Development Of Tissue Engineering Scaffolds Research Articles

3D bioprinting in otorhinolaryngology: from bench to clinical application

Three-dimensional (3D) bioprinting is a promising additive manufacturing technology that uses imaging data and computer-assisted deposition of biological materials or cells to reconstruct complex 3D structures accurately. This technology has progressed rapidly, in part because of its integration across multiple disciplines and combination with other technologies for clinical applications. Advances in experimental research and clinical applications related to otorhinolaryngology have led to the development of diagnostic and treatment methods based on 3D bioprinting, including the development of tissue engineering scaffolds, biosensors, organ chips, and organoids, surgical planning, graft construction, and medical education. Additionally, otorhinolaryngologists will be better equipped to treat tissue function defects with personalized printed graft implants. It is also expected that 3D printing can be used to build ideal in vitro models in the future to help solve existing research challenges. This article briefly introduces the relevant 3D bioprinting technologies and bioinks that can be used by otorhinolaryngologists and discusses their potential applications in otorhinolaryngology.

Piezocatalytically-induced controllable mineralization scaffold with bone-like microenvironment to achieve endogenous bone regeneration

Orderly hierarchical structure with balanced mechanical, chemical, and electrical properties is the basis of the natural bone microenvironment. Inspired by nature, we developed a piezocatalytically-induced controlled mineralization strategy using piezoelectric polymer poly-L-lactic acid (PLLA) fibers with ordered micro-nano structures to prepare biomimetic tissue engineering scaffolds with a bone-like microenvironment (pcm-PLLA), in which PLLA-mediated piezoelectric catalysis promoted the in-situ polymerization of dopamine and subsequently regulated the controllable growth of hydroxyapatite crystals on the fiber surface. PLLA fibers, as analogs of mineralized collagen fibers, were arranged in an oriented manner, and ultimately formed a bone-like interconnected pore structure; in addition, they also provided bone-like piezoelectric properties. The uniformly sized HA nanocrystals formed by controlled mineralization provided a bone-like mechanical strength and chemical environment. The pcm-PLLA scaffold could rapidly recruit endogenous stem cells, and promote their osteogenic differentiation by activating cell membrane calcium channels and PI3K signaling pathways through ultrasound-responsive piezoelectric signals. In addition, the scaffold also provided a suitable microenvironment to promote macrophage M2 polarization and angiogenesis, thereby enhancing bone regeneration in skull defects of rats. The proposed piezocatalytically-induced controllable mineralization strategy provides a new idea for the development of tissue engineering scaffolds that can be implemented for multimodal physical stimulation therapy.

Silk fibroin/polyacrylamide-based tough 3D printing scaffold with strain sensing ability and chondrogenic activity

Cartilage tissue plays an important role in our life activities. The poor self-repair capacity makes cartilage tissue engineering an urgent clinical demand. Among them, the development of tissue engineering scaffolds with both biomimetic features and microenvironment signal sensing abilities could significantly promote the development of cartilage tissue engineering. While most of the reported cartilage scaffolds have no intelligent sensing features. Herein, a ternary composite 3D printing scaffold with both strain sensing ability and desired mechanical property was developed, by using regenerated silk fibroin (RSF) and polyacrylamide (PAM) as main matrixes, and oxidized bacterial cellulose nanofibers (OBC) as filler. Then, the mechanical property, strain sensing ability and corresponding ectopic chondrogenic activity of the RSF/PAM/OBC 3D printing scaffold were comprehensively investigated and verified through in vitro and in vivo studies. Results showed that the RSF/PAM/OBC (OBC-6.3 wt%) scaffold owns effective strain sensing property and desired ectopic chondrogenesis capabilities in the subcutaneous microenvironment. It could be used for reliable monitoring the joint movements, related motion amplitudes, and also promoting the cartilage specifical genes expression. These features not only confirmed the great potential of these smart scaffolds for applications in tissue reconstruction and mechanical stimulus monitoring of the corresponding tissue microenvironment, but also proved the possibility of employing various 3D printing scaffolds as flexible bioelectronics.

