Polysaccharide-based materials for cartilage tissue engineering applications

Polysaccharide base electrospun nanofibrous scaffolds for cartilage tissue engineering: Challenges and opportunities

Polysaccharides, known as naturally abundant macromolecular materials which can be easily modified chemically, have always attracted scientists' interest due to their outstanding properties in tissue engineering. Moreover, their intrinsic similarity to cartilage ECM components, biocompatibility, and non-harsh processing conditions make polysaccharides an excellent option for cartilage tissue engineering. Imitating the natural ECM structure to form a fibrous scaffold at the nanometer scale in order to recreate the optimal environment for cartilage regeneration has always been attractive for researchers in the past few years. However, there are some challenges for polysaccharides electrospun nanofibers preparation, such as poor solubility (Alginate, cellulose, chitin), high viscosity (alginate, chitosan, and Hyaluronic acid), high surface tension, etc. Several methods are reported in the literature for facing polysaccharide electrospinning issues, such as using carrier polymers, modification of polysaccharides, and using different solvent systems. In this review, considering the importance of polysaccharide-based electrospun nanofibers in cartilage tissue engineering applications, the main achievements in the past few years, and challenges for their electrospinning process are discussed. After careful investigation of reported studies in the last few years, alginate, chitosan, hyaluronic acid, chondroitin sulfate, and cellulose were chosen as the main polysaccharide base electrospun nanofibers used for cartilage regeneration.

A biospecies-derived genomic DNA hybrid gel electrolyte for electrochemical energy storage

Intrinsic impediments, namely weak mechanical strength, low ionic conductivity, low electrochemical performance, and stability have largely inhibited beyond practical applications of hydrogels in electronic devices and remains as a significant challenge in the scientific world. Here, we report a biospecies-derived genomic DNA hybrid gel electrolyte with many synergistic effects, including robust mechanical properties (mechanical strength and elongation of 6.98 MPa and 997.42%, respectively) and ion migration channels, which consequently demonstrated high ionic conductivity (73.27 mS/cm) and superior electrochemical stability (1.64 V). Notably, when applied to a supercapacitor the hybrid gel-based devices exhibit a specific capacitance of 425 F/g. Furthermore, it maintained rapid charging/discharging with a capacitance retention rate of 93.8% after ∼200,000 cycles while exhibiting a maximum energy density of 35.07 Wh/kg and a maximum power density of 193.9 kW/kg. This represents the best value among the current supercapacitors and can be immediately applied to minicars, solar cells, and LED lightning. The widespread use of DNA gel electrolytes will revolutionize human efforts to industrialize high-performance green energy.

Multifunctional Bioactive Scaffolds from ARX-g-(Zn@rGO)-HAp for Bone Tissue Engineering: In Vitro Antibacterial, Antitumor, and Biocompatibility Evaluations

Advanced biomaterials are required with enhanced antibacterial and anticancer activities to obtain desirable biocompatibility during and after scaffold implantation in tissue engineering. Here, we report the development of a nanosystem by the hydrothermal method using different zinc (Zn) amounts and reduced graphene oxide (GO). Arabinoxylan, the nanosystem (Zn@rGO), and nanohydroxyapatite polymeric nanocomposites ARX-g-(Zn@rGO)/HAp were prepared by the free radical polymerization method, and porous bioactive scaffolds were fabricated via the freeze-drying technique. The structural, morphological, and elemental analyses of the bioactive scaffolds were conducted using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis. The wetting behavior was studied by a water contact meter and swelling in aqueous and phosphate-buffered saline solutions at 37 °C. The degradation was also studied in the phosphate-buffered saline solution at 37 °C. The increase in Zn content increased the pore size, and hydrophobic behavior shifted to hydrophilic (AGZ-1 = 131.40° at 0 s and 120.60° at 10 s to AGZ-1 = 81.30° at 0 s and 69.20° at 10 s) with the increase in contact time. Maximum swelling was observed in deionized water (AGZ-1 = 52.87%, AGZ-4 = 90.20%), followed by phosphate-buffered saline (PBS; AGZ-1 = 44.80%, AGZ-4 = 67.90%) and electrolyte (AGZ-1 = 32.40%, AGZ-4 = 63.47%), and biodegradation in PBS media increased (AGZ-1 = 36.80%, AGZ-4 = 55.92%). Antimicrobial activities against severe infection-causing pathogens and antitumor activity against U87 cell lines showed exceptional results. Cell viability and cell proliferation studies were conducted against preosteoblast cell lines, and increased cell viability and proliferation were observed from AGZ-1 to AGZ-4. Antimicrobial and anticancer activities were enhanced with the increase of Zn content in the Zn@rGO system. The bioactive scaffolds with different formulations could be potential biomaterials to treat and regenerate defected bone tissue.

