Zhou, Yansheng; (2024) Design strategies of PHB/chitosan based electrospun nanofibrous scaffolds in promising biomaterial. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

In recent years, the development of promising biomaterials that can stimulate tissue regeneration has become increasingly important, particularly in addressing Peripheral Nerve Injury (PNI). This condition, known for causing loss of nerve function, has garnered significant attention. Over the past two decades, research has progressively led to the discovery and advancement of novel, natural-based polymeric materials. These materials are used to construct scaffolds to tackle PNI challenges. The focus of this research is on the design of promising natural-based polymers, specifically Polyhydroxybutyrate (PHB) and chitosan (CS), for application in tissue implants. The study is divided into three distinct sections: an analysis of the stability of PHB/CS electrospun composites across various pH levels, surface modifications of PHB electrospun membrane to improve CS adhesion, and the study of forskolin release from polyethylene oxide (PEO) to PHB/CS co-electrospun fibre. This research presents an innovative approach and the potential application of PHB/CS natural-based polymeric scaffolds in tissue engineering. In the chapter on PHB/CS electrospun membrane fabrication, a first-time examination compares electrospinning process parameters and solution properties. Key factors such as applied voltages, working distances, flow rates, solvent types, viscosity, and conductivity are explored. Results indicate that trifluoracetic acid (TFA) and chloroform/dimethylformaldehyde (CF/DMF) effectively dissolve PHB. A crucial finding is that increasing PHB concentration to a 2:30 mass ratio initiates fibre electrospinning. SEM analysis shows uniform fibres are produced at PHB and CS ratios of 2:30 and 1:50, respectively. Optimal fabrication conditions are identified as voltages of 10 to 12 kV, flow rates between 1 to 1.25 ml/h, and working distances of 16 to 22 cm, enabling successful uniform fibre production. In the chapter examining the stability of PHB/CS under varying pH conditions, the materials demonstrated accelerated degradation in both acidic sodium lactate/HCl and alkaline NaOH solutions. Among three different mass ratios of CS (0, 1:100, and 1:50 m/m), the 1:50 m/m ratio exhibited the quickest degradation, followed by 1:100 and 0. In the chapter analyzing the adhesive properties of CS on PHB modified with potassium hydroxide (KOH) or hydrogen peroxide (H2O2) surface treatments, it was found that CS of varying concentrations successfully chemically bonded with PHB electrospun fibres. Notably, the adhesion in KOH-treated samples was 23% higher compared to H2O2-treated samples. In the chapter on the drug-release profile of PHB/CS, Forskolin-loaded PEO was electrospun with PHB/CS using different CF/DMF ratios in both single-jet and co-electrospinning techniques. The study revealed that a 10 w/v% PEO co-electrospun with an 8:2 CF/DMF volume ratio maintained a consistent release over 144 days with minimal pH change (pH=6.5 post-degradation). These findings suggest that PHB/CS electrospun membranes hold significant potential as tissue implant materials. Future research will delve into more comprehensive in vitro biocompatibility assessments and in vivo studies.

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