Self-assembly of cyclodextrins at the oil-water interface: surfactant-free emulsions and cyclodextrinosomes
April 3-7, 2016
We explored the self-assembly of cyclodextrins (CDs) at the oil-water interface through the formation of inclusion complexes (ICs) with the oil and further assemble into microcrystals at the oil-water interface[1-4]. We demonstrate the spontaneous formation of a dense layer of adsorbed CD-tetradecane IC microcrystals at the tetradecane-water interface whose morphology and size are dependent on the type of CD and oil used. At large oil volume fractions, this phenomenon led to the formation of a Pickering type of oil-in-water emulsion stabilised by adsorbed CD-oil microcrystals while at low oil volume fractions it completely solubilises the oil in the form of IC microcrystals. We also report the preparation of o/w emulsions stabilised by microcrystals of cyclodextrin-oil inclusion complexes. The inclusion complexes are formed by threading cyclodextrins from the aqueous phase on n-tetradecane or silicone oil molecules from the emulsion drop surface which grow further into microrods and micro-platelets depending on the type of cyclodextrin. These microcrystals remain attached at the surface of the emulsion drops and form densely packed layers. The novelty in this emulsion stabilisation mechanism is that molecularly dissolved cyclodextrin from the continuous aqueous phase is assembled into colloid particles directly onto the emulsion drop surface, i.e. molecular adsorption leads to effective Pickering stabilisation. The β-CD stabilised tetradecane-in-water emulsions were so stable that we used them as templates for preparation of cyclodextrinosomes after the removal of the core oil. We also report the preparation of CD-stabilized emulsions with a range of other oils and studied the effect of the salt concentration in the aqueous phase, the type of CD and the oil volume fraction on the type of emulsion formed. The CD-stabilized emulsions and cyclodextrinosomes can find applications in a range of surfactant-free formulations in cosmetics, home and personal care, and in pharmaceutical formulations as drug delivery vehicles.
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Vesselin N. Paunov and Baghali Mathapa, "Self-assembly of cyclodextrins at the oil-water interface: surfactant-free emulsions and cyclodextrinosomes" in "Design and Manufacture of Functional Microcapsules and Engineered Products", Chair: Simon Biggs, University of Queensland (Aus) Co-Chairs: Olivier Cayre, University of Leeds, UK Orlin D. Velev, North Carolina State University, USA Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/microcapsules/23
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