Preparation, characterization and biological test of 3D-scaffolds based on chitosan, fibroin and hydroxyapatite for bone tissue engineering

3D-printed poly(ethylene) glycol diacrylate (PEGDA)-chitosan-nanohydroxyapatite scaffolds: Structural characterization and cellular response

Polymer-based scaffolds with bioactive materials offer great potential in bone tissue engineering. Polyethylene glycol diacrylate (PEGDA) scaffolds fabricated via liquid crystal display 3D printing technique lack inherent osteoconductivity. To improve such properties, chitosan of 10 and 20 wt% and nanohydroxyapatite (nHA) (3-10 wt%) were incorporated into PEGDA scaffolds. nHA, synthesized via wet chemical precipitation, had a particle size of 28 nm and exhibited low crystallinity, as confirmed by X-ray diffraction. PEGDA-chitosan-nHA scaffolds underwent post-curing and 70 % ethanol leaching treatment. The presence of chitosan and nHA in the composite scaffolds was confirmed by their characteristic peaks. TGA analyses further verified nHA content correlating to the intended amount. The scaffolds featured interconnected pores ranging from 2891 to 3382 μm and porosities between 35 and 56 %. The swelling percentage and compressive modulus were reported at ~71-93 % and 0.52-1.18 MPa, respectively. Notably, PEGDA-chitosan-nHA scaffolds showed enhanced in vitro efficacy than pure PEGDA scaffolds, by promoting better MG63 cell adhesion (p < 0.05), higher proliferation and alkaline phosphatase (ALP) activity, particularly in scaffolds with 20 wt% chitosan across all incubation periods in cell proliferation and early osteoblast differentiation studies. These findings suggest that PEGDA-chitosan-nHA scaffolds have promising potential for bone tissue engineering applications.

Silk-Based 3D Porous Scaffolds for Tissue Engineering

Silk fibroin, extracted from the silk of the Bombyx mori silkworm, stands out as a biomaterial due to its nontoxic nature, excellent biocompatibility, and adjustable biodegradability. Porous scaffolds, a type of biomaterial, are crucial for creating an optimal microenvironment that supports cell adhesion and proliferation, thereby playing an essential role in tissue remodeling and repair. Therefore, this review focuses on 3D porous silk fibroin-based scaffolds, first summarizing their preparation methods and then detailing their regenerative effects on bone, cartilage, tendon, vascular, neural, skin, hepatic, and tracheal epithelial tissue engineering in recent years.

Chitosan-2D Nanomaterial-Based Scaffolds for Biomedical Applications

Chitosan (CS) and two-dimensional nanomaterial (2D nanomaterials)-based scaffolds have received widespread attention in recent times in biomedical applications due to their excellent synergistic potential. CS has garnered much attention as a biomedical scaffold material either alone or in combination with some other material due to its favorable physiochemical properties. The emerging 2D nanomaterials, such as black phosphorus (BP), molybdenum disulfide (MoS2), etc., have taken huge steps towards varying biomedical applications. However, the implementation of a CS-2D nanomaterial-based scaffold for clinical applications remains challenging for different reasons such as toxicity, stability, etc. Here, we reviewed different types of CS scaffold materials and discussed their advantages in biomedical applications. In addition, a different CS nanostructure, instead of a scaffold, has been described. After that, the importance of 2D nanomaterials has been elaborated on in terms of physiochemical properties. In the next section, the biomedical applications of CS with different 2D nanomaterial scaffolds have been highlighted. Finally, we highlighted the existing challenges and future perspectives of using CS-2D nanomaterial scaffolds for biomedical applications. We hope that this review will encourage a more synergistic biomedical application of the CS-2D nanomaterial scaffolds and their utilization clinical applications.

Development of a Novel Marine-Derived Tricomposite Biomaterial for Bone Regeneration

Bone tissue engineering is a promising treatment for bone loss that requires a combination of porous scaffold and osteogenic cells. The aim of this study was to evaluate and develop a tricomposite, biomimetic scaffold consisting of marine-derived biomaterials, namely, chitosan and fucoidan with hydroxyapatite (HA). The effects of chitosan, fucoidan and HA individually and in combination on the proliferation and differentiation of human mesenchymal stem cells (MSCs) were investigated. According to the SEM results, the tricomposite scaffold had a uniform porous structure, which is a key requirement for cell migration, proliferation and vascularisation. The presence of HA and fucoidan in the chitosan tricomposite scaffold was confirmed using FTIR, which showed a slight decrease in porosity and an increase in the density of the tricomposite scaffold compared to other formulations. Fucoidan was found to inhibit cell proliferation at higher concentrations and at earlier time points when applied as a single treatment, but this effect was lost at later time points. Similar results were observed with HA alone. However, both HA and fucoidan increased MSC mineralisation as measured by calcium deposition. Differentiation was significantly enhanced in MSCs cultured on the tricomposite, with increased alkaline phosphatase activity on days 17 and 25. In conclusion, the tricomposite is biocompatible, promotes osteogenesis, and has the structural and compositional properties required of a scaffold for bone tissue engineering. This biomaterial could provide an effective treatment for small bone defects as an alternative to autografts or be the basis for cell attachment and differentiation in ex vivo bone tissue engineering.