Advancing strategies towards the development of tissue engineering scaffolds: a review

Advancing strategies towards the development of tissue engineering scaffolds: a review

Biocomposite films based on chitosan and cerium oxide nanoparticles with promising regenerative potential

Polymeric nanocomposite materials have great potential in the development of tissue-engineered scaffolds because they affect the structure and properties of polymeric materials and regulate cell proliferation and differentiation. In this work, cerium oxide nanoparticles (CeONPs) were incorporated into a chitosan (CS) film to improve the proliferation of multipotent mesenchymal stem cells (MSCs). The citrate-stabilized CeONPs with a negative ζ-potential (−25.0 mV) were precoated with CS to obtain positively charged particles (+20.3 mV) and to prevent their aggregation in the composite solution. The composite CS–CeONP films were prepared in the salt and basic forms using a dry-cast process. The films obtained in both forms were characterized by a uniform distribution of CeONPs. The incorporation of CeONPs into the salt form of CS increased the stiffness of the CS–CeONP film, while the subsequent conversion of the film to the basic form resulted in a decrease in both the Young's modulus and the yield stress. The redox activity (Ce4+ ⇌ Ce3+) of cerium oxide in the CS–CeONP film was confirmed by thermal oxidative degradation. In vitro culture of MSCs showed that the CS–CeONP film has good biocompatibility, and in vivo experiments demonstrated its substantial regenerative potential.

A Review on Three-Dimensional Printed Silicate-Based Bioactive Glass/Biodegradable Medical Synthetic Polymer Composite Scaffolds.

In recent years, tissue engineering scaffolds have turned into the preferred option for the clinical treatment of pathological and traumatic bone defects. In this field, silicate-based bioactive glasses (SBGs) and biodegradable medical synthetic polymers (BMSPs) have attracted a great deal of attention owing to their shared exceptional advantages, like excellent biocompatibility, good biodegradability, and outstanding osteogenesis. Three-dimensional (3D) printed SBG/BMSP scaffolds can not only replicate the mechanical properties and microstructure of natural bone but also degrade in situ after service and end up being replaced by regenerated bone tissue in vivo. This review first consolidates the research efforts in 3D printed SBG/BMSP scaffolds, and then focuses on their composite mechanism. This review may help to provide a fresh perspective for SBG/BMSP composite system in bone regeneration. Impact statement SBG/BMSP composites have great potential in bone tissue regeneration and repair. This article reviews the research progress of three-dimensional printed SBG/BMSP scaffolds in recent years and summarizes the composite mechanism of SBG/BMSP system in bone tissue engineering, which contributes to the development of tissue engineering scaffolds.

Silk Fibroin Combined with Electrospinning as a Promising Strategy for Tissue Regeneration.

The development of tissue engineering scaffolds is of great significance for the repair and regeneration of damaged tissues and organs. Silk fibroin (SF) is a natural protein polymer with good biocompatibility, biodegradability, excellent physical and mechanical properties and processability, making it an ideal universal tissue engineering scaffold material. Nanofibers prepared by electrospinning have attracted extensive attention in the field of tissue engineering due to their excellent mechanical properties, high specific surface area, and similar morphology as to extracellular matrix (ECM). The combination of silk fibroin and electrospinning is a promising strategy for the preparation of tissue engineering scaffolds. In this review, the research progress of electrospun silk fibroin nanofibers in the regeneration of skin, vascular, bone, neural, tendons, cardiac, periodontal, ocular and other tissues is discussed in detail.

Facile Construction of Hybrid Hydrogels with High Strength and Biocompatibility for Cranial Bone Regeneration.

The significant efforts being made towards the utilization of artificial soft materials holds considerable promise for developing tissue engineering scaffolds for bone-related diseases in clinics. However, most of these biomaterials cannot simultaneously satisfy the multiple requirements of high mechanics, good compatibility, and biological osteogenesis. In this study, an osteogenic hybrid hydrogel between the amine-functionalized bioactive glass (ABG) and 4-armed poly(ethylene glycol) succinimidyl glutarate-gelatin network (SGgel) is introduced to flexibly adhere onto the defective tissue and to subsequently guide bone regeneration. Relying on the rapid ammonolysis reaction between amine groups (-NH2) of gelatin and ABG components and N-hydroxysuccinimide (NHS)-ester of tetra-PEG-SG polymer, the hydrogel networks were formed within seconds, offering a multifunctional performance, including easy injection, favorable biocompatibility, biological and mechanical properties (compressive strength: 4.2 MPa; storage modulus: 104 kPa; adhesive strength: 56 kPa), which could facilitate the stem cell viability, proliferation, migration and differentiation into osteocytes. In addition, the integration between the SGgel network and ABG moieties within a nano-scale level enabled the hybrid hydrogel to form adhesion to tissue, maintain the durable osteogenesis and accelerate bone regeneration. Therefore, a robust approach to the simultaneously satisfying tough adhesion onto the tissue defects and high efficiency for bone regeneration on a mouse skull was achieved, which may represent a promising strategy to design therapeutic scaffolds for tissue engineering in clinical applications.

