• International Journal of Industrial Entomology and Biomaterials
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• v.27 no.2
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• pp.312-316
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• 2013

Caffeine is a thermogenic agent that can be used in weight loss products. In order to achieve a sustained release of caffeine, silk fibroin (SF) film was uses as carrier. It has been shown that the loading method of caffeine into SF film affected the uniform distribution of caffeine in the SF film. When caffeine was added directly into SF solution, gelation has been occurred immediately and prevented the uniform distribution of caffeine. On the other hand, caffeine was dissolved in methanol in order to load the caffeine in SF film and crystallize the SF film at the same time. However, due to the fast evaporation of methanol, caffeine was recrystallized on the surface of SF film rather than penetrating into the film. Finally, caffeine was loaded into pre-crystallized SF film and uniform distribution of caffeine could be achieved. There was an initial burst of caffeine during the first 15 min, but after that a sustained release was achieved.

• International Journal of Industrial Entomology and Biomaterials
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• v.45 no.2
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• pp.56-69
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• 2022

Silk is a unique natural biopolymer with outstanding biocompatibility, high mechanical strength, and superior optical transparency. Due to its excellent properties, silk has been widely reported as an ideal biomaterial for several biomedical applications. Recently, fluorescent silk protein, a variant of native silk, has been reported as a biophotonic material with the potential for bioimaging and biosensing. Despite the realization of fluorescent silk, the traditional degumming process of fluorescence silk is crude and often results in fluorescence loss. The loss of fluorescent properties is attributed to the sensitivity of silk fibroin to temperature and solvent concentration during degumming. However, there is no comprehensive information on the influence of these processing parameters on fluorescence evolution and decay during fluorescent silk processing. Therefore, we conducted a spectroscopic study on fluorescence decay as a function of temperature, concentration, and duration for fluorescent silk cocoon degumming. Sodium carbonate solution was tested for degumming the fluorescent silk cocoons with different concentrations and temperatures; also, sodium carbonate solution is combined with Alcalase enzyme and triton x-100 to find optimal degumming conditions. Additionally, we conducted a molecular dynamics study to investigate the fundamental effect of temperature on the stability of the fluorescent protein. We observed degumming temperature as the prime source of fluorescent intensity reduction. From the MD study, fluorescence degradation originated from the thermal agitation of fluorescent protein Cα atoms and fluctuations of amino acid residues located in the chromophore region. Overall, degumming fluorescent silk with sodium carbonate and Alcalase enzyme solution at 25 ℃ preserved fluorescence.

• Textile Coloration and Finishing
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• v.14 no.4
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• pp.249-258
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• 2002

Natural silk is formed by two proteins : the crystalline fibroin (inside the silk thread) and amorphous sericin (as a tube outside the thread). The degumming process is used to eliminate the external sericin prior to dyeing ; generally it makes use of soaps at about pH 10. Sericin is the protein constituent that "gums"together the fibroin filaments of cocoon silk. It constitutes about 25% of the weight of the cocoon, is soluble in hot water and "gels" on cooling. The removal of sericin from raw silk, known as degumming, is a simple but important process usually employing hot dilute soap or alkaline solution and occasionally dilute acids or enzymic methods. During degumming, alkali is taken up by the sericin and the free acid from the soap is formed ; this may be deposited on the fiber, reducing the rate of degumming and protecting it from hydrolysis. Alkali is often added to maintain or restore the pH of the baths, but it is rarely used alone, since it leaves the silk rather harsh in handle. If complete sericin removal is required as for printing, sodium carbonate may be added. If the pH of the bath exceeds 11, the fibroin is attacked. Recently, According to the development of electrolysis, we can be obtained the electrolytic reduction water(above pH 11.5) and electrolytic oxidation water (below pH 3). The aim of this work was to study a degumming process using electrolytic water and a possibility of sericin recovery. The new degumming process used electrolytic water operates at $95^\circ{C}$ for 2hr. without any reagents. The wastewater of this process are formed by a solution of sericin in water. This conditions suggest the study of a possible recovery of this protein (sericin) which has an amino acid composition suitable for many used in cosmetics, textile finishing agents, animal feeding, etc. The degumming process using electrolytic water is available to reduce treatment costs and pollute and at the same time to recover sericin.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.634-638
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• 2003

For the investigation of the properties of aqueous fibroin solution, the variation of molecular weight by agregation of silk, morphology and difference of molecular weight at pI value was investigated. The distribution of molecular weight investigated using gel filtration chromatography and formation of aggregates were confirmed by using Field emission scanning electron microscope. The precipitation of fibroin solution at its pI value was compared by molecular weight distribution and the formation of fibroin aggregated were investigated. The aggregation kinetics were investigated at various condition.

