A review on recent advances and applications of fish collagen

Bioinspired Wearable Hydrogel Composite with Sustained Drug-Release for Wound Healing and Naked-Eye Visual Early Warning of Wound Dehiscence

Wound healing is critical to the structural and functional restoration of damaged tissue. However, effective wound closure and healing are always great challenges in regenerative engineering. This study provided bioinspired wearable hydrogel composites with drug-releasing hydrogel and nonclose-packed photonic crystals (NPCs) for wound therapy and naked-eye visual early warning of wound dehiscence. Molecular dynamics models and drug-releasing results illustrated the sustained drug release of ibuprofen, and the mechanical properties of the drug-releasing hydrogel were optimized with 1410% tensile strain by introducing fish collagen; their biocompatibility and adhesion were also improved. The structural color of the NPCs blue-shifted from 630 to 500 nm with 15.0% strain, and the original color was customized with poly(methyl methacrylate) (PMMA) concentration and acrylamide content. Compared with the gauze and the traditional hydrogels, the composite provided a moist environment and an effectively closed wound; the debridement and released drug avoided inflammation, and the rat wound was healed 40.5% on the third day and essentially 100% on the 14th day. The work provided a novel strategy for wound healing and naked-eye visual early warning when a wound deforms, which is expected to promote the synergistic development of clinical treatment and visualized early warning.

Dietary fishmeal replacement by Clostridium autoethanogenum protein meal influences the nutritional and sensory quality of turbot (Scophthalmus maximus) via the TOR/AAR/AMPK pathways

Clostridium autoethanogenum protein (CAP) is a promising protein source for aquaculture; however, how CAP influences fish quality is worth extensive research. We randomly allocated 630 turbot with initial body weights of about 180 g into 6 groups, with fishmeal-based control diet or diet with CAP replacing 15% (CAP15), 30% (CAP30), 45% (CAP45), 60% (CAP60), or 75% (CAP75) of fishmeal protein. After a 70-d feeding trial, the fillet yield (P = 0.015) and content of protein (P = 0.017), collagen (P < 0.001), hydroxyproline (P < 0.001), C20:5n-3 (P = 0.007), and ∑n-3/∑n-6 polyunsaturated fatty acids ratio (P < 0.001) in turbot muscle was found to decrease linearly with increasing CAP. However, turbot fed CAP15 diet maintained these parameters (P > 0.05). By contrast, the muscle hardness increased linearly with increasing CAP (P = 0.004), accompanied by linear reduction of muscle fiber area (P = 0.003) and expression of myogenesis-related genes, including cathepsin D (ctsd P < 0.001) and muscle ring finger protein 1 (murf 1, P < 0.001). Phosphorylation of protein kinase B (Akt, P < 0.001), target of rapamycin (TOR, P = 0.001), eukaryotic initiation factor 4E-binding protein 1 (4E-BP1, P < 0.001), and ribosomal protein S6 (S6, P < 0.001) decreased linearly; however, phosphorylation of AMP-activated protein kinase (AMPK, P < 0.001), eukaryotic initiation factor 2α (eIF2α, P < 0.001), and the abundance of activating transcription factor 4 (ATF4, P < 0.001) increased with increasing CAP, suggesting that the TOR signaling pathway was inhibited, and the amino acid response (AAR) and AMPK pathways were activated. Additionally, expression of genes related to protein degradation, including myogenic factor 5 (myf 5, P < 0.001), myogenic differentiation (myod, P < 0.001), paired box 7 (pax 7, P < 0.001), and ctsd (P < 0.001), decreased linearly with increasing CAP. In conclusion, CAP could be used to replace up to 15% of fishmeal without negatively impacting turbot quality. However, higher levels of CAP decreased fillet yield, muscle protein content, and muscle fiber diameter while increasing muscle hardness, which could be attributed to the inhibition of the TOR pathway and activation of the AAR and AMPK pathways.

Effect and mechanism of natural composite hydrogel from fish scale intercellular matrix on diabetic chronic wound repair

Diabetes mellitus is a chronic metabolic disease with prolonged low-grade inflammation and impaired cellular function, leading to poor wound healing. The treatment of diabetic wounds remains challenging due to the complex wound microenvironment. In view of the prominence of fish scales in traditional Chinese medicine and their wide application in modern medicine, we isolated the intercellular components in the scales of sea bass, obtained a natural composite hydrogel, fish scales gel (FSG), and applied it to diabetic chronic wounds. FSG was rich in collagen-like proteins, and possessed low-temperature gelation properties. In vitro, FSG was biocompatible and promoted fibroblast proliferation by approximately 40 %, endothelial cell migration by approximately 20 % and activated the M1 macrophages. In addition, FSG restored the function of fibroblasts and vascular endothelial cells damaged by high glucose. Importantly, FSG normalized the acute inflammatory response to impaired macrophages in a high-glucose microenvironment. Transcriptome analysis implies that this mechanism may involve enhanced cell signaling and cellular communication, improved sensitivity to cytokines, and activation of the TNF signaling pathway. Animal experiments confirmed that FSG significantly improved wound closure by approximately 15 % in diabetic rats, showing similar effects to acute wounds. In conclusion, the regulation of multiple cellular functions by FSG, especially the counterintuitive ability to induce acute inflammation, promoted diabetic wound healing and provides a novel therapeutic strategy for wound repair in diabetic patients.

The Impact of Gelatin and Fish Collagen on Alginate Hydrogel Properties: A Comparative Study

Hydrogel materials based on sodium alginate find versatile applications in regenerative medicine and tissue engineering due to their unique properties, such as biocompatibility and biodegradability, and the possibility of the customization of their mechanical properties, such as in terms of the individual requirements of separate clinical applications. These materials, however, have numerous limitations in the area of biological activity. In order to eliminate their limitations, sodium alginate is popularly applied in combination with added gelatin, which represents a product of collagen hydrolysis. Despite numerous beneficial biological properties, matrix materials based on gelatin have poor mechanical properties and are characterized by their ability for rapid degradation in an aqueous environment, particularly at the physiological temperature of the body, which significantly limits the independent application opportunities of this type of composition in the range of scaffolding production dedicated for tissue engineering. Collagen hydrogels, unlike gelatin, are characterized by higher bioactivity, dictated by a greater number of ligands that allow for cell adhesion, as well as better stability under physiological conditions. Fish-derived collagen provides a material that may be efficiently extracted without the risk of mammalian prion infection and can be used in all patients without religious restrictions. Considering the numerous advantages of collagen indicating its superiority over gelatin, within the framework of this study, the compositions of hydrogel materials based on sodium alginate and fish collagen in different concentrations were developed. Prepared hydrogel materials were compared with the properties of a typical composition of alginate with the addition of gelatin. The rheological, mechanical, and physicochemical properties of the developed polymer compositions were evaluated. The first trials of 3D printing by extrusion technique using the analyzed polymer solutions were also conducted. The results obtained indicate that replacing gelatin with fish collagen at an analogous concentration leads to obtaining materials with a lower swelling degree, better mechanical properties, higher stability, limited release kinetics of calcium ions cross-linking the alginate matrix, a slowed process of protein release under physiological conditions, and the possibility of extrusion 3D printing. The conducted analysis highlights that the optimization of the applied concentrations of fish collagen additives to composition based on sodium alginate creates the possibility of designing materials with appropriate mechanical and rheological properties and degradation kinetics adjusted to the requirements of specific applications, leading to the prospective opportunity to produce materials capable of mimicking the properties of relevant soft tissues. Thanks to its excellent bioactivity and lower-than-gelatin viscosity of the polymer solution, fish collagen also provides a prospective solution for applications in the field of 3D bioprinting.

