Chitin scaffolds in tissue engineering

Tissue engineering/regeneration is based on the hypothesis that healthy stem/progenitor cells either recruited or delivered to an injured site, can eventually regenerate lost or damaged tissue. Most of the researchers working in tissue engineering and regenerative technology attempt to create tissue replacements by culturing cells onto synthetic porous three-dimensional polymeric scaffolds, which is currently regarded as an ideal approach to enhance functional tissue regeneration by creating and maintaining channels that facilitate progenitor cell migration, proliferation and differentiation. The requirements that must be satisfied by such scaffolds include providing a space with the proper size, shape and porosity for tissue development and permitting cells from the surrounding tissue to migrate into the matrix. Recently, chitin scaffolds have been widely used in tissue engineering due to their non-toxic, biodegradable and biocompatible nature. The advantage of chitin as a tissue engineering biomaterial lies in that it can be easily processed into gel and scaffold forms for a variety of biomedical applications. Moreover, chitin has been shown to enhance some biological activities such as immunological, antibacterial, drug delivery and have been shown to promote better healing at a faster rate and exhibit greater compatibility with humans. This review provides an overview of the current status of tissue engineering/regenerative medicine research using chitin scaffolds for bone, cartilage and wound healing applications. We also outline the key challenges in this field and the most likely directions for future development and we hope that this review will be helpful to the researchers working in the field of tissue engineering and regenerative medicine.     

Polymer-based hydrogel scaffolds for skin tissue engineering applications: a mini-review

Polymer hydrogels consist of a three-dimensional (3D) structure with cross-linked networks rich in a huge amount of water through hydrogen-bonding interactions, making them highly hydrophilic. Due to their impressive hydrophilic characteristics and cell non-cytotoxicity, polymer hydrogels are useful tissue engineering tools for the organization of cells and tissues and organ regeneration. Many biomedical engineers and researchers have recently begun to utilize polymer hydrogels as tissue or cell culture environments and as scaffolds for the stable growth of organs in tissue engineering and regeneration medicine. This paper focuses on skin regeneration in polymer hydrogels where skin is a means of protecting the body from infection or physical or chemical damage. Generally, skin tissue that has incurred minor damage or wounds can regenerate and heal in a relatively short time, while severe injuries may require transplantation or artificial skin. For those purposes, skin culturing in an in vitro environment is essential, and the environment produced using polymer hydrogel scaffolds needs to be both similar to the real environment and safe for skin cell growth. This paper reviews post-2000 skin regeneration research in the field of tissue engineering, focusing specifically on polymer hydrogels; it also discusses some of the central perspectives and key issues.     

Development of 3D in Vitro Technology for Medical Applications

In the past few years, biomaterials technologies together with significant efforts on developing biology have revolutionized the process of engineered materials. Three dimensional (3D) in vitro technology aims to develop set of tools that are simple, inexpensive, portable and robust that could be commercialized and used in various fields of biomedical sciences such as drug discovery, diagnostic tools, and therapeutic approaches in regenerative medicine. The proliferation of cells in the 3D scaffold needs an oxygen and nutrition supply. 3D scaffold materials should provide such an environment for cells living in close proximity. 3D scaffolds that are able to regenerate or restore tissue and/or organs have begun to revolutionize medicine and biomedical science. Scaffolds have been used to support and promote the regeneration of tissues. Different processing techniques have been developed to design and fabricate three dimensional scaffolds for tissue engineering implants. Throughout the chapters we discuss in this review, we inform the reader about the potential applications of different 3D in vitro systems that can be applied for fabricating a wider range of novel biomaterials for use in tissue engineering.     

