Marine Collagen/Apatite Composite Scaffolds Envisaging Hard Tissue Applications

Enhancing Guided Bone Regeneration with a Novel Carp Collagen Scaffold: Principles and Applications

Bone defects resulting from trauma, surgery, and congenital, infectious, or oncological diseases are a functional and aesthetic burden for patients. Bone regeneration is a demanding procedure, involving a spectrum of molecular processes and requiring the use of various scaffolds and substances, often yielding an unsatisfactory result. Recently, the new collagen sponge and its structural derivatives manufactured from European carp (Cyprinus carpio) were introduced and patented. Due to its fish origin, the novel scaffold poses no risk of allergic reactions or transfer of zoonoses and additionally shows superior biocompatibility, mechanical stability, adjustable degradation rate, and porosity. In this review, we focus on the basic principles of bone regeneration and describe the characteristics of an "ideal" bone scaffold focusing on guided bone regeneration. Moreover, we suggest several possible applications of this novel material in bone regeneration processes, thus opening new horizons for further research.

In vivo assessment of marine vs bovine origin collagen-based composite scaffolds promoting bone regeneration in a New Zealand rabbit model

The ability of human tissues to self-repair is limited, which motivates the scientific community to explore new and better therapeutic approaches to tissue regeneration. The present manuscript provides a comparative study between a marine-based composite biomaterial, and another composed of well-established counterparts for bone tissue regeneration. Blue shark skin collagen was combined with bioapatite obtained from blue shark's teeth (mColl:BAp), while bovine collagen was combined with synthetic hydroxyapatite (bColl:Ap) to produce 3D composite scaffolds by freeze-drying. Collagens showed similar profiles, while apatite particles differed in their composition, being the marine bioapatite a fluoride-enriched ceramic. The marine-sourced biomaterials presented higher porosities, improved mechanical properties, and slower degradation rates when compared to synthetic apatite-reinforced bovine collagen. The in vivo performance regarding bone tissue regeneration was evaluated in defects created in femoral condyles in New Zealand rabbits twelve weeks post-surgery. Micro-CT results showed that mColl:BAp implanted condyles had a slower degradation and an higher tissue formation (17.9 ± 6.9 %) when compared with bColl:Ap implanted ones (12.9 ± 7.6 %). The histomorphometry analysis provided supporting evidence, confirming the observed trend by quantifying 13.1 ± 7.9 % of new tissue formation for mColl:BAp composites and 10.4 ± 3.2 % for bColl:Ap composites, suggesting the potential use of marine biomaterials for bone regeneration.

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.

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.

Assessing non-synthetic crosslinkers in biomaterial inks based on polymers of marine origin to increase the shape fidelity in 3D extrusion printing

In the past decade, there has been significant progress in 3D printing research for tissue engineering (TE) using biomaterial inks made from natural and synthetic compounds. These constructs can aid in the regeneration process after tissue loss or injury, but achieving high shape fidelity is a challenge as it affects the construct's physical and biological performance with cells. In parallel with the growth of 3D bioprinting approaches, some marine-origin polymers have been studied due to their biocompatibility, biodegradability, low immunogenicity, and similarities to human extracellular matrix components, making them an excellent alternative to land mammal-origin polymers with reduced disease transmission risk and ethical concerns. In this research, collagen from shark skin, chitosan from squid pens, and fucoidan from brown algae were effectively blended for the manufacturing of an adequate biomaterial ink to achieve a printable, reproducible material with a high shape fidelity and reticulated using four different approaches (phosphate-buffered saline, cell culture medium, 6% CaCl2, and 5 mM Genipin). Materials characterization was composed by filament collapse, fusion behavior, swelling behavior, and rheological and compressive tests, which demonstrated favorable shape fidelity resulting in a stable structure without deformations, and interesting shear recovery properties around the 80% mark. Additionally, live/dead assays were conducted in order to assess the cell viability of an immortalized human mesenchymal stem cell line, seeded directly on the 3D printed constructs, which showed over 90% viable cells. Overall, the Roswell Park Memorial Institute cell culture medium promoted the adequate crosslinking of this biopolymer blend to serve the TE approach, taking advantage of its capacity to hamper pH decrease coming from the acidic biomaterial ink. While the crosslinking occurs, the pH can be easily monitored by the presence of the indicator phenol red in the cell culture medium, which reduces costs and time.

