Fabrication Of Tissue Engineering Scaffolds Research Articles

Durotaxis and Topotaxis Orchestrated Guidance on Cell Migration in 3D Printed Scaffold/Hydrogel Composite

Printing three-dimensional (3D) scaffolds with suitable mechanical cues is an effective strategy for guiding tissue regeneration by inducing cell migration and growth. Nevertheless, many studies considered only one type of cue for 3D tissue engineering scaffold fabrication, such as topological cues, which is insufficient. To realize durotaxis- and topotaxis-orchestrated guidance on cell migration, a 3D printed scaffold/hydrogel composite was fabricated in this study. The porous scaffold provided a topological cue (topotaxis), and the combined hydrogel provided a compliance cue (durotaxis). The results indicated that the thin fibers of the scaffold induced cell migration, and the larger pore size and directed fiber number of the scaffold led to more uniform cell orientation (topotaxis). Furthermore, when collagen was cured to cover the scaffold to result in a compliance change, the cells in the collagen still sensed the scaffold topological cue and migrated along it (durotaxis). Collagen also provides a living space and nutrition for cells, thereby significantly increasing their number. The effects of durotaxis and topotaxis synthesis provide a promising solution for tissue engineering scaffold applications.

Wet 3D printing of biodegradable porous scaffolds to enable room-temperature deposition modeling of polymeric solutions for regeneration of articular cartilage

Tissue engineering has emerged as an advanced strategy to regenerate various tissues using different raw materials, and thus it is desired to develop more approaches to fabricate tissue engineering scaffolds to fit specific yet very useful raw materials such as biodegradable aliphatic polyester like poly (lactide-co-glycolide) (PLGA). Herein, a technique of ‘wet 3D printing’ was developed based on a pneumatic extrusion three-dimensional (3D) printer after we introduced a solidification bath into a 3D printing system to fabricate porous scaffolds. The room-temperature deposition modeling of polymeric solutions enabled by our wet 3D printing method is particularly meaningful for aliphatic polyester, which otherwise degrades at high temperature in classic fuse deposition modeling. As demonstration, we fabricated a bilayered porous scaffold consisted of PLGA and its mixture with hydroxyapatite for regeneration of articular cartilage and subchondral bone. Long-term in vitro and in vivo degradation tests of the scaffolds were carried out up to 36 weeks, which support the three-stage degradation process of the polyester porous scaffold and suggest faster degradation in vivo than in vitro. Animal experiments in a rabbit model of articular cartilage injury were conducted. The efficacy of the scaffolds in cartilage regeneration was verified through histological analysis, micro-computed tomography (CT) and biomechanical tests, and the influence of scaffold structures (bilayer versus single layer) on in vivo tissue regeneration was examined. This study has illustrated that the wet 3D printing is an alternative approach to biofabricate tissue engineering porous scaffolds based on biodegradable polymers.

Three-Dimensional Printing Methods for Bioceramic-Based Scaffold Fabrication for Craniomaxillofacial Bone Tissue Engineering.

Three-dimensional printing (3DP) technology has revolutionized the field of the use of bioceramics for maxillofacial and periodontal applications, offering unprecedented control over the shape, size, and structure of bioceramic implants. In addition, bioceramics have become attractive materials for these applications due to their biocompatibility, biostability, and favorable mechanical properties. However, despite their advantages, bioceramic implants are still associated with inferior biological performance issues after implantation, such as slow osseointegration, inadequate tissue response, and an increased risk of implant failure. To address these challenges, researchers have been developing strategies to improve the biological performance of 3D-printed bioceramic implants. The purpose of this review is to provide an overview of 3DP techniques and strategies for bioceramic materials designed for bone regeneration. The review also addresses the use and incorporation of active biomolecules in 3D-printed bioceramic constructs to stimulate bone regeneration. By controlling the surface roughness and chemical composition of the implant, the construct can be tailored to promote osseointegration and reduce the risk of adverse tissue reactions. Additionally, growth factors, such as bone morphogenic proteins (rhBMP-2) and pharmacologic agent (dipyridamole), can be incorporated to promote the growth of new bone tissue. Incorporating porosity into bioceramic constructs can improve bone tissue formation and the overall biological response of the implant. As such, employing surface modification, combining with other materials, and incorporating the 3DP workflow can lead to better patient healing outcomes.

Development and Evaluation of Biodegradable Core-Shell Microfibrous and Nanofibrous Scaffolds for Tissue Engineering Applications

