Fabrication of 3D aligned porous nanocellulose-based aerogel for enrichment of the histidine-containing polypeptides

The high-throughput immobilized metal affinity chromatography (IMAC) material is urgently required to improve the efficiency of separation and purification of tagged peptides in related biomedical applications. Herein, the amino-thiourea-modified nanocellulose (S-TOCN) -polyvinyl alcohol (PVA) composite aerogel with aligned pores was prepared by a directional freeze-casting technique and then used to immobilize metal ions (M2+) for the selective separation and purification of histidine-containing peptides from protein hydrolysates. The obtained S-TOCN-PVA materials with an oriented porous structure exhibited excellent mechanical properties, good adsorption performance, and reusability under optimal conditions. The adsorption capacity of the S-TOCN-PVA aerogel for metal ions was as follows: Cu2+>Ni2+>Zn2+>Co2+, and the higher metal ion chelating amount of the S-TOCN-PVA composite aerogel for Cu2+ and Ni2+ reached 87.21 mg/g at pH=7 and 83.66 mg/g at pH=6 in the 2 h incubation period, respectively. The enrichment effects of Cu2+/S-TOCN-PVA and Ni2+/S-TOCN-PVA aerogels with the selectivity of His-containing peptides from apricot kernel protein hydrolysates were up to 3.99 folds and 4.81 folds, respectively, for one cycle. Furthermore, after 5cycles, the Ni2+/S-TOCN-PVA aerogels remained at 87.5% of their initial adsorption capacity (848 mg/g), and the concentration increased by 39.05-fold. Molecular docking simulations show that the oxygen of the carboxyl group (-C-O and -CO) and the hydrogen of the imidazole group on the His molecule are mainly bonded to the hydrogen of the amino groups and the oxygen of the carboxyl group (C-O-C) in the structure of M2+/S-TOCN-PVA aerogels. The fabricated metal ion-immobilized 3D-aligned porous nanocellulose-based aerogels are promising IMAC materials for efficient separation and purification of the histidine-containing polypeptides from complicated biological samples.