Potential of Atlantic Codfish (Gadus morhua) Skin Collagen for Skincare Biomaterials

Collagen is the major structural protein in extracellular matrix present in connective tissues, including skin, being considered a promising material for skin regeneration. Marine organisms have been attracting interest amongst the industry as an alternative collagen source. In the present work, Atlantic codfish skin collagen was analyzed, to evaluate its potential for skincare. The collagen was extracted from two different skin batches (food industry by-product) using acetic acid (ASColl), confirming the method reproducibility since no significant yield differences were observed. The extracts characterization confirmed a profile compatible with type I collagen, without significant differences between batches or with bovine skin collagen (a reference material in biomedicine). Thermal analyses suggested ASColl's native structure loss at 25 °C, and an inferior thermal stability to bovine skin collagen. No cytotoxicity was found for ASColl up to 10 mg/mL in keratinocytes (HaCaT cells). ASColl was used to develop membranes, which revealed smooth surfaces without significative morphological or biodegradability differences between batches. Their water absorption capacity and water contact angle indicated a hydrophilic feature. The metabolic activity and proliferation of HaCaT were improved by the membranes. Hence, ASColl membranes exhibited attractive characteristics to be applied in the biomedical and cosmeceutical field envisaging skincare.

Marine-Inspired Approaches as a Smart Tool to Face Osteochondral Regeneration

The degeneration of osteochondral tissue represents one of the major causes of disability in modern society and it is expected to fuel the demand for new solutions to repair and regenerate the damaged articular joints. In particular, osteoarthritis (OA) is the most common complication in articular diseases and a leading cause of chronic disability affecting a steady increasing number of people. The regeneration of osteochondral (OC) defects is one of the most challenging tasks in orthopedics since this anatomical region is composed of different tissues, characterized by antithetic features and functionalities, in tight connection to work together as a joint. The altered structural and mechanical joint environment impairs the natural tissue metabolism, thus making OC regeneration even more challenging. In this scenario, marine-derived ingredients elicit ever-increased interest for biomedical applications as a result of their outstanding mechanical and multiple biologic properties. The review highlights the possibility to exploit such unique features using a combination of bio-inspired synthesis process and 3D manufacturing technologies, relevant to generate compositionally and structurally graded hybrid constructs reproducing the smart architecture and biomechanical functions of natural OC regions.

Advanced Polymeric Membranes as Biomaterials Based on Marine Sources Envisaging the Regeneration of Human Tissues

The self-repair capacity of human tissue is limited, motivating the arising of tissue engineering (TE) in building temporary scaffolds that envisage the regeneration of human tissues, including articular cartilage. However, despite the large number of preclinical data available, current therapies are not yet capable of fully restoring the entire healthy structure and function on this tissue when significantly damaged. For this reason, new biomaterial approaches are needed, and the present work proposes the development and characterization of innovative polymeric membranes formed by blending marine origin polymers, in a chemical free cross-linking approach, as biomaterials for tissue regeneration. The results confirmed the production of polyelectrolyte complexes molded as membranes, with structural stability resulting from natural intermolecular interactions between the marine biopolymers collagen, chitosan and fucoidan. Furthermore, the polymeric membranes presented adequate swelling ability without compromising cohesiveness (between 300 and 600%), appropriate surface properties, revealing mechanical properties similar to native articular cartilage. From the different formulations studied, the ones performing better were the ones produced with 3 % shark collagen, 3% chitosan and 10% fucoidan, as well as with 5% jellyfish collagen, 3% shark collagen, 3% chitosan and 10% fucoidan. Overall, the novel marine polymeric membranes demonstrated to have promising chemical, and physical properties for tissue engineering approaches, namely as thin biomaterial that can be applied over the damaged articular cartilage aiming its regeneration.

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.

Cell-Laden Marine Gelatin Methacryloyl Hydrogels Enriched with Ascorbic Acid for Corneal Stroma Regeneration

Corneal pathologies from infectious or noninfectious origin have a significant impact on the daily lives of millions of people worldwide. Despite the risk of organ rejection or infection, corneal transplantation is currently the only effective treatment. Finding safe and innovative strategies is the main goal of tissue-engineering-based approaches. In this study, the potential of gelatin methacryloyl (GelMA) hydrogels produced from marine-derived gelatin and loaded with ascorbic acid (as an enhancer of the biological activity of cells) was evaluated for corneal stromal applications. Marine GelMA was synthesized with a methacrylation degree of 75%, enabling effective photocrosslinking, and hydrogels with or without ascorbic acid were produced, encompassing human keratocytes. All the produced formulations exhibited excellent optical and swelling properties with easy handling as well as structural stability and adequate degradation rates that may allow proper extracellular matrix remodeling by corneal stromal cells. Formulations loaded with 0.5 mg/mL of ascorbic acid enhanced the biological performance of keratocytes and induced collagen production. These results suggest that, in addition to marine-derived gelatin being suitable for the synthesis of GelMA, the hydrogels produced are promising biomaterials for corneal regeneration applications.