Recent Advances of Natural Polysaccharide-based Double-network Hydrogels for Tissue Repair

Natural polysaccharide hydrogels have been extensively explored for many years due to their outstanding biocompatibility and biodegradability, which are very promising candidates as artificial soft materials for biomedical applications. However, their inferior mechanical performances greatly limited their applications. Introduction of double-network (DN) structure has been well documented to be an efficient strategy for significant improvement of the mechanical property of hydrogels. Here, recent progress of natural polysaccharide-based DN hydrogels is reviewed from the perspective of fundamental concepts on both design rationale and preparation strategies to biomedical application in tissue repair. Retrospect of the DN-strengthened polysaccharide hydrogels can give a deep insight into the fundamental relationship of such bio-based hydrogels among structural design, mechanical properties and practical demands, thereby prompting their translation to clinical application prospects.

Organic acid cross-linked 3D printed cellulose nanocomposite bioscaffolds with controlled porosity, mechanical strength, and biocompatibility

Herein, we fabricated chemically cross-linked polysaccharide-based three-dimensional (3D) porous scaffolds using an ink composed of nanofibrillated cellulose, carboxymethyl cellulose, and citric acid (CA), featuring strong shear thinning behavior and adequate printability. Scaffolds were produced by combining direct-ink-writing 3D printing, freeze-drying, and dehydrothermal heat-assisted cross-linking techniques. The last step induces a reaction of CA. Degree of cross-linking was controlled by varying the CA concentration (2.5–10.0 wt.%) to tune the structure, swelling, degradation, and surface properties (pores: 100-450 μm, porosity: 86%) of the scaffolds in the dry and hydrated states. Compressive strength, elastic modulus, and shape recovery of the cross-linked scaffolds increased significantly with increasing cross-linker concentration. Cross-linked scaffolds promoted clustered cell adhesion and showed no cytotoxic effects as determined by the viability assay and live/dead staining with human osteoblast cells. The proposed method can be extended to all polysaccharide-based materials to develop cell-friendly scaffolds suitable for tissue engineering applications.

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Chemically cross-linked polysaccharide-based 3D porous scaffolds were fabricated

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Physicochemical and mechanical properties increased with cross-linker concentration

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Lower cross-linker concentration led to higher porosity and interconnected pores

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Scaffolds promoted clustered cell adhesion and showed no cytotoxic effects

Bioprinting Scaffolds for Vascular Tissues and Tissue Vascularization

In recent years, tissue engineering has achieved significant advancements towards the repair of damaged tissues. Until this day, the vascularization of engineered tissues remains a challenge to the development of large-scale artificial tissue. Recent breakthroughs in biomaterials and three-dimensional (3D) printing have made it possible to manipulate two or more biomaterials with complementary mechanical and/or biological properties to create hybrid scaffolds that imitate natural tissues. Hydrogels have become essential biomaterials due to their tissue-like physical properties and their ability to include living cells and/or biological molecules. Furthermore, 3D printing, such as dispensing-based bioprinting, has progressed to the point where it can now be utilized to construct hybrid scaffolds with intricate structures. Current bioprinting approaches are still challenged by the need for the necessary biomimetic nano-resolution in combination with bioactive spatiotemporal signals. Moreover, the intricacies of multi-material bioprinting and hydrogel synthesis also pose a challenge to the construction of hybrid scaffolds. This manuscript presents a brief review of scaffold bioprinting to create vascularized tissues, covering the key features of vascular systems, scaffold-based bioprinting methods, and the materials and cell sources used. We will also present examples and discuss current limitations and potential future directions of the technology.

