Physicochemical Properties and Biocompatibility Evaluation of Collagen from the Skin of Giant Croaker (Nibea japonica)

The Antioxidant, Anti-Inflammatory and Moisturizing Effects of Camellia oleifera Oil and Its Potential Applications

Camellia oleifera oil (CO oil) extracted from C. oleifera seeds has a 2300-year consumption history in China. However, there is relatively little research regarding its non-edible uses. This study determined the physicochemical properties of CO oil extracted via direct pressing, identified its main components using GC-MS, and evaluated its antioxidant, moisturizing, and anti-inflammatory activities. The results revealed that CO oil's acid, peroxide, iodine, and saponification values were 1.06 ± 0.031 mg/g, 0.24 ± 0.01 g/100 g, 65.14 ± 8.22 g/100 g, and 180.41 ± 5.60 mg/g, respectively. CO oil's tocopherol, polyphenol, and squalene contents were 82.21 ± 9.07 mg/kg, 181.37 ± 3.76 mg/kg, and 53.39 ± 6.58 mg/kg, respectively; its unsaturated fatty acid (UFA) content was 87.44%, and its saturated fatty acid (SFA) content was 12.56%. CO oil also demonstrated excellent moisture retention properties, anti-inflammatory effects, and certain free radical scavenging. A highly stable CO oil emulsion with competent microbiological detection was developed using formulation optimization. Using CO oil in the emulsion significantly improved the formulation's antioxidant and moisturizing properties compared with those of the emulsion formulation that did not include CO oil. The prepared emulsion was not cytotoxic to cells and could reduce cells' NO content; therefore, it may have potential nutritional value in medicine and cosmetics.

Swim bladder-derived biomaterials: structures, compositions, properties, modifications, and biomedical applications

Animal-derived biomaterials have been extensively employed in clinical practice owing to their compositional and structural similarities with those of human tissues and organs, exhibiting good mechanical properties and biocompatibility, and extensive sources. However, there is an associated risk of infection with pathogenic microorganisms after the implantation of tissues from pigs, cattle, and other mammals in humans. Therefore, researchers have begun to explore the development of non-mammalian regenerative biomaterials. Among these is the swim bladder, a fish-derived biomaterial that is rapidly used in various fields of biomedicine because of its high collagen, elastin, and polysaccharide content. However, relevant reviews on the biomedical applications of swim bladders as effective biomaterials are lacking. Therefore, based on our previous research and in-depth understanding of this field, this review describes the structures and compositions, properties, and modifications of the swim bladder, with their direct (including soft tissue repair, dural repair, cardiovascular repair, and edible and pharmaceutical fish maw) and indirect applications (including extracted collagen peptides with smaller molecular weights, and collagen or gelatin with higher molecular weights used for hydrogels, and biological adhesives or glues) in the field of biomedicine in recent years. This review provides insights into the use of swim bladders as source of biomaterial; hence, it can aid biomedicine scholars by providing directions for advancements in this field.

Effects of ultrasound on the structural and functional properties of sheep bone collagen

The study evaluated the effect of an ultrasound-assisted treatment on the structural and functional properties of sheep bone collagen (SBC). The type and distribution of SBC were analyzed by proteome (shotgun) technology combined with liquid chromatography-tandem mass spectrometry. Compared with pepsin extraction, the ultrasound-assisted treatment significantly increased the collagen extraction rate by 17.4 pp (P < 0.05). The characteristic functional groups and structural integrity of collagen extracted by both methods were determined via Fourier transform infrared spectroscopy, ultraviolet absorption spectroscopy, and fluorescence spectroscopy. Circular dichroism spectra revealed that the ultrasound-assisted pretreatment reduced α-helix content by 1.6 pp, β-sheet content by 21.9 pp, and random coils content by 28.4 pp, whereas it increased β-turn content by 51.9 pp (P < 0.05), compared with pepsin extraction. Moreover, ultrasound-assisted treatment collagen had superior functional properties (e.g., solubility, water absorption, and oil absorption capacity) and foaming and emulsion properties, compared with pepsin extraction. Furthermore, the relative content of type I collagen in ultrasound-assisted extracted SBC was highest at 79.66%; only small proportions of type II, VI, X, and XI collagen were present. Peptide activity analysis showed that SBC had potential antioxidant activity, dipeptidyl peptidase 4 inhibitory activity, and angiotensin-converting enzyme inhibitory activity; it also had anticancer, antihypertensive, anti-inflammatory, and immunomodulatory effects.

Preventive effect of tilapia skin collagen hydrolysates on ulcerative colitis mice based on metabonomic and 16 S rRNA gene sequencing

BACKGROUND

Tilapia skin collagen hydrolysates (TSCHs) are the product of enzymatic hydrolysis of collagen, which is mainly extracted from tilapia skin. The components of TSCHs have recently been reported to play a preventive role in dextran sulfate sodium (DSS)-induced ulcerative colitis (UC). However, it has not been illustrated whether TSCHs can prevent against DSS-induced UC via the gut microbiota and its derived metabolites.

