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Electrospinning is a scaffold fabrication technique in tissue engineering that is both versatile and promising, with the objective of repairing or enhancing damaged tissues and organs. The addition of a diverse array of additives into the polymeric matrix has resulted in the exceptional mechanical, biological and functional properties of the electrospun scaffolds in synthetic tissues, which have attracted considerable attention. This review carefully examines the role of carbon nanotubes and nanoparticles in the electrospun scaffold manufacturing process. The final properties of scaffolds, including porosity, mechanical strength and cell interaction, were also examined in relation to the differences in the diameter of electrospun fibers. The diameter of the fibers is a critical factor in the performance of the scaffold. A decrease in fiber size frequently results in an increase in bioactivity and flexibility as a result of the larger surface area. On the contrary, fiber size increases mechanical strength. Therefore, our objective is to emphasize the significance of these additives and the critical role of fiber diameter in the optimization of scaffold properties, thereby highlighting their potential to interact effectively with cells. The review concludes by highlighting future research possibilities, with a focus on the ability of additive-enhanced tissue engineering to expand its medicinal uses. Additionally, this review demonstrates that the addition of carbon nanotubes greatly improves the strength and biological activity of electrospun scaffolds, while hydroxyapatite nanoparticles stimulate bone growth, expanding the possible uses of tissue engineering. This study aims to provide a comprehensive review of recent achievements while also providing the groundwork for future research on the optimization of tissue engineering procedures through the use of innovative additives and precise control over scaffold architecture.

This paper investigates the influence of anchor rods, planks and inner knee braces on the critical load of scaffolding systems under concentric and eccentric loads in construction. The steel rebar of grade 3 is used in place of the patent anchor rod in this study. The results show that the critical load of the scaffolding system increases by 1.5 times when anchor rods of a length of 30 cm are used on two sides of each story of the scaffolding system. The critical load increases by 4 times when the scaffolding system has both the anchor rods and plank. The critical load of the scaffolding system with the anchor rods placed on each story is twice as large as that with anchor rods added every two stories; the failure mode of the system also switches from the in-plane to out-of-plane mode. The 30-cm-long anchor rod, used in place of a steel bar of grade 3, provides a good lateral restraint to the scaffolding system. Moreover, the setup plank can significantly elevate the critical load of the scaffolding system; the critical load increases approximately 1.5 times under the concentric load, and increases up to 2.2 times under the TL/4 eccentric load, defined as a load applied at a quarter distance from the end. The anchor rod and the plank should always be included in a scaffolding system to improve its stability, especially under the eccentric loads in construction.

One area of tissue engineering concerns research into alternatives for new bone formation and replacing its function. Scaffolds have been developed to meet this requirement, allowing cell migration, bone tissue growth, transport of growth factors and nutrients, and the improvement of the mechanical properties of bone. Scaffolds are made from different biomaterials and manufactured using several techniques that, in some cases, do not allow full control over the size and orientation of the pores characterizing the scaffold. A novel hypothesis that a reaction–diffusion (RD) system can be used for designing the geometrical specifications of the bone matrix is thus presented here. The hypothesis was evaluated by making simulations in two- and three-dimensional RD systems in conjunction with the biomaterial scaffold. The results showed the methodology's effectiveness in controlling features such as the percentage of porosity, size, orientation, and interconnectivity of pores in an injectable bone matrix produced by the proposed hypothesis.

Hydrodynamic cellular environment plays an important role in translating engineered tissue constructs into clinically useful grafts. However, the cellular fluid dynamic environment inside bioreactor systems is highly complex and it is normally impractical to experimentally characterize the local flow patterns at the cellular scale. Computational fluid dynamics (CFD) has been recognized as an invaluable and reliable alternative to investigate the complex relationship between hydrodynamic environments and the regeneration of engineered tissues at both the macroscopic and microscopic scales. This review describes the applications of CFD simulations to probe the hydrodynamic environment parameters (e.g., flow rate, shear stress, etc.) and the corresponding experimental validations. We highlight the use of CFD to optimize bioreactor design and scaffold architectures for improved ex-vivo hydrodynamic environments. It is envisioned that CFD could be used to customize specific hydrodynamic cellular environments to meet the unique requirements of different cell types in combination with advanced manufacturing techniques and finally facilitate the maturation of tissue-engineered constructs.

