Highly efficient enrichment of phosvitin phosphopeptides by novel magnetic carboxymethyl chitosan nanoparticles decorated with Fe (III) ions

Functional immobilized metal affinity magnetic carboxymethyl chitosan nanoparticles (abbreviated as Fe3O4 (PEG + CM-CTS) @ Fe (III)) were conveniently applied for phosvitin phosphopeptides (PPPs) enrichment for the first time. The morphology of magnetic nanoparticles was observed by transmission electron microscope (TEM). It was found that the diameter of Fe3O4 (PEG + CM-CTS) @ Fe (III) was about 20 nm, and could easily aggregate by a magnet when suspending in the aqueous solution. In the PPPs enrichment study, the results obtained emphasized the role of pH, temperature and the initial concentration of the peptides solution in governing the efficiency and mechanism of affinity interactions. Due to the large specific surface area, the enrichment of PPPs onto the Fe3O4 (PEG + CM-CTS) @ Fe (III) nanoparticles was promising. The adsorption equilibrium of PPPs onto the obtained magnetic nanoparticles fitted well with the Langmuir model, and the nitrogen/phosphorus molar ratio (N/P) which at the maximum enrichment capacity for PPPs was 4.83. Due to the small diameter, the decrease of the N/P is particularly rapid in the early enrichment stages (0–30 min) to reach a plateau after 60 min. Compared with traditional methods, the need for preparation of phosvitin before purification is obviated and PPPs of higher purity were obtained. Since the preparation, surface modification and affinity separation processes of the magnetic nanoparticles are cost-effective, convenient and efficient, this type of Fe3O4 (PEG + CM-CTS) @ Fe (III) nanoparticles would bring advantages compared to conventional separation techniques of PPPs from chicken egg yolk, as well as for phosphopeptides enrichment in proteomics research.