Selective enrichment of glycopeptides/phosphopeptides using Fe₃O₄@Au-B(OH)₂@mTiO₂ core-shell microspheres

In this work, the bifunctional Fe₃O₄@Au-B(OH)₂@mTiO₂ core-shell core-shell microspheres were designed and synthesized for the selective enrichment of glycopeptides/ phosphopeptides. Due to the bifunctional property of the titanium dioxide and the boronic acid group, the microspheres were successfully applied to the enrichment of phosphopeptides and glycopeptides, evaluated by capturing phosphopeptides from tryptic digestion of model phosphoprotein bovine β-casein diluted to 2.0pgμL^-1 (8.0×10^-17molμL^-1) and glycopeptides from tryptic digestion of model glycoprotein horseradish peroxidase (HRP) diluted to 80pgμL^-1 (2.0×10^-15molμL^-1). The enrichment selectivity of the bifunctional microspheres was evaluated by capturing phosphopeptides from a peptide mixture of β-casein and bovine serum albumin (BSA) with the molar ratio of 1:1000 (4.2×10^-12mol of β-casein and 4.2×10^-9mol of BSA in 100μL) and glycopeptides from a peptide mixture of HRP and BSA up to the ratio of 1:100 (5.0×10^-12mol of HRP and 5.0×10^-10mol of BSA in 100μL).