Abstract
Electrostatic 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.
Highlights
Proteins and polysaccharides are polymers ubiquitous in nature
We investigate the impact of applying ultrasound to pre-formed insoluble macroscopically phase separated protein-chitosan complexes initially formed under low shear
This work demonstrates the use of protein-chitosan complexes for encapsulation and delivery of active compounds
Summary
Proteins and polysaccharides are polymers ubiquitous in nature Research into how they interact, in addition to their behaviours at surfaces and interfaces, has long been undertaken (Dickinson, 2006; Rodríguez Patino & Pilosof, 2011). Controlling the type and relative magnitude of these forces enables production of a wide range of material properties, and potentially, the prospect of physically compartmentalising compounds (i.e. functional ingredient encapsulation), a feature often considered desirable for functional food, pharmaceutical, and agrochemical formulation design (Chen, Remondetto, & Subirade, 2006; Hack et al 2012; Madene, Jacquot, Scher, & Desobry, 2006). Whilst it is recognised that such interactions impart many of the functional properties of foods, further research is required to develop uses in encapsulation and targeted delivery of active ingredients. “Active ingredients” in the broadest sense include crop protection products, pharmaceuticals, and nutrients
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