Degradable natural polymer hydrogels for articular cartilage tissue engineering

Articular cartilage has poor ability to heal once damaged. Tissue engineering with scaffolds of polymer hydrogels is promising for cartilage regeneration and repair. Polymer hydrogels composed of highly hydrated crosslinked networks mimic the collagen networks of the cartilage extracellular matrix and thus are employed as inserts at cartilage defects not only to temporarily relieve the pain but also to support chondrocyte proliferation and neocartilage regeneration. The biocompatibility, biofunctionality, mechanical properties, and degradation of the polymer hydrogels are the most important parameters for hydrogel‐based cartilage tissue engineering. Degradable biopolymers with natural origin have been widely used as biomaterials for tissue engineering because of their outstanding biocompatibility, low immunological response, low cytotoxicity, and excellent capability to promote cell adhesion, proliferation, and regeneration of new tissues. This review covers several important natural proteins (collagen, gelatin, fibroin, and fibrin) and polysaccharides (chitosan, hyaluronan, alginate and agarose) widely used as hydrogels for articular cartilage tissue engineering. The mechanical properties, structures, modification, and structure–performance relationship of these hydrogels are discussed since the chemical structures and physical properties dictate the in vivo performance and applications of polymer hydrogels for articular cartilage regeneration and repair. © 2012 Society of Chemical Industry     

Advances in Growth Factor Delivery for Bone Tissue Engineering

Shortcomings related to the treatment of bone diseases and consequent tissue regeneration such as transplants have been addressed to some extent by tissue engineering and regenerative medicine. Tissue engineering has promoted structures that can simulate the extracellular matrix and are capable of guiding natural bone repair using signaling molecules to promote osteoinduction and angiogenesis essential in the formation of new bone tissues. Although recent studies on developing novel growth factor delivery systems for bone repair have attracted great attention, taking into account the complexity of the extracellular matrix, scaffolding and growth factors should not be explored independently. Consequently, systems that combine both concepts have great potential to promote the effectiveness of bone regeneration methods. In this review, recent developments in bone regeneration that simultaneously consider scaffolding and growth factors are covered in detail. The main emphasis in this overview is on delivery strategies that employ polymer-based scaffolds for spatiotemporal-controlled delivery of both single and multiple growth factors in bone-regeneration approaches. From clinical applications to creating alternative structural materials, bone tissue engineering has been advancing constantly, and it is relevant to regularly update related topics.     

Alginate Based Scaffolds for Cartilage Tissue Engineering: A Review

Abstract

Many people, especially old and middle-aged, suffer from pain and disabilities caused by cartilage degradation. There are many surgical methods for cartilage treatment, however, none of them have shown acceptable results in long-term. Tissue engineering would be an acceptable approach for cartilage treatment. This includes cells, a carrier such as a matrix scaffold and signaling molecule. An ideal scaffold for cartilage tissue engineering should meet some requirements includes biocompatibility, biodegradability, and sufficient mechanical characteristic. While there are many suitable scaffolds made by natural and synthesis polymers, alginate- a natural polymer- has received good attention. Alginate offers many advantages for cartilage treatment; it has great potential in having tunable mechanical properties and easy manufacturing process. In the present paper, focusing on alginate as main scaffold constructive component, different studies on alginate based scaffolds in the form of physically, chemically and biologically crosslinked hydrogel, sponge, fiber, micro/nano particles and 3?D printed for articular cartilage tissue engineering are discussed and reviewed.     

组织工程支架材料及制备方法研究现状

组织工程支架已经广泛应用于皮肤、软骨、心血管、心脏等各种组织的修复中.组织工程材料分为天然材料和合成材料两大类,均需要具备良好的生物相容性.组织工程支架的制备方法主要有相分离、冷冻干燥、发泡、颗粒浸出、静电纺丝、3D打印等.现对组织工程支架所用到的材料、制备方法以及组织工程支架的应用进行综述.     