When preparing tissue engineering and regenerative medicine constructs, a commonly encountered problem is the failure of seeded cells to infiltrate the scaffold. In an increasing number of cases, constructs are being mechanically preconditioned with the expectation that preconditioning will enhance the construct's maturation and effectiveness by pre-exposing seeded cells to stimuli the tissue of interest experiences in vivo. However, whether or not mechanostimulation of a scaffold actually results in transmission of stimuli to the seeded cells remains poorly understood. The purpose of this research was to develop a model that quantifies how strain is transmitted to cells layered on a scaffold's surface compared to cells embedded within a scaffold. Three-dimensional finite element models representative of these conditions were created. When 10% strain was applied to the construct, embedded cells received the full imposed strain. However, cells growing on top of the scaffold received 5% strain within the first layer of cells, and the strain transmitted to cells in subsequent layers decreased exponentially with increasing distance from the scaffold's surface. When experimentally testing the model, strain-induced biological responses were muted in conditions where cell to scaffold contact was reduced. This research illustrates the importance of achieving cellular penetration and cell-to-scaffold contacts when mechanically conditioning tissue engineering constructs.

Tissue engineering is a promising approach to regenerate transplantable tissue or organ substitutes in vitro. However, the existing methods are based on seeding cells on macroscale polymer scaffolds, which are associated with several challenges including limited control over cell microenvironment, limited nutrient diffusion, directed cell alignment. The emerging bottom-up tissue engineering methods hold great potential to address these challenges by assembling building blocks into complex 3D tissue constructs. In this study, we developed a layer-by-layer assembly approach to recreate 3D cell-laden constructs. Our experiment showed the predefined channels form a vascular system and help the transplant cells to transport the requirement of culture cells in early case of cells attaching and growing up. It is an original concept to demonstrate the feasibility of forming a network with a vascular geometry in a biocompatible polymer and fabricated different scaffold with different cells. The concept was developed to create a complete branching vascular circulation in 3D on surface of mixture of chitosan and gelatin structures and pre-define the structure of channel for culturing smooth muscle for controlling the SMC growing up as smooth muscle fiber.

A dermal equivalent having a trilayered structure was designed by combining a silver nanoparticles incorporated chitosan film with a bilayer collagen-chitosan/silicon membrane dermal equivalent (BDE). The silver nanoparticles prepared at different conditions were characterized by UV-Vis and transmission electron microscopy (TEM). The macroscopic sharp and the microstructure of the trilayer dermal equivalent (TDE) were also studied. Then, the in vitro antibacterial property of TDE was evaluated by the antibacterial zone test. The effect of the incorporated silver nanoparticles on the resistance of wound infection was further studied by the in vivo animal test. The results prove that the silver nanoparticles incorporated TDE has a better antibacterial property, thus may be potentially applied to a broader field in skin repair such as full thickness defect and burn.

This paper describes the fabrication of microscopic building blocks used in the assembly of tissue engineering scaffolds. The fabrication of these microparts is challenging due to their small size (0.5×0.5×0.2mm overall, 60μm thickness) and complex 3-D shape. Another challenge is the requirement that the parts need to be stably fixed on the wafer but at the same time easily removed by a two-finger microgripper. We developed a MEMS process to solve these critical issues with the following features: (1) SU-8 is used as the material for the parts because it is biocompatible and photo-patternable; (2) The 3-D profile is obtained by combining molding on a patterned Si substrate and photolithography. The extremely flat surface of the part is obtained by careful reflow of the SU-8; (3) A large number of microparts are fabricated on a regular matrix and at the same time can be easily lifted to facilitate grasping by a microgripper in the subsequent automatic assembly process.