RESULTS

TSCHs are mainly composed of amino acids, which have similar characteristics to collagen, with most having a molecular weight below 5 kDa. In a mouse model of UC, TSCHs had no toxic effect at a dose of 60 g kg^-1 and could reduce body weight changes, colon length, histopathological changes and score, and the level of the serum inflammatory cytokine interleukin (IL)-6. Concurrently, 16 S rRNA sequencing showed that TSCHs significantly reduced the abundance of Bacteroidetes and Proteobacteria at the phylum level and norank_f__Muribaculaceae and Escherichia-Shigella at the genus level, while they increased the abundance of Firmicutes at the phylum level and Lachnoclostridium, Allobaculum, Enterorhabdus, and unclassified__f__Ruminococcaceae at the genus level. Target metabolomic analysis showed that TSCHs elevated the concentration of total acid, acetic acid, propanoic acid, and butanoic acid, but reduced isovaleric acid concentrations. Moreover, Pearson correlation analysis revealed that Allobaculum, unclassified_Ruminococcaceae, and Enterorhabdus were positively correlated with acetic acid and butyric acid, but not Escherichia-Shigella.

CONCLUSION

These findings suggest that TSCHs can prevent UC by modulating gut microbial and microbiota-derived metabolites. © 2023 Society of Chemical Industry.

Preparation, Characterization and ex vivo Skin Permeability Evaluation of Type I Collagen-Loaded Liposomes

Purpose

In the present study, we prepared collagen liposomes with the addition of polyol, which is expected to not only increase the solubility of collagen but also improve skin penetration.

Methods

Collagen liposomes were prepared by the film dispersion method, and their characteristics, integrity and biosafety were evaluated by Fourier transform infrared spectroscopy (FTIR), UV-VIS spectroscopy, polyacrylamide gel electrophoresis (SDS-PAGE), dynamic light scattering (DLS) and transmission electron microscope (TEM). The transdermal absorption of collagen and collagen liposomes were tested by an ex vivo horizontal Valia-Chien diffusion cell system.

Results

We first demonstrated that collagen extracted from bovine Achilles tendon was type I collagen. The results of DLS measurement and TEM observation showed that the collagen liposomes were spherical in shape with average diameter (75.34±0.93 nm) and maintained high stability at low temperature (4°C) for at least 42 days without toxicity. The encapsulation rate of collagen liposomes was 57.80 ± 0.51%, and SDS-PAGE analysis showed that collagen was intact in liposomes. Finally, permeability studies indicated that the collagen-loaded liposomes more easily penetrated the skin compared to collagen itself.

Conclusion

This study proposed a new method to improve the bioavailability and permeability of bovine type I collagen, which improves the applicability of collagen in biomedicine, cosmeceuticals and pharmaceutical industries.

Extraction and Characterization of Pepsin- and Acid-Soluble Collagen from the Swim Bladders of Megalonibea fusca

There is a growing demand for the identification of alternative sources of collagen not derived from land-dwelling animals. The present study explored the use of pepsin- and acid-based extraction protocols to isolate collagen from the swim bladders of Megalonibea fusca. After extraction, these acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) samples respectively were subjected to spectral analyses and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) characterization, revealing both to be comprised of type I collagen with a triple-helical structure. The imino acid content of these ASC and PSC samples was 195 and 199 residues per 1000 residues, respectively. Scanning electron microscopy demonstrated that samples of freeze-dried collagen exhibited a compact lamellar structure, while transmission electron microscopy and atomic force microscopy confirmed the ability of these collagens to undergo self-assembly into fibers. ASC samples exhibited a larger fiber diameter than the PSC samples. The solubility of both ASC and PSC was highest under acidic pH conditions. Neither ASC nor PSC caused any cytotoxicity when tested in vitro, which met one of the requirements for the biological evaluation of medical devices. Thus, collagen isolated from the swim bladders of Megalonibea fusca holds great promise as a potential alternative to mammalian collagen.

Identification of antioxidant peptides after digestion and absorption of isinglass by serum peptidomics and cellular antioxidant activity analysis

Isinglass, a dried product of the swim bladder, has been widely used in traditional Chinese medicine. This study attempts to identify natural antioxidant peptides after digestion and absorption of isinglass in vivo. The antioxidant effects of dietary isinglass were demonstrated by evaluating the activities of SOD, CAT and MDA contents in the mouse liver. Four novel antioxidant-related peptides (RLLWENGNLL, GSKAENPTNPGP, SPVPDLVPGSF and VPDLVPGSF) were screened based on serum peptidomics and amino acid composition. Furthermore, pretreating with four peptides significantly increased the cell viability, and SOD and CAT activities of AML12 cells with H₂O₂-mediated oxidative damage, meanwhile, significantly reduced the ROS level, MDA content and apoptosis rate and attenuated DNA damage. Therefore, it was concluded that pretreatment of the identified peptides had a protective effect on oxidatively damaged cells. This result can aid in the recognition of active peptides from isinglass consumption for potential application in nutraceuticals or functional ingredients in food.

