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.