Synthesis and characterization of a novel boronic acid-functionalized chitosan polymeric nanosphere for highly specific enrichment of glycopeptides

In this study we describe a method for highly specific enrichment of glycopeptides with boronic acid-functionalized chitosan polymeric nanospheres and matrix assisted laser desorption-ionization mass spectrometry (MALDI-MS). This is the first time chitosan has been used to create nanosphere support material for selective enrichment of glycopeptides by modification with glycidyl methacrylate (GMA) and derivatization with 3-aminophenylboronic acid (APB). Due to their multifunctional chemical moieties, these 20–100 nm chitosan–GMA–APB nanospheres have unique properties, such as good dispersibility, good biocompatibility and chemical stability, as well as augmented specificity with glycopeptides. Enrichment conditions were optimized by using trypsin digested glycoprotein horseradish peroxidase. The high specificity of chitosan–GMA–APB nanospheres was demonstrated by effectively enriching glycopeptides from a digest mixture of horseradish peroxidase and nonglycoproteins (bovine serum albumin (BSA)).