Analysis of the Skin and Brain Transcriptome of Normally Pigmented and Pseudo-Albino Southern Flounder (Paralichthys lethostigma) Juveniles to Study the Molecular Mechanisms of Hypopigmentation and Its Implications for Species Survival in the Natural Environment

Southern flounder skin pigmentation is a critical phenotypic characteristic for this species' survival in the natural environment. Normal pigmentation allows rapid changes of color for concealment to capture prey and UV light protection. In contrast, highly visible hypopigmented pseudo-albinos exhibit a compromised immune system and are vulnerable to predation, sensitive to UV exposure, and likely have poor survival in the wild. Skin and brain tissue samples from normally pigmented and hypopigmented individuals were analyzed with next-generation RNA sequencing. A total of 1,589,613 transcripts were used to identify 952,825 genes to assemble a de novo transcriptome, with 99.43% of genes mapped to the assembly. Differential gene expression and gene enrichment analysis of contrasting tissues and phenotypes revealed that pseudo-albino individuals appeared more susceptible to environmental stress, UV light exposure, hypoxia, and osmotic stress. The pseudo-albinos' restricted immune response showed upregulated genes linked to cancer development, signaling and response, skin tissue formation, regeneration, and healing. The data indicate that a modified skin collagen structure likely affects melanocyte differentiation and distribution, generating the pseudo-albino phenotype. In addition, the comparison of the brain transcriptome revealed changes in myelination and melanocyte stem cell activity, which may indicate modified brain function, reduced melanocyte migration, and impaired vision.

Development and Investigation of an Innovative 3D Biohybrid Based on Collagen and Silk Sericin Enriched with Flavonoids for Potential Wound Healing Applications

Skin tissue injuries necessitate particular care due to associated complex healing mechanisms. Current investigations in the domain of tissue engineering and regenerative medicine are focused on obtaining novel scaffolds adapted as potential delivery systems to restore lost tissue functions and properties. In this study, we describe the fabrication and evaluation of a novel 3D scaffold structure based on collagen and silk sericin (CollSS) enriched with microcapsules containing natural compounds, curcumin (C), and/or quercetin (Q). These 3D composites were characterized by FT-IR spectroscopy, water uptake, in vitro collagenase degradation, and SEM microscopy. Furthermore, they were biologically evaluated in terms of biocompatibility, cell adhesion, anti-inflammatory, and antioxidant properties. All tested materials indicated an overall suitable biocompatibility, with the best results obtained for the one containing both flavonoids. This study suggests the cumulative beneficial effect of C and Q, encapsulated in the same composite, as a potential non-invasive therapeutic strategy for skin tissue regeneration in patients suffering from chronic wounds.

Nanostarch-Stimulated Cell Adhesion in 3D Bioprinted Hydrogel Scaffolds for Cell Cultured Meat

Three-dimensional (3D) bioprinting has great potential in the applications of tissue engineering, including cell culturing meat, because of its versatility and bioimitability. However, existing bio-inks used as edible scaffold materials lack high biocompatibility and mechanical strength to enable cell growth inside. Here, we added starch nanoparticles (SNPs) in a gelatin/sodium alginate (Gel/SA) hydrogel to enhance printing and supporting properties and created a microenvironment for adherent proliferation of piscine satellite cells (PSCs). We demonstrated the biocompatibility of SNPs for cells, with increasing 20.8% cell viability and 36.1% adhesion rate after 5 days of incubation. Transcriptomics analysis showed the mechanisms underlying the effects of SNPs on the adherent behavior of myoblasts. The 1% SNP group had a low gel point and viscosity for shaping with PSCs infusion and had a high cell number and myotube fusion index after cultivation. Furthermore, the formation of 3D muscle tissue with thicker myofibers was shown in the SNP-Gel/SA hydrogel by immunological staining.

The Influence of Various Crosslinking Conditions of EDC/NHS on the Properties of Fish Collagen Film

The process of crosslinking improves the physicochemical properties of biopolymer-based composites, making them valuable for biomedical applications. EDC/NHS-crosslinked collagen materials have a significant potential for tissue engineering applications, due to their enhanced properties and biocompatibility. Chemical crosslinking of samples can be carried out in several ways, which is crucial and has a direct effect on the final properties of the obtained material. In this study, the effect of crosslinking conditions on the properties of collagen films using EDC and NHS was investigated. Studies included FTIR spectroscopy, AFM, swelling and degradation tests, mechanical testing and contact angle measurements. Evaluation of prepared collagen films indicated that both crosslinking agents and crosslinking conditions influenced film properties. Notable alternations were observed in the infrared spectrum of the sample, to which EDC was added directly to the fish collagen solution. The same sample indicated the lowest Young modulus, tensile strength and breaking force parameters and the highest elongation at break. All samples reached the maximum swelling degree two hours after immersion in PBS solution; however, the immersion-crosslinked samples exhibited a significantly lower degree of swelling and were highly durable. The highest roughness was observed for the collagen film crosslinked with EDC, whereas the lowest was observed for the specimen crosslinked with EDC with NHS addition. The crosslinking agents increased the surface roughness of the collagen film, except for the sample modified with the addition of EDC and NHS mixture. All films were characterized by hydrophilic character. The films' modification resulted in a decrease in their hydrophilicity and wettability. Our research allows for a comparison of proposed EDC/NHS crosslinking conditions and their influence on the physicochemical properties of fish collagen thin films. EDC and NHS are promising crosslinking agents for the modification of fish collagen used in biomedical applications.

Fish By-Product Collagen Extraction Using Different Methods and Their Application

The processing of fishery resources results in the production of a growing quantity of byproducts, including heads, skins, viscera, intestines, frames, and fillet cutoffs. These byproducts are either wasted or utilized for the production of low-value items and fish oil. Typically, fish processing industries use only 25%, while the remaining 75% is considered as waste by-products. This review presents a comprehensive review on the extraction of collagen from fish byproducts, highlighting numerous techniques including acid-soluble collagen (ASC), enzyme-soluble collagen (ESC), ultrasound extraction, deep eutectic solvent (DES) extraction, and supercritical fluid extraction (SFE). A detailed explanation of various extraction parameters such as time, temperature, solid to liquid (S/L) ratio, and solvent/pepsin concentration is provided, which needs to be considered to optimize the collagen yield. Moreover, this review extends its focus to a detailed investigation of fish collagen applications in the biomedical sector, food sector, and in cosmetics. The comprehensive review explaining the extraction methods, extraction parameters, and the diverse applications of fish collagen provides a basis for the complete understanding of the potential of fish-derived collagen. The review concludes with a discussion of the current research and a perspective on the future development in this research field.