3D Printed SiOC(N) Ceramic Scaffolds for Bone Tissue Regeneration: Improved Osteogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells

Bone tissue engineering has developed significantly in recent years as there has been increasing demand for bone substitutes due to trauma, cancer, arthritis, and infections. The scaffolds for bone regeneration need to be mechanically stable and have a 3D architecture with interconnected pores. With the advances in additive manufacturing technology, these requirements can be fulfilled by 3D printing scaffolds with controlled geometry and porosity using a low-cost multistep process. The scaffolds, however, must also be bioactive to promote the environment for the cells to regenerate into bone tissue. To determine if a low-cost 3D printing method for bespoke SiOC(N) porous structures can regenerate bone, these structures were tested for osteointegration potential by using human mesenchymal stem cells (hMSCs). This includes checking the general biocompatibilities under the osteogenic differentiation environment (cell proliferation and metabolism). Moreover, cell morphology was observed by confocal microscopy, and gene expressions on typical osteogenic markers at different stages for bone formation were determined by real-time PCR. The results of the study showed the pore size of the scaffolds had a significant impact on differentiation. A certain range of pore size could stimulate osteogenic differentiation, thus promoting bone regrowth and regeneration.     

Composite scaffolds for cartilage tissue engineering based on natural polymers of bacterial origin,thermoplastic poly(3‐hydroxybutyrate) and micro‐fibrillated bacterial cellulose

Cartilage tissue engineering is an emerging therapeutic strategy that aims to regenerate damaged cartilage caused by disease, trauma, ageing or developmental disorder. Since cartilage lacks regenerative capabilities, it is essential to develop approaches that deliver the appropriate cells, biomaterials and signalling factors to the defect site. Materials and fabrication technologies are therefore critically important for cartilage tissue engineering in designing temporary, artificial extracellular matrices (scaffolds), which support 3D cartilage formation. Hence, this work aimed to investigate the use of poly(3‐hydroxybutyrate)/microfibrillated bacterial cellulose (P(3HB)/MFC) composites as 3D‐scaffolds for potential application in cartilage tissue engineering. The compression moulding/particulate leaching technique employed in the study resulted in good dispersion and a strong adhesion between the MFC and the P(3HB) matrix. Furthermore, the composite scaffold produced displayed better mechanical properties than the neat P(3HB) scaffold. On addition of 10, 20, 30 and 40 wt% MFC to the P(3HB) matrix, the compressive modulus was found to have increased by 35%, 37%, 64% and 124%, while the compression yield strength increased by 95%, 97%, 98% and 102% respectively with respect to neat P(3HB). Both cell attachment and proliferation were found to be optimal on the polymer‐based 3D composite scaffolds produced, indicating a non‐toxic and highly compatible surface for the adhesion and proliferation of mouse chondrogenic ATDC5 cells. The large pores sizes (60 ‐ 83 µm) in the 3D scaffold allowed infiltration and migration of ATDC5 cells deep into the porous network of the scaffold material. Overall this work confirmed the potential of P(3HB)/MFC composites as novel materials in cartilage tissue engineering. © 2016 Society of Chemical Industry     

Halloysite clay nanotube in regenerative medicine for tissue and wound healing

The vital necessity of effective treatment at damaged tissue or wound site has resulted in emerging tissue engineering and regenerative medicine. Tissue engineering has been introduced as an alternative approach for common available therapeutic strategies in the terms of restoring deformed tissue structure and its functionality via the developing of new bio-scaffold. Designed three-dimensional (3D) scaffolds, alone or in combination with bioactive agents, should be able to stimulate and accelerate the development of engineered tissues and provide proper mechanical support during in-vivo implantation and later regeneration process. To cover it up, a series of new bio-structures with higher mechanical strength were designed through the combination of halloysite nanotubes (HNTs) into 3D bio-polymeric networks. HNTs clay mineral with its unique rod-like structure and distinctive chemical surface features, exhibits excellent biocompatibility and biosafety for doping into regenerative scaffolds to enhance their mechanical stiffness and biological performance. In this paper, the ongoing procedures of bone/cartilage tissue engineering and wound healing strategies focusing on the designing of 3D-HNTs bio-composites and their multi-cellular interactions in-vitro and in-vivo preclinical studies are reviewed. Furthermore, the challenges and prospects of 3D-HNTs and HNTs-based functional bio-devices for regenerative medicine are also discussed.     

