Ligand-free strategy for ultrafast and highly selective enrichment of glycopeptides using Ag-coated magnetic nanoarchitectures

Selective enrichment of glycopeptides from complicated biological samples is essential for MS-based glycoproteomics, but still remains a great challenge. In this study, we report an unprecedented ligand-free strategy for the selective enrichment of glycopeptides by simply utilizing the multivalent interaction between glycopeptides and silver nanoparticles (Ag-NPs) coated magnetic nanoarchitectures. The composite microspheres were deliberately designed to be constructed with a high-magnetic-response magnetic colloid nanocrystal cluster (MCNC) core, a poly(methacrylic acid) (PMAA) interim layer and a Ag-NPs functional shell with high coverage. Taking advantage of the reversible interaction of glycans with Ag-NPs and the high magnetic susceptibility of the magnetite core, the MCNC@PMAA@Ag-NPs microspheres possess remarkable selectivity for glycopeptides even at a low molar ratio of glycopeptides/non-glycopeptides (1 : 100) with a very rapid enrichment speed (only 1 min needed) and a simple operation procedure using magnetic separation. Applying this approach, we identified 127 unique glycopeptides mapped to 51 different glycoproteins from only 1 μL rat serum samples. These results clearly demonstrated that the MCNC@PMAA@Ag-NPs have great potential for purifying and identifying the low-abundant glycopeptides in complex biological samples.