Biomedical applications of chitosan/silk fibroin composites: A review

Natural polymers have been used in the biomedical fields for decades, mainly derived from animals and plants with high similarities with biomacromolecules in the human body. As an alkaline polysaccharide, chitosan (CS) attracts much attention in tissue regeneration and drug delivery with favorable biocompatibility, biodegradation, and antibacterial activity. However, to overcome its mechanical properties and degradation behavior drawbacks, a robust fibrous protein-silk fibroin (SF) was introduced to prepare the CS/SF composites. Not only can CS be combined with SF via the amide and hydrogen bond formation, but also their functions are complementary and tunable with the blending ratio. To further improve the performances of CS/SF composites, natural (e.g., hyaluronic acid and collagen) and synthetic biopolymers (e.g., polyvinyl alcohol and hexanone) were incorporated. Also, the CS/SF composites acted as slow-release carriers for inorganic non-metals (e.g., hydroxyapatite and graphene) and metal particles (e.g., silver and magnesium), which could enhance cell functions, facilitate tissue healing, and inhibit bacterial growth. This review presents the state-of-the-art and future perspectives of different biomaterials combined with CS/SF composites as sponges, hydrogels, membranes, particles, and coatings. Emphasis is devoted to the biological potentialities of these hybrid systems, which look rather promising toward a multitude of applications.

Global Trends in Natural Biopolymers in the 21st Century: A Scientometric Review

Since the 21st century, natural biopolymers have played an indispensable role in long-term global development strategies, and their research has shown a positive growth trend. However, these substantive scientific results are not conducive to our quick grasp of hotspots and insight into future directions and to understanding which local changes have occurred and which trend areas deserve more attention. Therefore, this study provides a new data-driven bibliometric analysis strategy and framework for mining the core content of massive bibliographic data, based on mathematical models VOS Viewer and CiteSpace software, aiming to understand the research prospects and opportunities of natural biopolymers. The United States is reported to be the most important contributor to research in this field, with numerous publications and active institutions; polymer science is the most popular subject category, but the further emphasis should be placed on interdisciplinary teamwork; mainstream research in this field is divided into five clusters of knowledge structures; since the explosion in the number of articles in 2018, researchers are mainly engaged in three fields: “medical field,” “biochemistry field,” and “food science fields.” Through an in-depth analysis of natural biopolymer research, this article provides a better understanding of trends emerging in the field over the past 22 years and can also serve as a reference for future research.

Fabrication and applications of bioactive chitosan-based organic-inorganic hybrid materials: A review

Organic-inorganic hybrid materials like bone, shells, and teeth can be found in nature, which are usually composed of biomacromolecules and nanoscale inorganic ingredients. Synergy of organic-inorganic components in hybrid materials render them outstanding and versatile performance. Chitosan is commonly used organic materials in bionic hybrid materials since its bioactive properties and could be controllable tailored by various means to meet complex conditions in different applications. Among these fabrication means, hybridization was favored for its convenience and efficiency. This review discusses three kinds of chitosan-based hybrid materials: hybridized with hydroxyapatite, calcium carbonate, and clay respectively, which are the representative of phosphate, carbonate, and hydrous aluminosilicates. Here, we reported the latest developments of the preparation methods, composition, structure and applications of these bioactive hybrid materials, especially in the biomedical field. Despite the great progress was made in bioactive organic-inorganic hybrid materials based on chitosan, some challenges and specific directions are still proposed for future development in this review.

Decellularized spinal cord meninges extracellular matrix hydrogel that supports neurogenic differentiation and vascular structure formation

Decellularization of extracellular matrices offers an alternative source of regenerative biomaterials that preserve biochemical structure and matrix components of native tissues. In this study, decellularized bovine spinal cord meninges (dSCM)-derived extracellular matrix hydrogel (MeninGEL) is fabricated by employing a protocol that involves physical, chemical, and enzymatic processing of spinal meninges tissue and preserves the biochemical structure of meninges. The success of decellularization is characterized by measuring the contents of residual DNA, glycosaminoglycans, and hydroxyproline, while a proteomics analysis is applied to reveal the composition of MeninGEL. Frequency and temperature sweep rheometry show that dSCM forms self-supporting hydrogel at physiological temperature. The MeninGEL possesses excellent cytocompatibility. Moreover, it is evidenced with immuno/histochemistry and gene expression studies that the hydrogel induces growth-factor free differentiation of human mesenchymal stem cells into neural-lineage cells. Furthermore, MeninGEL instructs human umbilical vein endothelial cells to form vascular branching. With its innate bioactivity and low batch-to-batch variation property, the MeninGEL has the potential to be an off-the-shelf product in nerve tissue regeneration and restoration.

