The binding of linear diamine counterions with different methylene chain lengths to the amino-acid-based surfactants undecanoic L-isoleucine (und-IL) and undecanoic L-norleucine (und-NL) was investigated with NMR spectroscopy. The counterions studied were 1,2-ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, and 1,6-diaminohexane. These counterions were all linear diamines with varying spacer chain lengths between the two amine functional groups. The sodium counterion was studied as well. Results showed that when the length of the counterion methylene chain was increased, the surfactants’ critical micelle concentrations (CMC) decreased. This decrease was attributed to diamines with longer methylene chains binding to multiple surfactant monomers below the CMC and thus acting as templating agents for the formation of micelles. The entropic hydrophobic effect and differences in diamine counterion charge also contributed to the size of the micelles and the surfactants’ CMCs in the solution. NMR diffusion measurements showed that the micelles formed by both surfactants were largest when 1,4-diaminobutane counterions were present in the solution. This amine also had the largest mole fraction of micelle-bound counterions. Finally, the und-NL micelles were larger than the und-IL micelles when 1,4-diaminobutane counterions were bound to the micelle surface. A model was proposed in which this surfactant formed non-spherical aggregates with both the surfactant molecules’ hydrocarbon chains and n-butyl amino acid side chains pointing toward the micelle core. The und-IL micelles, in contrast, were smaller and likely spherically shaped.
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Detergent/surfactant retention during ultrafiltration in the formulation of biotherapeutics
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.
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- Award ID(s):
- 1841474
- PAR ID:
- 10603454
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Biotechnology Progress
- Volume:
- 41
- Issue:
- 3
- ISSN:
- 8756-7938
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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