Preparation of Nile tilapia skin collagen powder by low-temperature and comprehensive evaluation of hemostasis and wound healing

Nile tilapia (hereinafter referred to as tilapia) is a species with high economic value and extensive cultivation. In this study, the low-temperature Nile tilapia skin collagen powder (TSCP) was prepared by liquid nitrogen freeze pulverization. After physical and chemical analysis of its properties, it was found that its characteristics were similar to those of type I collagen. The three-dimensional helix structure of protein peptide is good and non denatured. It shows that cryogenic temperature guarantees the activity of TSCP. In addition, TSCP has good biocompatibility. Specifically, it has good blood compatibility, lacks cytotoxicity, will not cause intradermal stimulation and acute systemic toxicity, and has no obvious rejection after implantation. In the rat liver hemorrhage model and wound repair model, compared with the commercially available bovine collagen powder (BSCP), TSCP has better blood coagulation ability: the shortest hemostatic time (135 s) and wound healing efficiency: the wound healing is obvious on the 14th day. The results of this study indicate that the TSCP is an ideal candidate for hemostatic agents and wound healing dressings.

Circ004463 promotes fibroblast proliferation and collagen I synthesis by sponging miR-23b and regulating CADM3/MAP4K4 via activation of AKT/ERK pathways

Skin thickness is closely related to the appearance of human skin, such as sagging and wrinkling, which primarily depends on the level of collagen I synthesized by fibroblasts in the dermal layer. To explore the underlying genetics of the development of skin thickness, we used the indigenous Chinese Chenghua pigs, considered to have superior skin thickness, as model animals. We first performed whole transcriptome sequencing analysis to identify significant skin morphological differences between Chenghua pigs and Large White pigs and obtained some differentially expressed coding RNAs (454 mRNAs) and noncoding RNAs (612 circRNAs, 188 miRNAs, and 19 lncRNAs); moreover, some competing endogenous RNA (ceRNA) networks were constructed. Interestingly, we then identified a circRNA, namely circ0044633, which plays an important role in promoting fibroblast proliferation along with myofibroblast transition and collagen I synthesis by sponging miR-23b and regulating CADM3 and MAP4K4 expression via activation of the downstream AKT and ERK pathways in vitro. Furthermore, overexpression of circ004463 increased the mouse skin thickness and collagen I content in vivo. These results revealed a whole transcript profile of skin tissue and identified an important circ0044633-miR-23b-CADM3/MAP4K4 axis related to fibroblast proliferation and collagen I synthesis during the development of skin thickness.

Monkfish (Lophius litulon) Peptides Ameliorate High-Fat-Diet-Induced Nephrotoxicity by Reducing Oxidative Stress and Inflammation via Regulation of Intestinal Flora

BACKGROUND

Renal damage and intestinal flora imbalance due to lipotoxicity are particularly significant in terms of oxidative stress and inflammation, which can be alleviated with bioactive peptides. The monkfish (Lophius litulon) is rich in proteins, which can be used as a source of quality bioactive peptides. This study aimed to examine the protective effect of monkfish peptides on renal injury and their potential role in regulating gut microbiota.

METHODS

Monkfish meat was hydrolyzed using neutral protease and filtered, and the component with the highest elimination rate of 2,2-diphenyl-1-picrylhydrazyl was named lophius litulon peptides (LPs). Lipid nephrotoxicity was induced via high-fat diet (HFD) feeding for 8 weeks and then treated with LPs. Oxidative stress, inflammatory factors, and intestinal flora were evaluated.

RESULTS

LP (200 mg/kg) therapy reduced serum creatinine, uric acid, and blood urea nitrogen levels by 49.5%, 31.6%, and 31.6%, respectively. Renal vesicles and tubules were considerably improved with this treatment. Moreover, the activities of superoxide dismutase, glutathione peroxidase, and total antioxidant capacity increased significantly by 198.7%, 167.9%, 61.5%, and 89.4%, respectively. LPs attenuated the upregulation of HFD-induced Toll-like receptor 4 and phospho-nuclear factor-kappa B and increased the protein levels of heme oxygenase 1, nicotinamide quinone oxidoreductase 1, and nuclear factor erythroid 2-related factor 2. The dysbiosis of intestinal microbiota improved after LP treatment.