Translational Research for Orthopedic Bone Graft Development

Designing biomaterials for bone-substitute applications is still a challenge regarding the natural complex structure of hard tissues. Aiming at bone regeneration applications, scaffolds based on natural collagen and synthetic nanohydroxyapatite were developed, and they showed adequate mechanical and biological properties. The objective of this work was to perform and evaluate a scaled-up production process of this porous biocomposite scaffold, which promotes bone regeneration and works as a barrier for both fibrosis and the proliferation of scar tissue. The material was produced using a prototype bioreactor at an industrial scale, instead of laboratory production at the bench, in order to produce an appropriate medical device for the orthopedic market. Prototypes were produced in porous membranes that were e-beam irradiated (the sterilization process) and then analysed by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), dynamic mechanical analysis (DMA), cytotoxicity tests with mice fibroblasts (L929), human osteoblast-like cells (MG63) and human MSC osteogenic differentiation (HBMSC) with alkaline phosphatase (ALP) activity and qPCR for osteogenic gene expression. The prototypes were also implanted into critical-size bone defects (rabbits' tibia) for 5 and 15 weeks, and after that were analysed by microCT and histology. The tests performed for the physical characterization of the materials showed the ability of the scaffolds to absorb and retain water-based solvents, as well as adequate mechanical resistance and viscoelastic properties. The cryogels had a heteroporous morphology with microporosity and macroporosity, which are essential conditions for the interaction between the cells and materials, and which consequently promote bone regeneration. Regarding the biological studies, all of the studied cryogels were non-cytotoxic by direct or indirect contact with cells. In fact, the scaffolds promoted the proliferation of the human MSCs, as well as the expression of the osteoblastic phenotype (osteogenic differentiation). The in vivo results showed bone tissue ingrowth and the materials' degradation, filling the critical bone defect after 15 weeks. Before and after irradiation, the studied scaffolds showed similar properties when compared to the results published in the literature. In conclusion, the material production process upscaling was optimized and the obtained prototypes showed reproducible properties relative to the bench development, and should be able to be commercialized. Therefore, it was a successful effort to harness knowledge from the basic sciences to produce a new biomedical device and enhance human health and wellbeing.

Silk fibroin nanocomposites as tissue engineering scaffolds - A systematic review

Silk fibroin is a protein with intrinsic characteristics that make it a good candidate as a scaffold for tissue engineering. Recent works have enhanced its benefits by adding inorganic phases that interact with silk fibroin in different ways. A systematic review was performed in four databases to study the physicochemical and biological performance of silk fibroin nanocomposites. In the last decade, only 51 articles contained either in vitro cell culture models or in vivo tests. The analysis of such works resulted in their classification into the following scaffold types: particles, mats and textiles, films, hydrogels, sponge-like structures, and mixed conformations. From the physicochemical perspective, the inorganic phase imbued in silk fibroin nanocomposites resulted in better stability and mechanical performance. This review revealed that the inorganic phase may be associated with specific biological responses, such as neovascularisation, cell differentiation, cell proliferation, and antimicrobial and immunomodulatory activity. The study of nanocomposites as tissue engineering scaffolds is a highly active area mostly focused on bone and cartilage regeneration with promising results. Nonetheless, there are still many challenges related to their application in other tissues, a better understanding of the interaction between the inorganic and organic phases, and the associated biological response.

Effect of Pore Size on Cell Behavior Using Melt Electrowritten Scaffolds

Tissue engineering technology has made major advances with respect to the repair of injured tissues, for which scaffolds and cells are key factors. However, there are still some issues with respect to the relationship between scaffold and cell growth parameters, especially that between the pore size and cells. In this study, we prepared scaffolds with different pore sizes by melt electrowritten (MEW) and used bone marrow mensenchymal stem cells (BMSCs), chondrocytes (CCs), and tendon stem cells (TCs) to study the effect of the scaffold pore size on cell adhesion, proliferation, and differentiation. It was evident that different cells demonstrated different adhesion and proliferation rates on the scaffold. Furthermore, different cell types showed differential preferences for scaffold pore sizes, as evidenced by variations in cell viability. The pore size also affected the differentiation and gene expression pattern of cells. Among the tested cells, BMSCs exhibited the greatest viability on the 200-μm-pore-size scaffold, CCs on the 200- and 100-μm scaffold, and TCs on the 300-μm scaffold. The scaffolds with 100- and 200-μm pore sizes induced a significantly higher proliferation, chondrogenic gene expression, and cartilage-like matrix deposition after in vitro culture relative to the scaffolds with smaller or large pore sizes (especially 50 and 400 μm). Taken together, these results show that the architecture of 10 layers of MEW scaffolds for different tissues should be different and that the pore size is critical for the development of advanced tissue engineering strategies for tissue repair.

Efficacy of Nano Composite Porous 3D Scaffold of Crab Shell and Al-Kharit Histological and Radiological for Bone Repair in Vivo

The present study was conducted to evaluate the effect of scaffold fabricated from Nano crab shell and Al-kharit (Papyrus Vaccine) for enhancing the healing of the experimentally induced bone defect in dogs. For this purpose, twenty healthy adult mongrel dogs were used in this study which divided randomly into two equal groups, under general anesthesia, 1 cm bone gap was created in the distal part of the tibia, that fixed by bone plate and screws. Nano crab shell scaffold was implanted. All experimental animals showed normal situation without any infection at the site of operation, while the radiography showed a periosteal and endosteal reaction. Moreover, the gaps were bridged faster in the treated group as compared with the control group. Treated animals showed new bone formation which represented by obvious lamellar bone, haversian canal and osteocyte cells in 90 days. In conclusion, the Nano crab shell scaffold gave better acceleration in the bone healing process, also this scaffolds may provide insight into the clinical repair of large bone defects

Additive manufacturing of hydroxyapatite-chitosan-genipin composite scaffolds for bone tissue engineering applications

