NMR Relaxometry at Quantification of the Captured Magnetic Nanoparticles by Cells

Abstract

The possibility of using the transverse relaxation time T2 of protons in aqueous media for quantitative measurement of the capture of magnetic nanoparticles by cells has been studied and demonstrated. The measurement of T2 was performed on a portable original NMR relaxometer with a measuring cell for a standard well of a biological plate. The novelty of the approach is that quantitative measurements of the capture kinetics were carried out using measurements of the proton relaxation time of the nutrient medium, which is determined by the remaining number of magnetic particles (not captured by the cells) in the medium. To study the kinetics of capture, two types of magnetic nanoparticles were synthesized: magnetite particles Fe₃O₄ and composite particles Fe@C with an iron-carbon shell structure. The surface of the particles was functionalized with amine-and carboxyl groups. The capture of aminated particles of Fe@C cells is established by microscopy and NMR-relaxometry by measuring the time T2. It is shown that the proposed method makes it possible to register very small concentrations of trapped magnetic nanoparticles equal to tens of pg/cell.