Protein glycosylation is one of the most complicated but significant post-translational modifications. Minor alterations in glycan structure can considerably affect the biology of a cell. Therefore, direct monitoring of glycan patterns of glycoproteins is closely related to cancer progression as well as metastasis. To profile glycan patterns of significant bio-samples, a chip-based method is proposed to selectively immobilize glycoproteins of interest. Here, boronic acid (BA) is a major component acting as an affinity head to direct the formation of a boronate diester ring with the diol groups of glycans. Following this step, a tosyl group functions as an electrophile to conduct an SN2 reaction with the nucleophilic residues of the boronated glycoproteins, next a reporter group is tagged onto the glycoprotein via an ether linkage. The BA-tosyl functionalized glass slide had been used to fabricate glycoprotein microarrays with highly conserved glycans. To enhance the immobilization efficiency and reduce the undesired nonspecific absorption, the strain-promoted alkyne-azide cycloaddition (SPAAC) conjugation chemistry and surface blocking conditions were carefully optimized for the collection of reliable data. The optimized glycoprotein microarray platform describes specific lectin-recognition patterns of glycoproteins of interest in E. coil lysate and fetal bovine serum, which encourages us for direct monitoring of glycan patterns from human sera without tedious sample preparation. To evaluate the applicability in real samples, sera samples of healthy individuals, lung cancer and pancreatic cancer patients have been analyzed by this new technique. Remarkably, the distinguishable glycan patterns of the three groups make them a powerful platform for cancer screening and pre-diagnosis.

Direct screening of glycan patterns from human sera by chemically functionalized slides

2019 Fall National Meeting

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