Marine collagen: Unveiling the blue resource-extraction techniques and multifaceted applications

Marine organisms such as fish and shellfish are composed of compounds with properties and characteristics that have been proven useful in a variety of sectors such as cosmetics, healthcare (wound healing), food industries, and tissue engineering. Collagen extraction from fish waste as a "blue resource" has attracted research attention over the past decade. Around 75 % of fish waste contains a high concentration of collagen. This has driven research in the conversion of these low-cost by-products into valuable products. Collagen extracted by acidic or/and enzymatic methods is gaining a lot of attention today due to its low cost and high yield. Fermentation and enzymatic hydrolysis stand out as one of the most environmentally sustainable and ecologically friendly methods for collagen extraction. Because of its great biocompatibility, excellent bioactivity, and low antigenicity, marine collagen is receiving more attention. Furthermore, collagen-derived peptides may exhibit interesting antioxidant activity, potent antihypertensive activity, and antimicrobial activity against different strains of bacteria. This review focuses on the advancements in extraction and detection methods of marine collagen, both from a technological and legislative standpoint, in addition to exploring its diverse range of application domains.

Interaction mechanism between hydroxychloroquine sulfate and collagen: Insights from multi-spectroscopy, molecular docking, and molecular dynamic simulation methods

Hydroxychloroquine sulfate (HCQ) can be used to treat various connective tissue diseases. Collagen, which is not only an important drug delivery carrier but also the main component in the connective tissue, is the focus of this study. Here, the interaction mechanism of HCQ with collagen was investigated through various spectroscopic and computational methods. It is found that HCQ binds to collagen spontaneously, primarily via hydrophobic interactions and some hydrogen bonds. The findings of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) verified that formation of HCQ-collagen complex and the amorphous structure, secondary structures, and microstructure of collagen were changed after HCQ binding. A decrease in the relaxation time of free water was observed in the collagen system when HCQ was added. Molecular docking demonstrated that HCQ was almost buried in the cavity of collagen via some hydrophobic interactions with one hydrogen bond, which conforms to the findings of the fluorescence and FTIR analyses. Molecular dynamic (MD) simulations further revealed the structural change information in the docking process. Hopefully, the information generated in this study can provide some useful insights for the research on the pharmacological mechanisms of HCQ in the treatment of the connective tissue diseases and the application of collagen as a drug carrier.

Advancements of fish-derived peptides for mucormycosis: a novel strategy to treat diabetic compilation

Mucormycosis, an extremely fatal fungal infection, is a major hurdle in the treatment of diabetes consequences. The increasing prevalence and restricted treatment choices urge the investigation of novel therapeutic techniques. Because of their effective antimicrobial characteristics and varied modes of action, fish-derived peptides have lately emerged as viable options in the fight against mucormycosis. This review examines the potential further application of fish-derived peptides in diagnosing and managing mucormycosis in relation to diabetic complications. First, we examine the pathophysiology of mucormycosis and the difficulties in treating it in diabetics. We emphasize the critical need for alternative therapeutic methods for tackling the limitations of currently available antifungal medicines. The possibility of fish-derived peptides as an innovative approach to combat mucormycosis is then investigated. These peptides, derived from several fish species, provide wide antimicrobial properties against a variety of diseases. They also have distinct modes of action, such as rupture of cell membranes, suppression of development, and modification of the host immunological response. Furthermore, we investigate the problems and prospects connected with the clinical application of fish-derived peptides. Ultimately, future advances in fish-derived peptides, offer interesting avenues for the management of mucormycosis in the context of diabetic comorbidities. More research and clinical trials are needed to properly investigate these peptide's therapeutic potential and pave the way for their adoption into future antifungal therapies.

Processing and post-processing of fish skin as a novel material in tissue engineering

As a natural material, fish skin contains significant amounts of collagen I and III, and due to its biocompatible nature, it can be used to regenerate various tissues and organs. To use fish skin, it is necessary to perform the decellularization process to avoid the immunological response of the host body. In the process of decellularization, it is crucial to conserve the extracellular matrix (ECM) three-dimensional (3D) structure. However, it is known that decellularization methods may also damage ECM strands arrangement and structure. Moreover, after decellularization, the post-processing of fish skin improves its mechanical and biological properties and preserves its 3D design and strength. Also, sterilization, which is one of the post-processing steps, is mandatory in pre-clinical and clinical settings. In this review paper, the fish skin decellularization methods performed and the various post-processes used to increase the performance of the skin have been studied. Moreover, multiple applications of acellular fish skin (AFS) and its extracted collagen have been reviewed.

Tilapia fish waste: An asset for tissue engineering - A review

Fisheries and aquaculture output have exploded due to an alarming increase in consumption due to the global understanding of the nutritional advantages of fish. Inadvertently, the methods produce a massive amount of fish waste, posing a serious environmental threat. Recycling this waste has now become a major point of controversy that must be resolved. It is critical to emphasize the utility of discarded marine by-products for the creation of high-value commodities such as marine collagen (MC), which can be considered a sustainable solution. Because of its biocompatibility, biodegradability, safety, minimal immunogenicity, and low production costs, MC has various benefits over terrestrial collagen. Many academics have recently become interested in the use of MC as a scaffold. This review focuses on the intriguing contribution of MC in the production of MC-based scaffolds.

Preparation of Enzyme-Soluble Swim Bladder Collagen from Sea Eel (Muraenesox cinereus) and Evaluation Its Wound Healing Capacity

In the present research, the enzyme-facilitated collagen from sea eel (Muraenesox cinereus) swim bladder was isolated, and the collagen characteristics were analyzed. Then, the collagen sponge was prepared and its potential mechanism in promoting skin wound healing in mice was further investigated. Collagen was obtained from the swim bladder of sea eels employing the pepsin extraction technique. Single-factor experiments served as the basis for the response surface method (RSM) to optimize pepsin concentration, solid-liquid ratio, and hydrolysis period. With a pepsin concentration of 2067 U/g, a solid-liquid ratio of 1:83 g/mL, and a hydrolysis period of 10 h, collagen extraction achieved a yield of 93.76%. The physicochemical analysis revealed that the extracted collagen belonged to type I collagen, and the collagen sponge displayed a fibrous structure under electron microscopy. Furthermore, in comparison to the control group, mice treated with collagen sponge dressing exhibited elevated activities of superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), and glutathione peroxidase (GSH-Px), and decreased levels of malondialdehyde (MDA), interleukin (IL)-1β, interleukin (IL)-6, and tumor necrosis factor (TNF)-α. The collagen sponge dressing effectively alleviated inflammation in the wound area, facilitating efficient repair and rapid healing of the skin tissue. During the initial phase of wound healing, the group treated with collagen sponge dressing exhibited an enhancement in the expressions of cluster of differentiation (CD)31, epidermal growth factor (EGF), transforming growth factor (TGF)-β1, and type I collagen, leading to an accelerated rate of wound healing. In addition, this collagen sponge dressing could also downregulate the expressions of CD31, EGF, and type I collagen to prevent scar formation in the later stage. Moreover, this collagen treatment minimized oxidative damage and inflammation during skin wound healing and facilitated blood vessel formation in the wound. Consequently, it exhibits significant potential as an ideal material for the development of a skin wound dressing.

