Electrochemical aptamer-based biosensing of glycan-conjugated targets

Abstract

As the most complex post-translational modification, glycosylation involves the covalent linking of glycan(s) to a biomolecule. The glycosylation of proteins, peptides, lipids, and nucleic acids results in the formation of diverse glycoconjugates, like glycoproteins, peptidoglycans, glycopeptides, glycolipids, lipopolysaccharides, and glycoRNAs, and glycoconjugates are also ubiquitous on the surface of extracellular vesicles (EVs), cells, bacteria, and viruses. The conjugated glycans are integral to cell recognition (e.g., adhesion and homing), cell trafficking, immune recognition, hormone-receptor binding, protein folding and stabilization, and many other biological processes. Currently, the glycan-conjugated biological objects have found widespread applications in disease diagnosis (e.g., glycoproteins, exosomes, and circulating tumor cells) and therapy (e.g., therapeutic monoclonal antibodies). Over the past decades, a variety of methods have been established for the quantitative assay of the glycan-conjugated biological objects, in light of their significant diagnostic and therapeutic values, using antibodies, aptamers, or affinity peptides as recognition ligands. Relative to other methods, the aptamer-based electrochemical biosensors (i.e., electrochemical aptasensors) have attracted much attention in recent years in the detection of the glycan-conjugated targets, by virtue of their intrinsic advantages such as low cost, good portability, simple instrument, superior stability and anti-interference capability, and high sensitivity and selectivity. This review summarizes the biological, diagnostic, and therapeutic significance of the glycan-conjugated biological objects, and then presents the progress in the electrochemical aptasensing of the glycan-conjugated biological objects, including glycoproteins, lipopolysaccharides (LPSs), exosomes, circulating tumor cells (CTCs), and pathogenic microbes (e.g., bacteria and viruses). Moreover, the challenges and future prospects of the electrochemical aptasensing of the glycan-conjugated biological objects are discussed.