Effect of Temperature on the Critical Micelle Concentration and Micellization Thermodynamic of Nonionic Surfactants: Polyoxyethylene Sorbitan Fatty Acid Esters
Abstract:In this study, non-ionic surfactants, polyoxyethylene sorbitan fatty acid esters (polysorbate) are chosen to examine the temperature effect on the CMC over a wide temperature range. The enthalpy and entropy of micelle formation are evaluated according to the phase separation model. The surface tension of solutions was determined by means of Du Nöuys ring. The CMC values were taken from the sharp breaks in the surface tension vs. logarithms of surfactant concentration plots. As the surfactants' chain length inc… Show more
“…At the same time, its surface tension above CMC decreases from about 38 mN/m at 20 ºC to about 12 mN/m at 80 ºC (Mohajeri and Noudeh, 2012). These data support the hypothesis that the increasing interfacial activity of polysorbate 20 promotes the continuation of the emulsification phenomena with temperature ramping, indirectly confirming the loss of the lipid structure previously hypothesized.…”
“…At the same time, its surface tension above CMC decreases from about 38 mN/m at 20 ºC to about 12 mN/m at 80 ºC (Mohajeri and Noudeh, 2012). These data support the hypothesis that the increasing interfacial activity of polysorbate 20 promotes the continuation of the emulsification phenomena with temperature ramping, indirectly confirming the loss of the lipid structure previously hypothesized.…”
“…These NMR experiments were done at 50°C. Increasing the solution temperature from 5°C to 50°C decreases the CMC of polysorbates (from 90 μM to 48 μM (1.9 times) for PS20, and from 36 μM to 12 μM (3 times) for PS80) 34 . Since CMC defines the maximum monomer concentration possible at equilibrium under micelle forming conditions and since CMC decreases with temperature, the K d values at 50°C will be higher than those measured by ITC at 5°C 35 , which implies that the polysorbate-bound protein population will be lower at 50°C under NMR conditions compared to that at 5°C.…”
We examined how polysorbate 20 (PS20; Tween 20) and polysorbate 80 (PS80; Tween 80) affect the higher order structure of a monoclonal antibody (mAb) and its Fab and Fc fragments, using near-UV circular dichroism and 2D NMR. Both polysorbates bind to the mAb with sub-millimolar affinity. Binding causes significant changes in the tertiary structure of mAb with no changes in its secondary structure. 2D 13C-1H methyl NMR indicates that with increasing concentration of polysorbates, the Fab region showed a decrease in crosspeak volumes. In addition to volume changes, PS20 caused significant changes in the chemical shifts compared to no changes in the case of PS80. No such changes in crosspeak volumes or chemical shifts were observed in the case of Fc region, indicating that polysorbates predominantly affect the Fab region compared to the Fc region. This differential effect of polysorbates on the Fab and Fc regions was because of the lesser thermodynamic stability of the Fab compared to the Fc. These results further indicate that PS80 is the preferred polysorbate for this mAb formulation, because it offers higher protection against aggregation, causes lesser structural perturbation, and has weaker binding affinity with fewer binding sites compared to PS20.
“…After storage for three months at room temperature there was no remarkable change in internal and external phase, which may leads to temporary aggregation and increase in droplets size [28].…”
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