Recent Advancements in 3D Printing of Polysaccharide Hydrogels in Cartilage Tissue Engineering

The application of hydrogels coupled with 3-dimensional (3D) printing technologies represents a modern concept in scaffold development in cartilage tissue engineering (CTE). Hydrogels based on natural biomaterials are extensively used for this purpose. This is mainly due to their excellent biocompatibility, inherent bioactivity, and special microstructure that supports tissue regeneration. The use of natural biomaterials, especially polysaccharides and proteins, represents an attractive strategy towards scaffold formation as they mimic the structure of extracellular matrix (ECM) and guide cell growth, proliferation, and phenotype preservation. Polysaccharide-based hydrogels, such as alginate, agarose, chitosan, cellulose, hyaluronan, and dextran, are distinctive scaffold materials with advantageous properties, low cytotoxicity, and tunable functionality. These superior properties can be further complemented with various proteins (e.g., collagen, gelatin, fibroin), forming novel base formulations termed "proteo-saccharides" to improve the scaffold's physiological signaling and mechanical strength. This review highlights the significance of 3D bioprinted scaffolds of natural-based hydrogels used in CTE. Further, the printability and bioink formation of the proteo-saccharides-based hydrogels have also been discussed, including the possible clinical translation of such materials.

Polysaccharide-Based Biomaterials in Tissue Engineering: A Review

In addition to proteins and nucleic acids, polysaccharides are an important type of biomacromolecule widely distributed in plants, animals, and microorganisms. Polysaccharides are considered as promising biomaterials due to their significant bioactivities, natural abundance, immunoactivity, and chemical modifiability for tissue engineering (TE) applications. Due to the similarities of the biochemical properties of polysaccharides and the extracellular matrix of human bodies, polysaccharides are increasingly recognized and accepted. Furthermore, the degradation behavior of these macromolecules is generally nontoxic. Certain delicate properties, such as remarkable mechanical properties and tunable tissue response, can be obtained by modifying the functional groups on the surface of polysaccharide molecules. The applications of polysaccharide-based biomaterials in the TE field have been growing intensively in recent decades, for example, bone/cartilage regeneration, cardiac regeneration, neural regeneration, and skin regeneration. This review summarizes the main essential properties of polysaccharides, including their chemical properties, crosslinking mechanisms, and biological properties, and focuses on the association between their structures and properties. The recent progress in polysaccharide-based biomaterials in various TE applications is reviewed, and the prospects for future studies are addressed as well. We intend this review to offer a comprehensive understanding of and inspiration for the research and development of polysaccharide-based materials in TE.

Recent advances in 3D printing: vascular network for tissue and organ regeneration

Over the past years, the fabrication of adequate vascular networks has remained the main challenge in engineering tissues due to technical difficulties, while the ultimate objective of tissue engineering is to create fully functional and sustainable organs and tissues to transplant in the human body. There have been a number of studies performed to overcome this limitation, and as a result, 3D printing has become an emerging technique to serve in a variety of applications in constructing vascular networks within tissues and organs. 3D printing incorporated technical approaches allow researchers to fabricate complex and systematic architecture of vascular networks and offer various selections for fabrication materials and printing techniques. In this review, we will discuss materials and strategies for 3D printed vascular networks as well as specific applications for certain vascularized tissue and organ regeneration. We will also address the current limitations of vascular tissue engineering and make suggestions for future directions research may take.

A strategy of tailoring polymorphs and nanostructures to construct self-reinforced nonswelling high-strength bacterial cellulose hydrogels

A serious decline in mechanical properties of polysaccharide hydrogels caused by swelling has always been a difficult problem which greatly limited their application especially in the medical field. Herein, nonswelling high-strength natural hydrogels based on self-reinforced double-crosslinked bacterial cellulose (SDBC) were prepared. Inspired by the concept of homogeneous composite materials, by regulating the ratio of LiOH/urea alkaline solvent, the aggregation structure and nanostructure of SDBC hydrogels can be controlled, thereby a unique nanofiber-network-self-reinforced (FNSR) structure was constructed and a new self-reinforcing mechanism is proposed. The prepared SDBC hydrogels have excellent mechanical properties at a high water content (>91%) for the combination of double-crosslinking and a unique FNSR structure, which can effectively prevent crack propagation and dissipate a large amount of energy. In particular, the compressive strength can reach 3.17 MPa which is 56 times that of native bacterial cellulose (BC). It is worth mentioning that no swelling occurs for the hydrogel, and the mechanical strength still remains in excess of 90% for 15 days in water, which is favorable for promising application in underwater equipment, implantable ionic devices, and tissue engineering scaffolds. This study also opens up a new horizon for the preparation of self-reinforced hydrogels.