The regeneration and repair of bone tissue is a multiphase process that requires a lot of attention, especially if stimulated through scaffold implantation. This review analyzes the process from both a biological and mechanical point of view through the analysis of the porosity and characteristics of the biomaterials that can provide optimal regeneration of bone tissue and functional vascularization that prevents implant failure. Particular attention is paid to the porosity of the new biomaterials and the related physiological effects and the angiogenesis process that the biomaterials themselves can stimulate, analyzing some of the works present in the literature.

Cartilage defects remain one of the most challenging musculoskeletal tissues to treat owing to its poor healing capacity. The lack of sufficient clinical treatments has led to a drive in tissue engineering advancements that combine chondrogenic cells with scaffolds to aid in cartilage regeneration. Nanoscale materials are commonly used in scaffold synthesis because of their ability to mimic the size of extracellular matrix (ECM). This review focuses on the use of nanostructured scaffolds in combination with cells for cartilage tissue engineering. We detail the fabrication methods and materials used to produce nanostructured scaffolds, with a focus on nanofibers and their role in modulating cell biology. Lastly, we discuss various techniques that further functionalize the nanostructured scaffolds to enhance cellular responses.

Scaffolds for tissue regeneration aim to temporarily support the damaged tissue site while allowing cells to infiltrate and regenerate functional tissue. As natural tissue is highly hierarchically organized, scaffold designs aim to follow these structural concepts. This review highlights current achievements in the field of hierarchically organized scaffolds with respect to scaffold preparation and morphological characterization. Special emphasis is placed on self-assembled structures and processing of polymer-based scaffolds with and without the application of templates. Morphological characterization techniques are discussed with respect to the hierarchical level (resolution) that can be achieved. Finally, a short outlook on future perspectives of hierarchically structured scaffolds for applications in the field of induced auto-regeneration and tissue engineering is given, and challenges in fundamental research, such as the usage of multifunctional polymers or multiscale morphological analysis as well as the implementation of modeling approaches for realization of defined scaffold designs or prediction of scaffold properties are discussed.

Selective laser sintering (SLS), a rapid prototyping technology, was investigated for producing bone tissue engineering scaffolds. Completely biodegradable osteoconductive calcium phosphate (Ca-P)/poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) scaffolds were successfully fabricated via SLS using Ca-P/PHBV nanocomposite microspheres. In the SLS manufacturing route, the architecture of tissue engineering scaffolds (pore shape, size, interconnectivity, etc.) can be designed and the sintering process can be optimized for obtaining scaffolds with desirable porous structures and mechanical properties. SLS was also shown to be very effective in producing highly complex porous structures using nanocomposite microspheres. To render SLS-formed Ca-P/PHBV scaffolds osteoinductive, recombinant human bone morphogenetic protein-2 (rhBMP-2) could be loaded onto the scaffolds. For achieving a controlled release of rhBMP-2 from scaffolds, surface modification of Ca-P/PHBV scaffolds by gelatin entrapment and heparin immobilization was needed. The immobilized heparin provided binding affinity for rhBMP-2. Surface modified Ca-P/PHBV nanocomposite scaffolds loaded with rhBMP-2 enhanced the proliferation of human umbilical cord derived mesenchymal stem cells (hUCMSCs) and also their alkaline phosphatase activity. In in vivo experiments using a rabbit model, surface modified Ca-P/PHBV nanocomposite scaffolds loaded with rhBMP-2 promoted ectopic bone formation, exhibiting their osteoinductivity. The strategy of combining advanced scaffold fabrication, nanocomposite material, and controlled growth factor delivery is promising for bone tissue regeneration.

Biodegradable polymers and bioactive ceramics are being combined in a variety of composite materials for tissue engineering scaffolds. Porous nano-biphasic calcium phosphate/gelatin structure was prepared by freeze-drying method. Pre-pores were created by using naphthalene with different particle sizes. Stabilization of gelatin network matrix carried out by EDC (N-(3-dimethyl aminopropyl)-N′-ethyl carbodiimide hydrochloride) with cross-linking method. Three different amount of gelatin (2, 6 and 10 mg/ml) solution were used to study the effect of gelatin amount on properties of the scaffold. Microstructural properties of scaffolds were characterized by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was used to determine the chemical composition of scaffold. Also the morphology and bending strength were investigated.