Preparation, Structural Characterization, and Stability of Low-Molecular-Weight Collagen Peptides-Calcium Chelate Derived from Tuna Bones

This study was conducted to prepare calcium chelate of low-molecular-weight tuna bone collagen peptides (TBCPLMW) with a high chelation rate and to identify its structural characteristics and stability. The optimum conditions for calcium chelation of TBCPLMW (TBCPLMW-Ca) were determined through single-factor experiments and response surface methodology, and the calcium-chelating capacity reached over 90% under the optimal conditions. The amino acid compositions implied that Asp and Glu played important roles in the formation of TBCPLMW-Ca. Structural characterizations determined via spectroscopic analyses revealed that functional groups such as -COO-, N-H, C=O, and C-O were involved in forming TBCPLMW-Ca. The particle size distributions and scanning electron microscopy results revealed that folding and aggregation of peptides were found in the chelate. Stability studies showed that TBCPLMW-Ca was relatively stable under thermal processing and more pronounced changes have been observed in simulated gastric digestion, presumably the acidic environment was the main factor causing the dissociation of the TBCPLMW-Ca. The results of this study provide a scientific basis for the preparation of a novel calcium supplement and is beneficial for comprehensive utilization of tuna bones.

Acellular fish skin for wound healing

Fish skin grafting as a new skin substitute is currently being used in clinical applications. Acceleration of the wound healing, lack of disease transmission, and low cost of the production process can introduce fish skin as a potential alternative to other grafts. An appropriate decellularization process allows the design of 3D acellular scaffolds for skin regeneration without damaging the morphology and extracellular matrix content. Therefore, the role of decellularization processes is very important to maintain the properties of fish skin. In this review article, recent studies on various decellularization processes as well as biological, physical, and mechanical properties of fish skin and its applications with therapeutic effects in wound healing were investigated.

The collagen market and knowledge, attitudes, and practices of Brazilian consumers regarding collagen ingestion

Collagen is considered a nutraceutical, and its consumption has been expanding due to the increased life expectancy, rising per capita income, and increased consumer awareness of health care. This study aimed to evaluate consumers' perceptions, knowledge, attitudes, and practices about the consumption of collagen-based products by using an online questionnaire and to correlate them with socio-economic data. A market survey (pharmacy stores and online) was also conducted to evaluate the available products. In total, 275 participants answered the survey, 73.3% from the Southeast region, mostly female (84.0%). Most participants reported three months as the period of collagen intake (31.6%), and the consumption period was associated with the perception of the health benefits (p < 0.001). Furthermore, the participants' knowledge and perceptions regarding collagen intake are frequently associated with dermatological and orthopedic changes. Collagen-based products supplementation is a growing market with a broad target audience (genders, age groups, and socio-economic levels). The commercial presentation of collagen has been diversified over the years, and powder collagen is the most consumed (52.7%) and cheapest compared with capsules, pills, or gummies. The results of the present study demonstrate that most consumers of this type of supplement associate its benefits with aesthetic care such as skin, hair, and nails, although the scientific literature has shown its effects in treating osteoarticular diseases, for example. Undoubtedly, the correct dose prescription, treatment time, and choice of product presentation must be analyzed carefully, as they significantly impact treatment results.

Collagens for surimi gel fortification: Type-dependent effects and the difference between type I and type II

Surimi products have unsatisfactory gel properties. Hence, this study evaluates the effect of collagen-adding on surimi gel properties and provides the first observation results regarding collagen type influence. With higher water solubility and more charged amino acids than type II, collagen type I intertwines with surimi myofibrillar proteins better to induce higher exposure of protein functional domains, more sufficient conformational changes of myosin and greater formation of chemical forces among proteins. These enhancements accelerate the gelation rate, leading to a well-stabilized surimi gel. The collagen I-containing surimi gels show more compact structures with uniformly distributed smaller pores than those containing collagen II, thereby providing the final products with higher water holding capacity and better textural profiles. As such, the surimi gel fortification performance of collagen I and the well-elucidated collagen-myofibrillar protein interaction mechanism will guide the further exploitation of collagen as an effective additive in the food industry.

Improvement of Structural, Rheological, and physicochemical properties of type I collagen by calcium lactate combined with ultrasound

Type I collagen has a relatively stable quality while quite resistant to digestion because of the complex triple helix structure. This study was conducted to explore the acoustic conditions of ultrasound (UD)-assisted calcium lactate processing of collagen and control the processing process through its sono-physico-chemical effects. The findings demonstrated that UD might lower the average particle size of collagen and increase its zeta potential. In contrast, the rise in calcium lactate concentration could dramatically limit the impact of UD processing. This may be because of its low acoustic cavitation effect, as demonstrated by the phthalic acid method (the fluorescence value decreased from 81245.67 to 18243.67). Poor changes in tertiary and secondary structures confirmed the detrimental effect of calcium lactate concentration on UD-assisted processing. Although UD-assisted calcium lactate processing can significantly alter the structure of collagen, the integrity of the collagen is basically preserved. Furthermore, the addition of UD and a trace amount of calcium lactate (0.1%) increased the roughness of the fiber structure. At this relatively low calcium lactate concentration, ultrasound improved the gastric digestibility of collagen by nearly 20%.

A review on background, process and application of electrospun nanofibers for tissue regeneration

Electrospinning is a versatile method which is used to synthesize nano/micro sized fibers under the influence of electric field. Electrospun nanoscaffolds are one of the widely accepted platforms for cultivating soft and hard tissues as they create a prefect micro-environment for cell adhesion, proliferation and differentiation. Nanoscaffolds are widely used in the field of tissue engineering due to their versatility in aiding the growth of different types of cells and tissues for varied applications. The composition, molecular weight and structure of polymer used to fabricate nanoscaffold plays an important role in determining the size and strength of the nanofibers prepared. This review gives information about the background, process and different types of polymers used in electrospinning. Recent advances in culturing liver cells, osteoblasts, skin cells, neural cells and coronary artery smooth muscle cells on nanoscaffolds are also elucidated.

Collagen, protein hydrolysates and chitin from by-products of fish and shellfish: An overview

Waste processing from fish and seafood manufacturers represents a sustainable option to prevent environmental contamination, and their byproducts offer different benefits. Transforming fish and seafood waste into valuable compounds that present nutritional and functional properties compared to mammal products becomes a new alternative in Food Industry. In this review, collagen, protein hydrolysates, and chitin from fish and seafood byproducts were selected to explain their chemical characteristics, production methodologies, and possible future perspectives. These three byproducts are gaining a significant commercial market, impacting the food, cosmetic, pharmaceutical, agriculture, plastic, and biomedical industries. For this reason, the extraction methodologies, advantages, and disadvantages are discussed in this review.