Delivery of bone morphogenetic protein-2 by crosslinking heparin to nile tilapia skin collagen for promotion of rat calvaria bone defect repair

Collagen has been widely used as a biomaterial for tissue regeneration. At the present, aqua-collagen derived from fish is poorly explored for biomedical material applications due to its insufficient thermal stability. To improve the bone repair ability and thermal stability of fish collagen, the tilapia skin collagen was crosslinked by EDC/NHS with heparin to bind specifically to BMP-2. The thermal stability of tilapia skin collagen crosslinked with heparin (HC-COL) was detected by differential scanning calorimetry (DSC). Cytotoxicity of HC-COL was assessed by detecting MC3T3-E1 cell proliferation using CCK-8 assay. The specific binding of BMP-2 to HC-COL was tested and the bioactivity of BMP-2-loaded HC-COL (HC-COL-BMP-2) was evaluated in vitro by inducing MC3T3-E1 cell differentiation. In vivo, the bone repair ability of HC-COL-2 was evaluated using micro-CT and histological observation. After crosslinking by EDC/NHS, the heparin-linked and the thermostability of the collagen of Nile Tilapia were improved simultaneously. HC-COL has no cytotoxicity. In addition, the binding of BMP-2 to HC-COL was significantly increased. Furthermore, the in vitro study revealed the effective bioactivity of BMP-2 binding on HC-COL by inducing MC3T3-E1 cells with higher ALP activity and the formation of mineralized nodules. In vivo studies showed that more mineralized and mature bone formation was achieved in HC-COL-BMP-2 group. The prepared HC-COL was an effective BMP-2 binding carrier with enough thermal stability and could be a useful biomaterial for bone repair.

Tannic acid: a versatile polyphenol for design of biomedical hydrogels

Tannic acid (TA), a natural polyphenol, is a hydrolysable amphiphilic tannin derivative of gallic acid with several galloyl groups in its structure. Tannic acid interacts with various organic, inorganic, hydrophilic, and hydrophobic materials such as proteins and polysaccharides via hydrogen bonding, electrostatic, coordinative bonding, and hydrophobic interactions. Tannic acid has been studied for various biomedical applications as a natural crosslinker with anti-inflammatory, antibacterial, and anticancer activities. In this review, we focus on TA-based hydrogels for biomaterials engineering to help biomaterials scientists and engineers better realize TA's potential in the design and fabrication of novel hydrogel biomaterials. The interactions of TA with various natural or synthetic compounds are deliberated, discussing parameters that affect TA-material interactions thus providing a fundamental set of criteria for utilizing TA in hydrogels for tissue healing and regeneration. The review also discusses the merits and demerits of using TA in developing hydrogels either through direct incorporation in the hydrogel formulation or indirectly via immersing the final product in a TA solution. In general, TA is a natural bioactive molecule with diverse potential for engineering biomedical hydrogels.

Marine origin biomaterials using a compressive and absorption methodology as cell-laden hydrogel envisaging cartilage tissue engineering

In the recent decade, marine origin products have been growingly studied as building blocks complying with the constant demand of the biomedical sector regarding the development of new devices for Tissue Engineering and Regenerative Medicine (TERM). In this work, several combinations of marine collagen-chitosan-fucoidan hydrogel were formed using a newly developed eco-friendly compressive and absorption methodology to produce hydrogels (CAMPH), which consists of compacting the biopolymers solution while removing the excess of water. The hydrogel formulations were prepared by blending solutions of 5% collagen from jellyfish and/or 3% collagen from blue shark skin, with solutions of 3% chitosan from squid pens and solutions of 10% fucoidan from brown algae, at different ratios. The biopolymer physico-chemical characterization comprised Amino Acid analysis, ATR-FTIR, CD, SDS-PAGE, ICP, XRD, and the results suggested the shark/jellyfish collagen(s) conserved the triple helical structure and had similarities with type I and type II collagen, respectively. The studied collagens also contain a denaturation temperature of around 30-32 °C and a molecular weight between 120 and 125 kDa. Additionally, the hydrogel properties were determined by rheology, water uptake ability, degradation rate, and SEM, and the results showed that all formulations had interesting mechanical (strong viscoelastic character) and structural stability properties, with a significant positive highlight in the formulation of H₃ (blending all biopolymers, i.e., 5% collagen from jellyfish, 3% collagen from skin shark, 3% chitosan and 10% of fucoidan) in the degradation test, that shows a mass loss around 18% over the 30 days, while the H₁ and H₂, present a mass loss of around 35% and 44%, respectively. Additionally, the in vitro cellular assessments using chondrocyte cells (ATDC5) in encapsulated state revealed, for all hydrogel formulations, a non-cytotoxic behavior. Furthermore, Live/Dead assay and Phalloidin/DAPI staining, to assess the cytoskeletal organization, proved that the hydrogels can provide a suitable microenvironment for cell adhesion, viability, and proliferation, after being encapsulated. Overall, the results show that all marine collagen (jellyfish/shark)-chitosan-fucoidan hydrogel formulations provide a good structural architecture and microenvironment, highlighting the H₃ biomaterial due to containing more polymers in their composition, making it suitable for biomedical articular cartilage therapies.

