Structural Studies of Nonionic Dodecanol Ethoxylates at the Oil–Water Interface: Effect of Increasing Head Group Size

Campana, Mario; Webster, John R. P.; Zarbakhsh, Ali

doi:10.1021/la502559r

Cited by 9 publications

(5 citation statements)

References 25 publications

(54 reference statements)

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“…While the textbooks and review articles also show the surfactants and co-surfactants forming a monolayer at the surfaces of the oil droplets in a cream, we show here that this interfacial layer is very diffuse, suggesting that it is significantly roughened, with the constituent molecules not aligned but staggered. Again, this is entirely consistent with the observations made by Zarbakhsh et al 22,39,40,42,43 wherein the surfactant and lipid layers that form at oil-water interfaces are shown to exhibit a pronounced roughening which cannot be explained simply by thermal broadening and is considered to arise instead because of a staggering of the molecules' hydrocarbon chains brought about by their dissolution within the oil and the resultant disruption of their side-by-side packing.…”

Section: Discussionsupporting

confidence: 90%

Revealing the Hidden Details of Nanostructure in a Pharmaceutical Cream

Ahmadi

Mahmoudi

et al. 2020

Sci Rep

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Creams are multi-component semi-solid emulsions that find widespread utility across a wide range of pharmaceutical, cosmetic, and personal care products, and they also feature prominently in veterinary preparations and processed foodstuffs. The internal architectures of these systems, however, have to date been inferred largely through macroscopic and/or indirect experimental observations and so they are not well-characterized at the molecular level. Moreover, while their long-term stability and shelflife, and their aesthetics and functional utility are critically dependent upon their molecular structure, there is no real understanding yet of the structural mechanisms that underlie the potential destabilizing effects of additives like drugs, anti-oxidants or preservatives, and no structure-based rationale to guide product formulation. In the research reported here we sought to address these deficiencies, making particular use of small-angle neutron scattering and exploiting the device of H/D contrast variation, with complementary studies also performed using bright-field and polarised light microscopy, smallangle and wide-angle X-ray scattering, and steady-state shear rheology measurements. through the convolved findings from these studies we have secured a finely detailed picture of the molecular structure of creams based on Aqueous Cream BP, and our findings reveal that the structure is quite different from the generic picture of cream structure that is widely accepted and reproduced in textbooks. Oil-in-water creams are widely used in pharmaceutical products formulated to treat conditions like atopic dermatitis, rosacea and psoriasis 1. They also form the basis of veterinary medications used to assist wound-healing and treat skin infections 2 , and they are the basis too of a great many personal care products, spanning make-up foundations, anti-perspirants, sun lotions and deodorants 3. All such products are complex, multi-component colloids in which the constituent oil and water phases are stabilised through the addition of one or more ionic, non-ionic or zwitterionic surfactants, in combination with one or more co-surfactants (sometimes referred to as consistency enhancers) which might be long chain fatty acids, fatty alcohols or monoglycerides 4,5. Other components which might be added include humectants such as propylene glycol, anti-oxidants like α-tocopherol acetate, and preservatives like phenoxyethanol 6. The molecular architecture of any given cream formulation will clearly vary according to its chemical composition, and this in turn will determine its chemical and physical stability, and also impact the cream's sensory aesthetics and efficacy as a cosmetic, pharmaceutical, or veterinary product. Despite much research into the properties of creams and their many years of use, however, our understanding of their internal molecular structure is still far from complete, with the unavoidable consequence, therefore, that they are still formulated only in a semi-empirical manner. Junginger and co-workers 7 ...

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Section: Discussionsupporting

confidence: 90%

Revealing the Hidden Details of Nanostructure in a Pharmaceutical Cream

Ahmadi

Mahmoudi

et al. 2020

Sci Rep

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“…However, maintaining a constant oil film thickness was a challenging task, and the methodology was applicable only to volatile oils. In recent years, an alternative methodology has been developed to control the oil via film coating, allowing more systematic studies of surfactant adsorption at the oil/water interface. − To avoid drastic attenuation of the neutron beam upon traversing the oil phase, a thin oil (hexadecane) layer is coated and then sandwiched between a silicon substrate and the aqueous phase. However, reflectivity from the silicon/oil interface interferes with that from the oil/water interface and must thus be minimized by matching the scattering length density (SLD or Nb ) of the oil to that of silicon.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Bovine Serum Albumin (BSA) at the Oil/Water Interface: A Neutron Reflection Study