Embryonic Stem Cell Differentiation to Cardiomyocytes on Nanostructured Scaffolds for Myocardial Tissue Regeneration

With recent advances in developmental and stem cell biology, the application of stem cells in tissue engineering has received great attention and designing of suitable scaffolds to support cell growth, differentiation, and functional tissue organization are advancing toward effective tissue regeneration. Regeneration of the infarct myocardium after myocardial infarction (MI), which is caused by the abrupt occlusion of one or more of the coronary arteries in the heart is one of the most demanding aspects in tissue engineering. Embryonic stem cells (ESCs) can differentiate into many cell types and has been considered as a cell source for cardiac regeneration. In this regard, nanofibrous scaffolds received great attention in tissue engineering field due to their similarity in morphology to native extracellular matrix (ECM) and various scaffolds have been studied as cardiac patches over the previous years. In this study poly (ε-caprolactone) (PCL)/gelatin nanofibrous scaffolds were fabricated by electrospinning and embroyonic bodies (EBs) were formed using ESCs seeded on the nanofibrous scaffolds. SEM images revealed cell outgrowth from EBs and the spreading of cells over the nanofibrous scaffolds were observed. Immunocytochemistry results showed the cellular expression of cardiac proteins, namely α-actinin and connexin 43 on the nanofibrous scaffolds indicating the differentiation of EBs to cardiomyocytes. Results of our study showed that PCL/gelatin nanofibrous scaffolds can act as a promising substrate for differentiation of EBs to cardiomyocytes and could be applied for cardiac tissue engineering.     

Implantation of Various Cell-Free Matrixes Does Not Contribute to the Restoration of Hyaline Cartilage within Full-Thickness Focal Defects

Articular cartilage is a highly organized tissue that has a limited ability to heal. Tissue engineering is actively exploited for joint tissue reconstruction in numerous cases of articular cartilage degeneration associated with trauma, arthrosis, rheumatoid arthritis, and osteoarthritis. However, the optimal scaffolds for cartilage repair are not yet identified. Here we have directly compared five various scaffolds, namely collagen-I membrane, collagen-II membrane, decellularized cartilage, a cellulose-based implant, and commercially available Chondro-Gide^® (Geistlich Pharma AG, Wolhusen, Switzerland) collagen membrane. The scaffolds were implanted in osteochondral full-thickness defects, formed on adult Wistar rats using a hand-held cutter with a diameter of 2.0 mm and a depth of up to the subchondral bone. The congruence of the articular surface was almost fully restored by decellularized cartilage and collagen type II-based scaffold. The most vivid restoration was observed 4 months after the implantation. The formation of hyaline cartilage was not detected in any of the groups. Despite cellular infiltration into scaffolds being observed in each group except cellulose, neither chondrocytes nor chondro-progenitors were detected. We concluded that for restoration of hyaline cartilage, scaffolds have to be combined either with cellular therapy or morphogens promoting chondrogenic differentiation.     

Polyphosphazenes—A Promising Candidate for Drug Delivery,Bioimaging, and Tissue Engineering: A Review

Synthetic polymer materials have been surged to the forefront of research in the fields of tissue engineering, drug delivery, and biomonitoring in recent years. Biodegradable synthetic polymers are increasingly needed as transient substrates for tissue regeneration and medicine delivery. In contrast to commonly used polymers including polyesters, polylactones, polyanhydrides, poly(propylene fumarates), polyorthoesters, and polyurethanes, biodegradable polyphosphazenes (PPZs) hold great potential for the purposes indicated above. PPZ's versatility in the synthetic process has enabled the production of a variety of polymers with various physico-chemical, and biological properties have been produced, making them appropriate for biomedical applications. Biocompatible PPZs are often used as scaffolds in the regeneration of skeleton, bones, and other tissues. PPZs have also received special attention as potential drug vehicles of high-value biopharmaceuticals such as anticancer drugs. Additionally, by incorporating fluorophores into the PPZ backbone to produce photoluminescent biodegradable PPZs, the utility of polyphosphazenes is further expanded as they are used in tracking the regeneration of the target tissue as well as the fate of PPZ based scaffolds or drug delivery vehicles. This review provides a summary of the evolution of PPZ applications in the fields of tissue engineering, drug delivery, and bioimaging in recent 5 years.     

