Viscosity effect on the brownian relaxation based detection for immunoassay applications

Abstract

Magnetic nanoparticles (MNPs) coated with Protein-G have been a model system to be used in different antibodies binding study. It is highly desirable to use a substrate-free biosensing system to detect antibodies binding in real-time. In this paper, we developed and applied a MNPs and search-coils integrated detection system, which is not only sensitive to the hydrodynamic volume of MNPs but also sensitive to the environment of MNPs, such as viscosity and temperature of the solution. We demonstrated that the viscosity effect influenced the amplitudes and phases of the 3rd (fH±2fL) and 5th (fH±4fL) harmonics for the mixed frequency testing scheme. The binding between antibodies and Protein-G on MNPs increased hydrodynamic volume of particles, as a result, it also changed the amplitudes and phases of harmonics, which are the object signals we need to analyze. We demonstrated that the viscosity of antibody solution is lower than that of MNP solution, and the antibody binding effect could be shielded by the viscosity effect to certain extent.

Magnetic particle spectroscopy-based bioassays: methods, applications, advances, and future opportunities

“…The MPS-based volumetric sensors explore the effect of hydrodynamic volume on Brownian relaxation-dominated SPIONs, the binding of proteins/aptamers to SPION surface increases the hydrodynamic size as well as the effective relaxation time, resulting in larger phase lag and smaller harmonic ratio. Beyond these aforementioned applications, the Brownian relaxation-dominated SPIONs have also been applied as mini-viscometers [16,[88][89][90][91] and mini-thermometers [79,83,115] due to the fact that the viscosity and temperature alter the relaxation time as well as the phase lag and harmonic ratio.…”

“…In MPS, also called 0D MPI, sinusoidal magnetic fields periodically drive SPIONs into magnetically saturated regions which exhibit magnetic responses that contain not only the driving field frequencies but also a series of harmonic frequencies. These harmonic components can be easily separated by means of appropriate filtering and they are directly related to characteristics of the SPIONs such as the viscosity [88][89][90][91] and temperature [79,92] of the SPION liquid medium as well as the conjugation of any chemicals or biological compounds onto SPIONs [3, 6-8, 81, 93].…”

Investigating the effect of magnetic dipole–dipole interaction on magnetic particle spectroscopy: implications for magnetic nanoparticle-based bioassays and magnetic particle imaging

“…In this work, a lab-based MPS system was used to monitor the magnetic responses of SPIONs with different particle concentrations c (varying from 0.1133 nmole ml −1 to 3.4 nmole ml −1 ), volume fractions f (varying from 0.001 to over 0.029), and inter-particle distances d (varying from below 78 nm to 245 nm). The MPS system setups have been reported by our previous works [36][37][38][39][40][41][42]. As shown in figure 3 a Dried powder is prepared by air drying the SPION suspension at room temperature for 6 h. b The SPION sample concentration used in this paper is expressed as the nanoparticle concentration: nmol/ml (particles).…”

Superparamagnetic nanoparticle-based viscosity test

“…Brownian relaxation of superparamagnetic nanoparticles has been proposed and investigated for a variety of biosensing applications. [3][4][5][6][7][8][9][10][11] Brownian relaxation-dominated superparamagnetic nanoparticles are sensitive to characteristics of the suspension environment such as temperature, 7,8 hydrodynamic volume of magnetic nanoparticle (MNP), 3,6 and viscosity. 6 Rauwerdink and Weaver 12 reported that by applying one alternating magnetic field on MNPs in water and glycerol mixtures, they are able to distinguish viscosities ranging from 0.96 to 9.81 cp by monitoring harmonic angles.…”

“…A high frequency sinusoidal magnetic field and a low frequency sinusoidal magnetic field are applied to MNP suspensions simultaneously [4][5][6]10,11,13,14 in a search coil detection system. The high frequency magnetic field produces harmonic signals by mixing frequency with the low frequency field.…”