Tissue can be looked upon as a cell composite, where cell expresses its functions, while extra cellular matrixes (ECMs) secreted provide cell information and do its matrix functions. Here ECMs are, physical and chemical networks consisted of proteins (e.g. collagen, fibronectin, laminin and vitronectin etc.) and glycosaminoglycans (GAGs, e.g. hyaluronic acid, chodroitin 4-sulfate, chodroitin 6-sulfate etc.). The idea cell-carrier should be the one, which most mimics the ECM. Therefore, chitosan in which the N-acetylglucosamine moiety is a structural feature also found in the GAGs, and gelatin, the partially denatured derivative of collagen were used to develop hiomaterials. They will exhibit related bioactivities, as their analogue and precursor, respectively.

Chitosan gelatin network based biomaterials can be applied as membrane, scaffold, surface modifier and non-viral vectorfor. DNA delivery in tissue engineering. Some of our activities were reported. These biomaterials have promising perspectives.

Cartilage injuries may be caused by trauma, biomechanical imbalance, or degenerative changes of joint. Unfortunately, cartilage has limited capability to spontaneous repair once damaged and may lead to progressive damage and degeneration. Cartilage tissue-engineering techniques have emerged as the potential clinical strategies. An ideal tissue-engineering approach to cartilage repair should offer good integration into both the host cartilage and the subchondral bone. Cells, scaffolds, and growth factors make up the tissue engineering triad. One of the major challenges for cartilage tissue engineering is cell source and cell numbers. Due to the limitations of proliferation for mature chondrocytes, current studies have alternated to use stem cells as a potential source. In the recent years, a lot of novel biomaterials has been continuously developed and investigated in various in vitro and in vivo studies for cartilage tissue engineering. Moreover, stimulatory factors such as bioactive molecules have been explored to induce or enhance cartilage formation. Growth factors and other additives could be added into culture media in vitro, transferred into cells, or incorporated into scaffolds for in vivo delivery to promote cellular differentiation and tissue regeneration.

Based on the current development of cartilage tissue engineering, there exist challenges to overcome. How to manipulate the interactions between cells, scaffold, and signals to achieve the moderation of implanted composite differentiate into moderate stem cells to differentiate into hyaline cartilage to perform the optimum physiological and biomechanical functions without negative side effects remains the target to pursue.

A biologically regenerated tooth may provide a new treatment for tooth loss. In this study, a tissue engineering approach was applied to demonstrate the tooth regeneration. The dental buds of the second molar tooth from 1.5-month-old miniature pigs were harvested by surgical operation before eruption. The dental bud tissues were cultured and expanded in vitro for three weeks to obtain dental bud cells (DBCs). The phenotypes of DBCs were identified with a flowcytometry, and the DBCs were seeded into a gelatin–chondroitin–hyaluronan tri-copolymer (GCHT) scaffold. The DBCs/GCHT scaffold constructs were implanted under dermis of nude mice's thoracic dorsum. Mice were sacrificed at predetermined intervals, and the developing tooth-like tissues were harvested for histological examinations. The present results of flowcytometry showed that the DBCs expressed specific surface markers of mesenchymal stem cells. Animal study revealed that the tooth-like structures expressed cytokeratin 14 at 4, 8, and 12 weeks postoperatively. The vascular endothelial growth factor was expressed on 12 weeks. Dentin-like mineralized tissue and dentin genetic-like cells were generated that expressed dentin martrix protein-1 on 16 and 20 weeks. Osteocytes were formed on 24 weeks and expressed osteopontin. This study reveals that the DBCs combined with an appropriate scaffold regenerated tooth-like structure with specific proteins for odontogenesis in nude mice.

