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Chemoenzymatic Synthesis of Branched Glycopolymer Brushes as the Artificial Glycocalyx for Lectin Specific Binding

Wang, Yuzhen, Gu, Lei, Xu, Fanli, Xin, Fengxue, Ma, Jiangfeng, Jiang, Min, Fang, Yan
Langmuir 2019 v.35 no.13 pp. 4445-4452
Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, binding capacity, bioengineering, cell membranes, concanavalin A, contact angle, dextransucrase, glycosylation, gold, maltose, mass spectrometry, polymerization, polymers, polysaccharides, quartz crystal microbalance, sucrose
The artificial glycocalyx fabricated by carbohydrates is of interest because it provides a platform to simulate the cell membranes that widely exist in the nature, and thus enable extensive applications to be implantable in bioengineering. Here, we present a green strategy combining two polymerization techniques, surface-initiated atom transfer radical polymerization (SI-ATRP) and enzyme-catalyzed elongation of polysaccharide, for fabricating densely packed branched glycopolymer brushes on the gold surface as the artificial glycocalyx. In this strategy, SI-ATRP is first performed to graft a linear polymer chain for anchoring maltose, which can be used as an enzyme acceptor for dextransucrase (DSase). Under DSase, a branched polysaccharide is efficiently formed through elongation of a sucrose substrate. Undoubtedly, enzymatic transglycosylation has unique advantages, such as being green, regio-, and stereo-selective, etc. The process of DSase-catalyzed polysaccharide is well monitored by a quartz crystal microbalance, and the grafting density of the glycopolymer brushes is estimated to be 0.7 chain nm–² with 23.0 nm dry thickness. The polysaccharide brushes display a branched structure consisting of α-d-glucose residues with 5% of α-1,3-linked shorter chain branches, and the branched structure is well characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, Fourier transform infrared/mirror reflection, water contact angle analysis, and atomic force microscopy. Compared with the linear maltose-anchored brushes, the branched glycopolymer analog prepared here shows high specific binding capacity of concanavalin A recognition, which should be of use in biomedical application.