Synthesis and characterization of biocompatible ferrofluid based on magnetite nanoparticles and its effect on immunoglobulin G as an immune protein

Abstract

The investigation of interaction between protein fundamental to the immune system, immunoglobulin G (IgG), and superparamegnetic iron oxide nanoparticles (SPIONs) helps in designing the cell separation, drug delivery and hyperthermia systems. For this reason, the superparamagnetic iron oxide nanoparticles (SPIONs) were prepared and coated with chitosan (CS) due to decrease of cytotoxicity. The chitosan coated superparamegnetic iron oxide nanoparticles (CS-SPIONs) were characterized by X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and the magnetic hyperthermia efficiency. The coating of SPIONs minimized the agglomeration with reduction in magnetic behavior and specific absorption rate (SAR). The internalization of CS-SPIONs into the cells was performed by Prussian blue staining. Zeta potential and dynamic light scattering (DLS) of ferrofluids in cell culture medium were evaluated. The cytotoxicity studies were evaluated on human foreskin fibroblast normal cell line, HFFF2 by MTT assay and annexin V/PI staining. The binding studies were carried out by multispectroscopic approaches. Absorption spectroscopy (UV–Vis) indicated that CS-SPIONs can bind to IgG. The fluorescence emission spectroscopy of IgG was quenched by CS-SPIONs. The quenching mechanism was a combination of static and dynamic as well as binding constant (1.84 × 104 M−1, 1.34 × 104 M−1 and 1.10 × 104 M−1 at 293 K, 298 K and 313 K, respectively) and number of binding sites (n = 1) were determined. The thermodynamic signature clearly indicated that hydrogen bonds and van der Waals forces play a main role in the binding process. The binding distance (2.1 nm) and energy transfer efficiency (0.69) were determined using Förster mechanism. Synchronous fluorescence studies indicated that the binding changes the microenvironment around tryptophan residues rather than tyrosine residues. In addition, three-dimensional fluorescence (3D), Far-UV CD spectrum, near-UV CD spectrum and ellipsometry results showed additional insight into conformational changes of IgG on binding with CS-SPIONs. These results provided CS-SPIONs as a biocompatible candidate for pharmacology and nanomedicine.