The design of a scaffold of bone tissue engineering plays an important role in ensuring cell viability and cell growth. Therefore, it is a necessity to produce an ideal scaffold by predicting and simulating the properties of the scaffold. Hence, the computational method should be adopted since it has a huge potential to be used in the implementation of the scaffold of bone tissue engineering. To explore the field of computational method in the area of bone tissue engineering, this paper provides an overview of the usage of a computational method in designing a unit cell of bone tissue engineering scaffold. In order to design a unit cell of the scaffold, we discussed two categories of unit cells that can be used to design a feasible scaffold, which are non-parametric and parametric designs. These designs were later described and being categorised into multiple types according to their characteristics, such as circular structures and Triply Periodic Minimal Surface (TPMS) structures. The advantages and disadvantages of these designs were discussed. Moreover, this paper also represents some software that was used in simulating and designing the bone tissue scaffold. The challenges and future work recommendations had also been included in this paper.
In this study, porous hydroxyapatite (HA) samples were fabricated via sponge techniques with the aid of sago as part of the binder mixture. Development processes for the production of porous bone graft substitutes are studied using polyurethane sponge. To obtain the optimum amount of binder for successful fabrication of porous HA were done. Initially, porous HA powder was synthesized using calcium hydroxide and orthorphosphoric acid. Meanwhile, sago was mixed with PVA in a certain ratio to be used as binder for preparing the porous HA. After a series of investigative tests were conducted to characterize the sintered samples, the use of the sago and polymeric mixture was found to successfully aid the fabrication of porous HA samples. In this investigation, comparison of physical and mechanical characteristics between samples prepared using difference techniques was made.
Respiratory diseases have a major impact on global health. The airway epithelium, which acts as a frontline defence, is one of the most common targets for inhaled allergens, irritants, or micro-organisms to enter the respiratory system. In the tissue engineering field, biomaterials play a crucial role. Due to the continuing high impact of respiratory diseases on society and the emergence of new respiratory viruses, in vitro airway epithelial models with high microphysiological similarities that are also easily adjustable to replicate disease models are urgently needed to better understand those diseases. Thus, the development of biomaterial scaffolds for the airway epithelium is important due to their function as a cell-support device in which cells are seeded in vitro and then are encouraged to lay down a matrix to form the foundations of a tissue for transplantation. Studies conducted in in vitro models are necessary because they accelerate the development of new treatments. Moreover, in comparatively controlled conditions, in vitro models allow for the stimulation of complex interactions between cells, scaffolds, and growth factors. Based on recent studies, the biomaterial scaffolds that have been tested in in vitro models appear to be viable options for repairing the airway epithelium and avoiding any complications. This review discusses the role of biomaterial scaffolds in in vitro airway epithelium models. The effects of scaffold, physicochemical, and mechanical properties in recent studies were also discussed.
Organ repair, regeneration, and transplantation are constantly in demand due to various acute, chronic, congenital, and infectious diseases. Apart from traditional remedies, tissue engineering (TE) is among the most effective methods for the repair of damaged tissues via merging the cells, growth factors, and scaffolds. With regards to TE scaffold fabrication technology, polyurethane (PU), a high-performance medical grade synthetic polymer and bioactive material has gained significant attention. PU possesses exclusive biocompatibility, biodegradability, and modifiable chemical, mechanical and thermal properties, owing to its unique structure-properties relationship. During the past few decades, PU TE scaffold bioactive properties have been incorporated or enhanced with biodegradable, electroactive, surface-functionalised, ayurvedic products, ceramics, glass, growth factors, metals, and natural polymers, resulting in the formation of modified polyurethanes (MPUs). This review focuses on the recent advances of PU/MPU scaffolds, especially on the biomedical applications in soft and hard tissue engineering and regenerative medicine. The scientific issues with regards to the PU/MPU scaffolds, such as biodegradation, electroactivity, surface functionalisation, and incorporation of active moieties are also highlighted along with some suggestions for future work.
