We 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 microplatelets depending on the type of cyclodextrin (CD) used. These microcrystals remain attached on the surface of the emulsion drops and form densely packed layers which resemble Pickering emulsions. The novelty of 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 this system as a template for preparation of cyclodextrinosomes. These structures were produced solely through formation of cyclodextrin-oil inclusion complexes and their assembly into a crystalline phase on the drop surface retained its stability after the removal of the core oil. The structures of CD-stabilised tetradecane-in-water emulsions were characterised using optical microscopy, fluorescence microscopy, cross-polarised light microscopy and WETSEM while the cyclodextrinosomes were characterised by SEM. We also report the preparation of CD-stabilised emulsions with a range of other oils, including tricaprylin, silicone oil, isopropyl myristate and sunflower oil. We 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-stabilised emulsions can be applied in a range of surfactant-free formulations with possible applications in cosmetics, home and personal care. Cyclodextrinosomes could find applications in pharmaceutical formulations as microencapsulation and drug delivery vehicles.

We investigated the self-assembly of cyclodextrin (CD) molecules at the tetradecane-aqueous solution interface through formation of inclusion complexes (ICs). We studied the surface activity of CDs at both the air-water and the oil-water interface. Although a-CD and b-CD are not surface active at the air-water interface, they form pseudo-surfactants as inclusion complexes with linear oil molecules at the oil-water interface. We discussed the factors affecting the formation of these ICs and their assembly into microcrystals at the oil-water interface. We discovered that the morphology and the size of the aggregates formed by these ICs are dependent on the type of CD and oil used. Lamella sheets and long microrods were obtained from a-CD molecules and tetradecane. In contrast, b-CD-tetradecane gave short microrods which assembled in microcrystals. We characterised the CD-tetradecane ICs using optical microscopy, SEM, TEM and FT-IR. The crystallinity of the ICs was assessed using cross-polarised light microscopy. We demonstrated the spontaneous formation of a dense layer of adsorbed CD-tetradecane IC microcrystals at the tetradecane-water interface. 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. This emulsion stabilisation mechanism with sustainable materials like CDs may find applications in surfactant free pharmaceutical and cosmetic formulations reducing the release of surfactants in the environment.

We report the fabrication of novel microcapsules with membranes of co-polymerised cyclodextrin (CD) and polyallylamine hydrochloride (PAH) which allows control of the membrane pore size depending on the type of CD used. The microcapsules were produced by interfacial cross-linking reaction of PAH and CDs with epichlorohydrin (EP) on the surface of oil-in-water emulsion templates. Our approach utilises the ability of the CD to form surface active inclusion complexes with inert linear oil molecules at the interface of the emulsion drops. The reaction was conducted with both CD and PAH adsorbing from the aqueous phase and the EP cross-linker coming from the oil phase, followed by the removal of the oil phase by solvent extraction. We demonstrated that the membrane properties can be tuned by choosing the type of oil used. We obtained hard and brittle CD-PAH co-polymeric shells by using silicone oil-in-water emulsions as sacrificial templates and soft deformable CD-PAH microcapsule membranes by templating tetradecane-in-water emulsions. The average microcapsule diameter reflected the emulsion drop size distribution and ranged between 20 and 65 micrometres. We also created CD-PAH Janus microcapsules containing both oil and void compartments which can be loaded simultaneously with both hydrophilic and hydrophobic payloads. We assessed the microcapsule morphology by optical microscopy and SEM and confirmed the inclusion of cyclodextrin into their membranes by FT-IR spectroscopy. We also studied the release kinetics of a model active component encapsulated in such CD-PAH microcapsules. Such microcapsules could find pharmaceutical and cosmetic applications as drug delivery vehicles and slow release formulations.

We describe two alternative methods for surface functionalisation of Saccharomyces cerevisiae cells with cyclodextrin molecules without affecting the cell viability. The first strategy involved using epichlorohydrin as a cross-linking agent which binds covalently the cyclodextrin to the glycoproteins on the cell wall. The second strategy of interfacing of the cells with CD involved polyelectrolyte mediated deposition of cyclodextrin sulphate on the cell surface. We used the formation of host-guest inclusion complex of a dye with the grafted cyclodextrins to estimate the average number of CD molecules grafted per cell which can reach up to hundreds of millions of CD molecules. This indicates more than one monolayer of CDs on the cell surface within the surface layer surrounding the yeast cell membrane. Fluorescein diacetate was used to check the viability of the cells after functionalisation. Living cells functionalised with CDs may find many potential applications as they can be loaded with drugs, immunosuppressants and other molecules forming inclusion complexes with their cyclodextrin interface. Therefore, we foresee such cells being used as novel selective biosorbents in polluted waters, whole cell biosensors, drug delivery, cell therapy and cell implants applications. 65 functionalised cells are filtrated from the solution. The advantage of using EP as a cross-linker for CD is that the reaction can be 65

We have fabricated nanoporous polyallylamine hydrochloride (PAH)-cyclodextrin co-polymeric microspheres using epichlorohydrin as a cross-linking agent. The structure and morphology of the microspheres were studied by optical and electron microscopy and FT-IR spectrometry was used to confirm the presence of cyclodextrin in the co-polymer. The encapsulating capability of these molecularly porous microspheres was tested by loading them with two fluorescing dyes whose localization within the microspheres was examined by Laser Scanning Confocal Microscopy (LSM). We tested the capacity of the microspheres to remove surfactants such as cetyltrimethyl ammonium bromide (CTAB), Sodium Dodecyl Sulphate (SDS) and organic dyes like Indophenol Blue from aqueous solutions. These results were confirmed using surface tension measurements and UV-vis spectroscopy. The CD-copolymeric microspheres showed significant capacity for encapsulation of molecules of varying polarities and different hydrophobicities, which makes them attractive for applications in a wide range of areas such as agrochemicals, water purification, pharmaceuticals, drug delivery, separation science and cosmetics.