Recent advances in decellularized biomaterials for wound healing

The skin is one of the most essential organs in the human body, interacting with the external environment and shielding the body from diseases and excessive water loss. Thus, the loss of the integrity of large portions of the skin due to injury and illness may lead to significant disabilities and even death. Decellularized biomaterials derived from the extracellular matrix of tissues and organs are natural biomaterials with large quantities of bioactive macromolecules and peptides, which possess excellent physical structures and sophisticated biomolecules, and thus, promote wound healing and skin regeneration. Here, we highlighted the applications of decellularized materials in wound repair. First, the wound-healing process was reviewed. Second, we elucidated the mechanisms of several extracellular matrix constitutes in facilitating wound healing. Third, the major categories of decellularized materials in the treatment of cutaneous wounds in numerous preclinical models and over decades of clinical practice were elaborated. Finally, we discussed the current hurdles in the field and anticipated the future challenges and novel avenues for research on decellularized biomaterials-based wound treatment.

Genome-Wide Pathway Exploration of the Epidermidibacterium keratini EPI-7T

Functional cosmetics industries using skin microbiome screening and beneficial materials isolated from key microorganisms are receiving increasing attention. Since Epidermidibacterium keratini EPI-7T was first discovered in human skin, previous studies have confirmed that it can produce a new pyrimidine compound, 1,1′-biuracil, having anti-aging effects on human skin. Therefore, we conducted genomic analyses to judge the use value of E. keratini EPI-7T and provide up-to-date information. Whole-genome sequencing analysis of E. keratini EPI-7T was performed to generate new complete genome and annotation information. E. keratini EPI-7T genome was subjected to comparative genomic analysis with a group of closely-related strains and skin flora strains through bioinformatic analysis. Furthermore, based on annotation information, we explored metabolic pathways for valuable substances that can be used in functional cosmetics. In this study, the whole-genome sequencing (WGS) and annotation results of E. keratini EPI-7T were improved, and through comparative analysis, it was confirmed that the E. keratini EPI-7T has more metabolite-related genes than comparison strains. In addition, we annotated the vital genes for biosynthesis of 20 amino acids, orotic acid, riboflavin (B2) and chorismate. In particular, we were able to prospect that orotic acid could accumulate inside E. keratini EPI-7T under uracil-enriched conditions. Therefore, through a genomics approach, this study aims to provide genetic information for the hidden potential of E. keratini EPI-7T and the strain development and biotechnology utilization to be conducted in further studies.

Biopolymer - A sustainable and efficacious material system for effluent removal

Undesired discharge of various effluents directly into the aquatic ecosystem can adversely affect water quality, endangering aquatic and terrestrial flora and fauna. Therefore, the conceptual design and fabrication of a sustainable system for alleviating the harmful toxins that are discharged into the atmosphere and water bodies using a green sustainable approach is a fundamental standpoint. Adsorptive removal of toxins (∼99% removal efficacy) is one of the most attractive and facile approaches for cleaner technologies that remediate the environmental impacts and provide a safe operating space. Recently, the introduction of biopolymers for the adsorptive abstraction of toxins from water has received considerable attention due to their eclectic accessibility, biodegradability, biocompatibility, non-toxicity, and enhanced removal efficacy (∼ 80-90% for electrospun fibers). This review summarizes the recent literature on the biosorption of various toxins by biopolymers and the possible interaction between the adsorbent and adsorbate, providing an in-depth perspective of the adsorption mechanism. Most of the observed results are explained in terms of (1) biopolymers classification and application, (2) toxicity of various effluents, (3) biopolymers in wastewater treatment and their removal mechanism, and (4) regeneration, reuse, and biodegradation of the adsorbent biopolymer.

Development of Decellularized Fish Skin Scaffold Decorated with Biosynthesized Silver Nanoparticles for Accelerated Burn Wound Healing

In this study, decellularized fish skin (DFS) scaffold decorated with silver nanoparticles was prepared for accelerating burn wound healing. The silver nanoparticles (AgNPs) synthesized by the green and facile method using Aloe vera leaf at different incubating times were characterized by using X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy, and Ultraviolet-Visible Spectroscopy (UV-Vis spectroscopy). The different characterizations confirmed that the sizes of AgNPs prepared by incubating for 6 hours and 12 hours were 29.1 nm and 35.2 nm, respectively. After that, the different concentrations of the smallest AgNPs were used to dope the DFS scaffold to determine the cell viability. Additionally, an agar well diffusion method was used to screen for antimicrobial activity. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were used to correlate the concentration of AgNPs with its bactericidal effect which was seen from 50 μg/ml. Then, the toxicity with human cells was investigated using a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay with no significant cell viability from the concentration of 50 μg/ml to 200 μg/ml compared to the cocultured and commercial treatments.

Recovery of Bioactive Compounds from Marine Organisms: Focus on the Future Perspectives for Pharmacological, Biomedical and Regenerative Medicine Applications of Marine Collagen

Marine environments cover more than 70% of the Earth's surface and are among the richest and most complex ecosystems. In terms of biodiversity, the ocean represents an important source, still not widely exploited, of bioactive products derived from species of bacteria, plants, and animals. However, global warming, in combination with multiple anthropogenic practices, represents a serious environmental problem that has led to an increase in gelatinous zooplankton, a phenomenon referred to as jellyfish bloom. In recent years, the idea of "sustainable development" has emerged as one of the essential elements of green-economy initiatives; therefore, the marine environment has been re-evaluated and considered an important biological resource. Several bioactive compounds of marine origin are being studied, and among these, marine collagen represents one of the most attractive bio-resources, given its use in various disciplines, such as clinical applications, cosmetics, the food sector, and many other industrial applications. This review aims to provide a current overview of marine collagen applications in the pharmacological and biomedical fields, regenerative medicine, and cell therapy.

Collagen Derived from Fish Industry Waste: Progresses and Challenges

Fish collagen garnered significant academic and commercial focus in the last decades featuring prospective applications in a variety of health-related industries, including food, medicine, pharmaceutics, and cosmetics. Due to its distinct advantages over mammalian-based collagen, including the reduced zoonosis transmission risk, the absence of cultural-religious limitations, the cost-effectiveness of manufacturing process, and its superior bioavailability, the use of collagen derived from fish wastes (i.e., skin, scales) quickly expanded. Moreover, by-products are low cost and the need to minimize fish industry waste's environmental impact paved the way for the use of discards in the development of collagen-based products with remarkable added value. This review summarizes the recent advances in the valorization of fish industry wastes for the extraction of collagen used in several applications. Issues related to processing and characterization of collagen were presented. Moreover, an overview of the most relevant applications in food industry, nutraceutical, cosmetics, tissue engineering, and food packaging of the last three years was introduced. Lastly, the fish-collagen market and the open technological challenges to a reliable recovery and exploitation of this biopolymer were discussed.

