Boronate-immobilized cellulose nanofiber-reinforced cellulose microspheres for pH-dependent adsorption of glycoproteins

High strength and excellent selectivity are two important aspects of porous cellulose microspheres as adsorbents for protein separation. For this purpose, self-reinforced all-cellulose microspheres (SCMs) with high strength were fabricated using natural cellulose nanofibers (CNFs) as fillers and then immobilized via 3-aminophenylbor-onic acids as affinity ligands for selective enrichment of glycoproteins. In particular, the inherent stiffness of entrapped CNFs endowed SCMs with more inflexibility, because the stress can be efficiently transferred from the network of SCMs to the stiff CNFs during the separation process. Besides, SCMs, as an all-cellulose material with homogenous surface chemistry and pore structure characteristics, are more suitable as supports for adsorbents. Finally, the SCMs were immobilized with 3-aminophenylboronic acids (BA/EPI-SCMs) and tested their perfor-mance in affinity adsorption of glycoproteins. BA/EPI-SCMs showed fast separation, high adsorption amount, and excellent selectivity toward glycoproteins.