CONCLUSIONS

LPs significantly improve antioxidant activity, reduce inflammatory cytokine levels, and regulate intestinal dysbiosis. Thus, LPs are potential compounds that can alleviate HFD-induced renal lipotoxicity.

Effects of low molecular weight peptides from monkfish (Lophius litulon) roe on immune response in immunosuppressed mice

This study aimed to investigate the immunomodulatory activation of low-molecular-weight peptides from monkfish (Lophius litulon) roe (named MRP) on cyclophosphamide (CTX)-induced immunosuppressed mice. Our results indicated that MRP (100 mg/kg/d BW) could significantly increase the body weight and immune organ index, and improve the morphological changes in the spleen and thymus of mice. These effects subsequently enhance the serum levels of interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, and immunoglobulin (Ig) A, IgM, and IgG. Furthermore, MRP could also improve CTX-induced oxidative stress, and activate the NF-κB and MAPK pathways in the spleen tissues. The findings reported herein indicate that MRP has a good immunomodulatory activation toward immunosuppressed mice, hence can potentially be developed as an immune adjuvant or functional food.

Production of Collagens and Protein Hydrolysates with Antimicrobial and Antioxidant Activity from Sheep Slaughter By-Products

This work aimed to produce collagens and hydrolysates with antimicrobial and antioxidant activity from sheep slaughter by-products. The by-products (sheep and lamb) were treated and extracted. The collagens were hydrolyzed with the enzyme Alcalase^®. The spectra of collagens and hydrolysates were similar (amide bands I, II, III, A, B). The bands presented by the collagens (α₁, α₂, β) were characteristic of type I collagen. The hydrolysates showed molecular weight peptides equal to/lower than 15 kDa. Collagens had a denaturation temperature of 39.32 (lamb) and 36.38 °C (sheep), whereas the hydrolysates did not undergo thermal transition. Hydrolysates showed lower values of antioxidant activity (AA) than the collagens. The collagens from lamb and from sheep displayed an AA of 13.4% (concentration of 0.0002%) and 13.1% (concentration of 0.0005%), respectively. At the concentration of 0.0020%, the lamb hydrolysates displayed an AA of 10.2%, whereas the sheep hydrolysates had an AA of only 1.98%. Collagen also showed higher antimicrobial activity compared to hydrolysates, requiring a lower concentration to inhibit the microorganisms tested. Sheep slaughter by-products proved to be a viable source for obtaining protein hydrolysates and collagens with antimicrobial and antioxidant activity, which can be applied in the development of nutraceuticals beneficial to human health.

Preparation and Characterization of Thermally Stable Collagens from the Scales of Lizardfish (Synodus macrops)

Marine collagen is gaining vast interest because of its high biocompatibility and lack of religious and social restrictions compared with collagen from terrestrial sources. In this study, lizardfish (Synodus macrops) scales were used to isolate acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). Both ASC and PSC were identified as type I collagen with intact triple-helix structures by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and spectroscopy. The ASC and PSC had high amino acids of 237 residues/1000 residues and 236 residues/1000 residues, respectively. Thus, the maximum transition temperature (T_max) of ASC (43.2 °C) was higher than that of PSC (42.5 °C). Interestingly, the T_max of both ASC and PSC was higher than that of rat tail collagen (39.4 °C) and calf skin collagen (35.0 °C), the terrestrial collagen. Solubility tests showed that both ASC and PSC exhibited high solubility in the acidic pH ranges. ASC was less susceptible to the “salting out” effect compared with PSC. Both collagen types were nontoxic to HaCaT and MC3T3-E1 cells, and ASC was associated with a higher cell viability than PSC. These results indicated that ASC from lizardfish scales could be an alternative to terrestrial sources of collagen, with potential for biomedical applications.

Enhanced Wound Healing Activity of Undenatured Type I Collagen Isolated from Discarded Skin of Black Sea Gilthead Bream (Sparus aurata) Conditioned as 3D Porous Dressing

Acid-soluble, undenatured, type I collagen (BSC) isolated, for the first time, from gilthead bream skin and the novel fabricated 3D porous wound dressing were analyzed for physicochemical and biological properties, in order to offer a safe alternative to commercial bovine collagen (BC) products. SDS-polyacrylamide analysis confirmed the purity of BSC preparation. The hydroxyproline content and temperature of denaturation of BSC were lower than those of BC, in accordance with the structural data recorded by FT-IR spectroscopy. However, certain concentrations of BSC stimulated the cell metabolism of L929 fibroblasts in a higher proportion than BC. The 3D wound dressing presented high porosity and low surface hydrophobicity that could help cell attachment and growth. The rapid biodegradation of BSC wound dressing could explain the improved in vitro cell migration and wound closure rate. In conclusion, the skin of gilthead bream from the Black Sea coast represented a valuable source for the biomedical industry, providing biocompatible, biodegradable collagen and 3D porous wound dressing, as novel material with enhanced wound healing activity.