Electrospinning is a promising technique for the fabrication of bioscaffolds in tissue engineering applications. Pertaining issues of multiple polymer jets and bending instabilities result in random paths which lend poor controllability over scaffolds morphology for affecting the porosity and mechanical stability. The present study alleviates these challenges by demonstrating a novel self-directing single jet taking a specifically patterned path to deposit fibers into circular and uniform scaffolds without tuning any externally controlled parameters. High-speed camera observation revealed that the charge retention and dissipation on the collected fibers caused rapid autojet switching between the two jetting modes, namely, a microcantilever-like armed jet motion and a whipping motion, which sequentially expand the area and thickness of the scaffolds, respectively, in a layered-like fashion. The physical properties showed that the self-switching dual-jet modes generated multilayered microfibrous scaffolds (MFSs) with dual morphologies and varied fiber packing density, thereby establishing the gradient porosity and mechanical strength (through buckled fibers) in the scaffolds. In vitro studies showed that as-spun scaffolds are cell-permeable hierarchical 3D microporous structures enabling lateral cell seeding into multiple layers. The cell proliferation on days 6 and 9 increased 21% and 38% correspondingly on MFSs than on nanofibrous scaffolds (NFSs) done by conventional multijets electrospinning. Remarkably, this novel and single-step process is highly reproducible and tunable for developing fibrous scaffolds for tissue engineering applications.
Porous structure, biocompatibility and biodegradability, large surface area, and drug-loading ability are some remarkable properties of zeolite structure, making it a great possible option for bone tissue engineering. Herein, we evaluated the potential application of the ZSM-5 scaffold encapsulated GEN with high porosity structure and significant antibacterial properties. The space holder process has been employed as a new fabrication method with interconnected pores and suitable mechanical properties. In this study, for the first time, ZSM-5 scaffolds with GEN drug-loading were fabricated with the space holder method. The results showed excellent open porosity in the range of 70-78% for different GEN concentrations and appropriate mechanical properties. Apatite formation on the scaffold surface was determined with Simulation body fluid (SBF), and a new bone-like apatite layer shaping on all samples confirmed the in vitro bioactivity of ZSM-5-GEN scaffolds. Also, antibacterial properties were investigated against both gram-positive and gram-negative bacteria. The incorporation of various amounts of GEN increased the inhibition zone from 24 to 28 (for E. coli) and 26 to 37 (for S. aureus). In the culture with MG63 cells, great cell viability and high cell proliferation after 7 days of culture were determined.
Maghemite (γ-Fe2O3) nanoparticle with its unique magnetic properties is recently known to enhance the cell growth rate. In this study, γ-Fe2O3 is mixed into polyvinyl alcohol (PVA) matrix and then electrospun to form nanofibers. Design of experiments was used to determine the optimum parameter settings for the electrospinning process so as to produce elctrospun mats with the preferred characteristics such as good morphology, Young's modulus and porosity. The input factors of the electrospinnning process were nanoparticles content (1-5%), voltage (25-35 kV), and flow rate (1-3 ml/h) while the responses considered were Young's modulus and porosity. Empirical models for both responses as a function of the input factors were developed and the optimum input factors setting were determined, and found to be at 5% nanoparticle content, 35 kV voltage, and 1 ml/h volume flow rate. The characteristics and performance of the optimum PVA/γ-Fe2O3 nanofiber mats were compared with those of neat PVA nanofiber mats in terms of morphology, thermal properties, and hydrophilicity. The PVA/γ-Fe2O3 nanofiber mats exhibited higher fiber diameter and surface roughness yet similar thermal properties and hydrophilicity compared to neat PVA PVA/γ-Fe2O3 nanofiber mats. Biocompatibility test by exposing the nanofiber mats with human blood cells was performed. In terms of clotting time, the PVA/γ-Fe2O3 nanofibers exhibited similar behavior with neat PVA. The PVA/γ-Fe2O3 nanofibers also showed higher cells proliferation rate when MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was done using human skin fibroblast cells. Thus, the PVA/γ-Fe2O3 electrospun nanofibers can be a promising biomaterial for tissue engineering scaffolds.