• Fibers and Polymers
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• v.6 no.3
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• pp.181-185
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• 2005

Silk fibroin (SF) nanofibers were prepared by electrospinning and their application as an enzyme immobilization support was attempted. By varying the concentration of SF dope solution the diameter of SF nanofiber was controlled. The SF nanofiber web had high capacity of enzyme loading, which reached to $5.6\;wt\%$. The activity of immobilized a-chymotrypsin (CT) on SF nanofiber was 8 times higher than that on silk fiber and it increased as the fiber diameter decreased. Sample SF8 (ca. 205 nm fiber diameter) has excellent stability at $25^{\circ}C$ by retaining more than $90\%$ of initial activity after 24 hours, while sample SF11 (ca. 320 nm fiber diameter) shows higher stability in ethanol, retaining more than $45\%$ of initial activity. The formation of multipoint attachment between enzyme and support might increase the stability of enzyme. From these results, it is expected that the electrospun SF nanofibers can be used as an excellent support for enzyme immobilization.

• International Journal of Industrial Entomology and Biomaterials
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• v.26 no.2
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• pp.81-88
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• 2013

Wet-spun silk fibers have attracted the attention of many researchers because of 1) the unique properties of silk as a biomaterial, including good biocompatibility and cyto-compatability and 2) the various methods available to control the structure and properties of the fiber. Cellulose nanofibrils (CNFs) have typically been used as a reinforcing material for natural and synthetic polymers. In this study, CNF-embedded silk fibroin (SF) nanocomposite fibers were prepared for the first time. The effects of CNF content on the rheology of the dope solution and the characteristics of wet-spun CNF/SF composite fibers were also examined. A 5% SF formic acid solution that contained no CNFs showed nearly Newtonian fluid behavior, with slight shear thinning. However, after the addition of 1% CNFs, the viscosity of the dope solution increased significantly, and apparent shear thinning was observed. The maximum draw ratio of the CNF/SF composite fibers decreased as the CNF content increased. Interestingly, the crystallinity index for the silk in the CNF/SF fibers was sequentially reduced as the CNF content was increased. This phenomenon may be due to the fact that the CNFs prevent ${\beta}$-sheet crystallization of the SF by elimination of formic acid from the dope solution during the coagulation process. The CNF/SF composite fibers displayed a relatively smooth surface with stripes, at low magnification (${\times}500$). However, a rugged nanoscale surface was observed at high magnification (${\times}10,000$), and the surface roughness increased with the CNF content.

• International Journal of Industrial Entomology and Biomaterials
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• v.33 no.2
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• pp.138-143
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• 2016

In the present study, silk fibroin (SF) was dissolved in $CaCl_2/H_2O/EtOH$ solution at $85^{\circ}C$. After the dissolution, the SF solution was cooled down and stored at $4^{\circ}C$ for 28 d. The stability of the solution's viscosity and electrospinnability was observed to examine the stability of SF molecules during storage in $CaCl_2/H_2O/EtOH$ solution. The viscosities of $SF/CaCl_2/H_2O/EtOH$ solution and SF formic acid solution did not change during 28 days' storage of SF in $CaCl_2/H_2O/EtOH$ solution. The electrospinnability of the SF solution, mean diameter of the electrospun SF fiber, and crystallinity index of electrospun SF web did not change, regardless of the length of the storage period. These results imply that SF molecules do not degrade during 28 days' storage in $CaCl_2/H_2O/EtOH$ solution.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2003.04a
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• pp.59-59
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• 2003

Silk sericin (SS) is one of essential components of cocoon filament, comprising granular and high molecular proteins with adhesive and gelatin-like characteristics. Silk fibroin (SF), another main component of cocoon filament, has been investigated by many researchers due to its good physicochenucal properties. Recently, Nam and Park reported that the effect of alcohol addition into the SF solution on the morphology and structural charateristics of SF. (omitted)

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2001.10a
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• pp.48-48
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• 2001

no Abstract, See Full Text

• Journal of Sericultural and Entomological Science
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• v.39 no.2
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• pp.169-173
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• 1997

The behavior of tyrosine(Tyr.) residue of Bombyx mori silk fiber from yellow fluorescent cocoon has been examined for the dependence of pH in aqueous silk solution under the presence of orange II salt. Through the peak separation of angular dependence of spectral pattern of 15N-Tyr. and [1-13C]-Tyr. between the fiber axis and the molecular bond direction, N-H bond in fiber as well as the orientation distribution around the fiber axis were analyzed. Also, and sericin component was obtained from these angular dependence of oriented spectral pattern. The pH dependence of the 13C NMR chemical shift of B. mori silk fibroin was examined in aqueous solution in the presince of orange II are broad at pH$\geq$7.0. However, these become sharper at pH$\geq$8.0 and remain sharp at higher pH. In these higher pH range, a chemical shift change occurs due to the deprotonation of the Tyr. side group of fibroin. At higher pH. such a hydrophobic cluster is destroyed because of the electrostatic interaction according to the deprotonation of the Tyr-OH group.