Sources, Extraction and Biomedical Properties of Polysaccharides

In the recent era, bioactive compounds from plants have received great attention because of their vital health-related activities, such as antimicrobial activity, antioxidant activity, anticoagulant activity, anti-diabetic activity, UV protection, antiviral activity, hypoglycemia, etc. Previous studies have already shown that polysaccharides found in plants are not likely to be toxic. Based on these inspirational comments, most research focused on the isolation, identification, and bioactivities of polysaccharides. A large number of biologically active polysaccharides have been isolated with varying structural and biological activities. In this review, a comprehensive summary is provided of the recent developments in the physical and chemical properties as well as biological activities of polysaccharides from a number of important natural sources, such as wheat bran, orange peel, barely, fungi, algae, lichen, etc. This review also focused on biomedical applications of polysaccharides. The contents presented in this review will be useful as a reference for future research as well as for the extraction and application of these bioactive polysaccharides as a therapeutic agent.

Chondrogenesis of human mesenchymal stem cells by microRNA loaded triple polysaccharide nanoparticle system

Degenerative cartilage is the pathology of severe depletion of extracellular matrix components in articular cartilage. In diseases like osteoarthritis, misregulation of microRNAs contributes the pathology and collectively leads to disruption of the homeostasis. In this study chondroitin sulfate/hyaluronic acid/chitosan nanoparticles were prepared and successfully characterized chemically and morphologically. Results demonstrated higher chondroitin sulfate amounts led smaller nanoparticles, but lower surface zeta potential due to high electronegativity. After optimization of chondroitin sulfate amounts regarding size and charge, nanoparticles were loaded with microRNA-149-5p, a therapeutic miRNA downregulated in osteoarthritis, and evaluated focusing on their loading efficiency, release behaviour, cytotoxicity and gene transfection efficiency in vitro. Results showed all nanoparticle formulations were non-toxic and promising gene delivery agents, due to increased levels of microRNA-149-5p and decreased mRNA levels of microRNA's target, FUT-1. Highest gene transfection efficiency was obtained with the nanoparticle formulation which had the highest chondroitin sulfate load and smallest size. In addition, owing to their high chondroitin sulfate cargo, all nanoparticles were reported to enhance chondrogenesis, which was demonstrated by gene expression analysis and sulfated glycosaminoglycan (sGAG) staining. The obtained data suggest that the delivery of microRNA-149-5p via polysaccharide based carriers could achieve collaborative impact in cartilage regeneration and have a potential to enhance osteoarthritis treatment.

Recent Strategies in Extrusion-Based Three-Dimensional Cell Printing toward Organ Biofabrication

Reconstructing human organs is one of the ultimate goals of the medical industry. Organ printing utilizing three-dimensional cell printing technology to fabricate artificial living organ equivalents has shed light on the advancement of this field into a new era. Among three currently applied techniques (inkjet, laser-assisted, and extrusion-based), extrusion-based cell printing (ECP) has evoked the majority of interest due to its low cost, wide range of applicable materials, and ease of spatial and depositional controllability. Major challenges in organ reconstruction include difficulties in precisely fabricating complex structural features, creating perfusable and functional vasculatures, and mimicking biophysical and biochemical characteristics in the printed constructs. In this review, we describe the merits and limitations of ECP for organ fabrication and discuss its recent advances aimed at overcoming these challenges. In addition, we delineate the expected future techniques for printing live tissue or organ substitutes.

Tissue engineering with gellan gum

Engineering complex tissues for research and clinical applications relies on high-performance biomaterials that are amenable to biofabrication, maintain mechanical integrity, support specific cell behaviours, and, ultimately, biodegrade. In most cases, complex tissues will need to be fabricated from not one, but many biomaterials, which collectively fulfill these demanding requirements. Gellan gum is an anionic polysaccharide with potential to fill several key roles in engineered tissues, particularly after modification and blending. This review focuses on the present state of research into gellan gum, from its origins, purification and modification, through processing and biofabrication options, to its performance as a cell scaffold for both soft tissue and load bearing applications. Overall, we find gellan gum to be a highly versatile backbone material for tissue engineering research, upon which a broad array of form and functionality can be built.