Additive manufacturing holds promise for the fabrication of three-dimensional scaffolds with precise geometry, to serve as substrates for the guided regeneration of natural tissue. In this work, a bioinspired approach is adopted for the synthesis of hybrid hydroxyapatite hydrogels, which were subsequently printed to form 3D scaffolds for bone tissue engineering applications. These hydrogels consist of hydroxyapatite nanocrystals, biomimetically synthesized in the presence of both chitosan and l-arginine. To improve their mechanical properties, chemical crosslinking was performed using a natural crosslinking agent (genipin), and their rheology was modified by employing an acetic acid/gelatin solution. Regarding the 3D printing process, several parameters (flow, infill and perimeter speed) were studied in order to accurately produce scaffolds with predesigned geometry and micro-architecture, while also applying low printing temperature (15 °C). Following the printing procedure, the 3D scaffolds were freeze dried in order to remove the entrapped solvents and therefore, obtain a porous interconnected network. Evaluation of porosity was performed using micro-computed tomography and nanomechanical properties were assessed through nanoindentation. Results of both characterization techniques, showed that the scaffolds' porosity as well as their modulus values, fall within the corresponding range of the respective values of cancellous bone. The biocompatibility of the 3D printed scaffolds was assessed using MG63 human osteosarcoma cells for 7 days of culturing. Cell viability was evaluated by MTT assay as well as double staining and visualized under fluorescence microscopy, while cell morphology was analyzed through scanning electron microscopy. Biocompatibility tests, revealed that the scaffolds constitute a cell-friendly environment, allowed them to adhere on the scaffolds' surface, increase their population and maintain high levels of viability.

Bioengineered three-dimensional physical constructs from quince seed mucilage for human adipose-derived mesenchymal stem cells

In this study, we aimed at fabricating a novel porous physical construct from quince seed mucilage for translational medicine applications. To achieve this goal, quince seed mucilage was extracted, molded, and freeze-dried. After being freeze-dried, the molded constructs were chemically crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide to maintain the mechanical integrity of the structure. The fabricated scaffolds were characterized in-depth by scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, thermogravimetric analysis, and dynamic mechanical analysis in addition to the swelling, liquid uptake, and porosity tests. The extraction yield of mucilage was calculated to be 6.28% ± 0.40% (n = 3). The swelling ratio of crosslinked quince seed mucilage–derived scaffolds was found to be 12,677.50% ± 388.82% (n = 3), whereas the porosity of crosslinked quince seed mucilage–derived scaffolds was 83.43% ± 2.84% (n = 3). The analyses confirmed the crosslinked quince seed mucilage–derived scaffolds to be possessed interconnected, highly porous structure. Afterward, human adipose-derived mesenchymal stem cells were seeded on the crosslinked quince seed mucilage–derived scaffolds, and the cell viability on the scaffolds was assessed with 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. The MTT results revealed the scaffolds not to be possessed any cytotoxic effect on seeded cells. Human adipose-derived mesenchymal stem cells adhesion and migration on the crosslinked quince seed mucilage–derived scaffolds were also evaluated histologically using hematoxylin and eosin staining in addition to scanning electron microscopy analysis. In conclusion, we believe that crosslinked quince seed mucilage–derived scaffolds have the potential to be an alternative to routinely used polysaccharides in regenerative medicine applications.

Nanobiocomposite based on natural polyelectrolytes for bone regeneration

We developed a composite hydrogel based on chitosan and carboxymethyl cellulose with nanometric hydroxyapatite (nHA) as filler (ranging from 0.5 to 5%), by ultrasonic methodology to be used for bone regeneration. The 3D porous-structure of the biocomposite scaffolds were confirmed by Scanning Electron Microscopy and Microtomography analysis. Infrared analysis did not show specific interactions between the organic components of the composite and nHA in the scaffold. The hydrogel properties of the matrices were studied by swelling and mechanical tests, indicating that the scaffold presented a good mechanical behavior. The degradation test demonstrated that the material is slowly degraded, while the addition of nHA slightly influences the degradation of the scaffolds. Biocompatibility studies carried out with bone marrow mesenchymal progenitor cells (BMPC) showed that cell proliferation and alkaline phosphatase activity were increased depending on the matrix nHA content. On the other hand, no cytotoxic effect was observed when RAW264.7 cells were seeded on the scaffolds. Altogether, our results allow us to conclude that these nanobiocomposites are promising candidates to induce bone tissue regeneration.

Mesoporous Hydroxyapatite Nanoparticles Mediate the Release and Bioactivity of BMP-2 for Enhanced Bone Regeneration

