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

► This report describes the highly specific capture of glycopeptides employing chitosan–GMA–APB nanospheres. ► These nanospheres have a diameter of 20–100nm and were synthesized for this work. ► MALDI-TOF-MS combined with use of these nanospheres is a simple and rapid approach for enrichment of glycopeptides. ► The binding affinity of boronic acid and glycopeptides is pH and solvent dependent. 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 20–100nm 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)).