The potential of electrospinning process to fabricate ultrafine fibers as building blocks for tissue engineering scaffolds is well recognized. The scaffold construct produced by electrospinning process depends on the quality of the fibers. In electrospinning, material selection and parameter setting are among many factors that contribute to the quality of the ultrafine fibers, which eventually determine the performance of the tissue engineering scaffolds. The major challenge of conventional electrospun scaffolds is the nature of electrospinning process which can only produce two-dimensional electrospun mats, hence limiting their applications. Researchers have started to focus on overcoming this limitation by combining electrospinning with other techniques to fabricate three-dimensional scaffold constructs. This article reviews various polymeric materials and their composites/blends that have been successfully electrospun for tissue engineering scaffolds, their mechanical properties, and the various parameters settings that influence the fiber morphology. This review also highlights the secondary processes to electrospinning that have been used to develop three-dimensional tissue engineering scaffolds as well as the steps undertaken to overcome electrospinning limitations.
In this article, gelatin/copper activated faujasites (CAF) composite scaffolds were fabricated by lyophilisation technique for promoting partial thickness wound healing. The optimised scaffold with 0.5% (w/w) of CAF, G (0.5%), demonstrated pore size in the range of 10-350 μm. Agar disc diffusion tests verified the antibacterial role of G (0.5%) and further supported that bacterial lysis was due to copper released from the core of CAF embedded in the gelatin matrix. The change in morphology of bacteria as a function of CAF content in gelatin scaffold was studied using SEM analysis. The confocal images revealed the increase in mortality rate of bacteria with increase in concentration of incorporated CAF in gelatin matrix. Proficient oxygen supply to needy cells is a continuing hurdle faced by tissue engineering scaffolds. The dissolved oxygen measurements revealed that CAF embedded in the scaffold were capable of increasing oxygen supply and thereby promote cell proliferation. Also, G (0.5%) exhibited highest cell viability on NIH 3T3 fibroblast cells which was mainly attributed to the highly porous architecture and its ability to enhance oxygen supply to cells. In vivo studies conducted on Sprague Dawley rats revealed the ability of G (0.5%) to promote skin regeneration in 20 days. Thus, the obtained data suggest that G (0.5%) is an ideal candidate for wound healing applications.
Volumetric Muscle Loss (VML) is associated with muscle loss function and often untreated and considered part of the natural sequelae of trauma. Various types of biomaterials with different physical and properties have been developed to treat VML. However, much work remains yet to be done before the scaffolds can pass from the bench to the bedside. The present review aims to provide a comprehensive summary of the latest developments in the construction and application of natural polymers-based tissue scaffolding for volumetric muscle injury. Here, the tissue engineering approaches for treating volumetric muscle loss injury are highlighted and recent advances in cell-based therapies using various sources of stem cells are elaborated in detail. An overview of different strategies of tissue scaffolding and their efficacy on skeletal muscle cells regeneration and migration are presented. Furthermore, the present paper discusses a wide range of natural polymers with a special focus on proteins and polysaccharides that are major components of the extracellular matrices. The natural polymers are biologically active and excellently promote cell adhesion and growth. These bio-characteristics justify natural polymers as one of the most attractive options for developing scaffolds for muscle cell regeneration.
A novel series of silver-doped mesoporous bioactive glass/poly(1,8-octanediol citrate) (AgMBG/POC) elastomeric biocomposite scaffolds were successfully constructed by a salt-leaching technique for the first time and the effect of inclusion of different AgMBG contents (5, 10, and 20 wt%) on physicochemical and biological properties of pure POC elastomer was evaluated. Results indicated that AgMBG particles were uniformly dispersed in the POC matrix and increasing the AgMBG concentration into POC matrix up to 20 wt% enhanced thermal behaviour, mechanical properties and water uptake ability of the composite scaffolds compared to those from POC. The 20%AgMBG/POC additionally showed higher degradation rate in Tris(hydroxymethyl)-aminomethane-HCl (Tris-HCl) compared with pure POC and lost about 26% of its initial weight after soaking for 28 days. The AgMBG phase incorporation also significantly endowed the resulting composite scaffolds with efficient antibacterial properties against Escherichia coli and Staphylococcus aureus bacteria while preserving their favorable biocompatibility with soft tissue cells (i.e., human dermal fibroblast cells). Taken together, our results suggest that the synergistic effect of both AgMBG and POC make these newly designed AgMBG/POC composite scaffold an attractive candidate for soft tissue engineering applications.