3D Composite scaffolds using strontium containing bioactive glasses

In this study, it was aimed to fabricate and characterize three-dimensional composite scaffolds derived from Sr-doped bioactive glass for bone tissue engineering applications. The scaffolds were fabricated by using polymer foam replication technique and coated with gelatin to be able to improve the properties of them. The porous scaffolds were successfully synthesized using optimized process parameters. Both coated and uncoated scaffolds favored precipitation of calcium phosphate layer when they were soaked in simulated body fluid (SBF). Gelatin coating improved the mechanical properties of the scaffold and also it did not change the bioactive behavior of the scaffold. It was observed that there was a good pore interconnectivity maintained in the scaffold microstructure. Results indicated that scaffolds can deliver controlled doses of strontium toward the SBF medium. That is the determinant for bone tissue regeneration, as far as strontium is known to positively act on bone remodeling.     

纳米纤维应用于组织工程的研究进展

组织工程支架的关键作用是起到引导细胞繁殖、生长,促进组织修复的一个过程。纳米纤维支架由于具有特殊的纳米效应,而更有利于细胞的黏附、增殖、功能化,因而被广泛应用于组织工程。本文分别介绍了纳米纤维支架在各类组织工程中应用,包括皮肤和创伤敷料组织工程、血管组织工程、神经组织工程、骨组织工程、软骨组织工程中应用的研究进展,同时介绍了纳米纤维支架药物控制释放中的应用。指出目前纳米技术还不成熟,需要从制备工艺的优化、基因工程的引入及纳米材料安全性能的科学评价等几方面解决纳米纤维支架在组织修复工程中面临的问题。     

Development of a novel glucosamine/silk fibroin–chitosan blend porous scaffold for cartilage tissue engineering applications

Silk fibroin–chitosan blend is reported to be an attractive scaffold material for tissue engineering applications. In our earlier study, we developed a scaffold having an optimal silk fibroin–chitosan blend ratio of 80:20 and proved its potentiality for cartilage tissue engineering applications. Glucosamine is one of the major structural components of cartilage tissue. The present work investigates the effect of glucosamine components on the physicochemical and biocompatibility properties of this scaffold. To this end, varied amounts of glucosamine were added to silk fibroin–chitosan blend with the aim of improving various scaffold properties. The addition of glucosamine components did not show any significant change in physicochemical properties of silk fibroin–chitosan blend scaffolds. The composite scaffold showed an open pore structure with desired pore size and porosity. However, cell culture study using human mesenchymal stem cells derived from umbilical cord blood revealed an overall increase in cell supportive properties of glucosamine-added scaffolds. Cell viability, cell proliferation and glycosaminoglycan assays confirmed enhanced cell viability and proliferation of mesenchymal stem cells. Thus, this study demonstrated the beneficial effect of glucosamine on improving the cell supportive property of silk fibroin–chitosan blend scaffolds making it more potential for cartilage tissue regeneration. To the best of our knowledge, this is the first report on the study of glucosamine-added silk fibroin–chitosan blend porous scaffolds seeded with mesenchymal stem cells derived from umbilical cord blood.     

Influence of Human Jaw Periosteal Cells Seeded β-Tricalcium Phosphate Scaffolds on Blood Coagulation