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.

Study of the immunologic response of marine-derived collagen and gelatin extracts for tissue engineering applications

The host immunologic response to a specific material is a critical aspect when considering it for clinical implementation. Collagen and gelatin extracted from marine sources have been proposed as biomaterials for tissue engineering applications, but there is a lack of information in the literature about their immunogenicity. In this work, we evaluated the immune response to collagen and/or gelatin from blue shark and codfish, previously extracted and characterized. After endotoxin evaluation, bone marrow-derived macrophages were exposed to the materials and a panel of pro- and anti-inflammatory cytokines were evaluated both for protein quantification and gene expression. Then, the impact of those materials in the host was evaluated through peritoneal injection in C57BL/6 mice. The results suggested shark collagen as the less immunogenic material, inducing low expression of pro-inflammatory cytokines as well as inducible nitric oxide synthase (encoded by Nos2) and high expression of Arginase 1 (encoded by Arg1). Although shark gelatin appeared to be the material with higher pro-inflammatory expression, it also presents a high expression of IL-10 (anti-inflammatory cytokine) and Arginase (both markers for M2-like macrophages). When injected in the peritoneal cavity of mice, our materials demonstrated a transient recruitment of neutrophil, being almost non-existent after 24 hours of injection. Based on these findings, the studied collagenous materials can be considered interesting biomaterial candidates for regenerative medicine as they may induce an activation of the M2-like macrophage population, which is involved in suppressing the inflammatory processes promoting tissue remodeling. STATEMENT OF SIGNIFICANCE: Marine-origin biomaterials are emerging in the biomedical arena, namely the ones based in marine-derived collagen/gelatin proposed as cell templates for tissue regeneration. Nevertheless, although the major cause of implant rejection in clinical practice is the host's negative immune response, there is a lack of information in the literature about the immunological impact of these marine collagenous materials. This work aims to contribute with knowledge about the immunologic response to collagen/gelatin extracted from blue shark and codfish skins. The results demonstrated that despite some differences observed, all the materials can induce a macrophage phenotype related with anti-inflammation resolution and then act as immuno-modulators and anti-inflammatory inducible materials.

Mineralized collagen as a bioactive ink to support encapsulation of human adipose stem cells: A step towards the future of bone regeneration

Bioprinting - printing with incorporated living cells - has earned special attention on tissue engineering approaches, aiming to closer reproduce the 3D microenvironment of the target tissue. However, it raises extra complexity related to the need to use cell-friendly printing conditions that still comply with material printing fidelity. Inspired by the composite nano structural organization of mineralized tissues, this work reports the efficiency of the chemical approach followed to in situ mineralize blue shark skin collagen, at a nano scale level, to ultimately produce stable inks. The influence of initial cellular density was evaluated by assessing three different concentrations (2.5, 5 and 7.5 × 10⁶ cells·ml^-1) of human adipose stem cells (hASC), with the higher density of encapsulated cells presenting improved viability in a long culture term. Immunodetection of osteogenic-related markers, like RUNX2 and osteopontin, 21 days after cell culture in basal conditions confirmed the potential of the ink to be applied for osteogenic purposes, which may be associated with the success of the cell-to-ink interaction and the Ca²⁺ ions released from the co-precipitated hydroxyapatite. A combination of mineralized shark collagen, alginate and hASC is thus proposed as a bioactive bioink with potential properties for regeneration of bone tissue.

Marine Collagen: A Promising Biomaterial for Wound Healing, Skin Anti-Aging, and Bone Regeneration

Marine organisms harbor numerous bioactive substances that can be utilized in the pharmaceutical and cosmetic industries. Scientific research on various applications of collagen extracted from these organisms has become increasingly prevalent. Marine collagen can be used as a biomaterial because it is water soluble, metabolically compatible, and highly accessible. Upon review of the literature, it is evident that marine collagen is a versatile compound capable of healing skin injuries of varying severity, as well as delaying the natural human aging process. From in vitro to in vivo experiments, collagen has demonstrated its ability to invoke keratinocyte and fibroblast migration as well as vascularization of the skin. Additionally, marine collagen and derivatives have proven beneficial and useful for both osteoporosis and osteoarthritis prevention and treatment. Other bone-related diseases may also be targeted by collagen, as it is capable of increasing bone mineral density, mineral deposition, and importantly, osteoblast maturation and proliferation. In this review, we demonstrate the advantages of marine collagen over land animal sources and the biomedical applications of marine collagen related to bone and skin damage. Finally, some limitations of marine collagen are briefly discussed.

