DBN-based ionic liquids with high capability for the dissolution of wool keratin

Author(s): Xue Liu ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Yi Nie ⁴ ^, ⁵ ^, ⁶ ^, ⁷ ^, ⁸ , Xianglei Meng ⁴ ^, ⁵ ^, ⁶ ^, ⁷ ^, ⁸ , Zhenlei Zhang ⁴ ^, ⁵ ^, ⁶ ^, ⁷ ^, ⁸ , Xiangping Zhang ⁴ ^, ⁵ ^, ⁶ ^, ⁷ ^, ⁸ , Suojiang Zhang ⁴ ^, ⁵ ^, ⁶ ^, ⁷ ^, ⁸

Publication date (Electronic): 2017

Journal: RSC Advances

Publisher: Royal Society of Chemistry (RSC)

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Abstract

Effects of ILs structures on the dissolution capability were systematically studied, and the optimal IL [DBNE]DEP with high dissolution capability for goat wool was finally obtained.

Abstract

An increasing interest has been manifested in the use of ionic liquids (ILs) as solvents for the dissolution of wool keratin due to their tunable and excellent properties, despite the fact that it is still a challenge that ILs with different structures have distinct dissolution capabilities for wool. In this study, a series of 1,5-diazabicyclo[4.3.0]-non-5-ene (DBN)-based ionic liquids with different anions have been designed and employed for the dissolution of wool keratin. The effects of the ILs structures on their dissolution capabilities were systematically studied, and the optimal IL with high dissolution capability for goat wool was finally obtained by overall considering the time taken for the goat wool complete dissolution and the properties of the regenerated keratin. It was found that both cations and anions, acting as the regulators for polarity ( ENT) and hydrogen-bond basicity ( β) of the ILs, have significant influence on the dissolution capabilities of the ILs, which play an important role in the design and synthesis of new functional ILs for the dissolution of wool keratin. Furthermore, the time taken for the complete dissolution of 8 wt% goat wool in the optimum IL 1-ethyl-1,5-diazabicyclo[4.3.0]-non-5-enium diethylphosphate ([DBNE]DEP) is 3 h at 393 K, and the relative crystallinity, content of α-helix, and decomposition temperature of the regenerated keratin from [DBNE]DEP are higher (60.99%, 57.88%, and 521 K, respectively) than that from other ILs. Moreover, the break ratio of the disulfide bond is reduced to only 53.46%. In addition, [DBNE]DEP could be easily reused at least 5 times with stable structures and good dissolving ability, and the non-newtonian index, n, of the DEP IL/keratin solutions is all about 0.8, which means that the DEP IL/keratin solution has good prospects in terms of spinning.

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Biodegradable materials based on silk fibroin and keratin.

Artur Cavaco-Paulo, Andréia Vasconcelos-dos-Santos, Giuliano Freddi (2008)

Wool and silk were dissolved and used for the preparation of blended films. Two systems are proposed: (1) blend films of silk fibroin and keratin aqueous solutions and (2) silk fibroin and keratin dissolved in formic acid. The FTIR spectra of pure films cast from aqueous solutions indicated that the keratin secondary structure mainly consists of alpha-helix and random coil conformations. The IR spectrum of pure SF is characteristic of films with prevalently amorphous structure (random coil conformation). Pure keratin film cast from formic acid shows an increase in the amount of beta-sheet and disordered keratin structures. The FTIR pattern of SF dissolved in formic acid is characteristic of films with prevalently beta-sheet conformations with beta-sheet crystallites embedded in an amorphous matrix. The thermal behavior of the blends confirmed the FTIR results. DSC curve of pure SF is typical of amorphous SF and the curve of pure keratin show the characteristic melting peak of alpha-helices for the aqueous system. These patterns are no longer observed in the films cast from formic acid due to the ability of formic acid to induce crystallization of SF and to increase the amount of beta-sheet structures on keratin. The nonlinear trend of the different parameters obtained from FTIR analysis and DSC curves of both SF/keratin systems indicate that when proteins are mixed they do not follow additives rules but are able to establish intermolecular interactions. Degradable polymeric biomaterials are preferred candidates for medical applications. It was investigated the degradation behavior of both SF/keratin systems by in vitro enzymatic incubation with trypsin. The SF/keratin films cast from water underwent a slower biological degradation than the films cast from formic acid. The weight loss obtained is a function of the amount of keratin in the blend. This study encourages the further investigation of the type of matrices presented here to be applied whether in scaffolds for tissue engineering or as controlled release drug delivery vehicles.