Study on the self-assembly property of type I collagen prepared from tilapia (Oreochromis niloticus) skin by different extraction methods

Dual functional profluorescent nitroxides for the detection of reactive oxygen species and inhibition of collagen degradation during reassembly

High content of reactive oxygen species (ROS) in the human body leads to oxidative stress and serious health problems, such as cancer and cardiovascular or bone diseases. It is also one of the agents that cause collagen damage. Herein, detection of ROS, scavenging of formed carbon-centered radicals and inhibition of collagen fragmentation were performed in a single operation using newly synthesized profluorescent nitroxide PN1via a switch-on approach. Reassembly of acid soluble collagen (ASC) in the presence of hydroxyl and hydroperoxyl radicals, representatives of ROS, was monitored to study the efficiency of the PN1 probe. Self-assembly curves of collagen fibril solution were in accordance with differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) observations, and indicated that PN1 efficiently inhibited the collagen chain scission. In order to prevent the leakage of the probe in materials, a PN2 monomer was successfully incorporated with MMA to form a profluorescent copolymer probe. Furthermore, PN1 and PN2-MMA copolymer probes offered high sensitivity of detection of ROS in the presence of collagen fibrils with detection limits of 1.1 and 2.7 μM, respectively. The mechanism of ROS detection and inhibition of collagen degradation by profluorescent nitroxides was proposed.

Collagen and gelatin: Structure, properties, and applications in food industry

Food-producing animals have the highest concentration of collagen in their extracellular matrix. Collagen and gelatin are widely used in food industry due to their specific structural, physicochemical, and biochemical properties, which enable them to improve health and nutritional value as well as to increase the stability, consistency, and elasticity of food products. This paper reviews the structural and functional properties including inherent self-assembly, gel forming, water-retaining, emulsifying, foaming, and thickening properties of collagen and gelatin. Then the colloid structures formed by collagen such as emulsions, films or coatings, and fibers are summarized. Finally, the potential applications of collagen and gelatin in muscle foods, dairy products, confectionary and dessert, and beverage products are also reviewed. The objective of this review is to provide the current market value, progress as well as applications of collagen and its derivatives in food industry.

Collagen Membrane as Water-Based Gel Electrolyte for Electrochromic Devices

Bio-based polymers are attracting great interest due to their potential for several applications in place of conventional polymers. In the field of electrochemical devices, the electrolyte is a fundamental element that determines their performance, and polymers represent good candidates for developing solid-state and gel-based electrolytes toward the development of full-solid-state devices. In this context, the fabrication and characterization of uncrosslinked and physically cross-linked collagen membranes are reported to test their potential as a polymeric matrix for the development of a gel electrolyte. The evaluation of the membrane's stability in water and aqueous electrolyte and the mechanical characterization demonstrated that cross-linked samples showed a good compromise in terms of water absorption capability and resistance. The optical characteristics and the ionic conductivity of the cross-linked membrane, after overnight dipping in sulfuric acid solution, demonstrated the potential of the reported membrane as an electrolyte for electrochromic devices. As proof of concept, an electrochromic device was fabricated by sandwiching the membrane (after sulfuric acid dipping) between a glass/ITO/PEDOT:PSS substrate and a glass/ITO/SnO₂ substrate. The results in terms of optical modulation and kinetic performance of such a device demonstrated that the reported cross-linked collagen membrane could represent a valid candidate as a water-based gel and bio-based electrolyte for full-solid-state electrochromic devices.

Physicochemical and Fibril Formation Properties of Pufferfish (Takifugu obscurus) Skin Collagen from Solvent Extraction in Different Conditions