Natural Biomaterials from Biodiversity for Healthcare Applications

Natural biomaterials originating during the growth cycles of all living organisms have been used for many applications. They span from bioinert to bioactive materials including bioinspired ones. As they exhibit an increasing degree of sophistication, natural biomaterials have proven suitable to address the needs of the healthcare sector. Here the different natural healthcare biomaterials, their biodiversity sources, properties, and promising healthcare applications are reviewed. The variability of their properties as a result of considered species and their habitat is also discussed. Finally, some limitations of natural biomaterials are discussed and possible future developments are provided as more natural biomaterials are yet to be discovered and studied.

Biomaterials from the sea: Future building blocks for biomedical applications

Marine resources have tremendous potential for developing high-value biomaterials. The last decade has seen an increasing number of biomaterials that originate from marine organisms. This field is rapidly evolving. Marine biomaterials experience several periods of discovery and development ranging from coralline bone graft to polysaccharide-based biomaterials. The latter are represented by chitin and chitosan, marine-derived collagen, and composites of different organisms of marine origin. The diversity of marine natural products, their properties and applications are discussed thoroughly in the present review. These materials are easily available and possess excellent biocompatibility, biodegradability and potent bioactive characteristics. Important applications of marine biomaterials include medical applications, antimicrobial agents, drug delivery agents, anticoagulants, rehabilitation of diseases such as cardiovascular diseases, bone diseases and diabetes, as well as comestible, cosmetic and industrial applications.

Marine-Derived Collagen as Biomaterials for Human Health

Collagen is a kind of biocompatible protein material, which is widely used in medical tissue engineering, drug delivery, cosmetics, food and other fields. Because of its wide source, low extraction cost and good physical and chemical properties, it has attracted the attention of many researchers in recent years. However, the application of collagen derived from terrestrial organisms is limited due to the existence of diseases, religious beliefs and other problems. Therefore, exploring a wider range of sources of collagen has become one of the main topics for researchers. Marine-derived collagen (MDC) stands out because it comes from a variety of sources and avoids issues such as religion. On the one hand, this paper summarized the sources, extraction methods and characteristics of MDC, and on the other hand, it summarized the application of MDC in the above fields. And on the basis of the review, we found that MDC can not only be extracted from marine organisms, but also from the wastes of some marine organisms, such as fish scales. This makes further use of seafood resources and increases the application prospect of MDC.

Diverse and Productive Source of Biopolymer Inspiration: Marine Collagens

Marine biodiversity is expressed through the huge variety of vertebrate and invertebrate species inhabiting intertidal to deep-sea environments. The extraordinary variety of "forms and functions" exhibited by marine animals suggests they are a promising source of bioactive molecules and provides potential inspiration for different biomimetic approaches. This diversity is familiar to biologists and has led to intensive investigation of metabolites, polysaccharides, and other compounds. However, marine collagens are less well-known. This review will provide detailed insight into the diversity of collagens present in marine species in terms of their genetics, structure, properties, and physiology. In the last part of the review the focus will be on the most common marine collagen sources and on the latest advances in the development of innovative materials exploiting, or inspired by, marine collagens.

Applications of marine collagens in bone tissue engineering

For decades, collagen has been among the most widely used biomaterials with several biomedical applications. Recently, researchers have shown a keen interest in collagen obtained from marine sources because of its biocompatibility, biodegradability, ease of extractability, safety, low immunogenicity, and low production costs. A wide variety of marine collagen-based scaffolds have been developed for bone tissue engineering, and these scaffolds display excellent biological effects. This review aims to provide an overview of the biological effects of marine collagen in bone engineering, such as promoting osteogenesis and collagen synthesis, inhibiting inflammation, inducing the differentiation of cartilage, and improving bone mineral density. Marine collagen holds great promise as a biomaterial in bone tissue engineering.

Engineering 3D printed bioactive composite scaffolds based on the combination of aliphatic polyester and calcium phosphates for bone tissue regeneration

In this study, polylactic acid (PLA) filled with hydroxyapatite (HA) or beta-tricalcium phosphate (TCP) in 5 wt% and 10 wt% of concentration were produced employing twin-screw extrusion followed by fused filament fabrication in two different architectures, varying the orientation of fibers of adjacent layers. The extruded 3D filaments presented suitable rheological and thermal properties to manufacture of 3D scaffolds envisaging bone tissue engineering. The produced scaffolds exhibited a high level of printing accuracy related to the 3D model; confirmed by micro-CT and electron microscopy analysis. The developed architectures presented mechanical properties compatible with human bone replacement. The addition of HA and TCP made the filaments bioactive, and the deposition of new calcium phosphates was observed upon 7 days of incubation in simulated body fluid, exemplifying a microenvironment suitable for cell attachment and proliferation. After 7 days of cell culture, the constructs with a higher percentage of HA and TCP demonstrated a significantly superior amount of DNA when compared to neat PLA, indicating that higher concentrations of HA and TCP could guide a good cellular response and increasing cell cytocompatibility. Differentiation tests were performed, and the biocomposites of PLA/HA and PLA/TCP exhibited earlier markers of cell differentiation as confirmed by alkaline phosphatase and alizarin red assays. The 3D printed composite scaffolds, manufactured with bioactive materials and adequate porous size, supported cell attachment, proliferation, and differentiation, which together with their scalability, promise a high potential for bone tissue engineering applications.

