Preparation and biocompatibility study of gelatin/kappa-carrageenan scaffolds

Recent Advances in Marine Biomaterials Tailored and Primed for the Treatment of Damaged Soft Tissues

The inherent self-repair abilities of the body often fall short when it comes to addressing injuries in soft tissues like skin, nerves, and cartilage. Tissue engineering and regenerative medicine have concentrated their research efforts on creating natural biomaterials to overcome this intrinsic healing limitation. This comprehensive review delves into the advancement of such biomaterials using substances and components sourced from marine origins. These marine-derived materials offer a sustainable alternative to traditional mammal-derived sources, harnessing their advantageous biological traits including sustainability, scalability, reduced zoonotic disease risks, and fewer religious restrictions. The use of diverse engineering methodologies, ranging from nanoparticle engineering and decellularization to 3D bioprinting and electrospinning, has been employed to fabricate scaffolds based on marine biomaterials. Additionally, this review assesses the most promising aspects in this field while acknowledging existing constraints and outlining necessary future steps for advancement.

Carrageenan-Based Compounds as Wound Healing Materials

The following review is focused on carrageenan, a heteroglycan-based substance that is a very significant wound healing biomaterial. Every biomaterial has advantages and weaknesses of its own, but these drawbacks are typically outweighed by combining the material in various ways with other substances. Carrageenans' key benefits include their water solubility, which enables them to keep the wound and periwound damp and absorb the wound exudate. They have low cytotoxicity, antimicrobial and antioxidant qualities, do not stick to the wound bed, and hence do not cause pain when removed from the wounded region. When combined with other materials, they can aid in hemostasis. This review emphasizes the advantages of using carrageenan for wound healing, including the use of several mixes that improve its properties.

An Overview on Collagen and Gelatin-Based Cryogels: Fabrication, Classification, Properties and Biomedical Applications

Decades of research into cryogels have resulted in the development of many types of cryogels for various applications. Collagen and gelatin possess nontoxicity, intrinsic gel-forming ability and physicochemical properties, and excellent biocompatibility and biodegradability, making them very desirable candidates for the fabrication of cryogels. Collagen-based cryogels (CBCs) and gelatin-based cryogels (GBCs) have been successfully applied as three-dimensional substrates for cell culture and have shown promise for biomedical use. A key point in the development of CBCs and GBCs is the quantitative and precise characterization of their properties and their correlation with preparation process and parameters, enabling these cryogels to be tuned to match engineering requirements. Great efforts have been devoted to fabricating these types of cryogels and exploring their potential biomedical application. However, to the best of our knowledge, no comprehensive overviews focused on CBCs and GBCs have been reported currently. In this review, we attempt to provide insight into the recent advances on such kinds of cryogels, including their fabrication methods and structural properties, as well as potential biomedical applications.

Biomimetic algal polysaccharide coated 3D nanofibrous scaffolds promote skin extracellular matrix formation

Development of functional biological substitutes for skin tissue engineering applications has observed several advancements over the past few decades. In this regard, intelligent extracellular matrix (ECM) mimetic scaffolds have recently evolved as a promising paradigm by presenting instructive cues directing cell-matrix communication, tissue remodeling and homeostasis. However, orchestring multitude attributes of skin ECM yet presents an intriguing challenge to be addressed. In the present work, we have developed an in vitro skin scaffold by coating a bio-mimetic ECM cue κ-carrageenan on electrospun nanofibers for the first time. κ-Carrageenan, a natural sulfated algal polysaccharide exhibits close similarity with native glucosaminoglycans (GAGs) of skin ECM. On the other hand, electrospun nanofibers resemble the 3D nano-topographic architecture of ECM. In the coated form, κ-carrageenan could provide the biochemical cues necessary for cellular functions on the nanofibrous scaffold, thereby mimicking the native 3D microenvironment of skin ECM. The nano-architecture of the electrospun matrix is retained in the fabricated scaffold even after coating with κ-carrageenan. The developed biomimetic scaffold significantly supplements adhesion, growth, infiltration, survival and proliferation of fibroblasts. Furthermore, enhanced gene expression and excessive secretion of collagen proteins by fibroblasts communicate a conducive skin ECM micro-environment formation on the algal polysaccharide coated nanofibrous scaffold. Taken together, these findings present a simple yet effective strategy for the fabrication of ECM mimetic scaffold for promising skin tissue engineering applications.

