A highly carboxylated sponge-like material: preparation, characterization and protein adsorption

Producing of high-purity protein products using separation materials is critical to the biopharmaceutical industry. Efforts to achieve protein adsorption materials with large adsorption capacity and high processing efficiency have been challenging. Herein, a highly carboxylated sponge-like monolithic adsorbent material was prepared by using SiO2 nanofibers as a rigid support framework, and esterification crosslinking reactants with polyvinyl alcohol (PVA)/polymeric carboxylic acid (polyacrylic acid, PAA) as a functional organic binder, which were modified in situ on the nanofiber framework. The obtained PVA/PAA sponge-like monolithic adsorbent material (PVA/PAA SMAM) exhibits a porous structure and possesses mechanical stability and recoverability of underwater compression. The high porosity provides more sites for carboxyl groups, making PVA/PAA SMAM rich in carboxyl groups. Experiments showed that PVA/PAA SMAM selectively adsorbes proteins with high isoelectric points. Using Cytochrome C (Cyt-C) as the main model protein with a high isoelectric point, the maximum adsorption of Cyt-C by the PVA/PAA SMAM at pH = 9 was 3079.3 mg/g with a rapid equilibration time (40 min), which is clearly superior to the currently reported Metal-organic frame structure (MOF) composites for Cyt-C adsorption. The isothermal adsorption model for the Cyt-C adsorption of the PVA/PAA SMAM material agrees well with the Freundlich adsorption model and the quasi-first kinetic model. Excellent mechanical and chemical structural stability endow the PVA/PAA SMAM material with protein elution capacity and good reusability, and secondary structure of the protein after elution was unchanged. Subsequently, selective adsorption and separation of Cyt-C from porcine heart supernatant was successfully achieved with PVA/ PAASMAM material. This work provides new materials with excellent performance for various bio-separation applications.