Chitosan-based hemostats are promising candidates for immediate hemorrhage control. However, they have some disadvantages and require further improvement to achieve the desired hemostatic efficiency. Here, a series of 1% Ga2O3-containing mesoporous bioactive glass-chitosan composite scaffolds (Ga-MBG/CHT) were constructed by the lyophilization process and the effect of various concentrations of Ga-MBG (10, 30, and 50 wt %) on the hemostatic function of the CHT scaffold was assessed as compared to that of Celox Rapid gauze (CXR), a current commercially available chitosan-coated hemostatic gauze. The prepared scaffolds exhibited >79% porosity and showed increased water uptake compared to that in CXR. The results of coagulation studies showed that pure CHT and composite scaffolds exhibited increased hemostatic performance with respect to CXR. Furthermore, the composite scaffold with the highest Ga-MBG content (50 wt %) had increased capability to enhancing thrombus generation, blood clotting, and platelet adhesion and aggregation than that of the scaffold made of pure CHT. The antibacterial efficacy and biocompatibility of the prepared scaffolds were also assessed by a time-killing assay and an Alamar Blue assay, respectively. Our results show that the antibacterial effect of 50% Ga-MBG/CHT was more pronounced than that of CHT and CXR. The cell viability results also demonstrated that Ga-MBG/CHT composite scaffolds had good biocompatibility, which facilitates the spreading and proliferation of human dermal fibroblast cells even with 50 wt % Ga-MBG loading. These results suggest that Ga-MBG/CHT scaffolds could be a promising hemostatic candidate for improving hemostasis in critical situations.
Mesoporous bioactive glass containing 1% Ga2O3 (1%Ga-MBG) is attractive for hemorrhage control because of its surface chemistry which can promote blood-clotting. The present study compares this proprietary inorganic coagulation accelerator with two commercial hemostats, CeloxTM (CX) and QuikClot Advanced Clotting Sponge PlusTM (ACS+). The results indicate that the number of adherent platelets were higher on the 1%Ga-MBG and CX surfaces than ACS+ whereas a greater contact activation was seen on 1%Ga-MBG and ACS+ surfaces than CX. 1%Ga-MBG not only resulted in larger platelet aggregates and more extensive platelet pseudopodia compared to CX and ACS+ but also significantly accelerated the intrinsic pathways of the clotting cascade. In vitro thrombin generation assays also showed that CX and ACS+ induced low levels of thrombin formation while 1%Ga-MBG had significantly higher values. 1%Ga-MBG formed a larger red blood cell aggregate than both CX and ACS+. Direct exposure of 1%Ga-MBG to fibroblast cells increased cell viability after 3 days relative to CX and ACS+, inferring excellent cytocompatibility. The results of this study promote 1%Ga-MBG as a promising hemostat compared to the commercially available products as it possesses essential factors required for coagulation activation.
The complex architecture of the cortical part of the bovine-femur was examined to develop potential tissue engineering (TE) scaffolds. Weight-change and X-ray diffraction (XRD) results show that significant phase transformation and morphology conversion of the bone occur at 500-750°C and 750-900°C, respectively. Another breakthrough finding was achieved by determining a sintering condition for the nucleation of hydroxyapatite crystal from bovine bone via XRD technique. Scanning electron microscopy results of morphological growth suggests that the concentration of polymer fibrils increases (or decreases, in case of apatite crystals) from the distal to proximal end of the femur. Energy-dispersive analysis of X-ray, Fourier transform infrared, micro-computer tomography, and mechanical studies of the actual composition also strongly support our microscopic results and firmly indicate the functionally graded material properties of bovine-femur. Bones sintered at 900 and 1000°C show potential properties for soft and hard TE applications, respectively.
