In Situ Evaluation of Nanoparticle–Protein Interactions by Dynamic Magnetic Susceptibility Measurements

Abstract

The use of dynamic magnetic susceptibility measurements is reported to study nanoparticle–protein interactions in situ. The technique consists of measuring the rotational diffusivity of thermally blocked magnetic nanoparticles (MNPs) in protein solutions. To illustrate the technique, the effect of nanoparticle zeta potential in carboxymethyl‐dextran‐coated MNPs and their interaction with model anionic and cationic proteins, such as bovine serum albumin (BSA), immunoglobulin G (IgG), fibrinogen (FIBR), apo‐transferrin (TRANS), lysozyme (LYZ), and histone (HIS), in a range of protein concentrations is studied. Experiments indicate that interactions between the negatively charged particles and the negatively charged proteins BSA, IgG, FIBR, and TRANS are negligible. However, positively charged proteins LYZ and HIS readily absorb onto the nanoparticles, as evidenced by an increase in size and eventual aggregation of the particles. Onset of this effect seems to happen at a lower concentration of HIS compared with LYZ. The technique could be applied to other particle surface coatings and to particles in complex protein mixtures, such as whole blood and serum, allowing systematic in situ studies of nanoparticle–protein interactions.

Optimization of synthesis and peptization steps to obtain iron oxide nanoparticles with high energy dissipation rates

“…It is important to note that hydrodynamic diameters obtained from χ’ and χ” were not always the same even when the same model was applied to fit experimental data. These differences occur because the mathematical expression for χ” has a numerator that is directly proportional to the cube of the hydrodynamic diameter, thus making χ” more sensitive to changes in values of the hydrodynamic diameter relative to χ’ [37]. …”

Assessing magnetic nanoparticle aggregation in polymer melts by dynamic magnetic susceptibility measurements

“…We have previously shown that quantitative nanoscale viscosity measurements can be obtained from DMS measurements [46]. We have also used this technique to monitor phase transitions in the surrounding media, colloidal stability of MNPs in simple fluids, and adsorption of proteins to MNPs [47][48][49]. Others have also applied this technique to evaluate the mobility of nanoparticles in polymer hydrogels [50] and to evaluate the rheological properties of the suspending fluid [51].…”

Alternating current (AC) susceptibility as a particle-focused probe of coating and clustering behaviour in magnetic nanoparticle suspensions

“…Thus, ACS measurements as a function of field frequency enable determination of the Brownian relaxation time and subsequently the hydrodynamic size of the particles using equation (2) above. Using this versatile characterization method, the formation of protein corona around MNPs caused by their surface charge 18,19 , the aggregation of MNPs within polymer nanocomposites 20 , and the mobility of MNPs in cells 19,21,22 , have been explored previously. Figure 1: Schematic showing the AC susceptibility versus frequency curve expected for blocked magnetic nanoparticles displaying Brownian relaxation.…”