(449e) In Situ Evaluation of Nanoparticle–Protein Interactions By Dynamic Magnetic Susceptibility Measurements

A technique to study protein-nanoparticle interactions in situ is proposed. The technique consists of magnetic measurements of the rotational diffusion of thermally blocked cobalt ferrite nanoparticles in protein solutions. To illustrate the technique we studied the effect of degree of carboxylic acid substitution in carboxymethyl dextran coated magnetic nanoparticles on their interaction with model proteins such as albumin (BSA), lysozyme (LYZ), immonuglobulin G (IgG), fibrinogen (FIBR), apo-transferrin (TRANS), and histone (HIS) in a wide range of protein concentrations. Experiments indicated that interactions between negatively charged particles and negatively charged proteins BSA, IgG, FIBR, and TRANS were negligible. On the other hand, positively charged proteins LYZ and HIS seemed to readily absorb on the particle surfaces, as evidence by an increase in size and eventual aggregation of the particles. Onset of this effect seemed to happen at lower concentration of HIS, compared to LYZ. The technique can be easily applied to the other particle surface coatings and to particles in complex protein mixtures such as serum, allowing systematic in situ studies of protein-nanoparticle interactions.