Recent development of tissue engineering scaffolds that mimic anatomical structures exhibits a tendency to use rapid prototyping technology, because it can be applied to precisely manufacture the designed objects from the computer-generated model. Among all of rapid prototyping approaches, combining with lithography is characterized with a high throughput of fabrication, especially for the fabrication of polymeric scaffolds. In this study, the aims were to: (1) synthesize the 2-hydroxyethyl methacrylate (HEMA)-capped poly(ethylene glycol) (PEG), which served as the cross-linker of the continuous phase of a poly(lactide-co-glycolide) (PLGA) scaffold and (2) fabricate the composite scaffolds through stereolithography. The synthetic process of the cross-linker was traced, and the end-point of the process was found to lie in 3 to 4 h depending on the molecular weight of the PEG used. The chemical structure of the cross-linker was found to be linear and symmetric to PEG and with a 1:2 molar ratio of PEG and HEMA. It was anticipated to form an interpenetrating network upon irradiating under UV light with PLGA serving as the main body of the scaffold. PEG1000–HEMA had better biocompatibility than those with shorter PEG chains. Scaffolds with two structural variants, square and hexagonal pores, designed by computer were demonstrated. It may further combine medical images to reconstruct tissues and organs for regenerative medicine.

Human bone tissue damage arises due to defects, injury, tumors, aging, and traffic accidents. It is one of the most challenging issues that need surgical development and advanced bone implants. Biocomposite-based bone has insufficient blood supply restricting the utilization for bone regeneration. It is often overcome by including scaffold having angiogenic factor delivery, in vitro and in vivo pre-vascularization. Bone and endothelial cell development and proliferation are stimulated by magnetic responsive scaffolds containing magnetic nanoparticles. Its porous structure allows cells to communicate and develop in all directions, which improves osteointegration. Scaffolds without seeded cells might have applications in bone tissue engineering (BTE) and it is mandatory to estimate in vitro and in vivo biocompatibility and degradation behavior. Three-dimensional (3D) printing opens the door to the creation of one-of-a-kind shapes and structures with specific properties. It helps to minimize the spread of germs during synthesis stage. The gamma rays minimize the infection communicated during transplantation but also damage the graft. When it comes to choosing biomaterials for cancellous and cortical bones, an artificial neural network has the highest recognition rate. This review paper explores the different potential approaches for bone grafting. Different techniques have been developed to create hydrogels with desirable properties for BTE, including non-toxicity, biocompatibility, controllability, and performance. A cell-free framework is used to stimulate bone regeneration, which helps in the bone the self-healing processes of bone fractures. The recent approach combines TE, material science, and genetic engineering for enhanced vascularization, restoring blood flow, and preventing cell death.

Myocardial infarction is the leading cause of chronic heart failure, an ominous disease entity with a wide prevalence in many countries. The morbidity and mortality of chronic heart failure remains high, despite recent pharmacologic advances and cardiac resynchronization therapy. After acute coronary occlusion, the necrotic area triggers a cascade of pathophysiologic events that may lead to structural and electrophysiological left ventricular remodeling, and eventually to progressive chronic heart failure. Therapeutic strategies targeting the repair of the infarcted myocardium aim at interrupting this vicious cycle and constitute an etiological and, as such, promising approach. However, after the initial enthusiasm accompanying early reports, subsequent preclinical and clinical studies unveiled several challenges associated with cell survival and proliferation, as well as abnormal electrophysiological responses after engraftment. In this chapter, we review the main cell sources that hold promise for clinical use, either alone or combined with growth factors and biomaterials, focusing on the acute and medium-term electrophysiological effects of cardiac regeneration approaches.

This chapter presents practical ways to use the whiteboard more effectively to foster mathematics learning. The constructivist’s view of learning advocates that knowledge must be built upon prior knowledge for learning to be relevant and meaningful. To foster mathematics learning, the whiteboard can be exploited as an instructional scaffold for sequencing mathematics visually so that students will have greater clarity of where the lesson starts, the connections within the lesson, and where the lesson is going. This coherent progression of a lesson facilitates students to organize their thinking and help students see the connections between different parts of the lesson. The use of the whiteboard to show connections between various mathematics concepts, present contrasting solutions and as a record of key concepts will be illustrated in this chapter.