Pepsin-solubilized Collagen Research Articles

Potency of Pepsin Soluble Collagen from Indonesian Local Goat Skin as an Antioxidant

Potency of Pepsin Soluble Collagen from Indonesian Local Goat Skin as an Antioxidant

Acid and Pepsin Soluble Collagens from Skin By-product of Red-bellied Pacu (Piaractus brachypomus): Extraction and Comparative Characterizations Towards Finding Substitute to Bovine and Porcine Collagen

ABSTRACT This investigation focused on the sustainable valorization of red-bellied pacu (RBP) skin towards finding an alternative to bovine and porcine collagen. Acid-soluble collagen (ASC, 45.8 ± 0.7%) and pepsin soluble collagen (PSC, 57.8 ± 1.9%) were successfully extracted from RBP skin and comparatively elucidated their characteristics and in-vitro fibril-forming potential. The extracted collagens were characterized as type I collagen and confirmed the well-preserved triple-helical configuration by sodium dodecyl sulphate polyacrylamide gel electrophoresis and Fourier transform-infrared spectroscopy analysis. Both ASC and PSC exhibited relatively better thermo-stability, and the denaturation temperatures were found to be 35.5–35.29 °C by differential scanning calorimetry analysis. Both collagens displayed higher (p ≤ 0.05) solubility at low NaCl concentrations. The extracted ASC and PSC showed the same degree of fibril-forming capacities and confirmed well-defined fibril morphologies. Overall, the results showed the possibilities of effectively exploring RBP skin as a potential alternative source for realistic and safe collagen for food, nutrition, pharmaceutical, and other applications.

Extraction Methods, Characterization and Biomedical Applications of Collagen: a Review

It is difficult to develop a standard extraction method for all types of collagen from different tissues due to the extreme diversity of collagen types. Some procedures are based on the isolation of acid, pepsin, and enzymatic soluble collagen, showing certain advantages and disadvantages. Other methods were also optimized to partially purify collagen and extract it easier than the methods currently used. Indeed, this review describes some advantages and disadvantages of these isolation methods. Moreover, major biomedical applications of collagen were reported. Given the great importance of biocompatible matrices in tissue engineering, the availability of native collagen should be investigated by refining the collagen extraction procedure.

Distinctive characteristics of collagen and gelatin extracted from Dosidicus gigas skin

SummarySquid skin, often discarded as processing by‐product, is a good resource of collagen/gelatin. In this study, acid soluble collagen (ASC), pepsin soluble collagen (PSC) and water soluble gelatin (WSG) were extracted from squid (Dosidicus gigas) skin and physicochemically examined. The lowest yield of 33.5% was obtained for ASC extracted at 4 °C, and the addition of pepsin increased the collagen yield by around 35.0% (PSC). The highest yield of 81.9% (WSG) was achieved by thermal extraction at 60 °C. A low temperature can largely retain the native helix structures of ASC and PSC, contrariwise, thermal treatment converted collagen into gelatin with unordered and renatured structures. The proline and hydroxyproline contents of ASC, PSC and WSG were 183/1000 residues, 194/1000 residues and 175/1000 residues, respectively. In addition, WSG showed a denaturation temperature at 80.7 °C which was much higher than that of ASC (24.2 °C) and PSC (26.2 °C), while a significant lower resistance towards enzymatic digestion.

Collagen isolation and characterization from Sardinella longiceps.