Tissue engineering offers auspicious opportunities in oral and maxillofacial surgery to heal bone defects. For this purpose, the combination of cells with stability-providing scaffolds is required. Jaw periosteal cells (JPCs) are well suited for regenerative therapies, as they are easily accessible and show strong osteogenic potential. In this study, we analyzed the influence of uncoated and polylactic-co-glycolic acid (PLGA)-coated β-tricalcium phosphate (β-TCP) scaffolds on JPC colonization and subsequent osteogenic differentiation. Furthermore, interaction with the human blood was investigated. This study demonstrated that PLGA-coated and uncoated β-TCP scaffolds can be colonized with JPCs and further differentiated into osteogenic cells. On day 15, after cell seeding, JPCs with and without osteogenic differentiation were incubated with fresh human whole blood under dynamic conditions. The activation of coagulation, complement system, inflammation, and blood cells were analyzed using ELISA and scanning electron microscopy (SEM). JPC-seeded scaffolds showed a dense cell layer and osteogenic differentiation capacity on both PLGA-coated and uncoated β-TCP scaffolds. SEM analyses showed no relevant blood cell attachment and ELISA results revealed no significant increase in most of the analyzed cell activation markers (β-thromboglobulin, Sc5B-9, polymorphonuclear (PMN)-elastase). However, a notable increase in thrombin-antithrombin III (TAT) complex levels, as well as fibrin fiber accumulation on JPC-seeded β-TCP scaffolds, was detected compared to the scaffolds without JPCs. Thus, this study demonstrated that besides the scaffold material the cells colonizing the scaffolds can also influence hemostasis, which can influence the regeneration of bone tissue.     

Mechanophysical Cues in Extracellular Matrix Regulation of Cell Behavior

The extracellular matrix (ECM) is a macromolecular network that can provide biochemical and structural support for cell adhesion and formation. It regulates cell behavior by influencing biochemical and physical cues. It is a dynamic structure whose components are modified, degraded, or deposited during connective tissue development, giving tissues strength and structural integrity. The physical properties of the natural ECM environment control the design of naturally or synthetically derived biomaterials to guide cell function in tissue engineering. Tissue engineering is an important field that explores physical cues of the ECM to produce new viable tissue for medical applications, such as in organ transplant and organ recovery. Understanding how the ECM exerts physical effects on cell behavior, when cells are seeded in synthetic ECM scaffolds, is of utmost importance. Herein we review recent findings in this area that report on cell behaviors in a variety of ECMs with different physical properties, i.e., topology, geometry, dimensionality, stiffness, and tension.     

Uniaxial Hydroxyapatite Growth on a Self-Assembled Protein Scaffold

Biomineralization is a crucial process whereby organisms produce mineralized tissues such as teeth for mastication, bones for support, and shells for protection. Mineralized tissues are composed of hierarchically organized hydroxyapatite crystals, with a limited capacity to regenerate when demineralized or damaged past a critical size. Thus, the development of protein-based materials that act as artificial scaffolds to guide hydroxyapatite growth is an attractive goal both for the design of ordered nanomaterials and for tissue regeneration. In particular, amelogenin, which is the main protein that scaffolds the hierarchical organization of hydroxyapatite crystals in enamel, amelogenin recombinamers, and amelogenin-derived peptide scaffolds have all been investigated for in vitro mineral growth. Here, we describe uniaxial hydroxyapatite growth on a nanoengineered amelogenin scaffold in combination with amelotin, a mineral promoting protein present during enamel formation. This bio-inspired approach for hydroxyapatite growth may inform the molecular mechanism of hydroxyapatite formation in vitro as well as possible mechanisms at play during mineralized tissue formation.     

Enhanced function of chondrocytes in a chitosan-based hydrogel to regenerate cartilage tissues by accelerating degradability of the hydrogel via a hydrolysable crosslinker

Chitosan-based hydrogels as scaffolds for culturing chondrocytes were prepared using linkers with and without hydrolysable poly(dl -lactide) (PLA) segments. The evaluation of the cultured chondrocytes in them indicated that the accelerated degradation of the hydrogel via hydrolysis of the PLA slightly promoted production of the sulfated glycosaminoglycan and drastically improved that of collagen from the encapsulated chondrocytes, which are the chondrospecific extracellular matrix components. Furthermore, the accelerated degradability significantly upregulated the gene expression for Collagen II production and downregulated that for Collagen I production of the encapsulated chondrocytes. Because major component of the articular cartilage tissue is Collagen II-rich hyaline cartilage, these results suggest the degradation of the scaffolds is an important parameter in cartilage tissue regeneration and the accelerated degradability may have benefits on promotion of cartilage tissue regeneration especially from the viewpoint of hyaline cartilage-like collagen production. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48893.