Search

Copyright of Journal of Almaty Technological University is the property of Almaty Technological University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Skin wound dressings are commonly used to stimulate and enhance skin tissue repair. Even if wounds seem easy to repair for clinicians and to replicate in an in vitro set-up for scientists, chronic wounds remain currently an open challenge in skin tissue engineering for patients with complementary diseases. The seemingly simple process of skin healing hides a heterogenous sequence of events, specific timing, and high level of organization and coordination among the involved cell types. Taken together, all these aspects make wound healing a unique process, but we are not yet able to completely repair the chronic wounds or to reproduce them in vitro with high fidelity. This review highlights the main characteristics and properties of a natural polymer, which is widely used as biomaterial, namely collagen and of its denatured form, gelatin. Available wound dressings based on collagen/gelatin and proposed variants loaded with bioactive compounds derived from plants are presented. Applications of these composite biomaterials are discussed with emphasis on skin wound healing. A perspective on current issues is given in the light of future research. The emerging technologies support the development of innovative dressings based exclusively on natural constituents, either polymeric or bioactive compounds. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Most tanneries use high proportions of Na2S and CaO during the dehairing step, resulting in effluents of high alkalinity and large amounts of suspended solid, besides the risk of liberating the toxic H2S. Solid waste rich in protein is another environmental problem of tanneries. Enzymes are an interesting technological tool for industry due to their biodegradability, nontoxic nature, and nonpolluting effluent generation. In the leather industry, proteases have been chosen as a promising eco-friendly alternative to Na2S/CaO dehairing. Extracts with high proteolytic activity have been obtained from fruits of Bromeliaceae species: Bromelia balansae Mez (Bb), Bromelia hieronymi Mez (Bh), and Pseudananas macrodontes (Morr.) Harms (Pm). In this work, Bb, Bh, and Pm have been studied for application in the leather industry, focusing in their dehairing properties. Enzymatic activities were measured against collagen, keratin, elastin, and epidermis while a dehairing assay was performed by employing cowhide. All extracts showed similar activity on collagen and epidermis, while Bh and Pm were the most active against keratin at the same caseinolytic unit (CU) values; Bh was the only extract active against elastin. Bb (1 CU/ml), Bh (1.5 CU/ml), and Pm (0.5 CU/ml) were able to depilate cowhide. Desirable characteristics of dehairing were observed for all extracts since hair pores did not show residual hair, grain surface was clean and intact, and collagen fiber bundles of dermis were not damaged. In conclusion, results here presented show that proteolytic extracts of Bromeliaceae species are promising eco-compatible tools for leather industry. [ABSTRACT FROM AUTHOR]

Extraction and characterization of collagen were carried out in rabbit skins as a new alternative for collagen type I. Acetic acid and pepsin were for the extraction of soluble and insoluble collagen, respectively. The enzymatic treatment yielded higher amount of collagen (71%). The average pH value was 6.3, no matter what the method of extraction was. Denaturation temperature of collagen was found at 36°C approximately in two different techniques: Rheometer and Differential Scanning Calorimetry (DSC). Despite the amount of collagen in solution was low, its viscosity was high because of the hydrodynamic behaviour of collagen molecules. Sodium dodecyl sulphate polyacrylamide gel electrophoresis results showed three different bands that reflected two alpha-chains and one beta-chain with molecular weights of 102, 118 and 220 kDa, respectively. Determination of hydroxyproline gave evidence that the extracted material was collagen. It was concluded that rabbit skin could be an alternative source for the extraction of collagen. [ABSTRACT FROM PUBLISHER]

