Fabrication of sub-micron protein-chitosan electrostatic complexes for encapsulation and pH-Modulated delivery of model hydrophilic active compounds

AbstractElectrostatic sub-micron complexes of a protein (sodium caseinate (NaCAS) or bovine serum albumin (BSA)) and a polysaccharide (chitosan) were fabricated by associative phase separation and investigated for use in encapsulation and pH-triggered delivery applications. Various factors have been studied with respect to the extent of complexing and the size and morphology of the complexes produced, including protein type and the biopolymer mixing ratio. The effect of applying ultrasound has been considered with a view to comminuting precipitates produced under low shear to the colloidal scale to form coacervates. A simple model is suggested to explain how the biopolymer mixing ratio influences the ability for application of ultrasound to convert macroscopically phase-separated complex precipitates into coacervates. Different factors, both from a formulation and processing viewpoint, were studied with respect to encapsulation efficiency (EE) of model hydrophilic actives: fluorescein, rhodamine B, and riboflavin. Release of fluorescein and rhodamine B was measured as function of pH in order to investigate the pH-responsive molecular release capability of the fabricated structures. It is envisaged this work will add to the current tool-box of pH-responsive molecular delivery approaches, including those in the areas of foods, pharmaceuticals, and agrochemicals

Food-grade Pickering emulsions stabilised with solid lipid particles

Aqueous dispersions of tripalmitin particles (with a minimum size of 130 nm) were produced, via a hot sonication method, with and without the addition of food-grade emulsifiers.</p

Design and development of emulsions for encapsulation and molecular delivery applications

The design and development of smart colloidal structures intended for molecular encapsulation and delivery of functional molecules is an area of intense academic and industrial interest. A major part of this area is focussed on stimulating molecular release using an external stimulus such as pH or temperature. Whilst controlled delivery technologies are a mainstay of the pharmaceutical industry, aligned industries that utilise formulation to deliver functional molecules are also targets for encapsulation technology implementation. This can be a key driver for ameliorating competition from generic manufacturers, as any resulting can patent protection can be applied to the formulation. Current approaches in colloidal encapsulation and molecular delivery have mainly been concerned with encasing and subsequent release of a single functional molecule. However, there is interest in being able to structure two or more functional molecules within a “simple” emulsion microstructure for dual release over different timescales. Within colloid science, emulsions offer significant potential in this area due to the potential for compartmentalisation within the multiphase components. This thesis focuses on the design and development of Pickering emulsions structured with two actives segregated within their microstructure. This was achieved through the fabrication of colloidal Pickering particles designed with the dual purpose of being both emulsion stabilisers and molecular carriers. The work ultimately combines colloid structure design, development and characterisation with molecular encapsulation and release studies