Publications scientifiques

Magnetic Immunoassays
P. I. Nikitin et al. (2007). Sensor Letters, 5, 1, 296-9.

Résumé. New low-noise detection method has been developed and used for design of a new type of biosensors based on detection of nano-sized superparamagnetic particles or magnetic beads that serve as labels for biochemical reactions. The method is based on non-linear magnetization of such particles. The particles are exposed to a magnetic field having components at two frequencies f1 and f2. The response is measured at combinatorial frequencies fi = m · f1 + n · f2, where m and n are integers (one of them can be zero). The integers can be varied to get the best signal-to-noise ratio, e.g., fi = f1 ±2 · f2. Several readers have been designed for the particles counting and used for different immunoassay formats, including those compatible with immunoconcentration and magnetic enrichment of antigens. Registration of 0.1 ng/ml of Y. pestis antigen and 103 cell/ml of Salmonella typhimurium has been demonstrated. The developed biosensing platforms can be used for medical diagnostics, points of care, food pathogen detection, water analysis, etc.

New type of biosensor based on magnetic nanoparticle detection
Petr I. Nikitin et al. (2007). Journal of Magnetism and Magnetic Materials, 311, 445-9.

Résumé. A new type of biosensor has been developed based on detection of nanosized superparamagnetic particles that serve as labels in bioreactions. The method is based on non-linear magnetic material detection by a magnetic field having components at two frequencies f1 and f2. The response is measured at the combinatorial frequencies fi = mf1+nf2, where m and n are integers, e.g., fi = f1 ± f2. Several highly sensitive readers of superparamagnetic particles have been designed and used for development of development of various formats of immunoassays, including those compatible with immunoconcentration and magnetic enrichment of antigen.

Quantitative real-time in vivo detection of magnetic nanoparticles by their nonlinear magnetization
M. P. Nikitin, Journal of Applied Physics 103, 07A304 (2008)

Résumé. A novel method of highly sensitive quantitative detection of magnetic nanoparticles (MP) in biological tissues and blood system has been realized and tested in real time in vivo experiments.
The detection method is based on nonlinear magnetic properties of MP and the related device can record a very small relative variation of nonlinear magnetic susceptibility up to 10−8 at room temperature, providing sensitivity of several nanograms of MP in 0.1 ml volume. Real-time quantitative in vivo measurements of dynamics of MP concentration in blood flow have been performed. A catheter that carried the blood flow of a rat passed through the measuring device. After an MP injection, the quantity of MP in the circulating blood was continuously recorded. The method has also been used to evaluate the MP distribution between rat’s organs. Its sensitivity was compared with detection of the radioactive MP based on isotope of 59Fe. The comparison of magnetic and radioactive signals in the rat’s blood and organ samples demonstrated similar sensitivity for both methods. However, the proposed magnetic method is much more convenient as it is safe, less expensive, and provides real-time measurements in vivo.Moreover, the sensitivity of the method can be further improved by optimization of the device geometry.