Research in the field of conservation utilizes the literature of the arts, humanities and sciences to help understand material change and to improve conservation practice. The challenge associated with the use of such a broad range of literature is the process of extrapolation, where oversimplification of unfamiliar concepts and the misuse of terminology can occur. The unintended consequences of misuses in language can lead to the original meaning being misconstrued and evolution of terminology which is unhelpful for the conservation profession and others beyond its disciplinary boundaries. Here we examine, discuss and define the meanings of terms related to collagen and gelatine commonly used in heritage science, in particular with respect to parchment artefacts. We also present the context in which terminology is used and potential pitfalls of the terminology to avoid future ambiguities. [ABSTRACT FROM AUTHOR]

Preservation or curing of hides and skins is performed as the primary step of leather processing. Common salt is employed as the conventional agent for curing purpose. Use of salt enhances the pollution load of tannery effluent which becomes highly contaminated with increased total dissolved solids and chlorides. To overcome this hurdle, researchers are in constant search of alternative preservation techniques which are either totally void of salt or use only a meager amount of salt. In the present study, we had explored the possibility of using Semecarpus anacardium nut extract as an alternative to salt for the curing process by assessing different parameters like hair slip, putrefaction odor, volatile nitrogen content, moisture content, bacterial count, and shrinkage temperature in comparison to the salt curing method. The antibacterial property of the plant extract was also investigated. The results obtained substantiated that the nut extract of S. anacardium effectively could preserve the skins for more than a month, by its antibacterial activity along with the dehydrating property of acetone. [ABSTRACT FROM AUTHOR]

Biomaterials are used as wound dressings and scaffolds, which are generally required to disperse by resorption into the body after tissue generation. Most methods employ relatively toxic cross-linking agent. In this study, an attempt has been made to prepare hybrid biodegradable films from bovine collagen by combining with cellulose derivatives without employing a cross-linking agent. The bovine hide trimmings were converted into soluble collagen and blended with 25, 50, 75, and 100% (wt/wt) 2-hydroxyethyl cellulose. These blends were cast into thin films and were analyzed for structure, thermal, mechanical, and biostability properties. It was found that the dry hybrid films have improved tensile strength in the range of 22 ± 4.6 to 58.9 ± 4.3 MPa, compared to the pure collagen films. On the other hand, hydrated films exhibited reduced strength and improved elongation compared to dry hybrid films. The structure of select films was investigated using scanning electron microscope (SEM) both in wet and dry state and found that the pore distribution is more in the wet state with high cellulose concentration. Differential scanning calorimetric (DSC) analysis showed that the thermal stability of dry hybrid films was improved moderately while the hydrated hybrid films exhibited enhanced hydrothermal stability compared to pure collagen films. The infrared (IR) spectral analysis of hybrid films reveals the presence of functional groups from both collagen and cellulose, especially the signature peaks of collagen triple helical structure. The equilibrium swelling and in-vitro biodegradability analysis proved that the presence of cellulose derivative could noticeably improve the biostability of the hybrid films leading to controlled degradation compared to the pure collagen films. Cell interaction studies show good biocompatibility and increased cell growth on the hybrid films as a function of cellulose concentration, although collagen is sourced from bovine hide trimmings of leather industry. [ABSTRACT FROM AUTHOR]

The US is the world's 3rd largest hide producing country and currently produces approximately 35 million cattle hides annually. The majority of hides are tanned into leather, which is composed of collagen fibers interwoven into fibrous networks. Most leather products are constantly exposed to outdoor environments, therefore UV and heat resistance are very important qualities, particularly for nonchrome-tanned (chrome-free) leather. In recent years, we have focused on using environmentally friendly antioxidants that will improve the UV and heat resistance of chrome-free leather. Tocopherols are well-known antioxidants commonly used in the cosmetic and food industries. They are known as potent free radical scavengers and highly protective agents for collagen fibers against UV damage. We have investigated their potential to improve the UV and heat resistance of chrome-free leather. Experiments were conducted by adding 5-12% α-tocopherol to the polymeric topcoat on the grain of chrome-free leather. The treated samples were tested in a weatherometer, where they were exposed to artificial sunlight. Colorfastness and mechanical property tests showed that α-tocopherol significantly improved UV and heat resistance of leather. Dynamic mechanical tests showed that α-tocopherol reduced the hardening effects on leather caused by UV irradiation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