Carrageenan hydrogel as a scaffold for skin-derived multipotent stromal cells delivery

Carrageenan is a thermoreversible polymer of natural origin widely used in food and pharmaceutical industry that presents a glycosaminoglycan-like structure. Herein, we show that kappa-type carrageenan extracted by a semi-refined process from the red seaweed Kappaphycus alvarezii displayed both chemical and structural properties similar to a commercial carrageenan. Moreover, both extracted carrageenan hydrogel and commercial carrageenan hydrogel can serve as a scaffold for in vitro culture of human skin-derived multipotent stromal cells, demonstrating considerable potential as cell-carrier materials for cell delivery in tissue engineering. Skin-derived multipotent stromal cells cultured inside the carrageenan hydrogels showed a round shape morphology and maintained their growth and viability for at least one week in culture. Next, the effect of the extracted carrageenan hydrogel loaded with human skin-derived multipotent stromal cells was evaluated in a mouse model of full-thickness skin wound. Macroscopic and histological analyses revealed some pointed ameliorated features, such as reduced inflammatory process, faster initial recovery of wounded area, and improved extracellular matrix deposition. These results indicate that extracted carrageenan hydrogel can serve as a scaffold for in vitro growth and maintenance of human SD-MSCs, being also able to act as a delivery system of cells to wounded skin. Thus, evaluation of the properties discussed in this study contribute to a further understanding and specificities of the potential use of carrageenan hydrogel as a delivery system for several applications, further to skin wound healing.

Silk fibroin/kappa-carrageenan composite scaffolds with enhanced biomimetic mineralization for bone regeneration applications

The combination of protein-polysaccharide in scaffolding together with the ability to induce bone-like apatite formation has become a promising approach to mimic extracellular matrix composition. In the present study, we developed and characterized new bioactive composite scaffolds from kappa-carrageenan/silk fibroin for bone regeneration applications. Three dimensional (3D) scaffolds were fabricated by adding various amounts of carrageenan to a silk fibroin solution, followed by freeze-drying. Various characterization techniques were applied to analyze such items as the structure, morphology, compressive strength, and bone-like apatite mineralization of the composites, which were then compared to those of pure fibroin scaffolds. The results demonstrated the formation of a highly porous structure with interconnected pores. The mean pore size and porosity both increased by increasing carrageenan content. Moreover, the addition of carrageenan to silk fibroin led to the formation of a bone-like apatite layer throughout the scaffolds after 7days of soaking them in simulated body fluid. Osteoblast-like cell (MG 63) culture experiments indicated that all scaffolds are biocompatible. The cells attached well to the surfaces of all scaffolds and tended to join their adjacent cells. However, higher carrageenan content led to better cellular proliferation and higher Alkaline phosphatase expression.

Preparation and Perfomance of an Aging-Resistant Nanocomposite Film of Binary Natural Polymer-Graphene Oxide

As one of the materials having a bionic structure, nacrelike layered composites, inspired by their natural hybrid structures, have been studied via a variety of approaches. Graphene oxide (GO), which differed from inert graphene, was used as a new building block because it could be readily chemically functionalized. Rather than natural polymers, synthetic polymers were most commonly used to fabricate nacrelike GO-polymer materials. However, naturally occurring polymers complied more easily with the requirements of biocompatibility, biodegradability, and nontoxicity. Here, a simple solution-casting method was used to mimic natural nacre and fabricate a self-assembled and aging-resistant binary natural polymer, (κ-carrageenan (κ-CAR)-Konjac glucomannan (KGM))-GO nanocomposites, with varying GO concentrations. The investigation results revealed that κ-CAR-KGM and GO mostly self-assemble via the formation of intermolecular hydrogen bonds to form a well-defined layered structure. The mechanical properties of the natural polymer-GO films were improved significantly compared to those of pure natural polymer films. With the addition of 7.5 wt % GO, the tensile strength (TS) and Young's modulus were found to increase by 129.5 and 491.5%, respectively. In addition, the composite films demonstrated high reliability and aging resistance as well as a definite TS after cold and hot shock and ozone aging tests, especially showing a superior ozone resistance. The composite films can potentially be used as biomaterials or packing materials.

