Tuneable Control of Interfacial Rheology and Emulsion Coalescence

Malcolm, Andrew S.; Dexter, Annette F.; Katakdhond, Jayant A.; Karakashev, Stoyan I.; Nguyen, Anh V.; Middelberg, Anton P. J.

doi:10.1002/cphc.200900023

Cited by 33 publications

(43 citation statements)

References 24 publications

(27 reference statements)

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“…These states can be interconverted by simple manipulation of pH or metal ion concentration (Dexter et al, 2006;Dexter and Middelberg, 2007). Malcolm et al (2009) have examined these peptide surfactants in a microfluidic device and have shown triggered control of coalescence, which was also related to changes in the rupture behavior of the thin film between interfaces. This novel interfacial rheology control offers a new strategy for controlling the stability of emulsions or foams, and also affords a new level of control over droplet coalescence in microfluidic devices.…”

Section: Interfacial Rheology Controlmentioning

confidence: 98%

Two-phase microfluidic flows

Zhao

Middelberg

2011

Chemical Engineering Science

342

201

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Section: Interfacial Rheology Controlmentioning

confidence: 98%

Two-phase microfluidic flows

Zhao

Middelberg

2011

Chemical Engineering Science

342

201

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“…Loss of film cross-linking resulted in rapid emulsion coalescence or foam collapse. 18,19,191,192 Neutron reflectometry showed AM1 concentration at the interface is not significantly altered by film formation or loss. This indicated that the switching of emulsion and foam stabilisation is due to loss of the mechanical properties of the interfacial film rather than surfactant desorption.…”

Section: Surfactantsmentioning

confidence: 95%

“…132 The surfactant properties of a series of reversibly cross-linkable α-helical peptides based on the sequence of Lac21 has been well studied, predominantly by the Middelberg group. 18,19,191,192 Peptide AM1 was designed based on the sequence of Lac21, where residues 9 and 20 were replaced with histidine 24 residues. 18,191 This positioning leaves the histidine residues facing the aqueous phase, but oriented towards neighbouring helices at the interface.…”

Section: Surfactantsmentioning

confidence: 99%

“…19 Under identical crosslinking conditions AFD4 gave stronger interfacial films and improved emulsion and foam stability compared to AM1. 19,192 Film formation by both AM1 and AFD4 was reversible through the addition of chelating agents or lowering pH to inhibit intramolecular crosslinking. Loss of film cross-linking resulted in rapid emulsion coalescence or foam collapse.…”

Section: Surfactantsmentioning

confidence: 99%

“…This indicated that the switching of emulsion and foam stabilisation is due to loss of the mechanical properties of the interfacial film rather than surfactant desorption. 18,19,192 The functionality of α-helical surfactant peptides possessing a high carboxylate content has also been investigated. The peptide Lac21E was designed based on the Lac21 sequence, 193 with the substitution of glutamate at positions 2, 3, 9, 10, 16 and 17 that are oriented towards bulk aqueous solution.…”

Section: Surfactantsmentioning

confidence: 99%

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Bioproduction and self-assembly of designer peptides

Fletcher¹

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Self-assembly is a powerful method for producing controlled morphologies at the nanometre scale. Peptides are biomolecules capable of self-assembly and have the potential for use in a variety of applications such as emulsion and foam stabilisation, wound healing and drug delivery. The investigation of peptide sequence-structure relationships is a rapidly advancing field of study, which in many cases now allows the targeted design of self-assembling peptides.While self-assembling peptides show potential in several fields, their large-scale adoption is limited by the high production expenses associated with conventional solid-phase synthesis. A potentially cheaper and more renewable approach to peptide production is bacterial expression. However, the bioproduction of peptides is a non-trivial process, and generally involves the expression of peptides as part of a fusion protein in which the target peptide is only a small portion of the expressed product. An alternate approach involves peptide concatemers, in which the target peptide makes up the majority of the expressed construct.The work reported in this thesis focused on the design, characterisation and bioproduction of self-assembling α-helical peptides. It was particularly focussed on the development of amphiphillic α-helical peptides with applications as surfactants and hydrogelators. The aim of this work was to further the field of de novo peptide design, while also investigating an approach for peptide bioproduction. This work aimed to combine the requirements for peptide bioproduction with end-use functionality.Chapter 2 details successful bioproduction of an anionic helical surfactant peptide EDP-11, as part of a charge-paired heteroconcatemer with the cationic expression partner RDP-4. The method utilised designed assembly of the constituent α-helical peptides to generate a stably folded coiled-coil concatemer. The polypeptide sequence was further optimized for molecular charge, hydropathy and predicted protease resistance. This process allowed expression of a soluble concatemer that accumulated to high levels (22% of total protein) in E. coli. The expressed concatemer possessed extreme stability to heat and proteases, allowing isolation by simple heat and pH precipitation, yielding concatemer at 130 mg per gram of dry cell weight and >99% purity. Key parameters used in designing the heteroconcatemer were then compared to those of all open reading frames of several reference ii proteomes in an attempt to gain insight into the mechanistic basis for the high stability of the designed miniprotein.Following bioproduction using this concatemer approach, further processing was required to produce monomeric peptides for use in surfactant applications. The design of acid-cleavable aspartate-proline sites within the concatemer sequence allowed for simple heat-and acid-mediated cleavage to give constituent peptides.Chapter 3 details characterization of cleavage of the expressed concatemer by coupled liquid chromatography-mass spectrometry and includes mod...

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Effects of fluid-fluid interfacial elasticity on droplet formation in microfluidic devices

et al. 2010

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in Wiley Online Library (wileyonlinelibrary.com).Biomolecules adsorb at fluid-fluid interfaces and can form a cohesive interfacial network imparting distinctive local interfacial mechanics. This modification of interfacial behavior is empirically known to significantly affect the stability and flow behavior of foams and emulsions. Droplet formation in the presence of interfacial networks is investigated in a flow-focusing microfluidic device using designed peptide surfactants, which allow decoupled control of interfacial rheology and interfacial tension. The influence of interfacial elasticity on droplet breakup, satellite droplet formation and droplet size are reported. The presence of high interfacial elasticity strongly affects the mechanism of droplet breakup by delaying neck thinning and altering interfacial shape at the point of droplet detachment, resulting in the suppression of satellite droplet formation and a decrease in droplet size. We report a correlation between dimensionless droplet size and a new dimensionless grouping which combines flow-rate ratio with the ratio of interfacial tension and interfacial elasticity.

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Tuneable Control of Interfacial Rheology and Emulsion Coalescence

Cited by 33 publications

References 24 publications

Two-phase microfluidic flows

Two-phase microfluidic flows

Bioproduction and self-assembly of designer peptides

Effects of fluid-fluid interfacial elasticity on droplet formation in microfluidic devices

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