Biocompatibility, hemostatic properties, and wound healing evaluation of tilapia skin collagen sponges

Dialyzed tilapia skin collagen sponge (DTSCS) and self-assembled tilapia skin collagen sponge (STSCS) were prepared by freeze-drying. The raw components used in the fabrication of DTSCS and STSCS were separated and purified from tilapia fish skin. It is anticipated that these collagen sponges could be developed into medical dressings for hemostasis and wound healing. The aim of the present research was to explore the possibility of DTSCS and STSCS as medical dressings and compare their differences by scanning electron microscopy (SEM), water absorption measurement, differential scanning calorimetry (DSC), measurement of porosity, cytotoxicity, hemolysis, in vivo biocompatibility, and evaluation of hemostatic performance and wound healing. The results indicate that DTSCS and STSCS are suitable materials for use in medical applications with a loose and porous structure, high water absorption, high porosity, and high thermal stability. The materials also displayed good biocompatibility, including excellent blood compatibility, a lack of cytotoxicity, with no apparent rejection following implantation. STSCS exhibited rapid hemostasis and promoted healing, with slightly greater efficacy than DTSCS. The hemostatic properties and promotion of healing in DTSCS was similar to that of commercial bovine collagen sponge. Therefore, DTSCS and STSCS both represented excellent potential candidate materials for use as hemostatic agents and wound dressings.

Optimization of Extraction of Bioactive Peptides from Monkfish (Lophius litulon) and Characterization of Their Role in H2O2-Induced Lesion

Background: Marine fish meat has been widely used for the extraction of bioactive peptides. This study was aimed to optimize the preparation of monkfish muscle peptides (LPs) using response surface methodology (RSM) and explore the antioxidant activities of <1 kDa LPs. Methods: Peptides were prepared from the muscles of monkfish (Lophius litulon), and five proteases were tested to hydrolyze muscle proteins. The hydrolysate that was treated using neutrase showed the highest degree of hydrolysis (DH) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities. Results: The optimized conditions were as follows: water/material ratio of 5.4:1, a time span of 5 h, pH of 7.0, enzyme concentration of 2000 U/g, and temperature of 45 °C; the maximum DPPH scavenging activity and DH were 92.861% and 19.302%, respectively. LPs exhibited appreciable antioxidant activities, including DPPH radical, hydroxyl radical, 2,2′-azinobis-3-ethylbenzthiazoline-6-sulphonate (ABTS) radical, and superoxide anion scavenging activities. LPs attenuated H₂O₂-related oxidative injury in RAW264.7 cells, reduced the reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and increased the superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) levels. Conclusion: We concluded that LPs could be an ideal source of bioactive peptides from monkfish and also have pharmaceutical potential.

Collagen Peptides from Swim Bladders of Giant Croaker (Nibea japonica) and Their Protective Effects against H2O2-Induced Oxidative Damage toward Human Umbilical Vein Endothelial Cells

Five different proteases were used to hydrolyze the swim bladders of Nibea japonica and the hydrolysate treated by neutrase (collagen peptide named SNNHs) showed the highest DPPH radical scavenging activity. The extraction process of SNNHs was optimized by response surface methodology, and the optimal conditions were as follows: a temperature of 47.2 °C, a pH of 7.3 and an enzyme concentration of 1100 U/g, which resulted in the maximum DPPH clearance rate of 95.44%. Peptides with a Mw of less than 1 kDa (SNNH-1) were obtained by ultrafiltration, and exhibited good scavenging activity for hydroxyl radicals, ABTS radicals and superoxide anion radicals. Furthermore, SNNH-1 significantly promoted the proliferation of HUVECs, and the protective effect of SNNH-1 against oxidative damage of H2O2-induced HUVECs was investigated. The results indicated that all groups receiving SNNH-1 pretreatment showed an increase in GSH-Px, SOD, and CAT activities compared with the model group. In addition, SNNH-1 pretreatment reduced the levels of ROS and MDA in HUVECs with H2O2-induced oxidative damage. These results indicate that collagen peptides from swim bladders of Nibea japonica can significantly reduce the oxidative stress damage caused by H2O2 in HUVECs and provides a basis for the application of collagen peptides in the food industry, pharmaceuticals, and cosmetics.

