Evaluation of keratin extraction from wool by chemical methods for bio-polymer application

This study investigated some physicochemical properties of keratin extracted from Merino wool using five chemical extraction methods: alkali hydrolysis, sulfitolysis, reduction, oxidation, and extraction using ionic liquid. The ionic liquid method produced the highest protein yield (95%), followed by sulfitolysis method (89%), while the highest extraction yield was obtained with the reduction method (54%). The lowest yield was obtained with the oxidation method (6%). The oxidation extract contained higher molecular weight (>40 kDa) protein components, whereas the alkali hydrolysis extract contained protein material of <10 kDa. The sulfitolysis, reduction, and ionic liquid extracts contained various protein components between 3.5 and 60 kDa. Keratin obtained from various extraction methods had different yield, morphology, and physicochemical properties. None of the samples were toxic to L929 fibroblast cells up to a concentration of 2.5 mg/mL. Apart from the alkali hydrolysis extract, all other keratin extracts (reduction, sulfitolysis, ionic liquid, and oxidation) showed Fourier transform infrared adsorption peaks attributed to the sulfitolysis–oxidation stretching vibrations of cysteine-S-sulfonated residues, with the oxidation extract showing the highest content of cysteine-S-sulfonated residues. This study indicates that the properties of the keratin extract obtained vary depending on the extraction method used, which has implications for use in structural biomaterial applications.

Fabrication and biological evaluation in vivo of an injectable keratin hydrogel as filler materials

Filler materials of soft tissue should have good biodegradable absorption and biocompatibility. To investigate feasibility of keratin hydrogels used as filler materials, a keratin with high molecular weight and self-assembly ability was extracted from human hair using a modified reduction method and was characterized using sodium dodecyl sulfate–polyacrylamide gel electrophoresis, Fourier transform infrared, and X-ray diffraction. An injectable keratin hydrogel was also prepared and its water absorption, cell toxicity, and histological behavior were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method and subcutaneously implanted experiment. The results showed that the modified extraction method could keep the activity of the keratin and provided the self-assembly crosslinked ability of the keratin. The water absorption of the keratin hydrogel could be controlled by adjusting some preparation parameters and the percentage of water absorption was up to 850%. In addition, the subcutaneous injection experiment for Sprague Dawley rats indicated that the keratin hydrogel had good biocompatibility and could promote the formation of angiogenesis as well as proliferation. It can be predicted that the keratin extracted from human hair and keratin hydrogel have good application prospects in the field of filler materials for soft tissue.

A simple material model to generate epidermal and dermal layers in vitro for skin regeneration

There is an urgent need for a rationally-designed, cellularized skin graft capable of reproducing the micro-environmental cues necessary to promote skin healing and regeneration. To address this need, we developed a composite scaffold, namely, CA/C-PEG, composing of a porous chitosan-alginate (CA) structure impregnated with a thermally reversible chitosan-poly(ethylene glycol) (C-PEG) gel to incorporate skin cells as a bi-layered skin equivalent. Fibroblasts were encapsulated in C-PEG to simulate the dermal layer while the keratinocytes were seeded on the top of CA/C-PEG composite scaffold to mimic the epidermal layer. The CA scaffold provided mechanical support for the C-PEG gel and the C-PEG gel physically segregated the keratinocytes from fibroblasts in the construct. Three different tissue culture micro-environments were tested: CA scaffolds without C-PEG cultured in cell culture medium without air-liquid interface (-gel-interface), CA scaffolds impregnated with C-PEG and cultured in cell culture medium without air-liquid interface (-gel-interface), and CA scaffolds impregnated with C-PEG cultured in cell culture medium with air-liquid interface (-gel- interface). We found that the presence of C-PEG increased the cellular proliferation rates of both keratinocytes and fibroblasts, and the air-liquid interface induced keratinocyte maturation. This CA/C-PEG composite scaffold design is able to recapitulate micro-environments relevant to skin tissue engineering, and may be a useful tool for future skin tissue engineering applications.

Effect of anti-TGF-β2 surface modification of polydimethylsiloxane on lens epithelial cell markers of posterior capsule opacification

Posterior capsule opacification is the most common complication of cataract surgery. Lens epithelial cells remaining in the capsular bag following surgery can undergo epithelial-to-mesenchymal transition and migrate from the anterior to the posterior capsule, leading to fibrosis, capsular wrinkling, and ultimately vision loss. Transforming growth factor-beta 2 has been shown to play a major role in epithelial-to-mesenchymal transition. Covalent tethering of anti-transforming growth factor-beta 2 to the surface of the intraocular lens material may inhibit epithelial-to-mesenchymal transition and the subsequent events, thus leading to a reduction in posterior capsule opacification. In this work, the antibody was tethered to the surface of polydimethylsiloxane as a model lens material via a poly(ethylene) glycol spacer. Surface characterization using a variety of methods demonstrated successful modification. The surface density of the anti-transforming growth factor-beta 2 was approximately 0.5 µg/cm2. The presence of transforming growth factor-beta 2 in cell culture medium stimulated production of extracellular matrix components such as collagen, fibronectin, laminin, and the fibrotic marker α-smooth muscle actin, by HLE-B3 cells. These effects were decreased but not completely eradicated by the presence of the anti-transforming growth factor-beta 2 antibody on the polydimethylsiloxane surface. These results suggest that surface modification with appropriate antifibrotic molecules has the potential to modulate cellular changes following cataract surgery and lead to a reduction in posterior capsule opacification.

Enzymatically cross-linked injectable gelatin gel as osteoblast delivery vehicle

Injectable and degradable hydrogels are potential candidates as cell delivery vehicles for the regeneration of osseous defects. We evaluated the potential of injectable enzymatically cross-linked gelatin gel as an osteoblast delivery vehicle using murine preosteoblast MC3T3-E1 cells. Injectable hydrogels were prepared by enzymatic cross-linking of the phenol derivatives of gelatin (tyramine-modified) in the presence of hydrogen peroxide (H2O2) and horseradish peroxidase. The effect of gelatin concentration on gel morphology and in supporting the adhesion and spreading of encapsulated MC3T3-E1 cells, activation of intercellular signaling in MC3T3-E1 cells by extracellular signal-regulated kinase phosphorylation, β-catenin and Runx2 was evaluated. Both tyramine-modified and unmodified gelatins as well as gelatin gels did not activate intercellular signaling pathways in MC3T3-E1 cells. The encapsulated cells in gelatin gel showed extracellular signal-regulated kinase phosphorylation and active β-catenin expression in the presence of inductive molecules such as insulin and LiCl. The gelatin gels formed from 10 to 25 mg/mL tyramine-modified gelatin supported the adhesion, spreading, and three-dimensional growth of MC3T3-E1 cells. However, the lack of activation of intercellular signaling in the gelatin gel indicates the need to add exogenous bioactive molecules to modulate the osteogenic functions of the encapsulated cells.