A simple and highly efficient method for enriching and separating glycoproteins in complex biological samples using polyethyleneimine- and boric acid-grafted metal-organic frameworks on magnetic nanospheres.

Alterations in glycosylation patterns have been observed in many diseases, including inflammatory, auto-immune, and infectious diseases as well as cancer. However, the low concentrations of glycoproteins in biological samples make it difficult to enrich and separate glycoproteins efficiently before determination. In this study, a composite material was prepared in which Fe₃O₄-based magnetic nanospheres were modified with polyethyleneimine (PEI)- and boric acid-grafted metal-organic frameworks (MOFs) to enable the selective enrichment and separation of glycoproteins from complex biological samples. With the coordination between amino and boric acid, a teamed boronate affinity (TBA) molecular group is formed, which enables the cyclization of boric acid and the cis-diol groups in glycoproteins to be achieved at physiological pH. In addition, the abundant hydrogen bonds between amino and glycoprotein also increase the affinity of the synthesized Fe₃O₄@MOF@PEI@BBA nanoparticles for glycoprotein. The adsorption capacities for ovalbumin, transferrin, and horseradish peroxidase were 489.3, 522.0, and 578.2 mg/g, respectively. Meanwhile, adsorption equilibrium was achieved within 30 min under mild physiological conditions (pH = 7.4, T = 25 °C).