Clinically advancing and promising polymer-based therapeutics

In this review article, we will examine the history of polymers and their evolution from provisional World War II materials to medical therapeutics. To provide a comprehensive look at the current state of polymer-based therapeutics, we will classify technologies according to targeted areas of interest, including central nervous system-based and intraocular-, gastrointestinal-, cardiovascular-, dermal-, reproductive-, skeletal-, and neoplastic-based systems. Within each of these areas, we will consider several examples of novel, clinically available polymer-based therapeutics; in addition, this review will also include a discussion of developing therapies, ranging from the in vivo to clinical trial stage, for each targeted area of treatment. Finally, we will emphasize areas of patient care in need of more effective, accessible, and targeted treatment approaches where polymer-based therapeutics may offer potential solutions.

Commercial Products for Osteochondral Tissue Repair and Regeneration

The osteochondral tissue represents a complex structure composed of four interconnected structures, namely hyaline cartilage, a thin layer of calcified cartilage, subchondral bone, and cancellous bone. Due to the several difficulties associated with its repair and regeneration, researchers have developed several studies aiming to restore the native tissue, some of which had led to tissue-engineered commercial products. In this sense, this chapter discusses the good manufacturing practices, regulatory medical conditions and challenges on clinical translations that should be fulfilled regarding the safety and efficacy of the new commercialized products. Furthermore, we review the current osteochondral products that are currently being marketed and applied in the clinical setting, emphasizing the advantages and difficulties of each one.

Bioactivity and mineralization of natural hydroxyapatite from cuttlefish bone and Bioglass® co-sintered bioceramics

In this study, bioactive hydroxyapatite (HAP)-based bioceramics starting from cuttlefish bone powders have been prepared and characterized. In particular, fragmented cuttlefish bone was co-sintered with 30 wt% of Bioglass^® -45S5 to synthesize HAP-based powders with enhanced mechanical properties and bioactivity. Commercial synthetic HAP was treated following the same procedure and used as a reference. The structure and composition of the bioceramics formulations were characterized using Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. After the thermal treatment of cuttlefish bone powder added with 30 wt% Bioglass, new phases with compositions of sodium calcium phosphate [Na₃ Ca₆ (PO₄ )₅ ], β-tricalcium phosphate [Ca₃ (PO₄ )] and amorphous silica were detected. In vitro cell culture studies were performed by evaluating proliferation, metabolic activity and differentiation of human osteoblast-like cells (MG63). Scaffolds made with cuttlefish bone powder exhibited increased apatite deposition, alkaline phosphatase activity and cell proliferation compared with commercial synthetic HAP. In addition, the ceramic compositions obtained after the combination with Bioglass^® further enhanced the metabolic activity of MG63 cell and promoted the formation of a well-developed apatite layer after 7 days of incubation in Dulbecco's modified Eagle's medium.

Fabrication of porous scaffolds with decellularized cartilage matrix for tissue engineering application

Due to the avascular nature of articular cartilage, damaged tissue has little capacity for spontaneous healing. Three-dimensional scaffolds have potential for use in tissue engineering approach for cartilage repair. In this study, bovine cartilage tissue was decellularized and chemically crosslinked hybrid chitosan/extracellular matrix (ECM) scaffolds were fabricated with different ECM weight ratios by simple freeze drying method. Various properties of chitosan/ECM scaffolds such as microstructure, mechanical strength, swelling ratio, and biodegradability rate were investigated to confirm improved structural and biological characteristics of chitosan scaffolds in the presence of ECM. The results indicated that by introducing ECM to chitosan, pore sizes in scaffolds with 1% and 2% ECM decreased and thus the mechanical properties were improved. The presence of ECM in the same scaffolds also improved the swelling ratio and biodegradation rate in the hybrid scaffolds. MTT cytotoxicity assays performed on chondrocyte cells cultured on chitosan/ECM scaffolds having various amounts of ECM showed that the greatest cell attachment belongs to the sample with intermediate ECM content (2% ECM). Overall, it can be concluded from all obtained results that the prepared scaffold with intermediate concentration of ECM could be a proper candidate for use in cartilage tissue engineering.

