nm. When 10 nm nanoparticle was used as probe, the upper limit of detection was 40.00 μg mL−1, and the analytical sensitivity was 1.81 μg mL−1. When 30 nm nanoparticle was used, the upper limit of detection was 3.00 μg mL−1, and the sensitivity was 0.014 and 0.13 μg mL−1 depending on the ratio of nanoparticle to antibody.
KeywordsElectron spin resonance Immunoassay Iron oxide nanoparticles Sepharose beads Rabbit IgG
This project was supported by the Research Startup Foundation of Jilin University (No. 450060521178).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
- 12.Chan DW. Immunoassay: a practical guide. Orlando: Academic Press; 1987.Google Scholar
- 22.Montgomery MR, Holtzman JL. Determination of serum morphine by the spin-label antibody technique. Drug Metab Dispos. 1974;2:391–5.Google Scholar
- 23.Montgomery MR, Holtzman JL, Leute RK, Dewees JS, Bolz G. Determination of diphenylhydantoin in human serum by spin immunoassay. Clin Chem. 1975;21:221–6.Google Scholar
- 26.Schall RF Jr, Tenoso HJ. Alternatives to radioimmunoassay: labels and methods. Clin Chem. 1981;27:1157–64.Google Scholar
- 28.Vistnes AI, Rosenqvist E, Frøholm LO. Spin membrane immunoassay for use in meningococcal serology. J Clin Microbiol. 1983;18:905–11.Google Scholar
- 31.Korchinski DJ, Taha M, Yang RZ, Nathoo N, Dunn JF. Iron oxide as an MRI contrast agent for cell tracking. Magn Reson Insights. 2015;8:15–29.Google Scholar
- 39.Wild D. The immunoassay handbook: theory and applications of ligand binding, ELISA and related techniques. Oxford: Elsevier; 2013.Google Scholar