Acid-solubilized (ASC) and pepsin-solubilized collagen (PSC) extracted at 4 °C (ASC-4 and PSC-4), 12 °C (ASC-12 and PSC-12), and 20 °C (ASC-20 and PSC-20) from the skin of farmed pufferfish (Takifugu obscurus) was characterized by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier-transform infrared spectroscopy (FTIR), and fibril-forming tests. The results indicate that extraction at 12 °C can effectively improve the extraction efficiency of natural collagen compared with extraction at 4 °C. However, extraction at 20 °C results in a decrease in molecular integrity, thus, inducing the resultant collagen to degrade or even lose fibril-forming ability. Transmission electron microscope (TEM) images revealed that ASC-4, PSC-4, ASC-12, and PSC-12 can assemble into fibrils with D-periodicities, and ASC-20 associated into molecular aggregates alongside partial D-banded fibrils, while no well-defined fibrils were observed in PSC-20. Scanning electron microscope (SEM) analysis confirmed the well-defined fibril morphologies of ASC-4, PSC-4, ASC-12, and PSC-12 with imino acid contents between 190.0 and 197.8 residues/1000 residues. The denaturation temperature of ASC-4, PSC-4, ASC-12 and PSC-12 was 30.0, 27.6, 25.9 and 22.7 °C, respectively. This study indicates that ASC and PSC extracted at 4 °C and 12 °C could be alternatives to terrestrial collagens for industrial applications.

A comparative study on cross-linking of fibrillar gel prepared by tilapia collagen and hyaluronic acid with EDC/NHS and genipin

Chemical cross-linking is an important step to grant satisfying properties to collagen-based materials. However, there are few comparative studies on crossing-linking of collagen-based fibrillar gels which are preferred biomaterials for similar properties to native tissues with different cross-linking agents. In this study, a fibrillar gel was fabricated with tilapia collagen and hyaluronic acid, and cross-linking conditions with EDC/NHS and genipin were discussed. Genipin gave gels much higher equilibrium cross-linking degree than EDC/NHS. ATR-FTIR and XPS showed EDC/NHS offered short-range cross-linking formed by amino and carboxyl groups in fibrils, while genipin induced long-range cross-linking by nucleophilic reaction through attack of amino groups in fibrils on carbon atoms at C-3 as well as ester groups in genipin, besides improved hydrogen bonds. XRD and SEM revealed the structural integrity of gels was strengthened after cross-linking, whereas fibril bundles disaggregated into thin fibrils. Consequently, swelling capacity and anti-degraded property were enhanced significantly, while thermal stability weakened. The fibrillar gels had good biocompatibility, but interestingly the appearance and migration of L929 fibroblasts were influenced by cross-linking degree. These results demonstrated that aquatic collagen-based fibrillar gel cross-linked by genipin had greater potential in biomaterials than EDC/NHS, whereas the cross-linking degree should be controlled.

Evaluation of physicochemical properties of Nile tilapia skin collagen extracted in acid médium

Tilapia has high-temperature tolerance, can breed in captivity, grow fast, and have excellent cost-benefit. Because of these characteristics, this species is of great interest in aquaculture and, currently, the most produced fish in Brazil. However, by increasing tilapia production, there was also a rise in the amount of organic waste, mainly from filleting, which discards 70% of waste. There are many studies on collagen extraction from tilapia skin as an alternative to reduce these residues and add commercial value. In this work, the extraction of protein concentrate was tested using an acid protocol, in which the tilapia skins underwent a pre-treatment in an acid medium and saline precipitation, with variations in time and concentration. After its extraction, the skin was evaluated for ash, moisture, protein, solubility, and pH. The protein concentrate obtained showed low ash contents, and the humidity is within those presented by the literature. The protein concentrate showed levels from 68.73 to 80.58% of protein and a low solubility between 4.03 to 6.93%. In conclusion, acid extraction is a possible means of collagen extraction, and tilapia skin is a good alternative to reuse waste generated in the fish industry.

Aquaponics-Derived Tilapia Skin Collagen for Biomaterials Development

Collagen is one of the most widely used biomaterials in health-related sectors. The industrial production of collagen mostly relies on its extraction from mammals, but several issues limited its use. In the last two decades, marine organisms attracted interest as safe, abundant, and alternative source for collagen extraction. In particular, the possibility to valorize the huge quantity of fish industry waste and byproducts as collagen source reinforced perception of fish collagen as eco-friendlier and particularly attractive in terms of profitability and cost-effectiveness. Especially fish byproducts from eco-sustainable aquaponics production allow for fish biomass with additional added value and controlled properties over time. Among fish species, Oreochromis niloticus is one of the most widely bred fish in large-scale aquaculture and aquaponics systems. In this work, type I collagen was extracted from aquaponics-raised Tilapia skin and characterized from a chemical, physical, mechanical, and biological point of view in comparison with a commercially available analog. Performed analysis confirmed that the proprietary process optimized for type I collagen extraction allowed to isolate pure native collagen and to preserve its native conformational structure. Preliminary cellular studies performed with mouse fibroblasts indicated its optimal biocompatibility. All data confirmed the eligibility of the extracted Tilapia-derived native type I collagen as a biomaterial for healthcare applications.

