In-Depth Analysis of Glycoprotein Sialylation in Serum Using a Dual-Functional Material with Superior Hydrophilicity and Switchable Surface Charge.

Sialylation typically occurs at the terminal of glycans, and its aberration often correlates with diseases including neurological diseases and cancer. However, the analysis of glycoprotein sialylation in complex biological samples is still challenging due to their low abundance. Herein, a histidine-bonded silica (HBS) material with a hydrophilic interaction and switchable surface charge was fabricated to enrich sialylated glycopeptides (SGPs) from the digest of proteomics samples. High selectivity toward SGPs was obtained by combining the superior hydrophilicity and switchable-charge characteristics. During the enrichment of sialylated glycopeptides from bovine fetuin digest, seven glycopeptides were detected even at the ratio of 1:5000 with the nonsialylated glycopeptides, demonstrating the high specificity of SGP enrichment by using HBS material. Then, HBS material was further utilized to selectively enrich SGPs from the protein digest of human serum, and 487 glycosites were identified from only 2 μL of human serum; 92.0% of the glycopeptides contained at least one sialic acid, indicating good performance for SGP enrichment by using HBS material. Furthermore, the prepared HBS material also has great potential applications in the analysis of glycoprotein sialylation from other complex biological samples.