Efficient delivery of bone morphogenetic protein-2 (BMP-2) with desirable bioactivity is still a great challenge in the field of bone regeneration. In this study, a silk fibroin/chitosan scaffold incorporated with BMP-2-loaded mesoporous hydroxyapatite nanoparticles (mHANPs) was prepared (SCH-L). BMP-2 was preloaded onto mHANPs with a high surface area before mixing with a silk fibroin/chitosan composite. Bare (without BMP-2) silk fibroin/chitosan/mHANP (SCH) scaffolds and SCH scaffolds with directly absorbed BMP-2 (SCH-D) were investigated in parallel for comparison. In vitro release kinetics indicated that BMP-2 released from the SCH-L scaffold showed a significantly lower initial burst release, followed by a more sustained release over time than the SCH-D scaffold. In vitro cell viability, osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), and the in vivo osteogenic effect of scaffolds in a rat calvarial defect were evaluated. The results showed that compared with bare SCH and SCH-D scaffolds, the SCH-L scaffold significantly promoted the osteogenic differentiation of BMSCs in vitro and induced more pronounced bone formation in vivo. Further studies demonstrated that the mHANP-mediated satisfactory conformational change and sustained release benefited the protection of the released BMP-2 bioactivity, as confirmed by alkaline phosphatase (ALP) activity and a mineralization deposition assay. More importantly, the interaction of BMP-2/mHANPs enhanced the binding ability of BMP-2 to cellular receptors, thereby maintaining its biological activity in osteogenic differentiation and osteoinductivity well, which contributed to the markedly promoted in vitro and in vivo osteogenic efficacy of the SCH-L scaffold. Taken together, these results provide strong evidence that mHANPs represent an attractive carrier for binding BMP-2 to scaffolds. The SCH-L scaffold shows promising potential for bone tissue regeneration applications.

The Effect of PEGDE Concentration and Temperature on Physicochemical and Biological Properties of Chitosan

Chitosan (CHT) is a polysaccharide with multiple claimed properties and outstanding biocompatibility, generally attributed to the presence of protonable amino groups rendering a cationic natural polymer. However, the effect of changes in CHT structure due to hydration is not considered in its performance. This study compares the effects on biocompatibility after drying at 25 °C and 150 °C scaffolds of chitosan, polyethylene glycol diglycidyl ether (PEGDE) crosslinked CHT (low, medium and high concentration) and glutaraldehyde (GA) crosslinked CHT. PEGDE crosslinked CHT showed a reduction in free amino groups and the amide I/II ratio, which exhaustive drying reduced further. In X-ray diffraction (DRX) analysis, PEGDE crosslinked CHT showed multiple peaks, whereas the crystallinity percentage was reduced with an increase in PEGDE concentration and thermal treatments at 150 °C. In a direct contact cell assay, high osteoblast viability was achieved at low and medium PEDGE concentrations, which was improved when the crosslinked scaffolds were thermally treated at 150 °C. This was attributed to its partial hydrophilicity, low crystallinity and low surface roughness; this in spite of the small reduction in the amount of free amino groups on the surface induced during drying at 150 °C. Furthermore, PEGDE crosslinked CHT scaffolds showed strong vinculin and integrin 1β expression, which render them suitable for bone contact applications.

Application of Chitosan in Bone and Dental Engineering

Chitosan is a deacetylated polysaccharide from chitin, the natural biopolymer primarily found in shells of marine crustaceans and fungi cell walls. Upon deacetylation, the protonation of free amino groups of the d-glucosamine residues of chitosan turns it into a polycation, which can easily interact with DNA, proteins, lipids, or negatively charged synthetic polymers. This positive-charged characteristic of chitosan not only increases its solubility, biodegradability, and biocompatibility, but also directly contributes to the muco-adhesion, hemostasis, and antimicrobial properties of chitosan. Combined with its low-cost and economic nature, chitosan has been extensively studied and widely used in biopharmaceutical and biomedical applications for several decades. In this review, we summarize the current chitosan-based applications for bone and dental engineering. Combining chitosan-based scaffolds with other nature or synthetic polymers and biomaterials induces their mechanical properties and bioactivities, as well as promoting osteogenesis. Incorporating the bioactive molecules into these biocomposite scaffolds accelerates new bone regeneration and enhances neovascularization in vivo.

Graphene-based 3D scaffolds in tissue engineering: fabrication, applications, and future scope in liver tissue engineering

Tissue engineering embraces the potential of recreating and replacing defective body parts by advancements in the medical field. Being a biocompatible nanomaterial with outstanding physical, chemical, optical, and biological properties, graphene-based materials were successfully employed in creating the perfect scaffold for a range of organs, starting from the skin through to the brain. Investigations on 2D and 3D tissue culture scaffolds incorporated with graphene or its derivatives have revealed the capability of this carbon material in mimicking in vivo environment. The porous morphology, great surface area, selective permeability of gases, excellent mechanical strength, good thermal and electrical conductivity, good optical properties, and biodegradability enable graphene materials to be the best component for scaffold engineering. Along with the apt microenvironment, this material was found to be efficient in differentiating stem cells into specific cell types. Furthermore, the scope of graphene nanomaterials in liver tissue engineering as a promising biomaterial is also discussed. This review critically looks into the unlimited potential of graphene-based nanomaterials in future tissue engineering and regenerative therapy.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Physiochemical characteristics and bone/cartilage tissue engineering potentialities of protein-based macromolecules - A review

Protein-based macromolecules such as keratin, silk fibroin, collagen, gelatin, and fibrin have emerged as potential candidate materials with unique structural and functional characteristics. Despite many advantages, the development of tissue-engineered constructs that can match the biological context of real tissue matrix remains a challenge in tissue engineering (TE). The tissue-engineered constructs should also support vascularization. Protein-based macromolecules, in pristine or combine form, provide a promising platform to engineer constructs with unique design and functionalities which are highly essential for an appropriate stimulation and differentiation of cells in a specific TE approach. However, much work remains to be undertaken with particular reference to in-depth interactions between constructed cues and target host tissues. Thus, modern advancements are emphasizing to understand critiques and functionalization of protein-based macromolecule that organize not only cellular activities but also tissue regenerations. In this review, numerous physicochemical, functional, and structural characteristics of protein-based macromolecules such as keratin, silk fibroin, collagen, gelatin, and fibrin are discussed. This review also presents the hope vs. hype phenomenon for tissue engineering. Later part of the review focuses on different requisite characteristics and their role in TE. The discussion presented here could prove highly useful for the construction of scaffolds with requisite features.

