Thesis (M.A.)--University of Hong Kong, 1966. / Also available in print.

Diss.--Zürich. / Vita. "Literaturübersicht": p. [154]-156.

Thèse--Berne. / Published also without thesis statement.

The general aim of the research presented in this thesis is to extend the application of microstructural and microchemical analytical techniques, with the longer term objective of better informing textile conservation. The ability to identify the components of threads in historic textiles and characterise their state of degradation is essential when considering potential conservation treatments. Three particular constituents are considered here, namely metals, and plant and silk fibres. Metal threads are found in wide variety of historically important textiles, and their composite nature can complicate characterisation and treatment. Examples from a range of sources were assessed by a range of microscopic and spectroscopic techniques. It was demonstrated that these approaches allowed the determination of the general type, composition, state of degradation and likely methods of manufacture of these materials. In addition, investigations of metal threads from two specific artefacts were performed: the Jesse Tapestry, a 15th century ecclesiastical hanging; and a piece of 19th century embroidered artwork, produced in the style of the 17th century. Cellulosic fibres can prove difficult to distinguish due to their similarities in composition and structure. The work presented here describes the development of an ATR FT-IR spectroscopic technique for the characterisation of six species of commonly encountered plant fibres, using linear discriminant analysis on peak intensity ratios, to allow differentiation on the basis of characteristic lignin and cellulose contents. Further investigations using a polarised ATR technique allowed the fibre microstructure to be probed, permitting further distinction, for example of hemp and flax, on the basis of the characteristic angles and senses of winding of the cellulose fibrils. Metal weighted silk fibres, found in many important artefacts, are particularly susceptible to deterioration and so are a special area of concern. The research has concentrated on developing a micro-methodology to assess these materials, and specifically to identify spectroscopic signatures that correlate to physical properties. In order to do so, samples of habutae silk were weighted, using historically accurate methods, then aged by means of either elevated temperatures or intense illumination. Physical properties were assessed by measurement of breaking strength and Young's modulus. Subsequently TGA, HPLC, UV/Visible and ATR analyses were carried out. A good correlation was found between the physical state of the fibres and both the retention time of the major silk peak (measured in the H P L C experiment) and an orientational order parameter (derived from the pol-ATR data).

No description available.

No description available.

No description available.

Lower back pain and intervertebral disc degeneration represent a global socio-economical problem affecting 266 million people annually, always increasing due to aging of the population. No restorative treatments are available. In case of chronic degeneration, surgical operation with spinal fusion or total disc replacement represents the best alternative. This leads to pain relief but reduces the patient’s mobility. Moreover, follow-ups and re-intervention due to weak osteointegration are common consequences of currently used metal prostheses. For this reason, there is an urgent need to develop customized regenerative approaches aimed at the restoration of IVD function, as well as the optimization of osteointegration in actual vertebral prostheses by creating hybrid metal implants with infill materials to better induce bone ingrowth. In this work, tissue engineering-based approaches have been exploited by tuning the remarkable properties of silk fibroin for two purposes, disc restoration via in situ 3D printing technique, and improvement of osteointegration of vertebral prostheses. In situ 3D printing is the most promising strategy for the development of a personalized medicine approach aimed at the restoration of IVD. However, silk fibroin application as pristine ink in 3D printing technique is hindered by its low viscosity. For this reason, the aim of the first part of the work has been the design and development of silk fibroin-based inks in situ applications, overcoming its intrinsic limitations. Specifically, a covalent crosslinking process consisting of a pre-photo-crosslinking prior to printing and in situ enzymatic crosslinking was designed. Two different silk fibroin molecular weights were characterized. We proved that despite the use of low concentration silk solutions, the synergistic effect of the covalent bonds with the shear forces applied in the nozzle enhanced silk secondary structure shift toward β-sheets conformation. The resultant hydrogels exhibited good mechanical properties, stability over time, and resistance to enzymatic degradation over 14 days, with no significant changes over time in their secondary structure and swelling behavior. The designed process was tunable and versatile, leading to good shape fidelity and printing resolutions, making real the application of silk fibroin-based inks for in situ applications. The results obtained represent an important step for further studies on the mimicry of the whole IVD structure. 2 In the second part of the work, silk fibroin has been evaluated as candidate infill material for metal prostheses to improve bone ingrowth and osteointegration. In two independent works, silk fibroin-based foams and methacrylate silk fibroin sponges were biologically characterized and the differentiation of bone marrow-derived human mesenchymal stem cells (hBM-MSCs) toward osteogenic phenotype was studied. Silk fibroin foams have been demonstrated to induce and support cells adhesion, migration, and differentiation, and to induce early mineralization phase since day 7 during the differentiative culture. Methacrylate silk fibroin foams have been fabricated with different photo-initiator concentrations and in presence/absence of a porogen. The impact of the composition on the pore size, mechanical properties, and stem cells differentiation was deeply investigated. We demonstrated that despite all the conditions well-supported cells differentiation, the lowest photo-initiator concentration in combination with the porogen used enhanced osteogenic differentiation as confirmed by gene expression tests.

published_or_final_version / Chinese Historical Studies / Master / Master of Arts

Silk fibroin has created a surge of interest for use as organic material due to its optical transparency, biocompatibility, biodegradability, and excellent physical properties. However, the implementation of silk films and structures into biomedical and sensing devices has been relatively low due to a lack of understanding of the mechanisms involved in such implementation. Increasing need for multifunctional high-performance organic materials has caused an emphasis on the ability of researchers to spatiotemporally pattern and control the structure and consequently functional properties of materials. Silk fibroin displays high potential for use as a controllable biomaterial that can be formed into a myriad of different structures for various applications. By implementation of an aqueous silk solution approach combining various fabrication techniques, several different pristine-silk and silk-composite membranes have been developed to investigate the importance of internal structuring. Different methods of investigation include: 1) incorporation of reinforcing nanoparticles within the silk matrix; 2) neutron reflectivity measurements of ultrathin silk films; 3) film patterning with nanoscale features followed by boundary organized surface mineralization of inorganic nanoparticles. The ultimate goal will be to provide fundamental data assisting in an increased knowledge of silk fibroin-based membranes and the effect of secondary structures on properties of interest.