Silk based bioinks for soft tissue reconstruction using 3-dimensional (3D) printing with in vitro and in vivo assessments

In the field of soft tissue reconstruction, custom implants could address the need for materials that can fill complex geometries. Our aim was to develop a material system with optimal rheology for material extrusion, that can be processed in physiological and non-toxic conditions and provide structural support for soft tissue reconstruction. To meet this need we developed silk based bioinks using gelatin as a bulking agent and glycerol as a non-toxic additive to induce physical crosslinking. We developed these inks optimizing printing efficacy and resolution for patient-specific geometries that can be used for soft tissue reconstruction. We demonstrated in vitro that the material was stable under physiological conditions and could be tuned to match soft tissue mechanical properties. We demonstrated in vivo that the material was biocompatible and could be tuned to maintain shape and volume up to three months while promoting cellular infiltration and tissue integration.

Multifunctional 3D printing of heterogeneous hydrogel structures

Multimaterial additive manufacturing or three-dimensional (3D) printing of hydrogel structures provides the opportunity to engineer geometrically dependent functionalities. However, current fabrication methods are mostly limited to one type of material or only provide one type of functionality. In this paper, we report a novel method of multimaterial deposition of hydrogel structures based on an aspiration-on-demand protocol, in which the constitutive multimaterial segments of extruded filaments were first assembled in liquid state by sequential aspiration of inks into a glass capillary, followed by in situ gel formation. We printed different patterned objects with varying chemical, electrical, mechanical, and biological properties by tuning process and material related parameters, to demonstrate the abilities of this method in producing heterogeneous and multi-functional hydrogel structures. Our results show the potential of proposed method in producing heterogeneous objects with spatially controlled functionalities while preserving structural integrity at the switching interface between different segments. We anticipate that this method would introduce new opportunities in multimaterial additive manufacturing of hydrogels for diverse applications such as biosensors, flexible electronics, tissue engineering and organ printing.

Encapsulation of human elastic cartilage-derived chondrocytes in nanostructured fibrin-agarose hydrogels

The generation of elastic cartilage substitutes for clinical use is still a challenge. In this study, we investigated the possibility of encapsulating human elastic cartilage-derived chondrocytes (HECDC) in biodegradable nanostructured fibrin-agarose hydrogels (NFAH). Viable HECDC from passage 2 were encapsulated in NFAH and maintained in culture conditions. Constructs were harvested for histochemical and immunohistochemical analyses after 1, 2, 3, 4 and 5 weeks of development ex vivo. Histological results demonstrated that it is possible to encapsulate HECDC in NFAH, and that HECDC were able to proliferate and form cells clusters expressing S-100 and vimentin. Additionally, histochemical and immunohistochemical analyses of the extracellular matrix (ECM) showed that HECDC synthetized different ECM molecules (type I and II collagen, elastic fibers and proteoglycans) in the NFAH ex vivo. In conclusion, this study suggests that NFAH can be used to generate biodegradable and biologically active constructs for cartilage tissue engineering applications. However, further cell differentiation, biomechanical and in vivo studies are still needed.

Seaweed polysaccharide-based hydrogels used for the regeneration of articular cartilage

This manuscript provides an overview of the in vitro and in vivo studies reported in the literature focusing on seaweed polysaccharides based hydrogels that have been proposed for applications in regenerative medicine, particularly, in the field of cartilage tissue engineering. For a better understanding of the main requisites for these specific applications, the main aspects of the native cartilage structure, as well as recognized diseases that affect this tissue are briefly described. Current available treatments are also presented to emphasize the need for alternative techniques. The following part of this review is centered on the description of the general characteristics of algae polysaccharides, as well as relevant properties required for designing hydrogels for cartilage tissue engineering purposes. An in-depth overview of the most well known seaweed polysaccharide, namely agarose, alginate, carrageenan and ulvan biopolymeric gels, that have been proposed for engineering cartilage is also provided. Finally, this review describes and summarizes the translational aspect for the clinical application of alternative systems emphasizing the importance of cryopreservation and the commercial products currently available for cartilage treatment.

Starch: State-of-the-Art, New Challenges and Opportunities

The chapter presents a brief account of various topics in starch-based blends, composites and nanocomposites, including structure–property relationships, preparation and characterization of starch nanocrystals, natural fibre-reinforced thermoplastic starch composites, applications of starch nanocrystal-based blends, composites and nanocomposites, chemically modified thermoplastic starches, outstanding features of starch-based hydrogel nanocomposites, fracture and failure of starch-based composites, application of starch-based nanocomposites in the food industry and effects of additives on the properties of starch.

