Chemoenzymatic syntheses of sialyl Lewis X–chitosan conjugate as potential anti-inflammatory agent

This paper describes the facile synthesis and bioevaluations of a novel conjugated polymer having tetrasaccharide SLeX branch and chitosan backbone (SLeX–chitosan conjugate). The synthesis was achieved by a convenient chemoenzymatic approach using an aldehyde-functionalized N-acetylglucosamine to branch it onto chitosan amino groups followed by three enzymatic reactions to further append galactose, sialic acid, and fucose residue to the branch. Surface plasmon resonance (SPR) study of SLeX–chitosan conjugate revealed a high affinity binding with E-selectin (Kd = 920 nM) and a potent inhibitory effect on the binding of E-selectin with SLeX–BSA (IC50 = 240 μM). By using biocompatible chitosan as the scaffold for presenting SLeX ligands, as well as the concise route tailored for the conjugate syntheses, the present study provides a practical method to explore safe and efficient anti-inflammatory agents.