Changes in the microstructure of the human aortic medial layer under biaxial loading investigated by multi-photon microscopy

Understanding the correlation between tissue architecture, health status, and mechanical properties is essential for improving material models and developing tissue engineering scaffolds. Since structural-based material models are state of the art, there is an urgent need for experimentally obtained structural parameters. For this purpose, the medial layer of nine human abdominal aortas was simultaneously subjected to equibiaxial loading and multi-photon microscopy. At each loading interval of 0.02, collagen and elastin fibers were imaged based on their second-harmonic generation signal and two-photon excited autofluorescence, respectively. The structural alterations in the fibers were quantified using the parameters of orientation, diameter, and waviness. The results of the mechanical tests divided the sample cohort into the ruptured and non-ruptured, and stiff and non-stiff groups, which were covered by the findings from histological investigations. The alterations in structural parameters provided an explanation for the observed mechanical behavior. In addition, the waviness parameters of both collagen and elastin fibers showed the potential to serve as indicators of tissue strength. The data provided address deficiencies in current material models and bridge multiscale mechanisms in the aortic media. Statement of significanceAvailable material models can reproduce, but cannot predict, the mechanical behavior of human aortas. This deficiency could be overcome with the help of experimentally validated structural parameters as provided in this study. Simultaneous multi-photon microscopy and biaxial extension testing revealed the microstructure of human aortic media at different stretch levels. Changes in the arrangement of collagen and elastin fibers were quantified using structural parameters such as orientation, diameter and waviness. For the first time, structural parameters of human aortic tissue under continuous loading conditions have been obtained. In particular, the waviness parameters at the reference configuration have been associated with tissue stiffness, brittleness, and the onset of atherosclerosis.

A Comprehensive Review of Biopolymer Fabrication in Additive Manufacturing Processing for 3D-Tissue-Engineering Scaffolds.

The selection of a scaffold-fabrication method becomes challenging due to the variety in manufacturing methods, biomaterials and technical requirements. The design and development of tissue engineering scaffolds depend upon the porosity, which provides interconnected pores, suitable mechanical strength, and the internal scaffold architecture. The technology of the additive manufacturing (AM) method via photo-polymerization 3D printing is reported to have the capability to fabricate high resolution and finely controlled dimensions of a scaffold. This technology is also easy to operate, low cost and enables fast printing, compared to traditional methods and other additive manufacturing techniques. This article aims to review the potential of the photo-polymerization 3D-printing technique in the fabrication of tissue engineering scaffolds. This review paper also highlights the comprehensive comparative study between photo-polymerization 3D printing with other scaffold fabrication techniques. Various parameter settings that influence mechanical properties, biocompatibility and porosity behavior are also discussed in detail.

Preparation and characterization of deer velvet antler/polyvinyl alcohol (DVA/PVA) scaffold for bone tissue engineering

Combining synthetic polymer with inorganic bioactive elements has been an exciting route for developing tissue engineering scaffolds, in particular for bone tissue regeneration. In this study we report the fabrication of novel porous scaffold composed of polyvinyl alcohol/ deer velvet antler (DVA/PVA) via freeze-drying technique. The, mineral content of deer velvet antler analyzed by ICPMS showed high content of calcium and phosphorus. Morphological observation revealed that the incorporation of DVA in the polymer matrix with the porous structures ranging from 35 to 100 µm. The FTIR demonstrated chemical interaction between DVA and PVA due to the reaction between calcium ions with hydroxyl. Thermal analysis showed significant temperature increase from 146.34°C to 384.48°C due to the degradation of the side chain of PVA and decomposition of the carbonate ions. The swelling behavior, the porosity, and the degradation rate of the DVA/PVA scaffold were meet the physiological demands of bone regeneration. After 7 days, DVA/PVA scaffold showed the increasing of water absorption and low degradation rate. Thus, the developed scaffold is believed to have a potential to be effectively used in bone tissue engineering applications.