Campana

Hosking

Petkov³

et al. 2015

Langmuir

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The structure of the adsorbed protein layer at the oil/water interface is essential to the understanding of the role of proteins in emulsion stabilization, and it is important to glean the mechanistic events of protein adsorption at such buried interfaces. This article reports on a novel experimental methodology for probing protein adsorption at the buried oil/water interface. Neutron reflectivity was used with a carefully selected set of isotopic contrasts to study the adsorption of bovine serum albumin (BSA) at the hexadecane/water interface, and the results were compared to those for the air/water interface. The adsorption isotherm was determined at the isoelectric point, and the results showed that a higher degree of adsorption could be achieved at the more hydrophobic interface. The adsorbed BSA molecules formed a monolayer on the aqueous side of the interface. The molecules in this layer were partially denatured by the presence of oil, and once released from the spatial constraint by the globular framework they were free to establish more favorable interactions with the hydrophobic medium. Thus, a loose layer extending toward the oil phase was clearly observed, resulting in an overall broader interface. By analogy to the air/water interface, as the concentration of BSA increased to 1.0 mg mL(-1) a secondary layer extending toward the aqueous phase was observed, possibly resulting from the steric repulsion upon the saturation of the primary monolayer. Results clearly indicate a more compact arrangement of molecules at the oil/water interface: this must be caused by the loss of the globular structure as a consequence of the denaturing action of the hexadecane.

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“…A recent study indicated that mAbs and nonionic surfactants might co-adsorb at the oil/water interface. 17 It is useful to understand how mAbs and surfactants adsorb alone 18 and as a mixture at the silicone oil/water interface and how the interfacial adsorption processes impact the structure of the adsorbed mAb molecules. This insight could help optimize formulation design and/or surface treatments.…”

Section: Introductionmentioning

confidence: 99%

Competitive Adsorption of a Monoclonal Antibody and Nonionic Surfactant at the PDMS/Water Interface

Shen

et al. 2023

Mol. Pharmaceutics

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Interfacial adsorption of monoclonal antibodies (mAbs) can cause structural deformation and induce undesired aggregation and precipitation. Nonionic surfactants are often added to reduce interfacial adsorption of mAbs which may occur during manufacturing, storage, and/or administration. As mAbs are commonly manufactured into ready-to-use syringes coated with silicone oil to improve lubrication, it is important to understand how an mAb, nonionic surfactant, and silicone oil interact at the oil/water interface. In this work, we have coated a polydimethylsiloxane (PDMS) nanofilm onto an optically flat silicon substrate to facilitate the measurements of adsorption of a model mAb, COE-3, and a commercial nonionic surfactant, polysorbate 80 (PS-80), at the siliconized PDMS/water interface using spectroscopic ellipsometry and neutron reflection. Compared to the uncoated SiO 2 surface (mimicking glass), COE-3 adsorption to the PDMS surface was substantially reduced, and the adsorbed layer was characterized by the dense but thin inner layer of 16 Å and an outer diffuse layer of 20 Å, indicating structural deformation. When PS-80 was exposed to the pre-adsorbed COE-3 surface, it removed 60 wt % of COE-3 and formed a co-adsorbed layer with a similar total thickness of 36 Å. When PS-80 was injected first or as a mixture with COE-3, it completely prevented COE-3 adsorption. These findings reveal the hydrophobic nature of the PDMS surface and confirm the inhibitory role of the nonionic surfactant in preventing COE-3 adsorption at the PDMS/water interface.

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Structural Studies of Nonionic Dodecanol Ethoxylates at the Oil–Water Interface: Effect of Increasing Head Group Size

Cited by 9 publications

References 25 publications

Revealing the Hidden Details of Nanostructure in a Pharmaceutical Cream

Revealing the Hidden Details of Nanostructure in a Pharmaceutical Cream

Adsorption of Bovine Serum Albumin (BSA) at the Oil/Water Interface: A Neutron Reflection Study

Competitive Adsorption of a Monoclonal Antibody and Nonionic Surfactant at the PDMS/Water Interface

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