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Title: Fabrication of ultrathin films from regenerated silk fibroin solution for biomaterial applications
Author: Yang, Luyuan
ISNI:       0000 0004 5919 8533
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2014
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Silk fibroin (SF) from the silkworm, Bombyx mori, is a natural fibrous protein with unique mechanical properties, biocompatibility and biodegradability. It has great potential in biomaterial applications for tissue engineering, drug delivery and biomedical devises. Most of the SF based biomaterials (e.g. films, scaffolds, hydrogels and electrospun fibres) are cast from regenerated silk fibroin (RSF) solution. Hence, it is important to acquire a comprehensive and deep understanding of the fibroin solution. This research applied a number of biophysical approaches, aiming to investigate the solution aggregation and interfacial adsorption behaviour of the SF polypeptides in aqueous solution. The methods for fabricating nanometre scale SF films are also explored carefully because well-controlled films and their surfaces enable direct characterisation of their interaction with other molecules and cells. Using the dynamic light scattering (DLS) technique, it was found that the particle size of newly made RSF peptides in solution was around 2.3~6.5 nm and they could remain stable for at least 10 weeks at 4 °C. Factors such as temperature, fibroin concentration, pH, alcohol and metallic ions can directly affect the assembly and aggregation of fibroin polypeptides as well as their solubility and stability in solution. The formation of large aggregation under certain conditions was possibly related to the conformational transition of SF from random coil/α-helix (Silk I) to β-sheets (Silk II). The interfacial adsorption of RSF solution at the SiO2/water interface was monitored by spectroscopic ellipsometry (SE), dual polarisation interferometry (DPI) and neutron reflection (NR). It was revealed that surface excess and thickness increased with concentration and decreased with rising pH and ionic strength. NR measurements revealed that the adsorbed polypeptide layers are characterised by a thin and dense inner region and a thick and diffuse outer region, a feature similar to the adsorbed layers from other polypeptides. The results from SE, DPI and NR are in good agreement. Multilayer ultrathin SF films were fabricated using the layer-by-layer spin coating method and were found to be stable in physiological conditions. The thickness and surface excess of the SF films were tuned by varying the concentrations while coating. Surface biocompatibility as demonstrated by MTT assays varied with the film thickness or the number of layers coated. With the aid of the cationic copolymer MPC30-DEA70, SF films successfully immobilised plasmid DNA, which demonstrates the potential of these multilayer SF films to be used in a drug delivery system. The ultrathin SF films were modified with gelatin (G). Preliminary cell culture experiments with 3T3 fibroblasts demonstrated that SF/G films with 1.2% ~ 20% (w/w) G content promoted cell attachment and proliferation compared with pure SF films. When films contain 10% ~ 20% (w/w) of G, they showed biocompatibility even superior to the pure G films. These enhanced cellular responses must result from improved film stability arising from SF and improved cytocompatibility arising from G.
Supervisor: Lu, Jian Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available