The Development of Tissue Engineering Scaffolds Using Matrix from iPS-Reprogrammed Fibroblasts.

Tissue engineering solutions have been widely explored for enhanced healing of skin wounds. Diabetic foot ulcers (DFU) are particularly challenging wounds to heal for a variety of reasons, including aberrant ECM, dysregulation of vascularization, and persistent inflammation. Tissue engineering approaches, such as porous collagen-based scaffolds, have shown promise in replacing the current treatments of surgical debridement and topical treatments. Collagen-glycosaminoglycan scaffolds, which are FDA approved for diabetic foot ulcers, can benefit from further functionalization by incorporation of additional signaling factors or extracellular matrix molecules. One option for this is to incorporate matrix from a rejuvenated cell source, as wounds in younger patients heal more quickly. Induced pluripotent stem cells (iPS) are generated from somatic cells and share many functional similarities with embryonic stem cells (ES), while avoiding the ethical concerns. Fibroblasts differentiated from iPS cells have been shown to enrich their ECM with glycosaminoglycan (GAGs), collagen Type III and fibronectin, to have an increased ECM production, and to be pro-angiogenic. Here we describe a technique to grow matrix from post-iPS fibroblasts, and to develop a scaffold from this matrix, in combination with collagen, with the goal of enhancing wound healing. By activating scaffolds with extracellular matrix (ECM) from fibroblasts derived from an iPS source (post-iPSF), the scaffolds are enriched with beneficial elements like GAGs, collagen type III, fibronectin, and VEGF. We believe these scaffolds can enhance skin regeneration and that the techniques can be modified for other tissue engineering applications.

Finite Element Analysis of Porosity Effects on Mechanical Properties for Tissue Engineering Scaffold

Porosity plays a vital role in the development of tissue engineering scaffolds. It influences the biocompatibility performance of the scaffolds by increasing cell proliferation and allowing the transportation of the nutrients, oxygen, and metabolites in the blood rapidly to generate new tissue structure. However, a high amount of porosity can reduce the mechanical properties of the scaffold. Thus, this study aims to determine the geometry of the porous structure of a scaffold which exhibits good mechanical properties while maintaining its porosity at a percentage of more than 80%. Circle and square geometries were used since they are categorized as simple geometry. A unit cell of 12mm x 12mm x 12mm for square shape and pore area of 25π mm2 for circle shape was modeled and simulated by using Finite Element Analysis. The simulation consists of a compression test that determines which geometry exhibits better Young’s Modulus. Since the circle geometry has better Young’s Modulus, the pore size was furthered varied while maintaining the porosity of the scaffold to be above 80%. The same method of the simulation was done on the models. The result shows that the smallest pore size model has the highest Young’s Modulus, which still able to maintain the porosity at 80%.

Optimization of Materials Composition and UV-VIS Light Wavelength Towards Curing Time Performance on Development of Tissue Engineering Scaffold

VAT photopolymerization 3D printing is a process that solidified a vat of liquid photopolymer resin solution into desired products in the presence of UV light. Achieving an optimal property with shorter curing time is an ultimate goal when using functional or special resins. In this study, the effect of wavelength with different compositions of UHT resin mixed PEG solution is studied. Different sources of light were identified, which is UV-A with a wavelength of 365 nm and VIS with a wavelength greater than 420 nm. The PEGconcentrations were varied at 40%, 50%, and 60%. While UHT concentration ratio added into solution was 30%, 50%, and 70%. It has been observed that the optimum curing under UV and VIS wavelength were 9.55 minutes and 17.48 minutes respectively. The feasible range to optimize results of curing time, PEG 48%and UHT 41% with the result 8.6 minutes for the UV-A. Meanwhile, for VISwavelength, PEG 49% and UHT 64% with the result 16 minutes. The success of this study will lead to further innovation on UV-VIS light source in 3D printing in terms of energy efficiency, safety, and cost as well as further evaluation of the performance with respect to the mechanical properties of tissue engineering scaffold.

