Dissolution Of Fibroin Research Articles

Synergy between silk fibroin and ionic liquids for active gas-sensing materials.

Silk fibroin is a biobased material with excellent biocompatibility and mechanical properties, but its use in bioelectronics is hampered by the difficult dissolution and low intrinsic conductivity. Some ionic liquids are known to dissolve fibroin but removed after fibroin processing. However, ionic liquids and fibroin can cooperatively give rise to functional materials, and there are untapped opportunities in this combination. The dissolution of fibroin, followed by gelation, in designer ionic liquids from the imidazolium chloride family with varied alkyl chain lengths (2–10 carbons) is shown here. The alkyl chain length of the anion has a large impact on fibroin secondary structure which adopts unconventional arrangements, yielding robust gels with distinct hierarchical organization. Furthermore, and due to their remarkable air-stability and ionic conductivity, fibroin ionogels are exploited as active electrical gas sensors in an electronic nose revealing the unravelled possibilities of fibroin in soft and flexible electronics.

Change of Silk Fibroin Molecular Mass During Dissolution in Ionic Liquids

Silk fibroin is a unique protein polymer with broad potential for medical applications. Fibroin is significantly degraded and the materials obtained from it have poor mechanical characteristics if silk fiber is dissolved in traditional solvents. The present work used gel electrophoresis to study the dissolution of fibroin in ionic liquids. Fibroin degradation was shown to increase with increasing temperature and dissolution time. The optimal conditions for dissolution that allowed the heavy and light chains of fibroin to be preserved intact were proposed.

Structure and properties of silk fibroin aerogels prepared by non-alkali degumming process

Silk fibroin aerogel generally suffers from weak mechanical properties, which limits its application in the high-performance materials. Hence, we develop a non-alkali urea degumming strategy for the raw silk to improve the mechanical properties of silk fibroin aerogel. The silk fibroin aerogel with a low density of 13.43 ± 0.77 mg/cm3 was fabricated successfully via silk fibroin dissolution, dilution and freeze-drying. We systematically analyze the solution properties of silk fibroin prepared via alkali degumming and non-alkali degumming. Meanwhile, the morphology and structure of aerogel are characterized by scanning electron microscopy, X-ray diffraction spectroscopy and Gaussian multi-peaks-fiting technique of infrared spectrum. Moreover, we investigate the effects of non-alkali degumming method on the mechanical properties and thermal stability of aerogels. The results manifest that the non-alkali urea degumming process reduces damage to silk fibroin, leading to the stable three-dimensional skeleton structure of the prepared aerogels. Furthermore, compared with the silk fibroin aerogel prepared by alkali degumming, the silk fibroin aerogel prepared by non-alkali degumming has higher crystallinity and content of β-sheet structure, resulting in the better mechanical properties and thermal stability. This work may pave the way for the fabrication of silk fibroin aerogel materials with high mechanical properties.

Dissolution behavior of silk fibroin in a low concentration CaCl2-methanol solvent: From morphology to nanostructure

Regenerated Silk biomaterials are usually pre-formed from silk fibroin solutions. However, the dissolution of silk fibroin in proper solvents by a simple and low cost way is still a challenge. Here, we employed a CaCl2-methanol solvent system with a very low CaCl2 concentration of 6wt% to dissolve silk fibroin. During the dissolution process, the evaporation of methanol cause the changing of solvation sheath of ions in the solvent. The remaining solvent with the incomplete solvation sheath is absorbed by the silk fiber and interacts with fibroin chains to complete the solvation sheath, which accounts for the dissolution of silk fibroin. Silk fibroin dissolution stops as all the solvation sheaths are complete. The final CaCl2 concentration is ca. 26% and silk fibroin is completely dissolved with a yield of about 90%. Silk fibroin is dissolved into multi-scale nanofibrils solution which is potential for producing regenerated silk fibroin materials for functional applications.

Prospects for Producing New Biomaterials Based on Fibroin

Methods for preparing solutions and materials based on the biopolymer fibroin were discussed. Thermal hydrolysis of fibroin at 220-300°C produced a mixture of water-soluble amino acids, dipeptides, and diketopiperazines. The diketopiperazine content increased with increasing hydrolysis temperature. Dissolution of fibroin in ionic liquids formed thixotropic solutions with properties that depended on the dissolution temperature. The ordering of films produced from the solutions depended on the contact time with the precipitant.