Abstract: Type I collagen (PSC-I) and type V collagen (PSC-V) were directly separated by DEAE-cellulose chromatography without salt precipitation from the skin of deep-sea redfish after limited pepsin digestion. The yields of PSC-I and PSC-V were 79.4% and 8.4%, respectively. The denaturation temperature of PSC-V (17.8°C) was significantly higher than that of PSC-I (15.9°C), as a result of its higher total content of imino acid (17.1%) and hydroxylation degree of proline and lysine (44.7%) than those of PSC-I (14.7% and 35.8%). However, the intrinsic viscosity and viscosity transition temperature span of PSC-I (14.4dL/g and 8°C) were considerably higher than those of PSC-I (13.5dL/g and 5°C), which could be attributed to its greater extent of triple helix and more intermolecular crosslinks as shown by SDS-PAGE pattern and infrared spectra. [Copyright &y& Elsevier]

Abstract: Collagen extracted from Atlantic salmon (Salmo salar L.) skin (which is normally discarded in the process of manufacture) was hydrolyzed with Alcalase and papain, and treated by multistage separation. The salmon skin collagen peptides (SSCP) obtained had high protein content (91.20±1.03%) and low molecular weights, 90.79% of which were less than 1000Da. SSCP was then separated by reversed-phase high performance liquid chromatography. Eleven major fractions were collected and their angiotensin I-converting enzyme (ACE) inhibitory activity was assayed. Fractions 5 and 7 displaying higher ACE inhibitory activity were subjected to mass spectrometer to identify the ACE inhibitory peptides. A total of eleven peptide sequences were identified, and two dipeptides, Ala-Pro and Val-Arg, were selected for further ACE inhibitory activity analysis. The ACE inhibitory activities of Ala-Pro (IC50 =0.060±0.001mg/ml) and Val-Arg (IC50 =0.332±0.005mg/ml) were found to be approximately 20- and 4-fold higher than that of SSCP (1.165±0.087mg/ml), respectively. [Copyright &y& Elsevier]

Solid state 13C-NMR spectra of pure tannin powders from four different sources - mimosa, quebracho, chestnut and tara - are readily distinguishable from each other, both in pure commercial powder form, and in leather which they have been used to tan. Groups of signals indicative of the source, and type (condensed vs. hydrolyzable) of tannin used in the manufacture are well resolved in the spectra of the finished leathers. These fingerprints are compared with those arising from leathers tanned with other common tanning agents. Paramagnetic chromium (III) tanning causes widespread but selective disappearance of signals from the spectrum of leather collagen, including resonances from acidic aspartyl and glutamyl residues, likely bound to Cr (III) structures. Aluminium (III) and glutaraldehyde tanning both cause considerable leather collagen signal sharpening suggesting some increase in molecular structural ordering. The 27Al-NMR signal from the former material is consistent with an octahedral coordination by oxygen ligands. Solid state NMR thus provides easily recognisable reagent specific spectral fingerprints of the products of vegetable and some other common tanning processes. Because spectra are related to molecular properties, NMR is potentially a powerful tool in leather process enhancement and quality or provenance assurance. [ABSTRACT FROM AUTHOR]

The thermal stability of sheepskin collagen cross-linked with chrome sulfate and mimosa (MI)–oxazolidine (OZ), respectively, had been researched in this experiment. All samples’ shrinkage temperatures ( Ts) are determined by a special Ts-testing-apparatus and denaturation temperatures ( Td) are determined by the differential scanning calorimetry. The relations between the modified collagens containing moisture and their hydrothermal stability, Ts or Td, were studied. The results show that the cross linking agents can enhance the thermal stability of modified collagen whose Ts are 109.8 and 110.6 °C for collagen treated with chrome and MI–OZ, respectively. When the samples contain 25–71.9% moisture for chrome leather and 20–71.1% for leather treated with MI–OZ, the hydrothermal stability will decrease with the increase of moisture. It was found that the difference between Ts and Td of collagen modified by chrome is more obvious than that of collagen modified with MI–OZ. And when the moisture of chrome leather exceeds 55%, Td cannot express thermal stability of modified collagen as a substitute for Ts, and the moisture is 40% for leather tanned with MI–OZ. [ABSTRACT FROM AUTHOR]