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

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

Progress in Modern Marine Biomaterials Research

The growing demand for new, sophisticated, multifunctional materials has brought natural structural composites into focus, since they underwent a substantial optimization during long evolutionary selection pressure and adaptation processes. Marine biological materials are the most important sources of both inspiration for biomimetics and of raw materials for practical applications in technology and biomedicine. The use of marine natural products as multifunctional biomaterials is currently undergoing a renaissance in the modern materials science. The diversity of marine biomaterials, their forms and fields of application are highlighted in this review. We will discuss the challenges, solutions, and future directions of modern marine biomaterialogy using a thorough analysis of scientific sources over the past ten years.

Bioprinting of Collagen: Considerations, Potentials, and Applications

Collagen is the most abundant extracellular matrix protein that is widely used in tissue engineering (TE). There is little research done on printing pure collagen. To understand the bottlenecks in printing pure collagen, it is imperative to understand collagen from a bottom-up approach. Here it is aimed to provide a comprehensive overview of collagen printing, where collagen assembly in vivo and the various sources of collagen available for TE application are first understood. Next, the current printing technologies and strategy for printing collagen-based materials are highlighted. Considerations and key challenges faced in collagen printing are identified. Finally, the key research areas that would enhance the functionality of printed collagen are presented.

Fish Collagen: Extraction, Characterization, and Applications for Biomaterials Engineering

The utilization of marine-based collagen is growing fast due to its unique properties in comparison with mammalian-based collagen such as no risk of transmitting diseases, a lack of religious constraints, a cost-effective process, low molecular weight, biocompatibility, and its easy absorption by the human body. This article presents an overview of the recent studies from 2014 to 2020 conducted on collagen extraction from marine-based materials, in particular fish by-products. The fish collagen structure, extraction methods, characterization, and biomedical applications are presented. More specifically, acetic acid and deep eutectic solvent (DES) extraction methods for marine collagen isolation are described and compared. In addition, the effect of the extraction parameters (temperature, acid concentration, extraction time, solid-to-liquid ratio) on the yield of collagen is investigated. Moreover, biomaterials engineering and therapeutic applications of marine collagen have been summarized.

From Food Waste to Innovative Biomaterial: Sea Urchin-Derived Collagen for Applications in Skin Regenerative Medicine

Collagen-based skin-like scaffolds (CBSS) are promising alternatives to skin grafts to repair wounds and injuries. In this work, we propose that the common marine invertebrate sea urchin represents a promising and eco-friendly source of native collagen to develop innovative CBSS for skin injury treatment. Sea urchin food waste after gonad removal was here used to extract fibrillar glycosaminoglycan (GAG)-rich collagen to produce bilayer (2D + 3D) CBSS. Microstructure, mechanical stability, permeability to water and proteins, ability to exclude bacteria and act as scaffolding for fibroblasts were evaluated. Our data show that the thin and dense 2D collagen membrane strongly reduces water evaporation (less than 5% of water passes through the membrane after 7 days) and protein diffusion (less than 2% of BSA passes after 7 days), and acts as a barrier against bacterial infiltration (more than 99% of the different tested bacterial species is retained by the 2D collagen membrane up to 48 h), thus functionally mimicking the epidermal layer. The thick sponge-like 3D collagen scaffold, structurally and functionally resembling the dermal layer, is mechanically stable in wet conditions, biocompatible in vitro (seeded fibroblasts are viable and proliferate), and efficiently acts as a scaffold for fibroblast infiltration. Thus, thanks to their chemical and biological properties, CBSS derived from sea urchins might represent a promising, eco-friendly, and economically sustainable biomaterial for tissue regenerative medicine.

Chondroitin sulfate and hydroxyapatite from Prionace glauca shark jaw: Physicochemical and structural characterization

In the present work, the potential of the Prionace glauca jaw as a source of both chondroitin sulfate and bioapatite is explored. The sandwich-type structure in cross section of the jaw based on alternate layers with prevalence in organic tissue or mineralized is shown and these bands respectively confirmed as CS or hydroxyapatite -enriched zones. As result of this, an optimized process in sequential steps for the recovery of both biomaterials and their purification process is proposed, by combining enzymatic proteolysis, chemical precipitation and separation using ultrafiltration membrane for CS production together with controlled thermal treatment for hydroxyapatite obtaining. The purified CS was characterized by Gel Permeation Chromatography, Nuclear Magnetic Resonance and Strong Anion Exchange Chromatography, revealing a polymeric material with a molecular weight of 67 kDa, and prevalent 6S-GalNAc sulfation (68%), followed by 4S-GalNAc (13%), a significant proportion of disulfated disaccharides (12%) and only 7% of non-sulfated units. In the case of the bioapatite a purified biphasic 60:40 porous calcium phosphate of hydroxyapatite: whitlockite/β-TCP was confirmed. Hydroxyapatite as major component (85%) was also obtained for jaws directly subjected to the thermal treatment. This proved the influence of the enzymatic hydrolysis and centrifugation on the composition of the mineral fraction.