Two Cosmetic Properties of an Ethanol Extract of a Cultured and Edible Red Macroalga, Bangia fuscopurpurea: Moisturizing and Whitening Effects

Previous studies have focused on the role of a cultured red macroalga Bangia fuscopurpurea as a functional food; however, except for antioxidant activity, there are no reports directly regarding the potential cosmetic properties of this alga. Our present study explored the moisturizing effect of its ethanol extract (BFH1) and used the tyrosinase activity inhibition assay to evaluate its in vitro whitening effect. The in vitro moisture-retention ability of BFH1 was similar to that of glycerol (positive control), but its moisture-absorption ability was significantly higher. The overall in vivo moisturizing effect of topical application of BFH1 in mice was similar to that of glycerol, but BFH1 did not cause significant changes in the oil content of the skin, and there were no obvious side effects regarding skin appearance and external behavior during treatment. BFH1 exerted in vitro tyrosinase inhibitory activity with a half-maximal inhibitory concentration (IC50) of 48.3 μg/mL (IC50 of positive control, vitamin C: 19.6 μg/mL). The total phenolic content of BFH1 was determined as 10.8 % ± 0.07 %. Thus, BFH1 has high potential to be turned into a cosmetic ingredient with moisturizing and whitening effects.

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.

Asian bullfrog (Rana tigerina) skin gelatin extracted by ultrasound-assisted process: Characteristics and in-vitro cytotoxicity

Impact of ultrasound-assisted process (UAP) on yield and characteristics of Asian bullfrog (Rana tigerina) skin gelatin was studied and the in-vitro cytotoxicity of the resulting frog skin gelatin was evaluated using CaCo-2, Raw264.7 and L929 cell lines. Different ultrasonication modes (5 min on-time with 25 min off-time (5/25) and 10 min on-time with 50 min off-times (10/50)) were implemented for different total ultrasonication times (10-60 min) during gelatin extraction at 55 °C. UAP could effectively augment yield and recovery of frog skin gelatin, compared with the typical process (without UAP). Different UAPs used affected characteristics and properties of gelatin differently. Increased total ultrasonication time increased color changes and turbidity of resulting gelatin and induced protein fragmentation, regardless of modes used. At the same total ultrasonication time, mode of 10/50 provided gelatin with higher hydroxyproline content and higher gel strength than 5/25 mode. Gelatin extracted by UAP with 10/50 mode for 60 min (FU) possessed high yield and good gel property. Gelling and melting temperatures and FTIR-spectra of FU were similar to those of gel from typical process. Based on in-vitro cytotoxicity toward different cell lines, frog skin gelatin could be used as biocompatible material, which could be safe for human consumption.

Pepsin-Soluble Collagen from the Skin of Lophius litulo: A Preliminary Study Evaluating Physicochemical, Antioxidant, and Wound Healing Properties

The structure of pepsin-solubilized collagen (PSC) obtained from the skin of Lophius litulon was analyzed using the sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). SDS-PAGE results showed that PSC from Lophius litulon skin was collagen type I and had collagen-specific α1, α2, β, and γ chains. FTIR results indicated that the infrared spectrum of PSC ranged from 400 to 4000 cm^-1, with five main amide bands. SEM revealed the microstructure of PSC, which consisted of clear fibrous and porous structures. In vitro antioxidant studies demonstrated that PSC revealed the scavenging ability for 2,2-diphenyl-1-picrylhydrazyl (DPPH), HO·, O₂^-·, and ABTS·. Moreover, animal experiments were conducted to evaluate the biocompatibility of PSC. The collagen sponge group showed a good biocompatibility in the skin wound model and may play a positive role in the progression of the healing process. The cumulative results suggest that collagen from the skin of Lophius litulon has potential applications in wound healing due to its good biocompatibility.

Marine Collagen Peptides Promote Cell Proliferation of NIH-3T3 Fibroblasts via NF-κB Signaling Pathway

Marine collagen peptides (MCPs) with the ability to promote cell proliferation and migration were obtained from the skin of Nibea japonica. The purpose of MCPs isolation was an attempt to convert the by-products of the marine product processing industry to high value-added items. MCPs were observed to contain many polypeptides with molecular weights ≤ 10 kDa and most amino acid residues were hydrophilic. MCPs (0.25–10 mg/mL) also exhibited 2, 2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, superoxide anion, and 2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activities. Furthermore, MCPs promoted the proliferation of NIH-3T3 cells. In vitro scratch assays indicated that MCPs significantly enhanced the scratch closure rate and promoted the migration of NIH-3T3 cells. To further determine the signaling mechanism of MCPs, western blotting was used to study the expression levels of nuclear factor kappa-B (NF-κB) p65, IκB kinase α (IKKα), and IκB kinase β (IKKβ) proteins of the NF-κB signaling pathway. Our results indicated protein levels of NF-κB p65, IKKα and IKKβ increased in MCPs-treated NIH-3T3 cells. In addition, MCPs increased the expression of epidermal growth factor (EGF), fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), and transforming growth factor (TGF-β) in NIH-3T3 cells. Therefore, MCPs, a by-product of N. japonica, exhibited potential wound healing abilities in vitro.

