Heat Induced Grafting of Poly(glycidyl methacrylate) on Polybutylene Terephthalate Nonwovens for Bioseparations

Abstract

Polybutylene terephthalate (PBT) nonwovens were successfully grafted with poly(glycidyl methacrylate) (polyGMA) using a heat induced grafting approach with the thermal initiator benzoyl peroxide (Bz 2 O 2 ). This grafting method resulted in complete, uniform, and conformal grafted layers around the PBT fibers that could be further functionalized as ion exchangers for protein capture. Protein binding capacities as high as 200 mg/g were achieved for ion exchange PBT nonwovens grafted to 20% weight gain using this heat induced grafting method. Compared to UV grafted polyGMA PBT nonwovens, the rates of protein adsorption are several times faster for the heat grafted polyGMA PBT nonwoven, reaching equilibrium within minutes; UV grafted polyGMA ion exchange PBT nonwovens require hours to reach equilibrium. This indicates that polyGMA grafts formed by heat induced grafting are thinner, and therefore more dense, than UV grafted layers with the same % weight gain. To further investigate the structural differences between the two grafting methods, targets of various molecular weights (ATP, lysozyme, BSA, hIgG) were adsorbed to the materials. Increasing the target size resulted in a decrease of target molecules bound for both grafting methods. However, the heat grafted nonwovens exhibited a much stronger dependence of protein molecular weight on protein capture, indicating that heat induced grafting results in a polyGMA layer that has a smaller free volume between chains available for protein binding compared to the UV grafting method. Protein adsorption isotherms for the two grafting methods confirmed that both methods resulted in similar strengths of protein binding, with dissociation constants on the order of K d = 10 −6 M which is consistent with ion exchange binding on polymer brush networks. Heat grafted polyGMA ion exchange PBT nonwovens showed excellent protein binding and elution.

Nonwoven Ion-Exchange Membranes with High Protein Binding Capacity for Bioseparations

“…Prior work has described the UV- and heat-induced grafting processes for creating ion exchange membranes from nonwoven fabrics [ 6 , 13 , 19 , 21 , 25 ]. This study presents recent progress aimed at optimizing the dynamic binding capacities of these membranes under flow conditions at a wide range of residence times, and testing the ability of the membranes to purify proteins from real cell culture supernatants.…”

“…For both anion (PBT-GMA-DEA) and cation (PBT-GMA-SO 3 ) exchangers, the functionalizations were performed at different reaction times and at different ligand densities by varying the initial concentration of DEA and sodium sulfite in the reaction mixtures. After functionalization, cation and anion exchange membranes were hydrolyzed in 0.1 M sulfuric acid solution at 50 °C for 16 h to reduce the remaining epoxy groups as to avoid nonspecific protein binding [ 21 ]. Finally, the membranes were thoroughly washed with an excess of Milli-Q water until the pH reached 7.0 and dried overnight at room temperature.…”

“…For protein purification applications, it is extremely important to have a high binding capacity for the desired proteins with low non-specific adsorption of unwanted host cell proteins. Previous work has studied the grafting of glycidyl methacrylate (GMA) on nonwoven membranes using ultraviolet (UV) light irradiation and heat-induced polymerization, and attaching ligands through the epoxy end groups of the GMA [ 17 , 19 , 21 , 22 ]. It is clear from these studies that GMA formed uniform and conformal coatings on the polybutylene terepthalate (PBT) nonwovens [ 6 , 17 ].…”

Purification of Adeno-Associated Virus (AAV) Serotype 2 from Spodoptera frugiperda (Sf9) Lysate by Chromatographic Nonwoven Membranes

“…The PBT nonwovens were modified with polyGMA by UV grafting according to our prior work [ 36 , 37 ]: 1 mL of GMA grafting solution comprising BP at 13.7 mg/mL dissolved in 20% v / v GMA in butanol was sprayed on the PBT nonwoven, which was sandwiched between two glass slides and irradiated with UV light (λ = 365 nm; intensity: 5 mW/cm 2 ) using an EN-180, lamp (Spectronics Corporation, Westbury, NY, USA). A grafting time of 19 min was used for all the membranes in this study to obtain grafting weight gains of 20% (calculated as the weight gain of the sample after GMA grafting divided by the nonwoven weight of the sample before grafting).…”

“…Our team has developed a class of nonwoven membrane adsorbers for the chromatographic purification of biologics, comprising polybutylene terephthalate (PBT) nonwoven fabrics grafted with polyglycidyl methacrylate (GMA) layers that can be functionalized with a variety of ligands [ 36 , 37 , 38 ]. These membranes exhibit excellent flow permeability, high binding capacity and selectivity towards proteins, and can be operated in bind-and-elute mode for product capture or flow-through mode for product polishing.…”