Synthesis and characterization of nanoparticles based on negatively charged xanthan gum and lysozyme

•XG/Ly NPs were first fabricated by two negatively charged polymers.•The physical interactions between XG and Ly were explored.•A tentative model of XG/Ly NP formation was provided.

Nanoparticles (XG/Ly NPs) were fabricated by like charged xanthan gum and lysozyme and the interactions between them in the preparation condition were further explored. The sizes, zeta potential, scanning electron microscope (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the NPs. The interactions between them were investigated through Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), hydrophobicity and rheological analysis. The results indicated that the size-controlled (61.7 nm–108 nm) XG/Ly NPs displayed a regular spherical morphology with favorable size distribution and stability for one month. Suffering from the alkali-coupled thermal treatment, they lost their natural structures, explored more hydrophobic areas accompanied by molecule rearrangement and gelation, and then interpenetrated in forming the NPs. Ly exhibited a trend from α-helix to β-sheet transition. The NPs possess internal hydrophobic regions that barely affected by the prepared conditions. The worthwhile endeavor prepared biopolymer NPs by a negatively charged protein and polysaccharide in a simple method, and attempted to provide some useful information in physical interactions and protein/polysaccharide NP fabrications.