Modulation of chondrogenic differentiation of human mesenchymal stem cells in jellyfish collagen scaffolds by cell density and culture medium

Studies on tissue-engineering approaches for the regeneration of traumatized cartilage focus increasingly on multipotent human mesenchymal stem cells (hMSCs) as an alternative to autologous chondrocytes. The present study applied porous scaffolds made of collagen from the jellyfish Rhopilema esculentum for the in vitro chondrogenic differentiation of hMSCs. Culture conditions in those scaffolds differ from conditions in high-density pellet cultures, making a re-examination of these data necessary. We systematically investigated the influence of seeding density, basic culture media [Dulbecco's modified Eagle's medium (DMEM), α-minimum essential medium (α-MEM)] with varying glucose content and supplementation with fetal calf serum (FCS) or bovine serum albumin (BSA) on the chondrogenic differentiation of hMSCs. Gene expression analyses of selected markers for chondrogenic differentiation and hypertrophic development were conducted. Furthermore, the production of cartilage extracellular matrix (ECM) was analysed by quantification of sulphated glycosaminoglycan and collagen type II contents. The strongest upregulation of chondrogenic markers, along with the highest ECM deposition was observed in scaffolds seeded with 2.4 × 10⁶ cells/cm³ after cultivation in high-glucose DMEM and 0.125% BSA. Lower seeding densities compared to high-density pellet cultures were sufficient to induce in vitro chondrogenic differentiation of hMSCs in collagen scaffolds, which reduces the amount of cells required for the seeding of scaffolds and thus the monolayer expansion period. Furthermore, examination of the impact of FCS and α-MEM on chondrogenic MSC differentiation is an important prerequisite for the development of an osteochondral medium for simultaneous osteogenic and chondrogenic differentiation in biphasic scaffolds for osteochondral tissue regeneration. Copyright © 2015 John Wiley & Sons, Ltd.

Nanoparticle-based bioactive agent release systems for bone and cartilage tissue engineering

The inability to deliver bioactive agents locally in a transient but sustained manner is one of the challenges on the development of bio-functionalized scaffolds for tissue engineering (TE) and regenerative medicine. The mode of release is especially relevant when the bioactive agent is a growth factor (GF), because the dose and the spatiotemporal release of such agents at the site of injury are crucial to achieve a successful outcome. Strategies that combine scaffolds and drug delivery systems have the potential to provide more effective tissue regeneration relative to current therapies. Nanoparticles (NPs) can protect the bioactive agents, control its profile, decrease the occurrence and severity of side effects and deliver the bioactive agent to the target cells maximizing its effect. Scaffolds containing NPs loaded with bioactive agents can be used for their local delivery, enabling site-specific pharmacological effects such as the induction of cell proliferation and differentiation, and, consequently, neo-tissue formation. This review aims to describe the concept of combining NPs with scaffolds, and the current efforts aiming to develop highly multi-functional bioactive agent release systems, with the emphasis on their application in TE of connective tissues.

An overview of the suitability of hydrogel-forming polymers for extrusion-based 3D-printing

In this review hydrogel-forming polymers that are suitable for extrusion-based 3D printing are evaluated.

Polysaccharides as Cell Carriers for Tissue Engineering: the Use of Cellulose in Vascular Wall Reconstruction

Polysaccharides are long carbohydrate molecules of monosaccharide units joined together by glycosidic bonds. These biological polymers have emerged as promising materials for tissue engineering due to their biocompatibility, mostly good availability and tailorable properties. This complex group of biomolecules can be classified using several criteria, such as chemical composition (homo- and heteropolysaccharides), structure (linear and branched), function in the organism (structural, storage and secreted polysaccharides), or source (animals, plants, microorganisms). Polysaccharides most widely used in tissue engineering include starch, cellulose, chitosan, pectins, alginate, agar, dextran, pullulan, gellan, xanthan and glycosaminoglycans. Polysaccharides have been applied for engineering and regeneration of practically all tissues, though mostly at the experimental level. Polysaccharides have been tested for engineering of blood vessels, myocardium, heart valves, bone, articular and tracheal cartilage, intervertebral discs, menisci, skin, liver, skeletal muscle, neural tissue, urinary bladder, and also for encapsulation and delivery of pancreatic islets and ovarian follicles. For these purposes, polysaccharides have been applied in various forms, such as injectable hydrogels or porous and fibrous scaffolds, and often in combination with other natural or synthetic polymers or inorganic nanoparticles. The immune response evoked by polysaccharides is usually mild, and can be reduced by purifying the material or by choosing appropriate crosslinking agents.

