Fabrication of highly carboxylated thermoplastic nanofibrous membranes for efficient absorption and separation of protein

Developing high-performance chromatographic media is of great significance for efficient protein adsorption and separation. Herein, the thermoplastic-poly(vinyl alcohol-co-ethylene) (EVOH) nanofibrous membranes (NFMs) were fabricated through structure controlled high-speed flow deposition process from EVOH nanofibrous suspensions. Butane tetracarboxylic acid (BTCA) was grafted onto EVOH NFMs to form chromatographic media by impregnation method. The obtained EVOH/BTCA NFMs with highly tortuous structure, excellent structural stability, good hydrophilicity and abundant active carboxyl groups possess selective absorption to positively charge proteins via electrostatic interaction. With increasing BTCA contents, the absorption capacity (take lysozyme as template protein) increased gradually and achieved a maximum absorption capacity of 749.3 mg/g. Meanwhile, the protein absorption performance of EVOH/BTCA NFMs is optimized by the properties of protein solution, physical properties of substrate EVOH NFMs and grafting temperature. EVOH/BTCA NFMs exhibit good reusability and maintain a relatively stable absorption capacity after 10 absorption-elution cycles. Furthermore, superior acid and alkaline resistance of EVOH/BTCA NFMs was proved through being treated in acid and alkaline solutions for 24 h. EVOH/BTCA NFMs can effectively extract lysozyme from egg white. A successful scale-up of such low-cost and high-performance membranes could provide some insights for the design and development of thermoplastic polymeric nanofibrous-based materials with protein separation and purification.