Silk scaffolds in bone tissue engineering: An overview

Bone tissue plays multiple roles in our day-to-day functionality. The frequency of accidental bone damage and disorder is increasing worldwide. Moreover, as the world population continues to grow, the percentage of the elderly population continues to grow, which results in an increased number of bone degenerative diseases. This increased elderly population pushes the need for artificial bone implants that specifically employ biocompatible materials. A vast body of literature is available on the use of silk in bone tissue engineering. The current work presents an overview of this literature from materials and fabrication perspective. As silk is an easy-to-process biopolymer; this allows silk-based biomaterials to be molded into diverse forms and architectures, which further affects the degradability. This makes silk-based scaffolds suitable for treating a variety of bone reconstruction and regeneration objectives. Silk surfaces offer active sites that aid the mineralization and/or bonding of bioactive molecules that facilitate bone regeneration. Silk has also been blended with a variety of polymers and minerals to enhance its advantageous properties or introduce new ones. Several successful works, both in vitro and in vivo, have been reported using silk-based scaffolds to regenerate bone tissues or other parts of the skeletal system such as cartilage and ligament. A growing trend is observed toward the use of mineralized and nanofibrous scaffolds along with the development of technology that allows to control scaffold architecture, its biodegradability and the sustained releasing property of scaffolds. Further development of silk-based scaffolds for bone tissue engineering, taking them up to and beyond the stage of human trials, is hoped to be achieved in the near future through a cross-disciplinary coalition of tissue engineers, material scientists and manufacturing engineers.

STATEMENT OF SIGNIFICANCE

The state-of-art of silk biomaterials in bone tissue engineering, covering their wide applications as cell scaffolding matrices to micro-nano carriers for delivering bone growth factors and therapeutic molecules to diseased or damaged sites to facilitate bone regeneration, is emphasized here. The review rationalizes that the choice of silk protein as a biomaterial is not only because of its natural polymeric nature, mechanical robustness, flexibility and wide range of cell compatibility but also because of its ability to template the growth of hydroxyapatite, the chief inorganic component of bone mineral matrix, resulting in improved osteointegration. The discussion extends to the role of inorganic ions such as Si and Ca as matrix components in combination with silk to influence bone regrowth. The effect of ions or growth factor-loaded vehicle incorporation into regenerative matrix, nanotopography is also considered.

Electrostatic flocking of chitosan fibres leads to highly porous, elastic and fully biodegradable anisotropic scaffolds

Electrostatic flocking - a common textile technology which has been applied in industry for decades - is based on the deposition of short polymer fibres in a parallel aligned fashion on flat or curved substrates, covered with a layer of a suitable adhesive. Due to their highly anisotropic properties the resulting velvet-like structures can be utilised as scaffolds for tissue engineering applications in which the space between the fibres can be defined as pores. In the present study we have developed a fully resorbable compression elastic flock scaffold from a single material system based on chitosan. The fibres and the resulting scaffolds were analysed concerning their structural and mechanical properties and the biocompatibility was tested in vitro. The tensile strength and Young's modulus of the chitosan fibres were analysed as a function of the applied sterilisation technique (ethanol, supercritical carbon dioxide, γ-irradiation and autoclaving). All sterilisation methods decreased the Young's modulus (from 14GPa to 6-12GPa). The tensile strength was decreased after all treatments - except after the autoclaving of chitosan fibres submerged in water. Compressive strength of the highly porous flock scaffolds was 18±6kPa with a elastic modulus in the range of 50-100kPa. The flocked scaffolds did not show any cytotoxic effect during indirect or direct culture of human mesenchymal stem cells or the sarcoma osteogenic cell line Saos-2. Furthermore cell adhesion and proliferation of both cell types could be observed. This is the first demonstration of a fully biodegradable scaffold manufactured by electrostatic flocking.

STATEMENT OF SIGNIFICANCE

Most tissues possess anisotropic fibrous structures. In contrast, most of the commonly used scaffolds have an isotropic morphology. By utilising the textile technology of electrostatic flocking, highly porous and clearly anisotropic scaffolds can be manufactured. Flocking leads to parallel aligned short fibres, glued on the surface of a substrate. Such structures are characterised by a high and adjustable porosity, accompanied by distinct stiffness in fibre direction. The present article describes for the first time a fully biodegradable flock scaffold, solely made of chitosan. Utilisation of only one material for manufacturing of flock substrate, adhesive and fibres allow a uniform degradation of the whole construct. Such a new type of scaffold can be of great interest for a variety of biomedical applications.

