Do Gyu Bae

Effect of degumming condition on the solution properties and electrospinnablity of regenerated silk solution.

The application of silk on tissue engineering scaffolds has been studied intensively because silk has an electrospinning technique using a good blood compatibility, excellent cytocompatibility and biodegradability. Silk consists of two polymers, fibroin and sericin. In spite of importance of sericin, most studies were focused on the fibroin only and the effect of residual sericin on the electrospinning performance of silk has not been considered. In this study, regenerated silk with different residual sericin contents was prepared by controlling the degumming conditions. The effects of the degumming conditions on the solution properties and electrospinning performance of silk were examined. The fast protein liquid chromatography (FPLC) measurements confirmed that the molecular weight of the regenerated silk decreased slightly with increasing residual sericin content. More molecular aggregation of silk occurred with increasing sericin content, resulting in an increase in the solution turbidity of formic acid. All silk formic acid solutions exhibited almost Newtonian fluid behavior and the viscosity increased with increasing sericin content. Interestingly, the dope solution viscosity of silk increased remarkably at sericin contents <1% (or degumming ratio >25%) leading to significant improvements in electrospinnability and an increase in the fiber diameter of the silk web.

Natural dyeing with black cowpea seed coat. I. Dyeing properties of cotton and silk fabrics

A new trial to determine the dyeing properties of cotton and silk fabrics with a black cowpea seed coat as crop waste was investigated. The natural dye anthocyanins were extracted from a black cowpea seed coat in an aqueous solution and used to dye silk and cotton. The optimal conditions for colorant extraction were an aqueous solution of a dried seed coat of black cowpea in a 1:10 liquor ratio at 70 °C for 4 hours with pH of 4. The best dye-uptake of silk and cotton fabric were obtained when the pH was 3.5 and 3.0 respectively, the temperature was 80 °C for 1 hour and the liquor ratio of black cowpea was 1:20. Different colors as dusky brown, brown, faint yellow, light green, reddish brown, cyan and green could be obtained using a various kind of mordants. The depth and brightness of color tones were affected by different dyeing and mordanting pH conditions. The colors of the fabrics were examined using a computer color matching system in terms of the K/S values and CIELAB color-difference values. The dyeing was evaluated using standard light, wash and heat fastness tests. Good wash and heat fastness were obtained but the poor light fastness indicated the need for improvement to fulfill the requirement for textile applications.

Electrospinning and Characterisation of Poly(vinyl alcohol) Blend Submicron Fibres in Aqueous Solutions

Poly(vinyl alcohol) (number-average degree of polymerisation 1700 (PVA-17) and 4000 (PVA-40)) blend submicron fibres were fabricated by the electrospinning method in an aqueous solution of 5–10% polymer concentration. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA) were utilised to characterise the morphology and physical properties of the PVA fibres. The role of PVA blend mass ratio and concentration and of processing parameters such as applied voltage and capillary-to-collector distance in the production of ultrafine submicron PVA blend fibres was investigated. Uniform PVA fibres with an average submicron-scale diameter (250–600 nm) could be prepared from a 7.5% PVA-17/PVA-40 blend solution with various mass ratios. With a lower PVA blend concentration (5%), using different PVA-17/PVA-40 mass ratios, beads appeared in the fibre morphology, and homogeneity was also absent. At a higher PVA blend concentration (10%), larger-diameter (<700 nm) ribbon-like fibres were produced. Moreover, with a higher percentage of PVA-40 in the PVA blend fibres, superior crystallinity, thermal stability, and mechanical properties could be obtained by comparison with PVA-17.

Preparation of new natural silk non-woven fabrics by using adhesion characteristics of sericin and their characterization

Electro-spun regenerated silk webs have been extensively studied for biomedical applications because of the simplicity of their fabrication methods However, the productivity of the electro-spinning process is low for web fabrication and the mechanical properties of the electro-spun silk web are not satisfactory, which restricts its commercialization. In this study, a new silk non-woven fabric was successfully fabricated by wetting and hot press treatments using the excellent binding characteristic of sericin. The effects of the press temperature and residual sericin content on the preparation, structure, and properties of the silk non-woven fabric were examined. A press temperature of 200°C was optimum for obtaining non-woven fabrics with best mechanical properties, without yellowing. The silk non-woven fabric could not be fabricated without sericin, and a minimum of 8% sericin was required to fabricate it. As the sericin content was increased, the strength and Youngs modulus of the silk non-woven fabric increased, while the tensile elongation remained constant. Regardless of the press temperature and sericin content, all the silk non-woven fabrics showed good cell viability, comparable to that of the tissue culture plate (TCP) used as a control until 4days, which however decreased compared to that of TCP after 7days.

Effect of molecular weight on the structure and mechanical properties of silk sericin gel, film, and sponge

In this study, the effect of the MW on the structure and properties of sericin film, sponge, and gel was examined. As the MW of sericin increased, the gelation of the sericin aqueous solution was found to be accelerated, and the gel strength, and the gel-sol transition temperature increased. Irrespective of the casting solvent (water and formic acid) and form of sericin (gel, film, or sponge), the crystallization of the sericins was accelerated. The mechanical properties of the sericin sponge were remarkably improved upon increasing the MW of sericin. The MW of sericin almost did not have an effect on the cell toxicity. As the MW of sericin is increased, the sericin sponge becomes denser and its porosity is reduced, leading to a decrease in the swelling ratio. These results indicate that various characteristics of the sericin forms can be modulated by controlling the MW of sericin, with enhanced potential for biomedical and cosmetic applications.