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Tangential flow microfiltration is easily adapted for batch and continuous bioreactor clarification. The permeate can be introduced directly to the subsequent capture step. However, the commercial use of tangential flow filtration (TFF) is limited by membrane fouling, leading to a compromised performance. Here, we explored the possibility of reducing membrane fouling by integrating a hydrocyclone as the primary clarification operation. The overflow from the hydrocyclone was introduced directly as the feed to the microfiltration module. Chinese hamster ovary cells were used as the feed stream to investigate the feasibility of this integrated process. A range of cell viabilities from 0% (cell lysate) to 96% were investigated. The cell densities ranged from 0.9 to 10 million cells per mL. Two commercially available hollow fiber microfiltration membranes were used, an essentially symmetric membrane and a reverse asymmetric membrane where the more open support structure faced the feed stream. The reverse asymmetric membrane was more resistant to fouling in the absence of an integrated hydrocyclone. Integrating a hydrocyclone led to a reduction in the flux decline for the symmetric membrane, but did not affect the performance of the reverse asymmetric membrane. The careful choice of membrane morphology and pore size is important when designing an integrated process. 

Abstract Surfactants like polysorbate (Tween®) are commonly used as excipients in the production of monoclonal antibodies and other recombinant proteins. The retention behavior of these excipients in the final ultrafiltration step can be difficult to predict due to the presence of both monomers and micelles. This study examined the retention of polysorbate during ultrafiltration through cellulose and polyethersulfone membranes with nominal molecular weight cutoffs of 10, 30, and 100 kDa. Novel flux stepping experiments were performed to examine the effects of concentration polarization on surfactant transmission. Polysorbate 20 transmission through the 30 kDamembrane was a strong function of the surfactant concentration, decreasing from nearly 100% for a 2.5 mg/L solution to <10% for a 50 mg/L solution due to high retention of the micelles. Polysorbate transmission was lower for the polyethersulfone membrane due to polysorbate adsorption. A simple mathematical model was developed to describe the polysorbate transmission accounting for the effects of concentration polarization as well as the presence of surfactant monomers and micelles. Model calculations were in good agreement with the experimental data, providing a framework for the analysis and design of ultrafiltration/diafiltration processes for biopharmaceutical formulations containing surfactants. 

One major challenge in the development of nanoparticle-based therapeutics, including viral vectors for the delivery of gene therapies, is the development of cost-effective purification technologies. The objective of this study was to examine fouling and retention behaviors during the filtration of model nanoparticles through membranes of different pore sizes and the effect of solution conditions. Data were obtained with 30 nm fluorescently labeled polystyrene latex nanoparticles using both cellulosic and polyethersulfone membranes at a constant filtrate flux, and both pressure and nanoparticle transmission were evaluated as a function of cumulative filtrate volume. The addition of NaCl caused a delay in nanoparticle transmission and an increase in fouling. Nanoparticle transmission was also a function of particle hydrophobicity. These results provide important insights into the factors controlling transmission and fouling during nanoparticle filtration as well as a framework for the development of membrane processes for the purification of nanoparticle-based therapeutics.