Physicochemical and Functional Properties of Type I Collagens in Red Stingray (Dasyatis akajei) Skin

Collagen is widely used in the pharmaceutical, tissue engineering, nutraceutical, and cosmetic industries. In this study, acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted from the skin of red stingray, and its physicochemical and functional properties were investigated. The yields of ASC and PSC were 33.95 ± 0.7% and 37.18 ± 0.71% (on a dry weight basis), respectively. ASC and PSC were identified as type I collagen by Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) analysis, possessing a complete triple helix structure as determined by UV absorption, Fourier transform infrared, circular dichroism, and X-ray diffraction spectroscopy. Contact angle experiments indicated that PSC was more hydrophobic than ASC. Thermal stability tests revealed that the melting temperature of PSC from red stingray skin was higher than that of PSC from duck skin, and the difference in the melting temperature between these two PSCs was 9.24 °C. Additionally, both ASC and PSC were functionally superior to some other proteins from terrestrial sources, such as scallop gonad protein, whey protein, and goose liver protein. These results suggest that PSC from red stingray skin could be used instead of terrestrial animal collagen in drugs, foods, cosmetics, and biological functional materials, and as scaffolds for bone regeneration.

Comparison of Physicochemical Characteristics and Fibril Formation Ability of Collagens Extracted from the Skin of Farmed River Puffer (Takifugu obscurus) and Tiger Puffer (Takifugu rubripes)

Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from the skin of river puffer (ASC-RP and PSC-RP) and tiger puffer (ASC-TP and PSC-TP) were extracted and physicochemically examined. Denaturation temperature (Td) for all the collagens was found to be 25.5-29.5 °C, which was lower than that of calf skin collagen (35.9 °C). Electrophoretic patterns indicated all four samples were type I collagen with molecular form of (α1)2α2. FTIR spectra confirmed the extracted collagens had a triple-helical structure, and that the degree of hydrogen bonding in ASC was higher than PSC. All the extracted collagens could aggregate into fibrils with D-periodicity. The fibril formation rate of ASC-RP and PSC-RP was slightly higher than ASC-TP and PSC-TP. Turbidity analysis revealed an increase in fibril formation rate when adding a low concentration of NaCl (less than 300 mM). The fibril formation ability was suppressed with further increasing of NaCl concentration, as illustrated by a reduction in the turbidity and formation degree. SEM analysis confirmed the well-formed interwoven structure of collagen fibrils after 24 h of incubation. Summarizing the experimental results suggested that the extracted collagens from the skin of river puffer and tiger puffer could be considered a viable substitute to mammalian-derived collagens for further use in biomaterial applications.

Physicochemical, antioxidant properties of giant croaker (Nibea japonica) swim bladders collagen and wound healing evaluation

Acid-solubilized collagen (ASC) and pepsin-solubilized collagen (PSC) were obtained from Nibea japonica swim bladders. The denaturation temperature (Td) of ASC and PSC was approximately 33.8 °C. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR) analyses indicated that ASC and PSC contained triple-helical type I collagen when compared to rat tail collagen type I. Moreover, the microstructure of collagen sponges was uniform and porous. In addition, ASC and PSC exhibited antioxidant properties and in vitro scratch assays showed that PSC at various concentrations (0, 12.5, 25, and 50 μg/mL) had significant effects on the scratch closure rate. Furthermore, collagen sponge from Nibea japonica swim bladders exhibited an increased efficacy of wound healing when compared to the control mice. The levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α in the collagen sponge treated mice were significantly decreased when compared to the control group. Thus, our results suggested that collagen sponge from Nibea japonica swim bladders has potential wound healing applications.

Immunomodulatory Activity of Low Molecular-Weight Peptides from Nibea japonica in RAW264.7 Cells via NF-κB Pathway

In this study, a low molecular-weight (Mw) peptide named NJP (<1 kDa), was purified from a protein hydrolysate of Nibea japonica by ultrafiltration, and its immunomodulatory effect on RAW264.7 cells was evaluated. The lactate dehydrogenase (LDH) and MTT assays were performed to explore the cytotoxicity of NJP. The results showed that NJP promoted cell proliferation and had no significant toxic effects on RAW264.7 cells. Moreover, the cells formed multiple pseudopodia indicating that they were in activated state. Further tests showed that NJP significantly promoted phagocytic capacity, and the secretion of proinflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β). It also increased the synthesis of nitric oxide (NO) by upregulating inducible nitric oxide synthase (iNOS) protein level. Flow cytometry revealed that NJP promoted cell cycle progression and increased the percentage of cells in G0/G1 phase. NJP promoted IκBα degradation, p65 and nuclear factor (NF)-κB activation and translocation by up-regulating IKKα/β protein expression. In conclusion, these results indicated that NJP exerts immunomodulatory effects on RAW264.7 cells through the NF-κB signaling pathway. Therefore, NJP can be incorporated in the production of functional foods or nutraceuticals.