Objective:Collagen is a fibrous protein that is primarily used in the pharmaceutical and biomedical industries. This study isolates and characterizes type-1 collagen from Sardine longiceps (scales, skin, and muscle).Materials and Methods:Collagen was isolated from S. longiceps using two methods: acid-solubilized collagen and pepsin-solubilized collagen. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) was used to estimate the molecular weight of isolated collagen. Ultraviolet (UV)-visible spectrophotometry analysis was used to confirm the collagen extracted (type-I collagen). The functional groups of isolated collagens were identified using fourier transform infrared (FTIR) analysis. The X-ray diffraction (XRD) technique was used to investigate the crystallinity of isolated collagen. The high-pressure liquid chromatography (HPLC) technique was used to study the amino acid composition.Results:SDS–PAGE of S. longiceps revealed molecular weights ranging from 116 kDa for α-2 to 97 kDa for α-1. UV-visible spectra showed an absorbance value below 300 nm, and the results confirmed type-I collagen. FTIR showed major functional groups like amide A, B, I, II, and III. XRD determined the crystallinity of isolated collagen. The HPLC results showed the presence of higher glycine content, followed by proline and hydroxyl proline in the extracted collagen.Conclusion:The overall study confirmed that fish waste materials (scales, skin, and muscles) could be used as an alternative source for collagen.

Characterization of pepsin-soluble collagen extracted from gourami (Osphronemus goramy) scales.

Periodontal regeneration is the anticipated result of periodontal tissue therapy. Of the many scaffold materials utilized, collagen has been shown to possess characteristics that strongly promote the periodontal regeneration process. Gourami (Osphronemusgoramy) scales can be utilized as an alternative source of collagen due to their abundant availability, the absence of risk of zoonosis, and lack of religious strictures against their use. To analyze the characteristics of collagen extracted from gourami scales. A combination of scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and in vitro enzymatic biodegradation analysis were employed to determine pore sizes, constituent functional groups, and the degradation rate of collagen extractedfrom gourami scales. Collagen extracted from gourami scales demonstrated an average porosity of 13.779 μm. The FTIR test results indicated Amide A, Amide B, Amide I, Amide II, and Amide III peaks. The degradation rate of extracted collagen from gourami scales was 92.00 ± 0.8165% on the first day, 95.75 ± 1.70783% on the third day and 100% on the seventh day. The pore sizes ofcollagen extracted from gouramy scalesare suitable for use as scaffold. FTIR analysis indicated that this collagen possessed a triple helix structure. Collagen extracted from gourami scales was completely degraded within seven days when treated with 0.6 g/mL collagenase solution.

Study of the thermodynamics and conformational changes of collagen molecules upon self-assembly

The emphasis on mechanism of collagen self-assembly shows great significance for development of collagen-based materials with targeted attributes. Here, combination of isothermal titration calorimetry (ITC) dilution experiments, circular dichroism (CD) and FTIR measurements were employed to investigate the thermodynamic differences and corresponding mechanisms associated with self-assembly of acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). Firstly, the microrheology measurements of ASC and PSC under the different temperatures (20 °C, 25 °C, 30 °C and 37 °C) had confirmed the temperature induced collagen aggregation. The several thermodynamic parameters (Gibbs free energy change, enthalpy change and entropy change) and the critical mass concentration (CMC) of ASC and PSC, obtained by ITC dilution experiments, decreased with the rising temperatures. The magnitudes of negative Gibbs free energy changes were always higher for ASC than that of PSC, indicating former was more energetically favorable. Besides, the self-assembly of both two collagens were driven by hydrophobic interactions, as evidenced by a negative heat capacity value (ΔCp,mic<0). Specifically, the hydrophobic effects improved due to the transformation of PPII into β-sheet conformations upon collagen self-assembly, as supported by differential CD spectra and FT-IR measurements. Overall, ASC had a higher PPII population than PSC at most temperatures, which may elaborate the thermodynamic differences of two collagens in terms of secondary structure.

Characteristics and Functional Properties of collagen extracted from Nile tilapia (Oreochromis niloticus) skin