Facile preparation of monolithic κ-carrageenan aerogels

To the best of our knowledge, it is the first study reporting the synthesis of monolithic κ-carrageenan aerogels with meso- and macroporous structures, being unique in physical and chemical properties. We demonstrate a novel method to synthesize κ-carrageenan aerogels in which potassium thiocyanate was used as the source of specific ions. Aerogels were characterized by envelope density analysis, scanning electron microscopy, nitrogen adsorption-desorption analysis, X-ray powder diffractometry and IR spectroscopy. By varying the concentration of κ-carrageenan between 0.5 and 3 wt%, the envelope density can be linearly increased from 40 to 160 kg m⁻³. The sulphate functional groups in the wet gel and the specific ions are the key factors controlling the volume shrinkage of aerogels which average about 66%. The aerogels exhibit a fibrillar structure similar to cellulose aerogels. The fibril thickness was observed to be 10-15 nm and the specific surface area was about 230 m² g⁻¹. The existing meso- and macroporous structures were confirmed by nitrogen adsorption-desorption isotherm analysis and scanning electron microscopy. The aerogels were completely pure, free of specific ions and confirmed to be amorphous by powder X-ray diffraction. Hence, these porous materials can provide a matrix with a chelating function which can be used as a host in many applications.

Surface modification of polycaprolactone scaffolds fabricated via selective laser sintering for cartilage tissue engineering

Surface modified porous polycaprolactone scaffolds fabricated via rapid prototyping techniques were evaluated for cartilage tissue engineering purposes. Polycaprolactone scaffolds manufactured by selective laser sintering (SLS) were surface modified through immersion coating with either gelatin or collagen. Three groups of scaffolds were created and compared for both mechanical and biological properties. Surface modification with collagen or gelatin improved the hydrophilicity, water uptake and mechanical strength of the pristine scaffold. From microscopic observations and biochemical analysis, collagen-modified scaffold was the best for cartilage tissue engineering in terms of cell proliferation and extracellular matrix production. Chondrocytes/collagen-modified scaffold constructs were implanted subdermally in the dorsal spaces of female nude mice. Histological and immunohistochemical staining of the retrieved implants after 8 weeks revealed enhanced cartilage tissue formation. We conclude that collagen surface modification through immersion coating on SLS-manufactured scaffolds is a feasible scaffold for cartilage tissue engineering in craniofacial reconstruction.

Three-dimensional supermacroporous carrageenan-gelatin cryogel matrix for tissue engineering applications

A tissue-engineered polymeric scaffold should provide suitable macroporous structure similar to that of extracellular matrix which can induce cellular activities and guide tissue regeneration. Cryogelation is a technique in which appropriate monomers or polymeric precursors frozen at sub-zero temperature leads to the formation of supermacroporous cryogel matrices. In this study carrageenan-gelatin (natural polymers) cryogels were synthesized by using glutaraldehyde and 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride and N-hydroxysuccinimide (EDC-NHS) as crosslinking agent at optimum concentrations. Matrices showed large and interconnected pores which were in the range of 60–100 μm diameter. Unconfined compression analysis showed elasticity and physical integrity of all cryogels, as these matrices regained their original length after 90% compressing from the original size. Moreover Young's modulus was found to be in the range of 4–11 kPa for the dry cryogel sections. These cryogels also exhibited good in vitro degradation capacity at 37 °C within 4 weeks of incubation. Supermacroporous carrageenan-gelatin cryogels showed efficient cell adherence and proliferation of Cos-7 cells which was examined by SEM. PI nuclear stain was used to observe cell-matrix interaction. Cytotoxicity of the scaffolds was checked by MTT assay which showed that cryogels are biocompatible and act as a potential material for tissue engineering and regenerative medicine.

Adipose stem cell-derived osteoblasts sustain the functionality of endothelial progenitors from the mononuclear fraction of umbilical cord blood

Vascularization is the most pressing issue in tissue engineering (TE) since ensuring that engineered constructs are adequately perfused after in vivo transplantation is essential for the construct's survival. The combination of endothelial cells with current TE strategies seems the most promising approach but doubts persist as to which type of endothelial cells to use. Umbilical cord blood (UCB) cells have been suggested as a possible source of endothelial progenitors. Osteoblasts obtained from human adipose-derived stem cells (hASCs) were co-cultured with the mononuclear fraction of human UCB for 7 and 21 days on carrageenan membranes. The expression of vWF and CD31, and the DiI-AcLDL uptake ability allowed detection of the presence of endothelial and monocytic lineages cells in the co-culture for all culture times. In addition, the molecular expression of CD31 and VE-cadherin increased after 21 days of co-culture. The functionality of the system was assessed after transplantation in nude mice. Although an inflammatory response developed, blood vessels with cells positive for human CD31 were detected around the membranes. Furthermore, the number of blood vessels in the vicinity of the implants increased when cells from the mononuclear fraction of UCB were present in the transplants compared to transplants with only hASC-derived osteoblasts. These results show how endothelial progenitors present in the mononuclear fraction of UCB can be sustained by hASC-derived osteoblast co-culture and contribute to angiogenesis even in an in vivo setting of inflammatory response.