Characterization of Cassava Fiber of Different Genotypes as a Potential Reinforcement Biomaterial for Possible Tissue Engineering Composite Scaffold Application

Cassava bagasse contains considerable amount of natural single elementary cellulose fibers and white thick root fiber (thick-core fiber) that has seen frequent application in the packaging industry as reinforcement for plastic composite development. However, a review of the literature was unable to find any study that characterized the material properties (such as tensile properties) of both the single elementary and white thick-core cassava cellulose fibers), and their application as potential reinforced filler in tissue engineering scaffold development. In this study, the tensile properties, morphology, crystallinity and thermal degradation profile of non-chemically treated single elementary cellulose fibers and thick-core fibers of different cassava genotypes were investigated. Fibers were tested according to ASTM C1557 under direct tension in a standard mechanical testing system and the cross-sectional area of the fractured regions of the fibers were determined using a 3D optical microscopy method. Cassava fibers of different genotypes did not show any significant difference in tensile properties, with average tensile strength ranging from (5.1–7.3 MPa), Young’s modulus (258–333 MPa) and failure strain (3.4–4.2 %). Tensile test conducted for several gage lengths did not influence the tensile strength and Young’s modulus of the fibers, however, strain-at-break depended on gage length. Single elementary and thick-core fibers showed similar surface morphology, degree of crystallinity (ranging from 21–40 %) and tensile properties with some variation in elastic modulus. Cassava fibers are thermally stable around 100–200 oC, where processing could be performed. Preliminary results showed an improvement in the mechanical properties of a gelatin scaffold when cassava cellulose microfibers were used as reinforcing fillers. The current findings show that cassava fiber has a reasonable mechanical strength, stiffness and thermal stability, and could be considered as a reinforced biomaterial to improve the mechanical integrity of tissue engineering scaffolds.

RGD peptide and graphene oxide co-functionalized PLGA nanofiber scaffolds for vascular tissue engineering.

In recent years, much research has been suggested and examined for the development of tissue engineering scaffolds to promote cellular behaviors. In our study, RGD peptide and graphene oxide (GO) co-functionalized poly(lactide-co-glycolide, PLGA) (RGD-GO-PLGA) nanofiber mats were fabricated via electrospinning, and their physicochemical and thermal properties were characterized to explore their potential as biofunctional scaffolds for vascular tissue engineering. Scanning electron microscopy images revealed that the RGD-GO-PLGA nanofiber mats were readily fabricated and composed of random-oriented electrospun nanofibers with average diameter of 558 nm. The successful co-functionalization of RGD peptide and GO into the PLGA nanofibers was confirmed by Fourier-transform infrared spectroscopic analysis. Moreover, the surface hydrophilicity of the nanofiber mats was markedly increased by co-functionalizing with RGD peptide and GO. It was found that the mats were thermally stable under the cell culture condition. Furthermore, the initial attachment and proliferation of primarily cultured vascular smooth muscle cells (VSMCs) on the RGD-GO-PLGA nanofiber mats were evaluated. It was revealed that the RGD-GO-PLGA nanofiber mats can effectively promote the growth of VSMCs. In conclusion, our findings suggest that the RGD-GO-PLGA nanofiber mats can be promising candidates for tissue engineering scaffolds effective for the regeneration of vascular smooth muscle.

Fabricating high mechanical strength γ-Fe2O3 nanoparticles filled poly(vinyl alcohol) nanofiber using electrospinning process potentially for tissue engineering scaffold