: Tilapia skin might be used as a new source of collagen, therefore collagen extracted from Nile tilapia skin can be utilized as food products because of its good functional properties. Two extraction methods were used to obtain acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from Nile tilapia skin. In this study, collagen was characterized in terms of FT-IR Spectrum, amino acid analysis, SDS-PAGE and Thermal denaturation temperatures (Td). Also, some major functional properties including solubility, oil and water absorption, emulsifying activity and stability, foaming ability, foam stability, and gelation properties were determined. The results showed that the yields of ASC and PSC were 4.30% and 1.84 % (on a wet weight basis), respectively. Amino acid composition analysis indicated that the imino acid content of ASC and PSC were found to be 172.10 and 164.18 residues per 1000 residues, respectively. SDS-PAGE results indicated that ASC and PSC were type I collagen. The FTIR Spectrum confirmed that the presence of a triple-helical structure characteristic of ASC and PSC. The denaturation temperature of ASC and PSC were 26⁰C and 25⁰C respectively. The solubility of ASC and PSC were highly solubilized in the pH range of 2–3. ASC and PSC had good water and oil absorption capacity. Gelation studies revealed that ASC and PSC have good gelation properties. Consequently, Nile tilapia skin could be used as a good source to extract ASC and PSC which can be used to add high value in the food industries.

Isolation and characterization of acid and pepsin soluble collagen extracted from sharpnose stingray (Dasyatis zugei) skin

This study aimed to isolate and characterize the acid soluble collagen (ASC) and pepsin soluble collagen (PSC) from the skin of the sharpnose stingray (Dasyatis zugei). Isolated ASC and PSC were subjected to chemical and physical characterizations. The yield of PSC (34.84±1.26%) was significantly higher than that of ASC (20.48±4.41%) (p&lt;0.05). There were no significant differences between ASC and PSC in terms of chemical composition (p&gt;0.05). Both ASC and PSC were thermally stable at high temperatures, with denaturation temperatures of 24.1°C and 25.2°C, respectively, and maximum temperatures of 31.94±0.13°C and 31.79±0.23°C, respectively. Fourier transform infrared (FTIR) investigations showed the presence of triple helical structure with strong hydrogen bonding in both ASC and PSC. Meanwhile, both collagens were highly solubilized at acidic pH but at different optimal pH. The surface morphologies of ASC and PSC were loose and possessed slender, less uniform and irregular fibrous network structures with large and irregular pores observed between the fibrils. This finding showed that the alternative source of marine collagen possesses good physicochemical properties which highly potential for nutraceutical, pharmaceutical or cosmeceutical application.

Extraction and Characterization of Collagen from Elasmobranch Byproducts for Potential Biomaterial Use.

With the worldwide increase of fisheries, fish wastes have had a similar increase, alternatively they can be seen as a source of novel substances for the improvement of society’s wellbeing. Elasmobranchs are a subclass fished in high amounts, with some species being mainly bycatch. They possess an endoskeleton composed mainly by cartilage, from which chondroitin sulfate is currently obtained. Their use as a viable source for extraction of type II collagen has been hypothesized with the envisaging of a biomedical application, namely in biomaterials production. In the present work, raw cartilage from shark (Prionace glauca) and ray (Zeachara chilensis and Bathyraja brachyurops) was obtained from a fish processing company and submitted to acidic and enzymatic extractions, to produce acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). From all the extractions, P. glauca PSC had the highest yield (3.5%), followed by ray ASC (0.92%), ray PSC (0.50%), and P. glauca ASC (0.15%). All the extracts showed similar properties, with the SDS-PAGE profiles being compatible with the presence of both type I and type II collagens. Moreover, the collagen extracts exhibited the competence to maintain their conformation at human basal temperature, presenting a denaturation temperature higher than 37 °C. Hydrogels were produced using P. glauca PSC combined with shark chondroitin sulfate, with the objective of mimicking the human cartilage extracellular matrix. These hydrogels were cohesive and structurally-stable at 37 °C, with rheological measurements exhibiting a conformation of an elastic solid when submitted to shear strain with a frequency up to 4 Hz. This work revealed a sustainable strategy for the valorization of fisheries’ by-products, within the concept of a circular economy, consisting of the use of P. glauca, Z. chilensis, and B. brachyurops cartilage for the extraction of collagen, which would be further employed in the development of hydrogels as a proof of concept of its biotechnological potential, ultimately envisaging its use in marine biomaterials to regenerate damaged cartilaginous tissues.

