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Comparative Study of Ultrasonication-Induced and Naturally Self-Assembled Silk Fibroin-Wool Keratin Hydrogel Biomaterials

Department of Physics and Astronomy, Rowan University, Glassboro, NJ 08028, USA
Department of Biomedical Engineering, Rowan University, Glassboro, NJ 08028, USA
Department of Chemical Engineering, Rowan University, Glassboro, NJ 08028, USA
Department of Biomedical and Translational Sciences, Rowan University, Glassboro, NJ 08028, USA
Author to whom correspondence should be addressed.
Academic Editor: John G. Hardy
Int. J. Mol. Sci. 2016, 17(9), 1497;
Received: 29 July 2016 / Revised: 24 August 2016 / Accepted: 30 August 2016 / Published: 7 September 2016
(This article belongs to the Special Issue Silk-Based Materials: From Production to Characterization)
PDF [8668 KB, uploaded 7 September 2016]


This study reports the formation of biocompatible hydrogels using protein polymers from natural silk cocoon fibroins and sheep wool keratins. Silk fibroin protein contains β-sheet secondary structures, allowing for the formation of physical cross-linkers in the hydrogels. Comparative studies were performed on two groups of samples. In the first group, ultrasonication was used to induce a quick gelation of a protein aqueous solution, enhancing the ability of Bombyx mori silk fibroin chains to quickly entrap the wool keratin protein molecules homogenously. In the second group, silk/keratin mixtures were left at room temperature for days, resulting in naturally-assembled gelled solutions. It was found that silk/wool blended solutions can form hydrogels at different mixing ratios, with perfectly interconnected gel structure when the wool content was less than 30 weight percent (wt %) for the first group (ultrasonication), and 10 wt % for the second group (natural gel). Differential scanning calorimetry (DSC) and temperature modulated DSC (TMDSC) were used to confirm that the fibroin/keratin hydrogel system was well-blended without phase separation. Fourier transform infrared spectroscopy (FTIR) was used to investigate the secondary structures of blended protein gels. It was found that intermolecular β-sheet contents significantly increase as the system contains more silk for both groups of samples, resulting in stable crystalline cross-linkers in the blended hydrogel structures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the samples’ characteristic morphology on both micro- and nanoscales, which showed that ultrasonic waves can significantly enhance the cross-linker formation and avoid phase separation between silk and keratin molecules in the blended systems. With the ability to form cross-linkages non-chemically, these silk/wool hydrogels may be economically useful for various biomedical applications, thanks to the good biocompatibility of protein molecules and the various characteristics of hydrogel systems. View Full-Text
Keywords: silk fibroin; wool keratin; hydrogel; DSC; FTIR; SEM; AFM silk fibroin; wool keratin; hydrogel; DSC; FTIR; SEM; AFM

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Vu, T.; Xue, Y.; Vuong, T.; Erbe, M.; Bennet, C.; Palazzo, B.; Popielski, L.; Rodriguez, N.; Hu, X. Comparative Study of Ultrasonication-Induced and Naturally Self-Assembled Silk Fibroin-Wool Keratin Hydrogel Biomaterials. Int. J. Mol. Sci. 2016, 17, 1497.

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