The use of electrospinning has gained substantial interest in the development of tissue engineering scaffolds due to its ability to produce nanoscale fibers which can mimic the geometry of extracellular tissues. Besides geometry, mechanical property is one of the main elements to be considered when developing tissue engineering scaffolds. In this study, the electrospinning process parameter settings were varied in order to find the optimum setting which can produce electrospun nanofibrous mats with good mechanical properties. Maghemite (γ-Fe2O3) was mixed with poly(vinyl alcohol) and then electrospun to form nanofibers. The five input variable factors involved were nanoparticles content, voltage, flow rate, spinning distance, and rotating speed, while the response variable considered was Young’s modulus. The performance of electrospinning process was systematically screened and optimized using response surface methodology. This work truly demonstrated the sequential nature of designed experimentation. Additionally, the application of various designs of experiment techniques and concepts was also demonstrated. Results revealed that electrospun nanofibrous mats with maximum Young’s modulus (273.51 MPa) was obtained at optimum input settings: 9 v/v% nanoparticle content, 35 kV voltage, 2 mL/h volume flow rate, 8 cm spinning distance, and 3539 r/min of rotating speed. The model was verified successfully by performing confirmation experiments. The nanofibers characterization demonstrated that the nanoparticles were well dispersed inside the nanofibers, and it also showed that the presence of defects on the nanofibers can decrease their mechanical strength. The biocompatibility performance was also evaluated and it was proven that the presence of γ-Fe2O3 enhanced the cell viability and cell growth rate. The developed poly(vinyl alcohol)/γ-Fe2O3 electrospun nanofiber mat has a good potential for tissue engineering scaffolds.

Synthesis of Chitosan-Based Sub-Micrometric Particles by Simple Coacervation

Due to its intrinsic biocompatibility, degradability, and antibacterial properties, chitosan is widely explored for biomedical and pharmaceutical applications, especially for the development of tissue engineering scaffolds and controlled drug delivery systems. In this work, physically crosslinked chitosan-based particles with submicrometric size were synthesized by means of a modified coacervation process, starting from aqueous solutions differing for the chitosan molecular weight and concentration. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) were used to analyse the particle morphology and the mean diameter yielded by the different synthesis parameters. Daily DLS measurements were also performed to monitor the expected swelling of the particles in a buffer solution, up to four days of storage. The experimental findings showed that submicrometric chitosan particles, with an average diameter in the range 150–400 nm, could be successfully produced, with both chitosan molecular weight and concentration affecting the particle size. Moreover, the smallest particles, among those synthesized, were found to be stable in water solutions up to three days. This seems to suggest the potential of the investigated particles for short-term biomedical applications, e.g., controlled drug delivery over time windows ranging from hours to days.

Development of highly porous biodegradable γ-Fe2O3/polyvinyl alcohol nanofiber mats using electrospinning process for biomedical application

The use of electrospinning process in fabricating tissue engineering scaffolds has received great attention in recent years due to its simplicity. The nanofibers produced via electrospinning possessed morphological characteristics similar to extracellular matrix of most tissue components. Porosity plays a vital role in developing tissue engineering scaffolds because it influences the biocompatibility performance of the scaffolds. In this study, maghemite (γ-Fe2O3) was mixed with polyvinyl alcohol (PVA) and subsequently electrospun to produce nanofibers. Five factors; nanoparticles content, voltage, flow rate, spinning distance, and rotating speed were varied to produce the electrospun nanofibrous mats with high porosity value. Empirical model was developed using response surface methodology to analyze the effect of these factors to the porosity. The results revealed that the optimum porosity (90.85%) was obtained using 5% w/v nanoparticle content, 35kV of voltage, 1.1ml/h volume flow rate of solution, 8cm spinning distance and 2455rpm of rotating speed. The empirical model was verified successfully by performing confirmation experiments. The properties of optimum PVA/γ-Fe2O3 nanofiber mats such as fiber diameter, mechanical properties, and contact angle were investigated. In addition, cytocompatibility test, in vitro degradation rate, and MTT assay were also performed. Results revealed that high porosity biodegradable γ-Fe2O3/polyvinyl alcohol nanofiber mats have low mechanical properties but good degradation rates and cytocompatibility properties. Thus, they are suitable for low load bearing biomedical application or soft tissue engineering scaffold.

Constructing a highly bioactive 3D nanofibrous bioglass scaffold via bacterial cellulose-templated sol-gel approach

A novel three-dimensional (3D) nanofibrous bioactive glass (BG) scaffold was prepared via a template assisted sol-gel route using a 3D bacterial cellulose aerogel as the template followed by calcination. SEM and TEM results revealed that the as-prepared BG nanofibers had a diameter as small as 16 nm and the BG scaffold had a 3D interconnected porous structure. The in vitro bioactivity test confirmed that the BG nanofibrous scaffold was highly bioactive. The strategy presented in this work may open a new avenue for the development of tissue engineering scaffolds with fine inorganic nanofibers.