Characterization and comparison of collagen extracted from the skin of the Nile tilapia by fermentation and chemical pretreatment

Chemical pretreatment of collagen raw materials is time-consuming and environmentally hazardous. Collagen extraction after fermentation pretreatment has not been reported. We extracted and characterized acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from Nile tilapia (Oreochromis niloticus) skin following fermentation and chemical treatments and comparatively evaluated the feasibility of fermentation. Fermentation-ASC (FASC) and fermentation-PSC (FPSC) yields (4.76 and 8.14 wt%, respectively) were slightly but not significantly higher than chemical-ASC (CASC) and chemical-PSC (CPSC) yields (4.27 and 7.60 wt%, respectively). All extracts were identified as type I collagens by SDS-PAGE and retained their triple helical structure well, as confirmed through Fourier transform infrared spectroscopy. All collagen microstructures under scanning electron microscopy were multi-layered aggregates. These collagens also had similar biochemical properties (i.e. denatured between 36.5 and 37.1 °C, high soluble at pH 1–4 and at <3% [w/v] NaCl). Therefore, fermentation method is a viable alternative for pretreating collagen extraction materials.

Effects of single- and tri-frequency ultrasound on self-assembly and characterizations of bionic dynamic rat stomach digestion of pepsin-soluble collagen from chicken leg skin

Chicken feet, aplenty by-products in the chicken industry, are rich in collagen and contain abundant amino acids so that it can be used as an important source for the collagen market. Pepsin-soluble collagen (PSC) was extracted from chicken leg skin and explored the effects of single- and tri-frequency ultrasound on the self-assembly and vitro digestion characteristics. By the diverging and tri-frequency ultrasound reactor, PSC was treated with 20 kHz/270w (C20H5m), 40 kHz/270w (C40H5m), 60 kHz/270w (C60H5m), 20/40/60 kHz/90w × 3 (CtH5m) for 5 min. Results showed that ultrasound could accelerate the process of collagen self-assembly, and 60 kHz/270w was the fastest. Microfiber diameters of C60H5m were 65–89 nm, which was significantly lower than the control without ultrasound (80–161 nm). The digestion results indicated polypeptides with relative molecular weights founded in the range 200–5000 Da were exceeded 85%. The final digested product had the highest content of oligopeptide, consistent rheological properties, and elastic behavior. The cavitation and mechanical of ultrasound have effects on the self-assembly process and collagen gel structure and digestion characteristics, which is of great significance for the development of the chicken industry and collagen market.

Characterization of acid soluble collagen (ASC) and pepsin soluble collagen (PSC) extracted from shortfin scad (Decapterus macrosoma) waste

Fish waste management is one of the biggest impacts towards the environment. However, it is one of the rich sources of protein. Therefore, the aim of this study was to isolate and characterize acid soluble collagen (ASC) and pepsin soluble collagen (PSC) from shortfin scad (Decapterus macrosoma) waste, with the yields of ASC (3.35±3.43%) and PSC (0.10±0.13%) respectively. The isolated ASC and PSC from shortfin scad waste were characterized on chemical composition, protein concentration, structural properties by FTIR, solubility and morphology properties compared to the commercial collagen from tilapia (Oreochromis niloticus) scales. In terms of chemical composition, PSC showed better than ASC, since it contains comparatively higher in protein (26.97±1.02%) by Kjeldahl method and protein concentration (2.69±0.47 mg/mL) by biuret method, compared to ASC. The FTIR investigations also certified the existence of spacial triplehelical structures of collagens that are important for collagen backbones. Solubility results showed that both ASC and PSC are high insolubility at acidic pH with the lowest solubilisation point at the range of alkali condition. The morphological analysis of both ASC and PSC were almost similar too, as there were fibrils and porous structure. Therefore, collagen from shortfin scad waste, could be a useful alternative, with the potential to be used in food ingredient, biomedical, pharmaceutical and nutraceuticals industries