Agarose drug delivery systems upgraded by surfactants inclusion: critical role of the pore architecture

Anionic or non-ionic surfactants have been introduced in agarose-based hydrogels aiming to tailor the release of drugs with different solubility. The release of a hydrophilic model drug, Theophylline, shows the predictable release enhancement that varies depending on the surfactant. However, when the hydrophobic Tolbutamide is considered, an unexpected retarded release is observed. This effect can be explained not only considering the interactions established between the drug loaded micelles and agarose but also to the alteration of the freeze-dried hydrogels microstructure. It has been observed that the modification of the porosity percentage as well as the pore size distribution during the lyophilization plays a critical role in the different phenomena that take place as soon as desiccated hydrogel is rehydrated. The possibility of tailoring the pore architecture as a function of the surfactant nature and percentage can be applied from drug control release to the widespread and growing applications of materials based on hydrogel matrices.

From basics to clinical: a comprehensive review on spinal cord injury

Spinal cord injury (SCI) is a devastating neurological disorder that affects thousands of individuals each year. Over the past decades an enormous progress has been made in our understanding of the molecular and cellular events generated by SCI, providing insights into crucial mechanisms that contribute to tissue damage and regenerative failure of injured neurons. Current treatment options for SCI include the use of high dose methylprednisolone, surgical interventions to stabilize and decompress the spinal cord, and rehabilitative care. Nonetheless, SCI is still a harmful condition for which there is yet no cure. Cellular, molecular, rehabilitative training and combinatorial therapies have shown promising results in animal models. Nevertheless, work remains to be done to ascertain whether any of these therapies can safely improve patient's condition after human SCI. This review provides an extensive overview of SCI research, as well as its clinical component. It starts covering areas from physiology and anatomy of the spinal cord, neuropathology of the SCI, current clinical options, neuronal plasticity after SCI, animal models and techniques to assess recovery, focusing the subsequent discussion on a variety of promising neuroprotective, cell-based and combinatorial therapeutic approaches that have recently moved, or are close, to clinical testing.

Leveraging "raw materials" as building blocks and bioactive signals in regenerative medicine

Components found within the extracellular matrix (ECM) have emerged as an essential subset of biomaterials for tissue engineering scaffolds. Collagen, glycosaminoglycans, bioceramics, and ECM-based matrices are the main categories of "raw materials" used in a wide variety of tissue engineering strategies. The advantages of raw materials include their inherent ability to create a microenvironment that contains physical, chemical, and mechanical cues similar to native tissue, which prove unmatched by synthetic biomaterials alone. Moreover, these raw materials provide a head start in the regeneration of tissues by providing building blocks to be bioresorbed and incorporated into the tissue as opposed to being biodegraded into waste products and removed. This article reviews the strategies and applications of employing raw materials as components of tissue engineering constructs. Utilizing raw materials holds the potential to provide both a scaffold and a signal, perhaps even without the addition of exogenous growth factors or cytokines. Raw materials contain endogenous proteins that may also help to improve the translational success of tissue engineering solutions to progress from laboratory bench to clinical therapies. Traditionally, the tissue engineering triad has included cells, signals, and materials. Whether raw materials represent their own new paradigm or are categorized as a bridge between signals and materials, it is clear that they have emerged as a leading strategy in regenerative medicine. The common use of raw materials in commercial products as well as their growing presence in the research community speak to their potential. However, there has heretofore not been a coordinated or organized effort to classify these approaches, and as such we recommend that the use of raw materials be introduced into the collective consciousness of our field as a recognized classification of regenerative medicine strategies.

Biomaterials to prevascularize engineered tissues

Tissue engineering promises to restore tissue and organ function following injury or failure by creating functional and transplantable artificial tissues. The development of artificial tissues with dimensions that exceed the diffusion limit (1-2 mm) will require nutrients and oxygen to be delivered via perfusion (or convection) rather than diffusion alone. One strategy of perfusion is to prevascularize tissues; that is, a network of blood vessels is created within the tissue construct prior to implantation, which has the potential to significantly shorten the time of functional vascular perfusion from the host. The prevascularized network of vessels requires an extracellular matrix or scaffold for 3D support, which can be either natural or synthetic. This review surveys the commonly used biomaterials for prevascularizing 3D tissue engineering constructs.