Abstract: Due to the structural hierarchy of collagen and the fiber weave pattern within skins and hides, leathers exhibit complicated viscoelastic behaviors. In this study, the stress-relaxation behaviors of chrome-tanned cattlehide shoe upper leathers were investigated. A generalized Maxwell model with four units is used to describe the stress-relaxation behavior of leather held at the strains of 23.0%, 30.9%, 37.2%, 42.6% and 51.9%, respectively. A method to get a three-dimensional stress-relaxation diagram with stress–strain–time coordinate is introduced in this paper, from which the stress of leathers at different strain and relaxation times can be predicted. With stress-relaxation measurement of cattlehide shoe upper leathers and a suitable curve fitting, the three-dimensional stress-relaxation diagram of cattlehide shoe upper leathers is built up. This method can also be applied to other solid viscoelastic materials with a suitable curve fitting equation. [Copyright &y& Elsevier]

In the conventional dehairing process of leather manufacture, animal skins are subjected to a drastic chemical treatment using lime and sodium sulfide. Sulfide reduces disulfide bonds in keratin present in hair and epidermis and thereby detaches them from skin. Lime, being an alkali, contributes to opening up of collagen fiber structure by cleaving a major portion of the glycosaminoglycans from proteoglycans, the interfibrillar elements of skin connective tissue. Currently, as an alternative to chemical dehairing, enzyme based dehairing processes using proteases avoiding the use of lime and sulfide are being developed because of their environmental benefits. Though both chemical as well as enzymatic dehairing processes are aimed at removing noncollagenous proteins and proteoglycans in addition to fiber opening, the mechanism of enzymatic process is distinct from that of the chemical process. In this study, we attempt to study in detail the mechanism of hair saving enzymatic dehairing process for skins using a bacterial protease against the customary hair burn chemical dehairing process. Quantitative analysis shows that the collagen content remains unaffected in both treatments but there is a marked reduction of proteoglycan constituents from dehaired pelts in the enzymatic process when compared to lime–sulfide process. This is further substantiated by histochemical examination of the sections of dehaired pelts using different stains as well as immunohistochemical studies on the removal of decorin. HPLC profile shows that decorin is extensively degraded by the bacterial protease. This study conclusively demonstrates that proteolytic degradation of decorin and subsequent removal of proteoglycan aggregates play an important role in the opening up of the collagen fiber bundles during enzymatic dehairing. [Copyright &y& Elsevier]

The ever-increasing attention to the environmental impact of leather industry has necessitated the development of enzyme-based processes as potent alternatives to pollution causing chemicals. In this study, a hair saving process is developed for dehairing of skins and hides using a bacterial alkaline protease preparation, completely eliminating the use of lime and sulfide. To evaluate the efficacy of the enzymatic process, comparative studies have been carried out with two controls; a conventional lime–sulfide process and enzyme-assisted process using commercial dehairing enzyme with reduced quantities of lime and sulfide. The developed process requires a shorter duration of 6h for complete dehairing of skins and hides than control groups and also, it avoids the use of silicate carriers since the enzymatic dehairing is carried out by dip method. Histological and scanning electron microscopic analyses of the dehaired pelts obtained from enzymatic process reveal complete removal of hair and epidermis with moderate opening up of fiber structure in both dermis and corium. Moreover, the collagen is not damaged and resulting in a leather of good quality. The developed process has resulted in a remarkable reduction of effluent load in terms of biochemical oxygen demand, chemical oxygen demand, total dissolved solids and total suspended solids. Physicochemical studies conclusively show that the leathers produced by enzymatic process are equivalent to or better than that obtained by control systems. Thus, the developed enzymatic process offers immense potential for greener mode of dehairing of skins and hides in leather industry coupled with environmental excellence. [Copyright &y& Elsevier]