Thermal stable characteristics of acid- and pepsin-soluble collagens from the carapace tissue of Chinese soft-shelled turtle (Pelodiscus sinensis)

The carapace from the Chinese soft-shelled turtle (Pelodiscus sinensis) is used as a traditional Chinese medicine. Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from turtle carapace were isolated and characterized to screen novel collagen material in this study. Yields of 1.0% and 2.8% were obtained for ASC and PSC which contained glycine as the major amino acid and had high imino acid content. Both collagens had maximum ultraviolet absorption peaks of 220 nm. SDS-PAGE revealed that the structure of both collagens was similar, belonging to type I collagen. Relative viscosities of collagens were decreased as the temperature increased. Collagens showed minimum solubility at pH 8 and maximum solubility at a salt concentration of 3%. The denaturation temperature (Td) of PSC was higher whereas the melting temperature was lower than that of ASC. Both ASC and PSC appeared to be spongy like microstructure with fibrillar pores shown by scanning electron microscopy. The results suggest that collagens isolated from turtle carapace has high thermal stability with potential uses as new substitute for mammalian collagen in medicinal, food or biomaterial fields. However, their biological or pharmacological activities are needed to be further studied.

Structural characterization and in vitro immunogenicity evaluation of amphibian-derived collagen type II from the cartilage of Chinese Giant Salamander (Andrias davidianus)

Collagen type II (CT-II) has unique biological activities and functions, yet the knowledge on amphibian-derived CT-II is rare. Herein, acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were successfully isolated and characterized from the cartilage of Chinese Giant Salamander (CGS). The in vitro immunogenicity of collagen was then evaluated and compared with that of the standard bovine CT-II (SCT-II) by T-lymphocyte cell proliferation activity. Results demonstrated that ASC and PSC were predominantly CT-II along with minor collagen type I and maintained intact triple-helical structure of nature collagen. Compared with SCT-II, higher glycine content (337.80 and 339.93 residues/1000 residues) and lower degree of proline hydroxylation (51.81% and 52.52%) were observed in ASC and PSC. Additionally, PSC showed comparable T d (63 °C) and higher T m (109 °C) than SCT-II (64 °C and 103 °C, respectively), indicating its high thermal and structural stability. SEM revealed that the lyophilized ASC and PSC had interconnected porous network structures of collagen-based materials. Moreover, different from SCT-II, both ASC and PSC presented no immunogenicity because they did not cause obvious proliferation of murine T-lymphocyte regardless of the induced concentration of collagen increased from 8 to 417 μg/mL. These data suggested that the amphibian-derived CGS cartilage collagens avoid the immunogenic risk of terrestrial animal collagen, and show high thermal stability and potential advantage in biomedical application.

A New Method of Gelatin Modified Collagen and Viscoelastic Study of Gelatin-Collagen Composite Hydrogel

