Abstract
Liquid-phase magnetic immunoassay (MIA) using magnetic nano-particles (MNPs) has been studied as a more rapid method compared to optical methods for inspecting proteins and viruses. MIA can estimate the number of conjugated antibodies without being washed differently from conventional optical immunoassay. However, in the case of the liquid phase, it is considered that the magnetic properties of MNPs are affected by physical properties such as viscosity and impurity substances such as biological substances contained in the blood. In this study, the effect of sodium chloride (NaCl) in buffer and serum solution was evaluated to reveal the effect of serum because the sodium (Na+) and chloride (Cl-) ions in the serum dominate ion balance of blood. The measurement results of AC magnetic susceptibility and a dynamic light scattering (DLS) showed that the aggregation of MNPs was largely affected by the concentration of NaCl. This effect of the NaCl could be explained by shielding of the surface charge of MNPs by ions in the solution. Although the concentrations of NaCl in the buffer and serum solution were almost same, we found that MNPs were aggregated more in their size for those in the serum solution because of other impurities, such as proteins. These results suggest evaluation of effects of the contaminants in serum and optimization of polymer coatings of MNPs could be important factors to realize measurements of magnetic immunoassay with high accuracy.
Highlights
Magnetic nano-particles (MNPs) have been studied for medical diagnostic purposes—as the imaging agents of magnetic resonance imaging (MRI), hyperthermia, and drag delivery.[1,2,3] Among them, liquid-phase magnetic immunoassay (MIA) using magnetic nano-particles (MNPs) has been studied as a more rapid method compared to optical methods for inspecting such as proteins and viruses.[4]
Liquid-phase magnetic immunoassay (MIA) using magnetic nano-particles (MNPs) has been studied as a more rapid method compared to optical methods for inspecting proteins and viruses
Conventional optical immunoassays like Enzyme-Linked Immunosorbent Assay[5] need to be washed to remove unbounded antibodies from solutions; the MIA can estimate the number of conjugated antibodies without being washed because the alternating (AC) magnetic properties of MNP beads vary when the antibodies are bounded with antigens
Summary
Magnetic nano-particles (MNPs) have been studied for medical diagnostic purposes—as the imaging agents of magnetic resonance imaging (MRI), hyperthermia, and drag delivery.[1,2,3] Among them, liquid-phase magnetic immunoassay (MIA) using MNPs has been studied as a more rapid method compared to optical methods for inspecting such as proteins and viruses.[4]. The MIA generally uses polymer-coated MNP beads, on the surface of which antibodies are immobilized to detect conjugation with antigens. Conventional optical immunoassays like Enzyme-Linked Immunosorbent Assay[5] need to be washed to remove unbounded antibodies from solutions; the MIA can estimate the number of conjugated antibodies without being washed because the alternating (AC) magnetic properties of MNP beads vary when the antibodies are bounded with antigens. AC magnetic signal changes by volume change due to the antigen - antibody binding reaction, because the AC magnetic signal depends on rotation of magnetic moment within the particle; the viscosity of the sample solution is considered to affect the AC magnetic properties.[9,10]. Our study revealed that the MNP beads in the serum solution exhibited AC magnetic properties different from those of MNP beads in the buffer solution though the viscosity of the solution was similar.[11]. Scitation.org/journal/adv includes Na+ and Cl- ions to AC magnetic properties of MIA, the concentration dependence of properties of sodium chloride in the solutions was measured
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