Isolation and processing of silk proteins for biomedical applications

Silk proteins of silkworms are chiefly composed of core fibroin protein and glycoprotein sericin that glues fibroin. Unique mechanical properties, cyto-compatibility and controllable biodegradability facilitate the use of fibroin in biomedical applications. Sericin serves as additive in cosmetic and food industries, as mitotic factor in cell culture media, anti-cancerous drug, anticoagulant and as biocompatible coating. For all these uses; aqueous solutions of silk proteins are preferred. Therefore, an accurate understanding of extraction procedure of silk proteins from their sources is critical. A number of protocols exist, amongst which it is required to settle a precise and easy one with desired yield and least down-stream processing. Here, we report extraction of proteins employing methods mentioned in literature using cocoons of mulberry and nonmulberry silks. This study reveals sodium carbonate salt-boiling system is the most efficient sericin extraction procedure for all silk variants. Lithium bromide is observed as the effective fibroin dissolution system for mulberry silk cocoons; whereas heterogeneous species-dependent result is obtained in case of nonmulberry species. We further show the effect of common post processing on nanoscale morphology of mulberry silk fibroin films. This knowledge eases the adoption and fabrication of silk biomaterials in devices and therapeutic delivery systems.

Novel silk fibroin films prepared by formic acid/hydroxyapatite dissolution method

Bombyx mori silk fibroin from the silkworm was firstly found to be soluble in formic acid/hydroxyapatite system. The rheological behavior of silk fibroin solution was significantly influenced by HAp contents in dissolved solution. At the same time, silk fibroin nanofibers were observed in dissolved solution with 103.6±20.4nm in diameter. Moreover, the structure behavior of SF films prepared by formic acid/hydroxyapatite dissolution method was examined. The secondary structure of silk fibroin films was attributed to silk II structure (β-sheet), indicating that the hydroxyapatite contents in dissolved solution were not significantly affected by the structure of silk fibroin. The X-ray diffraction results exhibited obviously hydroxyapatite crystalline nature existing in silk fibroin films; however, when the hydroxyapatite content was 5.0wt.% in dissolved solution, some hydroxyapatite crystals were converted to calcium hydrogen phosphate dehydrate in silk fibroin dissolution process. This result was also confirmed by Fourier transform infrared analysis and DSC measurement. In addition, silk fibroin films prepared by this dissolution method had higher breaking strength and extension at break. Based on these analyses, an understanding of novel SF dissolution method may provide an additional tool for designing and synthesizing advanced materials with more complex structures, which should be helpful in different fields, including biomaterial applications.

Thermochemical study on the dissolution and regeneration of fibroin from solutions in imidazole-based ionic liquids

The enthalpies of dissolution of fibroin in imidazole-based ionic liquids were determined, and the contribution of polymer crystal structure decomposition to the enthalpy of dissolution was estimated. The heat of mixing of imidazole ionic liquid with water was described.

Studies on the dissolution of silk fibroin

It is well known that silk fibroin dissolves in the concentrated aqeous solution of neutral salt such as CaCl2 or LiBr. In this study, Some alcohols were added to the CaCl2 solution, and the dissolution of fibroin in the solution was investigated. It was found that the addition of a proper quontity of monohydric alcohol, such as CH3OH and C2H5OH improves the shlubility. C2H5OH is more effectives for the increase sf the solubility than CH3OH under equal molar addition. The addition of dihydric alcohol (C2H4(OH)2) or trihydric alcohol (C3H5(OH)3) decreases the dissolution of silk fibroin.