Selected suitable seed cell, scaffold and growth factor could maximize the repair effect using tissue engineering method in spinal cord injury

Spinal cord injury usually leads to permanent disability, which could cause a huge financial problem to the patient. Up to now there is no effective method to treat this disease. The key of the treatment is to enable the damage zone axonal regeneration and luckily it could go through the damage zone; last a connection can be established with the target neurons. This study attempts to combine stem cell, material science and genetic modification technology together, by preparing two genes modified adipose-derived stem cells and inducing them into neuron direction; then by compositing them on the silk fibroin/chitosan scaffold and implanting them into the spinal cord injury model, seed cells can have features of neuron cells. At the same time, it could stably express the brain-derived neurotrophic factor and neurotrophin-3, both of which could produce synergistic effects, which have a positive effect on the recovery of spinal cord. The spinal cord scaffold bridges the broken end of the spinal cord and isolates with the surrounding environment, which could avoid a scar effect on the nerve regeneration and provide three-dimensional space for the seed cell growth, and at last we hope to provide a new treatment for spinal cord injury with the tissue engineering technique.

Modified chitosan scaffolds: Proliferative, cytotoxic, apoptotic, and necrotic effects on Saos-2 cells and antimicrobial effect on Escherichia coli

Scaffolds used in tissue engineering applications should have high biocompatibility with minimum allergic, toxic, apoptotic, or necrotic effects on the growing cells and newly forming tissue and, if possible, have antimicrobial property to prevent infection at the host site. In this study, novel micro-fibrous chitosan scaffolds, having mineralized bioactive surface to enhance cell adhesion and a model antibiotic (gentamicin) to prevent bacterial attack, were prepared. The effects of the scaffolds on proliferation, viability, apoptosis, and necrosis of Saos-2 cells are reported for the first time. Wet spinning technique was used in the scaffold preparation and biomineralization was achieved by incubating them in five-time concentrated simulated body fluid for 2, 7, or 14 days (coded as CH-BM/2, CH-BM/7, and CH-BM/14, respectively). Gentamicin, an effectively used antibiotic in bone treatments, was loaded by vacuum-pressure cycle. Energy-dispersive X-ray results demonstrated that Ca/P ratio of the mineral phase varies depending on the incubation period. When the scaffolds were cultured with Saos-2 cells, cell adhesion and extracellular matrix formation occurred on all types of scaffolds. Alamar Blue cytotoxicity tests showed correlation among mineral concentration and cytotoxicity where CH-BM/2 had significantly more favorable properties. For all types of scaffolds, apoptosis and necrosis were less than 10%, meaning the samples are biocompatible. Gentamicin-loaded scaffolds showed high antimicrobial efficacy against Escherichia coli. The presence of mineral phase enhanced the adhesive capacity of cells and entrapment efficiency of antibiotic. These results suggest that the bioactive and antimicrobial scaffolds prepared in this study can act as promising matrices in bone tissue engineering applications.

Chitosan based biocomposite scaffolds for bone tissue engineering

The clinical demand for scaffolds and the diversity of available polymers provide freedom in the fabrication of scaffolds to achieve successful progress in bone tissue engineering (BTE). Chitosan (CS) has drawn much of the attention in recent years for its use as graft material either as alone or in a combination with other materials in BTE. The scaffolds should possess a number of properties like porosity, biocompatibility, water retention, protein adsorption, mechanical strength, biomineralization and biodegradability suited for BTE applications. In this review, CS and its properties, and the role of CS along with other polymeric and ceramic materials as scaffolds for bone tissue repair applications are highlighted.

Silk scaffolds for musculoskeletal tissue engineering

The musculoskeletal system, which includes bone, cartilage, tendon/ligament, and skeletal muscle, is becoming the targets for tissue engineering because of the high need for their repair and regeneration. Numerous factors would affect the use of musculoskeletal tissue engineering for tissue regeneration ranging from cells used for scaffold seeding to the manufacture and structures of materials. The essential function of the scaffolds is to convey growth factors as well as cells to the target site to aid the regeneration of the injury. Among the variety of biomaterials used in scaffold engineering, silk fibroin is recognized as an ideal material for its impressive cytocompatibility, slow biodegradability, and excellent mechanical properties. The current review describes the advances made in the fabrication of silk fibroin scaffolds with different forms such as films, particles, electrospun fibers, hydrogels, three-dimensional porous scaffolds, and their applications in the regeneration of musculoskeletal tissues.

MicroRNA-26a-modified adipose-derived stem cells incorporated with a porous hydroxyapatite scaffold improve the repair of bone defects

Tissue-engineered bone substitutes are frequently used to repair bone defects. Adipose-derived stem cells (ASCs) are a promising source of cells for repairing bone tissue, however, insufficient osteogenic potency remains the main obstacle for their application. The present study aimed to enhance the osteogenic potency of ASCs by transfection of microRNA (miR)-26a, a novel osteogenic and angiogenic promoting miRNA. An inverted fluorescence microscope was used to observe transfection efficiency, while a scanning electron microscope was used to detect morphological alterations. Cell proliferation was monitored continuously for 7 days using a Cell Counting kit-8 assay. Osteogenic differentiation was determined by reverse transcription quantitative polymerase chain reaction, alkaline phosphatase (ALP) staining, collagen secretion and extracellular matrix (ECM) mineralization. ASCs were incorporated with a porous hydroxyapatite (HA) scaffold to create a novel tissue-engineered bone substitute and inserted into the critical tibia defect of rats. New bone formation was evaluated by hematoxylin and eosin and Masson's trichrome staining. The results demonstrated that miR-26a was successfully delivered into the cytoplasm, while the morphology and proliferation of ASCs were not significantly altered. Osteogenic-associated genes were markedly upregulated and ALP production, collagen secretion and ECM mineralization were all increased following transfection of miR-26a. Histological evaluation demonstrated that the modified cells accompanied with a porous HA scaffold markedly promoted new bone formation within the defective area. In conclusion, miR-26a transfection significantly improved the osteogenic potency of ASCs suggesting that modified ASCs incorporated with a HA scaffold may be used as a potential bone substitute.