Pure collagen materials are expensive with poor mechanical properties, which need modifications in most cases. As the degradation product of collagen, gelatin is cheap, degradable and biocompatible, but few literatures have reported the research about gelatin-collagen composite materials. This is because gelatin and collagen have different soluble temperatures—gelatin is soluble in hot water (≥30 °C) and swells in cold water. However, a low temperature (2–10 °C) is required to prepare and store collagen solution, and neutral collagen solution denatures quickly above the room temperature. In this study, gelatin was ground into powders and swelled in neutral bovine tendon pepsin-soluble collagen solution (BPSC) to form a homogeneous gelatin-collagen mixture, in light of the swelling characteristics of gelatin in cold water. The assembly properties and gel properties of this composite material were further studied. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) test results showed that the bovine tendon collagen had typical type-I collagen structural characterizations with two α chains of about 100 kDa and one β chain of about 200 kDa; while the SDS-PAGE pattern of gelatin displayed bands continuously distributed from 30 to 200 kDa. Amino acid composition analysis test indicated that the content of polar amino acids and the sum of acidic and base amino acids for gelatin were higher than that of BPSC. Studies on gel properties demonstrated that gelatin-collagen mixed solution had collagen-like assembly characteristics and assembly kinetics. The moduli of the assembled gel at 35 °C were equivalent to that of pure bovine tendon collagen system; moreover, the system moduli didn’t change with time with elastic moduli (G′) of about 40 Pa. However, at 25 °C, the moduli of gelatin-collagen composite hydrogel increased with the extension of time, its G′ increased about 18 times within 8 h, and the ratio of elastic modulus to viscous modulus (G″) increased 4.6 times, showing a significant aging effect of structural strength. Meanwhile, the mechanical strength of the composite hydrogel was also regulated by temperature—the gel was highly elastic (G′≈3,000 Pa, G′>>G″) at a low temperature (5 °C); as the temperature rose, the system moduli gradually decreased and the elastic gel transformed into waterlike fluid at 50 °C little by little. What’s more, gelatin-collagen composite hydrogel also had reversible sol-gel performances and self-healing capability similar to the gelatin hydrogel. This novel preparation method for preparing composite materials and the resultant composite hydrogel are expected to be used in the fields of natural food gels, injectable hydrogels, cell scaffolds, drug sustained-release materials and so on, and improve and promote the processing performances, price and large-scale production of collagen-based materials.

Characterization of fish collagen from blue shark skin and its application for chitosan- collagen composite coating to preserve red porgy (Pagrus major) meat.

Pepsin soluble collagen (PSC) was extracted from blue shark (Prionace glauca) skin and was used for chitosan-collagen composite coating to investigate coating effects on fresh red porgy (Pagrus major) fillet quality during storage at 4°C. Total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), pH, K value, drip loss, and sensory evaluation scores were measured as deterioration indexes. Results show that coating by 1% of chitosan solutions containing 0.0%-0.8% of PSC significantly improved most deterioration indexes. Coating by 1% of chitosan solution containing 0.8% of PSC yielded the best results for K value, drip loss, and sensory evaluation, although the other indexes show no clear PSC concentration dependence. These results indicate 1% of chitosan solution containing 0.8% of PSC as the best coating formulation examined in this study. PRACTICAL APPLICATIONS: Aquatic products have high contents of water and protein. Their qualities are likely to decline because of endogenous chemical and enzyme reactions, and also because of the role of spoilage and pathogenic microorganisms during storage. The edible collagen and chitosan coating suggested by this research is biodegradable, biocompatible, cost effective, and is able to meet the requirements for food quality and storage duration. Pepsin soluble collagen (PSC) is an aquatic product processing by-product that makes the maximum use of resources. As described herein, a composite formulation comprising collagen and chitosan improves preservation effects of different types of coatings. A more high-quality and effective edible coating formulation was obtained, thereby extending the red porgy fillet shelf life.

Structural feature and self-assembly properties of type II collagens from the cartilages of skate and sturgeon.

Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted and purified from the cartilages of skate and sturgeon. Their typical structure and physicochemical properties were evaluated by circular dichroism (CD), X-ray diffraction (XRD), and so on. Results showed that the extracted collagen was likely identified as collagen-II composed of three α-chains (135kDa), with the typical peptide sequence of Gly-X-Y. It showed the collagen retained the native and intact triple helical structure, and its intensity ratio of the positive and negative absorption peaks (Rpn) was 0.19-0.25. In addition, the extracted collagen exhibited obvious self-assembly behavior with the concentration above 0.3mg/mL, the adjustment of pH 7.4-7.6 and the NaCl concentration of 120mmol/L. The critical aggregate mass concentrations of pepsin-soluble collagens from skate and sturgeon were 0.93 and 0.86g/L, respectively. Therefore, collagens from skate and sturgeon cartilages have potential commercial application.

