The focus of this MPhil project is the isolation of keratin from hair and wool by using two different methods in order to obtain keratin in sufficient quantity and quality to synthesise hydrogels using the reactivity of thiol groups in keratin (Michael addition reactions), as well as some preliminary works for gel casting by photo-crosslinking reactions and 3D printing. This thesis includes four chapters briefly introduced below.
Chapter 1 introduces the main topics covered in this thesis by providing a quick definition of the concepts concerning polymer chemistry, natural polymers and hydrogels. In addition, a review of the literature follows this section by referring to the most relevant works published with regards to the natural occurrence, properties and isolation methods of keratin. Finally, the chapter presents the applications of keratin in the biomedical sector, describing some of the derived materials that can be obtain from keratin.
Chapter 2 reports the methodology implemented in this thesis. The methods include two isolation procedures by using reducing agents (Na2S method) and denaturing agents (Shindai). The experimental procedures for the synthesis of hydrogels by Michael addition reactions, photo-crosslinking reactions and early work on gel casting by 3D-prining are described in this chapter. Furthermore, the analytical techniques used to characterise the obtained products are also covered.
Chapter 3 details the results obtained from the experimental work along with a discussion explaining the observations made on the data obtained with regards to the keratin isolated from wool and hair from reduction with Na2S and Shindai method. The implications of these isolation methods are discussed along with the determination of the solubility of the keratins, their molecular weight by GPCGPC and thiol content by Ellman’s assay. Fundamental characterisation of the extracted keratins by NMR, FTIR and UV-vis spectroscopy are also discussed in this chapter. Similarly, for the synthesis of the keratin-based hydrogels by Michael addition reactions the morphology observed by SEM as well as some visual observations made on the obtained gels are explained in terms of the properties imparted by the acrylates/methacrylates keratin was combined with (PEG-DA, Soybean oil epoxidised acrylate and methacrylated alginate). Subsequently, the discussion moves on the photo-crosslinking experiments on methacrylated alginate in an attempt to physically combined this system with keratin. The photo-crosslinked gels were also tested for water retention by swelling studies and as drug delivery system of antioxidant glutathione.
Chapter 4 condenses the main ideas and information gathered throughout the research work by providing conclusions as well as projecting further work that should be carried out in future studies.