PHA based Core Sheath Fibrous Structures for Healthcare Engineering

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PHAs are FDA approved polymers produced by bacteria under nutrient limiting conditions using renewable carbon sources. There are two types of PHAs (Figure 1), short chain length PHAs, scl-PHAs, (C3-C5 units) such as P(3HB) and medium chain length PHAs, mcl-PHAs, (C6-C16 units) such as P(3HO-co-3HD). The degradation products of PHAs are much less acidic than those of PLA and PLGA, and are natural metabolites, hence PHAs are less inflammatory and immunogenic in nature. Also, PHAs degrade by surface erosion and therefore PHA-based scaffolds degrade in a controlled predictable manner, a great advantage as compared to PLA and PLGA that degrade by bulk erosion. Another advantage of using PHAs is the tuneability of their properties. By varying the bacterial strain/carbon source/media composition/fermentation conditions during production, the PHA monomer content and consequently their material properties and degradability can be tailored. A relatively novel technology for polymer fibre technology is the development of core-sheath fibres using pressurised gyration (PG). This technology allows the production of core-sheath bicomponent polymer fibres in a single-step with scale-up possibilities (~4 kg h-1). Layered fibres are formed where the thin sheath can contain a functional polymer and the core can be a more traditional strength-bearing biopolymer.There are many biomedical applications that require non-woven fibre-based sheets/scaffolds such as wound healing patches, cardiac patches, periosteum replacements, heart valves, hernia meshes, meshes for urinary incontinence, maxillofacial replacements. In this project the production of a range of PHA-based core-sheath fibre sheets will be optimised and their use in a variety of applications, including bone, skin and cardiac TE will be established.