Sustainable production of biofuels and bioderivatives from aquaculture and marine waste

The annual global fish production reached a record 178 million tonnes in 2020, which continues to increase. Today, 49% of the total fish is harvested from aquaculture, which is forecasted to reach 60% of the total fish produced by 2030. Considering that the wastes of fishing industries represent up to 75% of the whole organisms, the fish industry is generating a large amount of waste which is being neglected in most parts of the world. This negligence can be traced to the ridicule of the value of this resource as well as the many difficulties related to its valorisation. In addition, the massive expansion of the aquaculture industry is generating significant environmental consequences, including chemical and biological pollution, disease outbreaks that increase the fish mortality rate, unsustainable feeds, competition for coastal space, and an increase in the macroalgal blooms due to anthropogenic stressors, leading to a negative socio-economic and environmental impact. The establishment of integrated multi-trophic aquaculture (IMTA) has received increasing attention due to the environmental benefits of using waste products and transforming them into valuable products. There is a need to integrate and implement new technologies able to valorise the waste generated from the fish and aquaculture industry making the aquaculture sector and the fish industry more sustainable through the development of a circular economy scheme. This review wants to provide an overview of several approaches to valorise marine waste (e.g., dead fish, algae waste from marine and aquaculture, fish waste), by their transformation into biofuels (biomethane, biohydrogen, biodiesel, green diesel, bioethanol, or biomethanol) and recovering biomolecules such as proteins (collagen, fish hydrolysate protein), polysaccharides (chitosan, chitin, carrageenan, ulvan, alginate, fucoidan, and laminarin) and biosurfactants.

Evaluation of the biocompatibility of fish skin collagen with the mesenchymal stem cells in in vitro cultures

There are scarce published data suggesting, that collagen extracted from fish skin may be an attractive alternative to mammalian-derived collagen for the in vitro cell cultures. In this study, we investigated proliferation potential and differentiation capability into osteogenic and adipogenic lineages of rat adipose-derived mesenchymal stem cells (rASCs) and human adipose-derived mesenchymal stem cells (hASCs) cultured on collagen extracted from silver carp and African sharptooth catfish skins, compared with commercially available mammalian collagen and collagen-free culture dishes. Our results revealed no significant differences between fish collagen and mammalian collagen in supporting cell viability and proliferation capacity. Fish-derived collagen is a cheap material derived from production waste, does not contain transmissible pathogens of mammalian origin, supports human cell cultures at comparable level to conventional collagen sources, and may be considered as the product of choice for the in vitro cell cultures.

3D Biocomposites Comprising Marine Collagen and Silica-Based Materials Inspired on the Composition of Marine Sponge Skeletons Envisaging Bone Tissue Regeneration

Ocean resources are a priceless repository of unique species and bioactive compounds with denouement properties that can be used in the fabrication of advanced biomaterials as new templates for supporting the cell culture envisaging tissue engineering approaches. The collagen of marine origin can be sustainably isolated from the underrated fish processing industry by-products, while silica and related materials can be found in the spicules of marine sponges and diatoms frustules. Aiming to address the potential of biomaterials composed from marine collagen and silica-based materials in the context of bone regeneration, four different 3D porous structure formulations (COL, COL:BG, COL:D.E, and COL:BS) were fabricated by freeze-drying. The skins of Atlantic cod (Gadus morhua) were used as raw materials for the collagen (COL) isolation, which was successfully characterized by SDS-PAGE, FTIR, CD, and amino acid analyses, and identified as a type I collagen, produced with a 1.5% yield and a preserved characteristic triple helix conformation. Bioactive glass 45S5 bioglass® (BG), diatomaceous earth (D.E.) powder, and biosilica (BS) isolated from the Axinella infundibuliformis sponge were chosen as silica-based materials, which were obtained as microparticles and characterized by distinct morphological features. The biomaterials revealed microporous structures, showing a porosity higher than 85%, a mean pore size range of 138-315 μm depending on their composition, with 70% interconnectivity which can be favorable for cell migration and ensure the needed nutrient supply. In vitro, biological assays were conducted by culturing L929 fibroblast-like cells, which confirmed not only the non-toxic nature of the developed biomaterials but also their capability to support cell adhesion and proliferation, particularly the COL:BS biomaterials, as observed by calcein-AM staining upon seven days of culture. Moreover, phalloidin and DAPI staining revealed well-spread cells, populating the entire construct. This study established marine collagen/silica biocomposites as potential scaffolds for tissue engineering, setting the basis for future studies, particularly envisaging the regeneration of non-load-bearing bone tissues.

Research Progress on Nutritional Value, Preservation and Processing of Fish-A Review

The global population has rapidly expanded in the last few decades and is continuing to increase at a rapid pace. To meet this growing food demand fish is considered a balanced food source due to their high nutritious value and low cost. Fish are rich in well-balanced nutrients, a good source of polyunsaturated fatty acids and impose various health benefits. Furthermore, the most commonly used preservation technologies including cooling, freezing, super-chilling and chemical preservatives are discussed, which could prolong the shelf life. Non-thermal technologies such as pulsed electric field (PEF), fluorescence spectroscopy, hyperspectral imaging technique (HSI) and high-pressure processing (HPP) are used over thermal techniques in marine food industries for processing of most economical fish products in such a way as to meet consumer demands with minimal quality damage. Many by-products are produced as a result of processing techniques, which have caused serious environmental pollution. Therefore, highly advanced technologies to utilize these by-products for high-value-added product preparation for various applications are required. This review provides updated information on the nutritional value of fish, focusing on their preservation technologies to inhibit spoilage, improve shelf life, retard microbial and oxidative degradation while extending the new applications of non-thermal technologies, as well as reconsidering the values of by-products to obtain bioactive compounds that can be used as functional ingredients in pharmaceutical, cosmetics and food processing industries.

Advanced application of collagen-based biomaterials in tissue repair and restoration

In tissue engineering, bioactive materials play an important role, providing structural support, cell regulation and establishing a suitable microenvironment to promote tissue regeneration. As the main component of extracellular matrix, collagen is an important natural bioactive material and it has been widely used in scientific research and clinical applications. Collagen is available from a wide range of animal origin, it can be produced by synthesis or through recombinant protein production systems. The use of pure collagen has inherent disadvantages in terms of physico-chemical properties. For this reason, a processed collagen in different ways can better match the specific requirements as biomaterial for tissue repair. Here, collagen may be used in bone/cartilage regeneration, skin regeneration, cardiovascular repair and other fields, by following different processing methods, including cross-linked collagen, complex, structured collagen, mineralized collagen, carrier and other forms, promoting the development of tissue engineering. This review summarizes a wide range of applications of collagen-based biomaterials and their recent progress in several tissue regeneration fields. Furthermore, the application prospect of bioactive materials based on collagen was outlooked, aiming at inspiring more new progress and advancements in tissue engineering research.

Graphical Abstract

High-efficiency secretory expression and characterization of the recombinant type III human-like collagen in Pichia pastoris

Collagen, the highest content protein in the body, has irreplaceable biological functions, and it is widespread concerned in food, beauty, and medicine with great market demand. The gene encoding the recombinant type III human-like collagen α1 chain fragment was integrated into P. pastoris genome after partial amino acids were substituted. Combined with promoter engineering and high-density fermentation technology, soluble secretory expression with the highest yield of 1.05 g L-1 was achieved using two-stage feeding method, and the purity could reach 96% after affinity purification. The determination of N/C-terminal protein sequence were consistent with the theoretical expectation and showed the characteristics of Gly-X-Y repeated short peptide sequence. In amino acid analysis, glycine shared 27.02% and proline 23.92%, which were in accordance with the characteristics of collagen. Ultraviolet spectrum combined with Fourier transform infrared spectroscopy as well as mass spectrometry demonstrated that the target product conformed to the characteristics of collagen spectrums and existed as homologous dimer and trimer in the broth. This work provided a sustainable and economically viable source of the recombinant type III human-like collagen.