Determining Resistance to Protein Turnover in Aged Skeletal Muscle Collagen Using a Novel Stable Isotope Timecourse Approach

BACKGROUNDAged skeletal muscle presents with an accumulation of extracellular matrix (ECM) proteins, including collagen, that are stiffer and fibrotic (i.e., unresolvable and resistant to turnover) which alters the cellular microenvironment leading to reduced muscle function. A limitation of current assessments of protein turnover using a single timepoint is that they do not account for how much of a protein pool is actively turning over. In addition, defining the proportion of the protein pool actively turning over also informs on how much of the same pool is fibrotic. Thus, determining aging muscle changes in both collagen protein synthesis and the collagen protein pool actively turning over is vital for a more comprehensive understanding of fibrosis in aged skeletal muscle ECM.PURPOSETo test the hypothesis that with age the fraction of collagen proteins actively turning over would decrease, indicating an increase in fibrotic collagen, and that the fraction of the protein pool turning over would be inverse to the amount of collagen cross‐linking and overall protein oxidative damage.METHODSYoung adult (6 mo.) and old (23 mo.) female C57BL/6 mice were labeled with the stable isotope deuterium oxide (D2O) for 4, 15, 30, 45, or 60 days (n=3–5/timepoint). Gastrocnemius muscles were analyzed for collagen protein synthesis (k 1/day) and the plateau (P) value for fraction new as a novel indicator of the protein pool capable of turning over (with 1.0 equal to 100% of the total pool turning over). Collagen cross‐linking was assessed using a pepsin digestion collagen solubility and hydroxyproline assay and Western Blotting for lysyl oxidase (LOX, catalyzes collagen cross‐links), while muscle protein carbonylation was assessed as a marker of oxidative damage.RESULTSCollagen protein synthesis and collagen plateau fraction new were significantly (p &lt; 0.05) lower in old compared to young (0.011±0.002 vs 0.027±0.003 k 1/day and 0.141±0.015 vs 0.280±0.051 P, respectively). The lower collagen turnover in old compared to young muscle was paralleled by higher total LOX expression (20183±600 vs 16333±435 arbitrary density units, respectively), lower pepsin soluble collagen (15.1±1.28 vs 37.4±5.96 ng/mg muscle, respectively), higher pepsin insoluble (285±17.5 vs 201±16.4 ng/mg muscle, respectively) and total collagen (303±19.8 vs 237±18.4 ng/mg muscle, respectively), and unchanged protein carbonylation (0.083±0.002 vs 0.083±0.008 arbitrary density units, respectively).CONCLUSIONSThe pool of collagen proteins actively turning over was significantly reduced in aged compared to young muscle, indicating that a greater proportion of the collagen proteins in aged muscle were fibrotic. The reduced proportion of collagen turning over was associated with increased markers of collagen cross‐linking, but not overall protein oxidative damage. Further research is warranted to identify which individual ECM proteins become fibrotic with aging to develop therapeutics to rescue muscle function.Support or Funding InformationThis research was supported by NIA Training Grant T32AG052363.

Comprehensive Assessment of Nile Tilapia Skin (Oreochromis niloticus) Collagen Hydrogels for Wound Dressings.

Collagen plays an important role in the formation of extracellular matrix (ECM) and development/migration of cells and tissues. Here we report the preparation of collagen and collagen hydrogel from the skin of tilapia and an evaluation of their potential as a wound dressing for the treatment of refractory wounds. The acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted and characterized using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), differential scanning calorimetry (DSC), circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) analysis. Both ASC and PSC belong to type I collagen and have a complete triple helix structure, but PSC shows lower molecular weight and thermal stability, and has the inherent low antigenicity. Therefore, PSC was selected to prepare biomedical hydrogels using its self-aggregating properties. Rheological characterization showed that the mechanical strength of the hydrogels increased as the PSC content increased. Scanning electron microscope (SEM) analysis indicated that hydrogels could form a regular network structure at a suitable PSC content. Cytotoxicity experiments confirmed that hydrogels with different PSC content showed no significant toxicity to fibroblasts. Skin repair experiments and pathological analysis showed that the collagen hydrogels wound dressing could significantly accelerate the healing of deep second-degree burn wounds and the generation of new skin appendages, which can be used for treatment of various refractory wounds.