It is necessary to understand the changes that occur during the initial processing of lamb skins, because these will affect the final quality of the leather. The types of collagen, their macro and micro structures, the presence of proteins other than collagens, and the quantity and the type of proteoglycans, all have a profound effect on the quality of leather. Proteins isolated from untreated or raw sheep skin and from pickled skin (skins treated with sodium sulfide and lime followed by bating with enzymes, then preserved in sodium chloride and sulfuric acid) were significantly different when analysed by use of 2D gel electrophoresis and mass spectrometry. Agarose gel electrophoresis with a very sensitive sequential staining procedure has been used to identify the glycosaminoglycans present in raw and treated skin and their impact on quality of leather. Results showed that effective removal of proteoglycans acting as inter-fibrillar adhesives of collagen fibrils seemed to improve leather quality. Removal of these molecules not only opens up the fibre structure of the skin but may also be important in wool removal. The presence of elastin, which imparts elastic properties to skin, is of significant importance to tanners. The amino acids desmosine and isodesmosine, found exclusively in elastin, were quantitatively analysed to assess the role of elastin in leather quality. [ABSTRACT FROM AUTHOR]

Abstract: Widely insoluble collagen of skin was transformed into soluble hydrolysates by thermo-mechanical treatment in an internal mixer. During this treatment the fibrous structure of collagen disappeared. The degree of solubility depended on the duration of the treatment. Warm aqueous solutions of the hydrolysates were able to form stiff gels when cooled. However, the molecular weight distribution was totally different from that of gelatine. The increase of solubility showed that molecular weight decreases and that covalent bonds were cleaved. There were no hints that specific peptide bonds were cleaved more easily than others because the SEC showed no specific peaks. In contrast to gelatine manufacture, the thermo-mechanical treatment did not lead to a topochemical hydrolysis. This is one of the most important differences between gelatines and the samples which were produced by thermo-mechanical treatment. A second difference is the high content of very high molecular material in the samples. [Copyright &y& Elsevier]

• The first comprehensive study on the chemical and structural composition of alpaca skin. • The first report on the Small angle X-ray scattering (SAXS) of alpaca skin. • The crosslinking profile of the alpaca skin is measured. • No correlation is found between the amino acid sequence of collagen C-telopeptide and the type of crosslinks in alpaca skin. Alpacas (Vicugna pacos) produce a high-value fibre and leather that is increasingly sought after for the production of luxury goods. Although several studies have addressed the genetics and gene expression of alpaca skin, particularly those associated with colour, little is known about the structural and molecular compositions of alpaca skin. In this study, alpaca skin was analysed using small angle X-ray scattering (SAXS), analytical and physical methods. Using SAXS, the axial periodicity (65.1 nm) and intermolecular lateral packing distance (1.47 nm) of collagen in alpaca skin are determined to be similar to the previous studies on skins from other animal species. The collagen crosslinking profile in alpaca skin shows the presence of six crosslinks including pyridinoline and deoxypyridinoline and this is different from other animal skins. We hypothesised that the biosynthesis of pyridinoline and deoxypyridinoline in biological tissues is driven by a combination of several factors including amino acid sequence of collagen type I and lysyl hydroxylase activity. In this work, we showed that alpaca skin collagen crosslinks are diverse and their relative concentrations are different from other animal skins. We also detected histidinohydroxylysinonorleucine crosslink in alpaca skin which lacks histidine in its C-terminal telopeptide of type I collagen. [ABSTRACT FROM AUTHOR]