Effects of collagen peptides from Micropterus salmoides skin on oxidative damage induced by cyclophosphamide in mice

To investigate the protective effect of collagen peptide from Micropterus salmoides skin (CPMs) on oxidative damage induced by cyclophosphamide in mice. Balb/c female mice were divided into blank, model (cyclophosphamide, CTX), positive control (levamisole hydrochloride), and collagen peptide low-, medium-, and high-dose groups. The results showed that CPMs increase the body mass and immune-related organ indexes, such as liver and kidneys of immunosuppressed mice. The activities of ALT, AST, UA, BUN, and MDA in the liver and kidney tissues decreased significantly, while those of SOD and GSH-Px increased significantly. CPMs can relieve the pathological damage to immune organs. CPMs significantly increase the activities of IL-2, IgG, and TNF-α in serum and SOD activity, while the MDA content was decreased compared to the model group. CPMs can exert a protective effect on cyclophosphamide-induced oxidative damage and have application prospects in the field of health food.

Collagen fabricated delivery systems for wound healing: A new roadmap

Collagen is a biopolymer found in the animal body. It is one of the most abundant proteins in the extracellular matrix that provides strength to the skin, joints, and bones in the human body. It is an important source of elasticity and strength in the extracellular matrix and contributes to the structural and physiological integrity of tissues. Collagen plays an important role in regulating the wound healing process. It helps in wound healing by attracting fibroblasts and encouraging new collagen formation in the wound bed. Therefore, it can be used as a supplementary aid for wound treatment to accelerate the healing process. A prominent benefit of incorporating collagen in wound dressings is its ability to enhance the healing process for critical wounds. Not only collagen but various collagen-containing systems are being prepared to boost its efficacy in wound healing. Different strategies like nanoscale reductions, biopolymers, and incorporating anti-inflammatory and antimicrobial drugs with collagen have been reported. This review article emphasizes the use of collagen for wound healing and various collagen fabricated delivery systems such as nanofibres, nanoparticles, hydrogels, films, and sponges that aid in the healing of wounds.

New Amorphous Hydrogels with Proliferative Properties as Potential Tools in Wound Healing

The study and discovery of bioactive compounds and new formulations as potential tools for promoting the repair of dermoepidermal tissue in wound healing is of continuing interest. We have developed a new formulation of amorphous hydrogel based on sodium alginate (NaAlg); type I collagen, isolated by the authors from silver carp tails (COL); glycerol (Gli); Aloe vera gel powder (AV); and silver nanoparticles obtained by green synthesis with aqueous Cinnamomum verum extract (AgNPs@CIN) and vitamin C, respectively. The gel texture of the amorphous hydrogels was achieved by the addition of Aloe vera, demonstrated by a rheological analysis. The evaluations of the cytotoxicity and cell proliferation capacity of the experimental amorphous hydrogels were performed against human foreskin fibroblast Hs27 cells (CRL-1634-ATCC). The developed gel formulations did not show a cytotoxic effect. The hydrogel variant containing AgNPs@CIN in a concentration of 8 µg Ag/gel formulation and hydrogel variant with vitamin C had proliferative activity. In addition, the antibacterial activity of the hydrogels was evaluated against S. aureus ATCC 6538, Ps. aeruginosa ATCC 27853, and E. coli ATCC 25922. The results demonstrated that the gel variant based on AgNPs@CIN in a concentration of 95 µg Ag/gel formulation and the hydrogel based on vitamin C show antibacterial activity. Therefore, the developed hydrogels with AgNPs@CIN and vitamin C could be promising alternatives in wound healing.

Rheological Method for Determining the Molecular Weight of Collagen Gels by Using a Machine Learning Technique

This article presents, for the first time, the results of applying the rheological technique to measure the molecular weights (Mw) and their distributions (MwD) of highly hierarchical biomolecules, such as non-hydrolyzed collagen gels. Due to the high viscosity of the studied gels, the effect of the concentrations on the rheological tests was investigated. In addition, because these materials are highly sensitive to denaturation and degradation under mechanical stress and temperatures close to 40 °C, when frequency sweeps were applied, a mathematical adjustment of the data by machine learning techniques (artificial intelligence tools) was designed and implemented. Using the proposed method, collagen fibers of Mw close to 600 kDa were identified. To validate the proposed method, lower Mw species were obtained and characterized by both the proposed rheological method and traditional measurement techniques, such as chromatography and electrophoresis. The results of the tests confirmed the validity of the proposed method. It is a simple technique for obtaining more microstructural information on these biomolecules and, in turn, facilitating the design of new structural biomaterials with greater added value.

Extraction of Biocompatible Collagen From Blue Shark Skins Through the Conventional Extraction Process Intensification Using Natural Deep Eutectic Solvents

The disposal of large amounts of skin waste resulting from the blue shark fishing industry presents several industrial and environmental waste management concerns. In addition, these marine subproducts are interesting sources of collagen, a fibrous protein that shows high social and economic interest in a broad range of biomedical, pharmaceutical, and cosmetic applications. However, blue shark wasted skins are a poorly explored matrix for this purpose, and conventional collagen recovery methodologies involve several pre-treatment steps, long extraction times and low temperatures. This work presents a new green and sustainable collagen extraction approach using a natural deep eutectic solvent composed of citric acid:xylitol:water at a 1:1:10 molar ratio, and the chemical characterization of the extracted collagen by discontinuous electrophoresis, thermogravimetric analysis, Fourier transformed infrared spectroscopy and circular dichroism. The extracted material was a pure type I collagen, and the novel approach presented an extraction yield 2.5 times higher than the conventional one, without pre-treatment of raw material and reducing the procedure time from 96 to 1 h. Furthermore, the in vitro cytotoxicity evaluation, performed with a mouse fibroblasts cell line, has proven the biocompatibility of the extracted material. Overall, the obtained results demonstrate a simple, quick, cheap and environmentally sustainable process to obtain marine collagen with promising properties for biomedical and cosmetic applications.

Protein by-products: Composition, extraction, and biomedical applications

Significant upsurge in animal by-products such as skin, bones, wool, hides, feathers, and fats has become a global challenge and, if not properly disposed of, can spread contamination and viral diseases. Animal by-products are rich in proteins, which can be used as nutritional, pharmacologically functional ingredients, and biomedical materials. Therefore, recycling these abundant and renewable by-products and extracting high value-added components from them is a sustainable approach to reclaim animal by-products while addressing scarce landfill resources. This article appraises the most recent studies conducted in the last five years on animal-derived proteins' separation and biomedical application. The effort encompasses an introduction about the composition, an overview of the extraction and purification methods, and the broad range of biomedical applications of these ensuing proteins.