Development and Characterization of Squalene-Loaded Topical Agar-Based Emulgel Scaffold: Wound Healing Potential in Full-Thickness Burn Model

Full-thickness burns pose a major challenge for clinicians to handle because of their restricted self-healing ability. Even though several approaches have been implemented for repairing these burnt skin tissue defects, all of them had unsatisfactory outcomes. Moreover, during recent years, skin tissue engineering techniques have emerged as a promising approach to improve skin tissue regeneration and overcome the shortcomings of the traditional approaches. Although previous literatures report the wound healing effects of the squalene oil, in the current study, for the first time, we developed a squalene-loaded emulgel-based scaffold as a novel approach for potential skin regeneration. This squalene-loaded agar-based emulgel scaffold was fabricated by using physical cross-linking technique using lecithin as an emulsifier. Characterization studies such as X-ray diffraction, Fourier-transform infrared spectroscopy, and field emission scanning electron microscopy revealed the amorphous nature, chemical interactions, and cross-linked capabilities of the developed emulgel scaffold. The squalene-loaded emulgel scaffold showed excellent wound contraction when compared with the agar gel and negative control. In case of the histopathology and recent immunohistochemistry findings, it was clearly evidenced that squalene-loaded emulgel promoted faster rate of the revascularization and macrophage polarization in order to enhance the burn wound healing. Moreover, the findings also revealed that the incorporation of squalene oil into the formulation enhances collagen deposition and accelerates the burnt skin tissue regeneration process. Finally, we conclude that the squalene-loaded emulgel scaffold could be an effective formulation used in the treatment of the burnt skin tissue defects.

Cell-Laden Biomimetically Mineralized Shark-Skin-Collagen-Based 3D Printed Hydrogels for the Engineering of Hard Tissues

Mineralization processes based on coprecipitation methods have been applied as a promising alternative to the most commonly used methods of polymer-ceramic combination, direct mixing, and incubation in simulated body fluid (SBF) or modified SBF. In the present study, for the first time, the in situ mineralization (ideally hydroxyapatite formation) of blue shark (Prionace glauca (PG)) collagen to fabricate 3D printable cell-laden hydrogels is proposed. In the first part, several parameters for collagen mineralization were tested until optimization. The hydroxyapatite formation was confirmed by FT-IR, XRD, and TEM techniques. In the second part, stable bioinks combining the biomimetically mineralized collagen with alginate (AG) (1:1, 1:2, 1:3, and AG) solution were used for 3D printing of hydrogels. The addition of Ca²⁺ ions into the system did present a synergistic effect: by one side, the in situ mineralization of the collagen occurred, and at same time, they were also useful to ionically cross-link the blends with alginate, avoiding the addition of any cytotoxic chemical cross-linking agent. Mouse fibroblast cell line survival during and after printing was favored by the presence of PG collagen as exhibited by the biological performance of the hydrogels. Inspired in a concept of marine byproduct valorization, 3D bioprinting of in situ mineralized blue shark collagen is thus proposed as a promising approach, envisioning the engineering of mineralized tissues.

Enhanced Growth of Lapine Anterior Cruciate Ligament-Derived Fibroblasts on Scaffolds Embroidered from Poly(l-lactide-co-ε-caprolactone) and Polylactic Acid Threads Functionalized by Fluorination and Hexamethylene Diisocyanate Cross-Linked Collagen Foams