Preparation of self-assembled collagen fibrillar gel from tilapia skin and its formation in presence of acidic polysaccharides

Fibrillar gel of pepsin-solubilized collagen from tilapia skin was prepared by self-assembly in neutral phosphate buffer at 28 °C. Then effects of acidic polysaccharides, such as sodium alginate (SA), chondroitin sulfate (CS), and hyaluronic acid (HA), on the formation and properties of self-assembled fibrillar gel were investigated. SA and CS prolonged gelling time, whereas HA had no obvious effect. SA made fibril network denser, while CS and HA induced the presence of larger ordered structures. All the acidic polysaccharides broadened the D-periodicity of fibrils. SA and HA increased the maximum mechanical strength of gel to 39.64 and 34.49 kN/m², respectively, significantly higher than that of pure collagen gel (14.53 kN/m²), while that only 17.20 kN/m² after CS introduced. HA had no evident effect on enzymatic resistance, while SA and CS decreased. Therefore, tilapia skin collagen with HA has a higher potential as a biomaterial than that with CS or SA.

Extraction and Characterization of Self-Assembled Collagen Isolated from Grass Carp and Crucian Carp

Collagens were extracted from grass carp skin (GCC), grass carp scales (GSC), and crucian carp skin (CCC) using an acid-enzyme combination method, and their characteristics and self-assembly properties were analyzed. Electrophoretic patterns characterized all three as type I collagens. An ultraviolet analysis identified the optimal wavelengths for collagen detection, while a Fourier transform infrared spectroscopy analysis confirmed the triple-helical structure of the collagens. The GCC, GSC, and CCC had denaturation temperatures of 39.75, 34.49, and 39.05 °C, respectively. All three were shown to self-assemble into fibrils at 30 °C in the presence of NaCl, but the fibril formation rate of CCC (40%) was slightly higher than those of GCC (28%) and GSC (27%). The GSC were shown to form a more strongly intertwined fibril network with a characteristic D-periodicity. The fish collagens extracted in this study have potential applications in the development of functionalized materials.

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.

Telopeptide-dependent xenogeneic collagen co-assembly

The function of telopeptide in xenogeneic collagen co-assembly was shown.

Study on the kinetic self-assembly of type I collagen from tilapia (Oreochromis niloticus) skin using the fluorescence probe thioflavin T

The kinetic self-assembly of type I collagen from tilapia (Oreochromis niloticus) skin was characterized by the fluorescence method based on thioflavin T (ThT). The fluorescence probe could bind to the active monomeric collagen with a higher ordered degree of molecule, which displayed the pH and ionic strength dependence, the binding constant higher at neutral pH and proportional to the NaCl concentration. Compared to the turbidity method, ThT was more suitable to characterize the nucleation phase of collagen self-assembly. The nucleus size was determined through the ThT fluorescence and linear-polymerization model. At various pH and ionic strength, the nucleus size was nearly identical, either one or two monomers, demonstrating that one or two active monomeric collagen formed into the nucleus and different pH and ionic strength didn't alter the self-assembly mechanism of collagen. This approach was beneficial to advance the understanding of the kinetic self-assembly of the fish-sourced collagen in vitro.

Self-aggregation of water-dispersible nanocollagen helices

The self-aggregation of water-dispersible native collagen nanofibrils has been investigated to generate hierarchical networks with structural variation from helicity to layering.

Technical note on the isolation and characterization of collagen from fish waste material

The aim of this manuscript was to evaluate the major technical problems on the isolation and characterization of the collagen from fish waste materials that were usually faced by the growing researchers. Although the original research article published by authors contributed new information to the literature, some of them were failed to provide sufficient details in order to reproduce the study as well as could not adequately interpret/compared the results with other publications. Therefore, it is required to research the technical problems during the isolation and characterization of the collagen. This technical note provides the information which is crucial for the reader's and growing researchers for understanding as an essential part of the published research studies about the collagen extraction and characterization. Hence, this technical note may be helpful to those working on the collagen extraction and characterization from fish/marine waste materials.