Hemoglobin I from Lucina pectinata on Collagen Scaffold: A Prospective Hydrogen Sulfide Scavenger

Hydrogen sulfide (H2S), independently of being a toxic gas with a characteristic smell of rotten eggs, is a crucial signaling molecule with significant physiological functions. Given the rapid diffusivity of the gas, it is a challenge to develop robust sensors and biomarkers to quantify free or bound H2S. In addition, there is the need to further develop a robust biosystem to efficiently trap or scavenge H2S from different producing environments. The work presented here uses recombinant met-aquo rHbI (rHbI-H2O) immobilization techniques on collagen to determine its ability to bind H2S due to its high affinity ( $1.24\times {10}^8$  M-1). The hemeprotein will function as a scavenger on this scaffold system. UV-Vis absorption and UV-Vis diffuse reflectance (%R) spectroscopy of rHbI-H2O and rHbI-sulfide (rHbI-H2S) complex in solution and collagen scaffold demonstrated that the heme chromophore retains its reactivity and properties. UV-Vis diffuse reflectance measurements, transformed using the Kubelka-Munk function (K-M function), show a linear correlation ( $R_2=0.9987$ and 0.9916) of rHbI-H2O and rHbI-H2S within concentrations from 1 μM to 35 μM for derivatives. The extraordinary affinity of rHbI-H2O for H2S suggests recombinant met-aquo HbI in a collagen scaffold is an excellent scavenger moiety for hydrogen sulfide. These findings give insight into H2S trapping using the rHbI-H2O-collagen scaffold, where the rHbI-H2S concentration can be determined. Future pathways are to work toward the development of a met-aquo rHbI collagen solution capable of being printed as single drops on polymer, cotton or chromatographic paper. Upon exposure of these matrixes to H2S, the rHbI-H2S complex is formed and its concentration determined using UV-Vis diffuse reflectance technique.

Design and Characterization of a Bioinspired Polyvinyl Alcohol Matrix with Structural Foam-Wall Microarchitectures for Potential Tissue Engineering Applications

Traditional medical soft matrix used in a surgical treatment or in wound management was not good enough in both the structural support and interconnectivity to be applied in tissue engineering as a scaffold. Avian skeleton and feather rachises might be good reference objects to mimic in designing a scaffold material with good structural support and high interconnectivity because of its structural foam-wall microarchitectures and structural pneumaticity. In this study, a biomimetic airstream pore-foaming process was built up and the corresponding new medical soft matrix derived from polyvinyl alcohol matrix (PVAM) with air cavities inspired by avian skeleton and feather rachises was prepared. Furthermore, the resulting medical soft matrix and bovine Achilles tendon type I collagen could be employed to prepare a new collagen-containing composite matrix. Characterization, thermal stability and cell morphology of the bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix with open-cell foam-wall microarchitectures were studied for evaluation of potential tissue engineering applications. TGA, DTG, DSC, SEM and FTIR results of new bioinspired PVA matrix were employed to build up the effective system identification approach for biomimetic structure, stability, purity, and safety of target soft matrix. The bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix would be conductive to human hepatoblastoma HepG2 cell proliferation, migration, and expression which might serve as a promising liver cell culture carrier to be used in the biological artificial liver reactor.

Polyethylene Oxide Assisted Fish Collagen-Poly-ε-Caprolactone Nanofiber Membranes by Electrospinning

Fish collagen has higher biocompatibility and lower immunogenicity than terrestrial collagen, and is currently one of the important raw materials for preparing biological materials. In this study, PEO was used as a spinning aid to prepare fish skin collagen-PCL nanofiber membranes by electrospinning, and the process was optimized to get smooth nanofibers. The morphological and mechanical properties of collagen-PCL nanofiber membranes were assessed by scanning electron microscopy (SEM). The changes in chemical composition due to the incorporation of collagen into PCL and PEO were determined by Fourier Transform infrared spectroscopy (FTIR). The biocompatibility of the collagen-PCL nanofiber membranes was evaluated in vitro in cultures of mouse fibroblasts and in vivo by subcutaneous implantation studies in rats. It was found that the diameter of the spun fibers became fine and smooth when the ratio of the collagen/PCL increased. The finally obtained nanofiber had good mechanical strength, porosity, and hydrophilicity, and could promote cell adhesion and proliferation. The FC-PCL nanofiber membrane prepared by this route opens a new way to prepare fish collagen biomaterials with electrospinning.

Protein-Based Hydrogels: Promising Materials for Tissue Engineering

The successful design of a hydrogel for tissue engineering requires a profound understanding of its constituents' structural and molecular properties, as well as the proper selection of components. If the engineered processes are in line with the procedures that natural materials undergo to achieve the best network structure necessary for the formation of the hydrogel with desired properties, the failure rate of tissue engineering projects will be significantly reduced. In this review, we examine the behavior of proteins as an essential and effective component of hydrogels, and describe the factors that can enhance the protein-based hydrogels' structure. Furthermore, we outline the fabrication route of protein-based hydrogels from protein microstructure and the selection of appropriate materials according to recent research to growth factors, crucial members of the protein family, and their delivery approaches. Finally, the unmet needs and current challenges in developing the ideal biomaterials for protein-based hydrogels are discussed, and emerging strategies in this area are highlighted.

Engineering Vascularizing Electrospun Dermal Grafts by Integrating Fish Collagen and Ion-Doped Bioactive Glass

Utilizing bioactive molecules from organic sources in combination with inorganic materials for enhanced tissue regeneration has been a focus of recent scientific advancements. Some recent studies showed the potential of some specialized bioactive glass for healing of soft tissues; the role of Rohu (Labeo rohita) skin-derived collagen, a biopolymer in tissue regeneration and cutaneous healing, is yet to be established. So, we have fabricated four different types of electrospun mats as wound dressing materials/dermal grafts by combining locally sourced fish (Rohu) skin-derived collagen with novel composition of bioactive glass (Fcol/BAG) without and with dopants (3% and 5% Cu and Co, respectively and their binary) aimed at achieving an accelerated wound healing. FTIR and EDX mapping indicated successful integration of collagen and ion-doped bioactive glass in electrospun mats. Microfibers' architectural features and composition provided a cytocompatible and nontoxic environment conducive to adhesion, spreading, and proliferation of human dermal fibroblasts in vitro; in addition, they were hemocompatible with rabbit red blood cells. Better cutaneous wound healing in rabbits was achieved by treating with Fcol/CoBAG and Fcol/CuCoBAG microfibers with respect to improved wound closure, well-formed continuous epidermis, higher wound maturity, and regulated deposition of extracellular matrix components; mature collagen and elastin. Notably, a significantly (p < 0.01) higher density of blood vessels/positive CD 31 staining was observed in fish collagen/ion-doped bioactive glass microfibrous mat treated wounds suggesting efficient neo-vascularization during early stages of the healing process particularly attributable to copper and cobalt ions in the doped bioactive glass. Enhanced vascularizing ability of these engineered dermal composite grafts/wound dressings along with efficient remodeling of cutaneous structural components (ECM) could collectively be ascribed to bioactive properties of bioactive glass and stimulatory roles of copper, cobalt ions, and fish collagen. Our study demonstrates that a fish collagen/Cu and Co-doped bioactive glass microfibrous mat could potentially be used as a low-cost dressing material/dermal graft for augmented cutaneous wound healing.