Characterization and Cell Culture of a Grafted Chitosan Scaffold for Tissue Engineering

Poly(vinyl alcohol) (PVA) was grafted to chitosan to form a porous scaffold. The PVA-g-chitosan 3D scaffold was then observed by Fourier transform infrared spectroscopy (FT-IR). The water absorbency of PVA-g-chitosan was increased 370% by grafting. Scanning electron microscope (SEM) observations of the material revealed that the 3D scaffold is highly porous when formed using a homogenizer at 300 rpm. Compression testing demonstrated that as the amount of chitosan increases, the strength of the 3D scaffold strength reached showed that, by increasing the amount of chitosan, the strength of the 3D scaffold could be increased to 16 × 10−1 MPa. Over 35 days of enzymatic degradation, the 3D scaffold was degraded by various enzymes at rates of up to 10%.In vitrotests showed good cell proliferation and growth in the 3D scaffold.

Hydroxyapatite and silk combination-coated dental implants result in superior bone formation in the peri-implant area compared with hydroxyapatite and collagen combination-coated implants

PURPOSE

The objective of this study was to compare bone formation after installation of uncoated (UC), hydroxyapatite-coated (HA), collagen plus HA-coated (CH), and silk plus HA-coated (SH) implants.

MATERIALS AND METHODS

Implants in the UC group had acid-etched surfaces. Surface coating was applied using the aerosol deposition method. Cellular responses on the coated surfaces were examined with scanning electron microscopy. Cellular responses to the surfaces were studied with the corresponding coated discs and MG63 cells. Subsequently, 3-(4, 5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alkaline phosphatase (ALP) assays were performed. Peri-implant bone formation was evaluated with the rabbit tibia model. Twenty-four implants from each group were installed. The animals were sacrificed 6 weeks after implant installation. Peri-implant bone formation and implant-to-bone contact were measured in histologic sections. Significance of differences across groups was evaluated using analysis of variance.

RESULTS

Scanning electron microscopic images showed that the CH and SH groups exhibited cells that appeared more spread out than those in the other groups. The SH group exhibited the highest value in the MTT assay. The CH group exhibited the highest level of ALP activity. Comparisons of these modifications with the acid-etched surfaces showed that the CH and SH groups displayed significantly greater peri-implant bone formation (P < .001).

CONCLUSION

The SH group displayed significantly greater new bone formation and bone-to-implant contact than did the other groups.

Insights on the interactions of chitosan with phospholipid vesicles. Part II: Membrane stiffening and pore formation

The interactions between the polysaccharide chitosan and phospholipids are studied using giant unilamellar vesicles (GUVs). We explore both bare GUVs incubated in chitosan solution post vesicle formation and GUVs prepared using a reverse-phase method where the polymer is adsorbed on both sides of the membrane leaflet. The fluctuations of the vesicle membrane are significantly reduced in the presence of chitosan as characterized by the bending rigidity, which increases with chitosan concentration denoting physical restrictions imposed to the bilayer as a consequence of the interaction with the polysaccharide. In the absence of chitosan, the rigidity of the bare phosphatidylcholine vesicles is also observed to increase (about 3-fold) upon the incorporation of a small fraction (10 mol %) of phosphatidylglycerol. Pore formation caused by chitosan is evidenced by loss of optical contrast of the giant vesicles denoting exchange between internal and external solutions through the pores. Our study provides evidence for the potential of chitosan to affect the bilayer permeability and to disrupt negatively charged membranes as well as to promote adhesiveness of vesicles on glass surfaces.

Use of a silk fibroin-chitosan scaffold to construct a tissue-engineered corneal stroma

PURPOSE

To construct a scaffold using silk fibroin (SF) and chitosan (CS) that could replace the corneal stroma with the biological characteristics of the scaffold materials still intact.

METHODS

To develop an organotypic corneal stroma, SF and CS were chosen to synthesise the tissue-engineered bioscaffold. We cultured primary rabbit corneal epithelial cells and corneal stromal cells in vitro. Keratocytes were used to assess cytotoxicity on SF-CS (SFCS) blends, which was determined by a Cell Counting Kit-8 assay. The corneal lamellar scaffolds were developed with sequential culture techniques to form cell-scaffold constructs. Implantation was tested in 15 New Zealand White rabbits. The corneal substitutes were analysed by light and electron microscopy.

RESULTS

The reconstructed lamellar cornea was comparable to native tissue, with high levels of K3/12 expression in the corneal epithelial cells and vimentin in the stromal cells; moreover, the morphology and the position of the cells could be distinguished by histological methods. There was no sign of any immune reaction in or around the transplanted discs 12 weeks after implantation.

CONCLUSION

A SFCS scaffold might be a suitable blend for corneal tissue engineering.