Preparation And Characterization Of Bioactive Delivery Systems Based On Gemini Alkyl O-glucoside Surfactants And Ovalbumin

In this work,a series of bioactive delivery systems,such as micelle,niosome,polymer-coated niosome,nanoparticle,nanogel,and emulsion were prepared,employing gemini alkyl O-glucoside surfactants and ovalbumin as main wall materials.The loading capacity of these delivery systems for bioactives such as curcumin,catechin laurates,and fish oil was investigated.The modulating effects of these delivery systems on the stability and functionality of bioactives was evaluated and the related mechanism was discussed.The main results were addressed below.1.Gemini alkyl O-glucoside surfactant/quaternary ammonium surfactants mixed micelles were prepared and improvement of trianionic curcumin(Cur^3-)stability via mixed micelle encapsulation was evaluated.Results suggested that mixed micelles tend to form a more compact and hydrophobic palisade layer than quaternary ammonium surfactant micelles.Additionally,the stronger hydrophobic interaction while weaker electrostatic interaction allowed Cur^3-to locate more deeply in the palisade layer of mixed micelles than that in the palisade layer of quaternary ammonium surfactant micelles.Consequently,mixed micelles were more effective in shielding Cur^3-from the external environment and blocking its degradation.2.The loading capacity of gemini dodecyl O-glucoside?Gemini-C12?-based niosome for catechin laurates was evaluated as well as the effect of niosome encapsulation on the antioxidant activity of catechin laurates.Results revealed that niosome displayed high loading capacity for catechin laurates as they adopted a vertical orientation in the vesicle membrane.Catechin laurates stiffened the niosome bilayer and improved the main phase transition temperature at low concentrations but created a remarkable increase in the membrane fluidity afterward.Compared with free catechins,encapsulated catechin laurates exhibited higher lipid-oxidation inhibitory capacity because they preferentially concentrated in the liposome membrane.3.Stable sodium carboxymethyl cellullose?CMC-Na?coated niosome were successfully prepared through an electrostatic deposition method and the effect of CMC-Na decoration on the stability of niosome was investigated.The thermodynamic parameters suggested that the binding process was entropy driven and energetically favourable.The concentration of polyelectrolyte required to afford secondary niosomes with small size and finer stability was estimated by an empirical model and was found to be in excellent agreement with our experimental results.CMC-Na decoration improved the stability of niosome under pH variation,thermal treatment,and osmotic stress,it also improved the retention rate of core agent during heat treatment.4.The interaction between thermally denatured ovalbumin?OVA?and Gemini-C12 was characterized and the modulating effects of Gemini-C12 concentration on the properties of gliadin nanoparticles stabilized by OVA-Gemini-C12 complex was investigated.When the concentration of Gemini-C12 below critical micelle concentration?CMC?,Gemini-C12 could decrease the interfacial tension and enhance the adsorption strength of OVA on particle surface,thereby increasing the nucleation rate and giving gliadin nanoparticles with smaller size.Besides,the monomeric cosurfactant could plug the vacancies left by OVA at solid-liquid interface and therefore prohibit the aggregation and agglomeration of gliadin nanoparticles during storage and freeze-drying.Above CMC,free micelles were formed in the bulk and the surfactant molecules tended to reside in micelles rather than be adsorbed at the solid-liquid interface,resulting in gliadin nanoparticles with larger size and lower storage stability and redispersibility.5.Ovalbumin-dextran nanogels were fabricated via the Maillard reaction followed by a heat-gelation process and their potential to improve curcumin bioavailability was investigated using an in vitro gastrointestinal tract.Nanogels displayed a spherical structure with finer pH stability,storage stability,and redispersibility.Curcumin was loaded into nanogels by a pH-driven method and the incorporation of curcumin affected the morphology of nanogels marginally.Both the transformation and bioaccessibility of curcumin were improved via nanogel and nanoparticle encapsulation.The transformation of curcumin in nanogels was significantly higher than that in ovalbumin nanoparticle.On the other hand,the bioaccessibility was similar for curcumin in nanogels and nanoparticle,which would arise from the fact that nanogels and nanoparticles adopted fairly similar characteristics after simulated digestion.6.Conjugates of ovalbumin with catechins were synthesized through a free radical grafting approach and the stabilizing effect of ovalbumin and conjugates on fish oil emulsion was evaluated.The antioxidant activity of ovalbumin was appreciably improved via catechin grafting due to the introduction of large amount of phenolic hydroxyl group.The catechin-grafting reaction altered the secondary structure of ovalbumin and improved its surface hydrophobicity and tertiary flexibility.Compared with that emulsified by OVA,fish oil emulsion coated by conjugates showed smaller droplet size,better storage stability,less viscosity and enhanced oxidative stability.In general,the lipid oxidation was pH-dependent,being more pronounced at pH 7.0 than at pH 3.5 for all emulsions,which might arise from the repulsion of transition metals by positively charged lipid droplets at pH 3.5.