Non‐bioengineered silk gland fibroin protein: Characterization and evaluation of matrices for potential tissue engineering applications

The possibility of using wild non-mulberry silk protein as a biopolymer remains unexplored compared to domesticated mulberry silk protein. One of the main reasons for this was for not having any suitable method of extraction of silk protein fibroin from cocoons and silk glands. In this study non-bioengineered non-mulberry silk gland fibroin protein from tropical tasar silkworm Antheraea mylitta, is regenerated and characterized using 1% (w/v) sodium dodecyl sulfate (SDS). The new technique is important and unique because it uses a mild surfactant for fibroin dissolution and is advantageous over other previous reported techniques using chaotropic salts. Fabricated fibroin films are smooth as confirmed by atomic force microscopy. Circular dichroism spectrometry along with Fourier transformed infrared spectroscopy and X-ray diffraction reveal random coil/alpha-helix conformations in regenerated fibroin which transform to beta-sheets, resulting in crystalline structure and protein insolubility through ethanol treatment. Differential scanning calorimetry shows an increase in glass transition (Tg) temperature and enhanced degradation temperature on alcohol treatment. Enhanced cell attachment and viability of AH927 feline fibroblasts were observed on fibroin matrices. Higher mechanical strength along with controllable water stability of regenerated gland fibroin films make non-mulberry Indian tropical tasar silk gland fibroin protein a promising biomaterial for tissue engineering applications.

A novel method for dissolution and stabilization of non‐mulberry silk gland protein fibroin using anionic surfactant sodium dodecyl sulfate

The importance of silk protein has increased because of its potential use as a natural biopolymer for tissue engineering and biomedical applications. In this report we show a novel and ecofriendly method for dissolution of gland silk protein fibroin. Non-mulberry silk fibroin from mature fifth instar larvae of Antheraea mylitta was found to be optimally soluble in 1% (w/v) anionic surfactant sodium dodecyl sulfate (SDS). Regenerated fibroin showed distinct bands of approximately 395 and 197 kDa on electrophoresis in non-reducing and reducing conditions, respectively. Enhanced fibroin dissolution via internalization of hydrophobic amino groups inside a hydrophilic amino acid core in the form of micelles was observed. Prolonged storage stability without gelation of SDS-extracted fibroin was seen. Atomic force microscopy showed micellar aggregation with mean micellar aggregation size of 8 nm. Circular dichroism spectroscopy revealed predominantly helical conformation due to surfactant addition with internal protein conformational changes as revealed by fluorescence spectroscopic studies.

Regeneration of Bombyx mori silk by electrospinning. Part 3: characterization of electrospun nonwoven mat

Regenerated Bombyx mori silk fibroin in formic acid was electrospun and the morphological, chemical and mechanical properties of these nanofibers were examined by field emission environmental scanning electron microscopy (FESEM), Raman spectroscopy (RS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and tensile testing. FESEM indicated that the average fiber diameter was less than 100nm and circular in cross section. This paper maps the silk fibroin molecular conformations of each step of the sample preparation and the electrospinning process. The secondary structural compositions (random and β-sheet) of the fibroin were determined by FTIR and RS. The crystallinity index of the electrospun fiber, calculated as the intensity ratio of 1624 (β-sheet) and 1663 (random) cm−1 FTIR bands was higher than that of the pristine fiber. Raman spectra of the amide I (1665cm−1, random) to amide III (1228cm−1, β-sheet) ratio of the electrospun fiber was less than that of the pristine fiber indicative of higher β-sheet content. The fiber crystallinity, determined by XRD, showed a lower value for the electrospun fiber. The electrospun fiber shows small but significant increases in the β-sheet content in comparison with the pristine fiber. Dissolution of fibroin in formic acid enhances β-sheet crystallization and may facilitate β-sheet formation in electrospun fiber. The electrospun random silk mat had a Young's modulus, ultimate tensile strength and strain of 515MPa, 7.25MPa and 3.2%, respectively.

STUDIES ON THE DISSOLUTION OF SILK FIBROIN

It is well known that silk fibroin dissolves in the concentrated aqeous solution of neutral salt such as CaCl2 or LiBr. In this study, Some alcohols were added to the CaCl2 solution, and the dissolution of fibroin in the solution was investigated. It was found that the addition of a proper quontity of monohydric alcohol, such as CH3OH and C2H5OH improves the shlubility. C2H5OH is more effectives for the increase sf the solubility than CH3OH under equal molar addition. The addition of dihydric alcohol (C2H4(OH)2) or trihydric alcohol (C3H5(OH)3) decreases the dissolution of silk fibroin.