Scaffolds with structural features similar to the extracellular matrix stimulate rapid osteogenic differentiation in favorable microenvironment and with growth factor supplementation. In this study, the osteogenic potential of electrospun poly-l-lactide/hydroxyapatite/collagen (PLLA/Col/HA, PLLA/HA and PLLA/Col) scaffolds were tested in vitro with the supplementation of platelet derived growth factor-BB (PDGF-BB). Cell attachment and topography, mineralization, extracellular matrix protein localization, and gene expression of the human mesenchymal stromal cells were compared between the fibrous scaffolds PLLA/Col/HA, PLLA/Col, and PLLA/HA. The levels of osteocalcin, calcium, and mineralization were significantly greater in the PLLA/Col/HA and PLLA/HA compared with PLLA/Col. High expression of fibronectin, intracellular adhesion molecule, cadherin, and collagen 1 (Col1) suggests that PLLA/Col/HA and PLLA/HA scaffolds had superior osteoinductivity than PLLA/Col. Additionally, osteopontin, osteocalcin, osterix, Runt-related transcription factor 2 (Runx2), and bone morphogenic protein (BMP2) expression were higher in PLLA/Col/HA and PLLA/HA compared with PLLA/Col. In comparison with PLLA/Col, the PLLA/Col/HA and PLLA/HA scaffolds presented a significant upregulation of the genes Runx2, Col 1, Integrin, osteonectin (ON), bone gamma-carboxyglutamic acid-containing protein (BGALP), osteopontin (OPN), and BMP2. The upregulation of these genes was further increased with PDGF-BB supplementation. These results show that PDGF-BB acts synergistically with PLLA/Col/HA and PLLA/HA to enhance the osteogenic differentiation potential. Therefore, this combination can be used for the rapid expansion of bone marrow stromal cells into bone-forming cells for tissue engineering.
We investigated the efficacy of a muscle-stuffed vein (MSV) seeded with neural-transdifferentiated human mesenchymal stem cells as an alternative nerve conduit to repair a 15-mm sciatic nerve defect in athymic rats. Other rats received MSV conduit alone, commercial polyglycolic acid conduit (Neurotube®), reverse autograft, or were left untreated. Motor and sensory functions as well as nerve conductivity were evaluated for 12 weeks, after which the grafts were harvested for histological analyses. All rats in the treatment groups demonstrated a progressive increase in the mean Sciatic Functional Index (motor function) and nerve conduction amplitude (electrophysiological function) and showed positive withdrawal reflex (sensory function) by the 10th week of postimplantation. Autotomy, which is associated with neuropathic pain, was severe in rats treated with conduit without cells; there was mild or no autotomy in the rats of other groups. Histologically, harvested grafts from all except the untreated groups exhibited axonal regeneration with the presence of mature myelinated axons. In conclusion, treatment with MSV conduit is comparable to that of other treatment groups in supporting functional recovery following sciatic nerve injury; and the addition of cells in the conduit alleviates neuropathic pain. Impact Statement It is shown that pretreated muscle-stuffed vein conduit is comparable to that of commercial nerve conduit and autograft in supporting functional recovery following peripheral nerve injury. The addition of neural-differentiated mesenchymal stem cells in the conduit is shown to alleviate neuropathic pain.
