Silk fibroin (SF) microspheres were prepared by a water-in-oil emulsion solvent evaporation method without any surfactants. The water and oil phases were SF aqueous solution and paraffin, respectively. The SF microspheres with spherical shape and smooth surface were separated into the size ranges of <80 µm, 80-150 µm and >150 µm. SF conformation of the microspheres was investigated by Fourier transform infrared spectroscopy while scanning electron microscopy used for morphological observation. After being treated with methanol, the SF conformation was changed from random coil to β-sheet form. Finally, the influence of particle size on protein adsorption efficiency was studied. Bovine serum albumin (BSA) was chosen as a model protein to carry out an immobilization test onto the SF microspheres by non-covalent adsorption. Efficiency of BSA adsorption was significantly increased with decreasing the SF microsphere size.
Porous silk fibroin (SF) microparticles were prepared by a simple one-step water-in-oil emulsificationdiffusion method. Aqueous SF solution and organic phase solvent were used as water and oil phases, respectively. Four organic solvents with different water solubility were studied, i.e., ethyl acetate, diethyl ether, dichloromethane, and chloroform. Influences of organic phase solvent, water/oil volume ratio, and SF concentration on SF microparticle characteristics were investigated. It was found that shape of the SF microparticles depended upon the type of organic phase solvent. The SF microparticles with hollow or bowl-like shape were fabricated when organic solvents with higher water solubility, which are ethyl acetate and diethyl ether, were used as the continuous oil phase. While using organic solvents with lower water solubility, i.e., dichloromethane and chloroform resulted in the spherical shape SF microspheres. The water/oil volume ratios and the SF concentrations did not affect on the bowl-like and spherical shapes of SF microparticles. Results from scanning electron microscope shows that all the SF microparticle matrices were porous structures. Using ethyl acetate and diethyl ether as the oil phase gave larger SF microparticle sizes than using dichloromethane and chloroform. The influences of water/oil volume ratio and the SF concentration showed slightly effect on the sizes of SF microparticles.
The brittleness of poly(L-lactide) (PLLA) bioplastic is the main disadvantage for practical applications. Herein, we report the synthesis of high-molecular-weight PLLA- b-poly(ethylene glycol)- b-PLLA (PLLA-PEG-PLLA) block copolymers by ring-opening polymerization of LLA. The highly flexible PLLA-PEG-PLLAs were prepared by reactive melt blending with an epoxy-based chain extender formed as long-chain branched structures. The effects of PEG block length and content of chain extender were investigated. The results showed that the chain extension reaction reduced crystallinities of the PLLA-PEG-PLLAs. All the chain-extended PLLA-PEG-PLLA films had no phase separation. The lower crystallinities of PLLA-PEG-PLLA films obtained with higher contents of chain extender enhanced the film drawability. The longer PEG block length resulted in higher strain at break and lower stress at the break of PLLA-PEG-PLLA films. These chain-extended PLLA-PEG-PLLAs have potential for use as highly flexible bioplastics.
This study aimed to prepare Silk Fibroin (SF) and Gelatin (G) blend film and study its morphology, secondary structure and thermal properties compared to native SF and G films. The films were prepared from the SF solution by casting on the polystyrene plates. They were investigated their secondary structure by fourier transform-infrared (FTIR) spectroscopy, morphology using Scanning Electron Microscope (SEM). In addition, Thermogravimetric Analysis (TG) and Differential TG (DTG) were used for thermal properties investigation. The results found that the SF/G blend film composed of both alpha-helix and beta-sheet structures which were similar characteristics of the native SF and G. This result was similar to the TG and DTG analysis according to blending between SF and G is not enhancing thermal stability of the film. However, changes in some absorption bands and temperatures were also observed from the blend film. The result suggested that chemical interaction and hydrogen bonding between SF and G could be formed. The formation could be affected to the uniform of the surface throughout the film under SEM.
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