Highly efficient enrichment of low-abundance intact proteins by core-shell structured Fe3O4-chitosan@graphene composites

In proteomics research, the screening and monitoring of disease biomarkers is still a major challenge, mainly due to their low concentration in biological samples. However, the universal enrichment of intact proteins has not been further studied. In this work, we developed a Fe3O4-chitosan@graphene (Fe3O4-CS@G) core-shell composite to enrich low-abundance proteins from biological samples. Fe3O4-CS@G composite holds chitosan layer decorated Fe3O4 core, which improves the hydrophilicity of materials greatly. Meanwhile, the graphene nanosheets shell formed via electrostatic assembly endows the composite with huge surface area (178 m(2)/g). The good water dispersibility ensures the sufficient contact opportunities between graphene composites and proteins, and the large surface area provides enough adsorption sites for the enrichment of proteins. Using Fe3O4-CS@G, four standard proteins Cyt-c, BSA, Myo and OVA were enriched with better adsorption capacity and recovery rate, compared with previously reported magnetic graphene composites. Additionally, the mechanism of compared to is corrected into compared with. proteins adsorption on Fe3O4-CS@G was further studied, which indicates that hydrophobic and electrostatic interaction work together to facilitate the universal and efficient enrichment of proteins. Human plasma sample was employed to further evaluate the enrichment performance of Fe3O4-CS@G. Eventually, 123 proteins were identified from one of SAX fractions of human plasma, which is much better than commercial Sep-pak C18 enrichment column (39 proteins). All these outstanding performances suggest that Fe3O4-CS@G is an ideal platform for the enrichment of low-abundance intact proteins and thus holds great potential to facilitate the identification of biomarkers from biological samples in proteomics research.