Decellularized native extracellular matrix (ECM) biomaterials are widely used in tissue engineering and have reached clinical application as biomesh implants. To enhance their regenerative properties and postimplantation performance, ECM biomaterials could be functionalized via immobilization of bioactive molecules. To facilitate ECM functionalization, we developed a metabolic glycan labeling approach using physiologic pathways to covalently incorporate click-reactive azide ligands into the native ECM of a wide variety of rodent tissues and organs in vivo, and into the ECM of isolated rodent and porcine lungs cultured ex vivo. The incorporated azides within the ECM were preserved after decellularization and served as chemoselective ligands for subsequent bioconjugation via click chemistry. As proof of principle, we generated alkyne-modified heparin, immobilized it onto azide-incorporated acellular lungs, and demonstrated its bioactivity by Antithrombin III immobilization and Factor Xa inhibition. The herein reported metabolic glycan labeling approach represents a novel platform technology for manufacturing click-reactive native ECM biomaterials, thereby enabling efficient and chemoselective functionalization of these materials to facilitate tissue regeneration and repair.
The mechanical, thermal, and morphological properties of a 3D porous Pennisetum purpureum (PP)/polylactic acid (PLA) based scaffold were investigated. In this study, a scaffold containing P. purpureum and PLA was produced using the solvent casting and particulate leaching method. P. purpureum fibre, also locally known as Napier grass, is composed of 46% cellulose, 34% hemicellulose, and 20% lignin. PLA composites with various P. purpureum contents (10%, 20%, and 30%) were prepared and subsequently characterised. The morphologies, structures and thermal behaviours of the prepared composite scaffolds were characterised using field-emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The morphology was studied using FESEM; the scaffold possessed 70-200μm-sized pores with a high level of interconnectivity. The moisture content and mechanical properties of the developed porous scaffolds were further characterised. The P. purpureum/PLA scaffold had a greater porosity factor (99%) and compression modulus (5.25MPa) than those of the pure PLA scaffold (1.73MPa). From the results, it can be concluded that the properties of the highly porous P. purpureum/PLA scaffold developed in this study can be controlled and optimised. This can be used to facilitate the construction of implantable tissue-engineered cartilage.
The in vitro degradation and mechanical properties of a 3D porous Pennisetum purpureum (PP)/polylactic acid (PLA)-based scaffold were investigated. In this study, composite scaffolds with PP to PLA ratios of 0%, 10%, 20%, and 30% were immersed in a PBS solution at 37°C for 40 days. Compression tests were conducted to evaluate the compressive strength and modulus of the scaffolds, according to ASTM F451-95. The compression strength of the scaffolds was found to increase from 1.94 to 9.32MPa, while the compressive modulus increased from 1.73 to 5.25MPa as the fillers' content increased from 0wt% to 30wt%. Moreover, field emission scanning electron microscopy (FESEM) and X-ray diffraction were employed to observe and analyse the microstructure and fibre-matrix interface. Interestingly, the degradation rate was reduced for the PLA/PP20scaffold, though insignificantly, this could be attributed to the improved mechanical properties and stronger fibre-matrix interface. Microstructure changes after degradation were observed using FESEM. The FESEM results indicated that a strong fibre-matrix interface was formed in the PLA/PP20scaffold, which reflected the addition of P. purpureum into PLA decreasing the degradation rate compared to in pure PLA scaffolds. The results suggest that the P. purpureum/PLA scaffold degradation rate can be altered and controlled to meet requirements imposed by a given tissue engineering application.
This study aimed to evaluate the bioactivities and biocompatibilities of porous polylactic acid (PLA) reinforced with cellulose nanofiber (CNF) scaffolds. The in vitro degradation behaviors of the porous PLA/CNF scaffolds were systematically measured for up to 8 weeks in a phosphate-buffered saline medium at 37 °C. The reinforcement of CNF resisted the biodegradation of the scaffolds. The in vitro cytotoxicity and biocompatibility of the scaffolds were determined using the Beas2B American Type Culture Collection cells. The 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide cytotoxicity and proliferation tests showed that the scaffolds were non-toxic, and epithelial cells grew well on the scaffold after 7 days of culture, whereas the percentage of cell proliferation on the PLA/CNF15 scaffold was the largest, 130 %. A scratch wound-healing assay was performed to evaluate the suitability of the scaffolds for cell migration. The results demonstrated that the scaffolds exhibited good cell migration towards nearly complete wound closure.