Collagen Extracted from Bigeye Tuna (Thunnus obesus) Skin by Isoelectric Precipitation: Physicochemical Properties, Proliferation, and Migration Activities

Collagen was extracted from bigeye tuna (Thunnus obesus) skins by salting-out (PSC-SO) and isoelectric precipitation (PSC-IP) methods. The yield of the PSC-IP product was approximately 17.17% (dry weight), which was greater than the yield obtained from PSC-SO (14.14% dry weight). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that collagen from bigeye tuna skin belongs to collagen type I. Inductively coupled plasma mass spectrometry results indicate that the heavy metal abundance in PSC-IP was lower than the maximum acceptable amounts according to Chinese regulatory standards. In addition, results from a methylthiazolyldiphenyl-tetrazolium bromide assay and an in vitro scratch assay demonstrated that PSC-IP could promote the proliferation and migration of NIH-3T3 fibroblasts. Overall, results suggest PSC-IP could be used to rapidly extract collagen from marine by-products instead of traditional salting-out methods. Collagen from bigeye tuna skin may also have strong potential for cosmetic and biomedical applications.

High Throughput Identification of Antihypertensive Peptides from Fish Proteome Datasets

Antihypertensive peptides (AHTPs) are a group of small peptides with the main role to block key enzymes or receptors in the angiotensin genesis pathway. A great number of AHTPs have been isolated or digested from natural food resources; however, comprehensive studies on comparisons of AHTPs in various species from the perspective of big data are rare. Here, we established a simplified local AHTP database, and performed in situ mapping for high throughput identification of AHTPs with high antihypertensive activity from high-quality whole proteome datasets of 18 fish species. In the 35 identified AHTPs with reported high activity, we observed that Gly-Leu-Pro, Leu-Pro-Gly, and Val-Ser-Val are the major components of fish proteins, and AHTP hit numbers in various species demonstrated a similar distributing pattern. Interestingly, Atlantic salmon (Salmo salar) is in possession of far more abundant AHTPs compared with other fish species. In addition, collagen subunit protein is the largest group with more matching AHTPs. Further exploration of two collagen subunits (col4a5 and col8a1) in more fish species suggested that the hit pattern of these conserved proteins among teleost is almost the same, and their phylogeny is consistent with the evolution of these fish species. In summary, our present study provides basic information for the relationship of AHTPs with fish proteins, which sheds light on rapid discovery of marine drugs or food additives from fish protein hydrolysates to alleviate hypertension.

Inhibition of Prostate Cancer DU-145 Cells Proliferation by Anthopleura anjunae Oligopeptide (YVPGP) via PI3K/AKT/mTOR Signaling Pathway

We investigated the antitumor mechanism of Anthopleura anjunae oligopeptide (AAP-H, YVPGP) in prostate cancer DU-145 cells in vitro and in vivo. Results indicated that AAP-H was nontoxic and exhibited antitumor activities. Cell cycle analysis indicated that AAP-H may arrest DU-145 cells in the S phase. The role of the phosphatidylinositol 3-kinase/protein kinase B/mammalian rapamycin target protein (PI3K/AKT/mTOR) signaling pathway in the antitumor mechanism of APP-H was investigated. Results showed that AAP-H treatment led to dose-dependent reduction in the levels of p-AKT (Ser473), p-PI3K (p85), and p-mTOR (Ser2448), whereas t-AKT and t-PI3K levels remained unaltered compared to the untreated DU-145 cells. Inhibition of PI3K/AKT/mTOR signaling pathway in the DU-145 cells by employing inhibitor LY294002 (10 μM) or rapamycin (20 nM) effectively attenuated AAP-H-induced phosphorylation of AKT and mTOR. At the same time, inhibitor addition further elevated AAP-H-induced cleaved-caspase-3 levels. Furthermore, the effect of AAP-H on tumor growth and the role of the PI3K/AKT/mTOR signaling pathway in nude mouse model were also investigated. Immunohistochemical analysis showed that activated AKT, PI3K, and mTOR levels were reduced in DU-145 xenografts. Western blotting showed that AAP-H treatment resulted in dose-dependent reduction in p-AKT (Ser473), p-PI3K (p85), and p-mTOR (Ser2448) levels, whereas t-AKT and t-PI3K levels remained unaltered. Similarly, Bcl-xL levels decreased, whereas that of Bax increased after AAP-H treatment. AAP-H also increased initiator (caspase 8 and 9) and executor caspase (caspase 3 and 7) levels. Therefore, the antitumor mechanism of APP-H on DU-145 cells may involve regulation of the PI3K/AKT/mTOR signaling pathway, which eventually promotes apoptosis via mitochondrial and death receptor pathways. Thus, the hydrophobic oligopeptide (YVPGP) can be developed as an adjuvant for the prevention or treatment of prostate cancer in the future.