Reconstruction of ruptured anterior cruciate ligaments (ACLs) is limited by the availability and donor site morbidity of autografts. Hence, a tissue engineered graft could present an alternative in the future. This study was undertaken to determine the performance of lapine (L) ACL-derived fibroblasts on embroidered poly(l-lactide-co-ε-caprolactone) (P(LA-CL)) and polylactic acid (PLA) scaffolds in regard to a tissue engineering approach for ACL reconstruction. Surface modifications of P(LA-CL)/PLA by gas-phase fluorination and cross-linking of a collagen foam using either ethylcarbodiimide (EDC) or hexamethylene diisocyanate (HMDI) were tested regarding their influence on cell adhesion, growth and gene expression. The experiments were performed using embroidered P(LA-CL)/PLA scaffolds that were seeded dynamically or statically with LACL-derived fibroblasts. Scaffold cytocompatibility, cell survival, numbers, metabolic activity, ultrastructure and sulfated glycosaminoglycan (sGAG) synthesis were evaluated. Quantitative real-time polymerase chain reaction (QPCR) revealed gene expression of collagen type I (COL1A1), decorin (DCN), tenascin C (TNC), Mohawk (MKX) and tenomodulin (TNMD). All tested scaffolds were highly cytocompatible. A significantly higher cellularity and larger scaffold surface areas colonized by cells were detected in HMDI cross-linked and fluorinated scaffolds compared to those cross-linked with EDC or without any functionalization. By contrast, sGAG synthesis was higher in controls. Despite the fact that the significance level was not reached, gene expressions of ligament extracellular matrix components and differentiation markers were generally higher in fluorinated scaffolds with cross-linked collagen foams. LACL-derived fibroblasts maintained their differentiated phenotype on fluorinated scaffolds supplemented with a HMDI cross-linked collagen foam, making them a promising tool for ACL tissue engineering.

Marine Collagen as A Promising Biomaterial for Biomedical Applications

This review focuses on the expanding role of marine collagen (MC)-based scaffolds for biomedical applications. A scaffold-a three-dimensional (3D) structure fabricated from biomaterials-is a key supporting element for cell attachment, growth, and maintenance in 3D cell culture and tissue engineering. The mechanical and biological properties of the scaffolds influence cell morphology, behavior, and function. MC, collagen derived from marine organisms, offers advantages over mammalian collagen due to its biocompatibility, biodegradability, easy extractability, water solubility, safety, low immunogenicity, and low production costs. In recent years, the use of MC as an increasingly valuable scaffold biomaterial has drawn considerable attention from biomedical researchers. The characteristics, isolation, physical, and biochemical properties of MC are discussed as an understanding of MC in optimizing the subsequent modification and the chemistries behind important tissue engineering applications. The latest technologies behind scaffold processing are assessed and the biomedical applications of MC and MC-based scaffolds, including tissue engineering and regeneration, wound dressing, drug delivery, and therapeutic approach for diseases, especially those associated with metabolic disturbances such as obesity and diabetes, are discussed. Despite all the challenges, MC holds great promise as a biomaterial for developing medical products and therapeutics.

Scaffolding Strategies for Tissue Engineering and Regenerative Medicine Applications

During the past two decades, tissue engineering and the regenerative medicine field have invested in the regeneration and reconstruction of pathologically altered tissues, such as cartilage, bone, skin, heart valves, nerves and tendons, and many others. The 3D structured scaffolds and hydrogels alone or combined with bioactive molecules or genes and cells are able to guide the development of functional engineered tissues, and provide mechanical support during in vivo implantation. Naturally derived and synthetic polymers, bioresorbable inorganic materials, and respective hybrids, and decellularized tissue have been considered as scaffolding biomaterials, owing to their boosted structural, mechanical, and biological properties. A diversity of biomaterials, current treatment strategies, and emergent technologies used for 3D scaffolds and hydrogel processing, and the tissue-specific considerations for scaffolding for Tissue engineering (TE) purposes are herein highlighted and discussed in depth. The newest procedures focusing on the 3D behavior and multi-cellular interactions of native tissues for further use for in vitro model processing are also outlined. Completed and ongoing preclinical research trials for TE applications using scaffolds and hydrogels, challenges, and future prospects of research in the regenerative medicine field are also presented.

Evaluation of Differentiated Bone Cells Proliferation by Blue Shark Skin Collagen via Biochemical for Bone Tissue Engineering

Collagen from a marine resource is believed to have more potential activity in bone tissue engineering and their bioactivity depends on biochemical and structural properties. Considering the above concept, pepsin soluble collagen (PSC) and acid soluble collagen (ASC) from blue shark (Prionace glauca) skin were extracted and its biochemical and osteogenic properties were investigated. The hydroxyproline content was higher in PSC than ASC and the purified collagens contained three distinct bands α₁, α2, and β dimer. The purity of collagen was confirmed by the RP-HPLC profile and the thermogravimetric data showed a two-step thermal degradation pattern. ASC had a sharp decline in viscosity at 20⁻30 °C. Scanning electron microscope (SEM) images revealed the fibrillar network structure of collagens. Proliferation rates of the differentiated mouse bone marrow-mesenchymal stem (dMBMS) and differentiated osteoblastic (dMC3T3E1) cells were increased in collagen treated groups rather than the controls and the effect was dose-dependent, which was further supported by higher osteogenic protein and mRNA expression in collagen treated bone cells. Among two collagens, PSC had significantly increased dMBMS cell proliferation and this was materialized through increasing RUNX2 and collagen-I expression in bone cells. Accordingly, the collagens from blue shark skin with excellent biochemical and osteogenic properties could be a suitable biomaterial for therapeutic application.