Tissue engineering scaffolds as three-dimensional substrates may serve as ideal templates for tissue regeneration by simulating the structure of the extracellular matrix (ECM). Many biodegradable synthetic polymers, either hydrophobic, like Poly-ε-caprolactone (PCL), or hydrophilic, like Poly(Vinyl Alcohol) (PVA), are widely used as candidate bioactive materials for fabricating tissue engineering scaffolds. However, a combination of good cytocompatibility of hydrophilic polymers with good biomechanical performance of hydrophobic polymers could be beneficial for the in vivo performance of the scaffolds. In this study, we aimed to fabricate biodegradable fibrous scaffolds by combining the properties of hydrophobic PCL with those of hydrophilic PVA and evaluate their properties in comparison with pristine PCL scaffolds. Therefore, single-layered PCL scaffolds, sequential tri-layered (PVA/PCL/PVA), and core-shell (PVA as shell and PCL as core) composite scaffolds were developed utilizing the electrospinning technique. The material structural and biomechanical properties of the electrospun scaffolds, before and after their hydrolytic degradation over a seven-month period following storage in phosphate-buffered saline (PBS) at 37 °C, were comprehensively compared. In addition, human embryonic kidney cells (HEK-293) were cultured on the scaffolds to investigate potential cell attachment, infiltration, and proliferation. The results demonstrated the long-term efficacy of core-shell biodegradable fibrous scaffolds in comparison to single-layers PCL and tri-layers PVA/PCL/PVA, not only due to its superior morphological characteristics and mechanical properties, but also due to its ability to promote homogeneous cell distribution and proliferation, without any external chemical or physical stimuli.Graphical

Biomimetic hydroxyapatite and strontium-doped derivatives from crab shells and their ingenious scaffold fabrication for bone tissue engineering

The success of the most commonly used bio-ceramics in current medicine, hydroxyapatite (HAp), is due to its similar chemical and structural properties with the human bone tissue. The current research aims to calcine crab shells, a bio-waste source, to synthesize HAp, and dope it with strontium (Sr) to use it as a sustainable and economical source for bone tissue engineering. Different temperatures (900°, 1000°, and 1100 °C) were used for the calcination process. FE-SEM analysis showed the importance of temperature for morphology. The variance in the Ca/P ratio was revealed by EDX analysis. The higher the calcination temperature, the more pronounced were the peaks of HAp and (β-Tricalcium Phosphate) β-TCP were revealed by X-Ray Diffraction (XRD) analysis. Moreover, as the concentration of Sr2+ increased, both the crystallite size and crystallinity index (CI) of HAp decreased, as confirmed by XRD analysis. ATR-FTIR analysis showed the best-defined bond types (O-H, P-O, etc.). TGA and DSC analysis revealed the loss of adsorbed water and the appearance of endothermic peaks, respectively. To create a possible bone transplant substitute, scaffolds from HAp and strontium-doped HAp (Sr-HAp) were prepared utilising the foam replica method. At a Sr2+ doping of 1% (w/w) and a calcination temperature of 1100 °C, the highest percent cell viability was obtained, as determined by the MTT test. These results indicate that the concentration of the dopant (Sr2+) have a significant influence on the properties of the final material suitable for bone regeneration in situ.

MXene and Xene: promising frontier beyond graphene in tissue engineering and regenerative medicine.

The emergence of 2D nanomaterials (2D NMs), which was initiated by the isolation of graphene (G) in 2004, revolutionized various biomedical applications, including bioimaging and -sensing, drug delivery, and tissue engineering, owing to their unique physicochemical and biological properties. Building on the success of G, a novel class of monoelemental 2D NMs, known as Xenes, has recently emerged, offering distinct advantages in the fields of tissue engineering and regenerative medicine. In this review, we focus on the comparison of G and Xene materials for use in fabricating tissue engineering scaffolds. After a brief introduction to the basic physicochemical properties of these materials, recent representative studies are classified in terms of the engineered tissue, i.e., bone, cartilage, neural, muscle, and skin tissues. We analyze several methods of improving the clinical potential of Xene-laden scaffolds using state-of-the-art fabrication technologies and innovative biomaterials. Despite the considerable advantages of Xene materials, critical concerns, such as biocompatibility, biodistribution and regulatory challenges, should be considered. This review and collaborative efforts should advance the field of Xene-based tissue engineering and enable innovative, effective solutions for use in future tissue regeneration.

Scaffold fabrication for tissue engineering based on radiation copolymerization of polymer blends: (I) Zein/poly (vinyl butyral) blends

AbstractThe main objective of this work is to fabricate scaffold material for tissue engineering and using Vero (monkey kidney cells)/Paulownia tomentosa cells as model cells. For this objective, copolymer blends of poly(vinyl butyral) (PVB) and Zein, the main constituent, have been fabricated as thin films. Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and x‐ray diffraction (XRD) were used to characterize the copolymer blends. The findings showed that Zein component degradation caused the gel fraction percentage to decrease with higher irradiation doses. Zein's thermal characteristics are also decreased by the addition of PVB polymer, but they are improved by irradiation to 10 kGy through promoting phase adhesion and the generation of free radicals at boundary surfaces. Vero (Monkey kidney) cells proliferate more rapidly in the blend Zein/PVB (85/15%) irradiated to 45 kGy than in the unirradiated one. On the other hand, the Paulownia tomentosa cells proliferation was died.Highlights Copolymer blends of Zein and PVB were prepared by gamma irradiation. The copolymers were fabricated as scaffold material for tissue engineering using monkey kidney cells. PVB and Zein copolymer were characterized by FT‐IR, SEM, DSC, and XRD. The Zein/PVB (85/15%)—45 kGy has monkey kidney cells proliferation better than unirradiated one.

Feasibility of caffeic acid as a crosslinking agent in modifying acellular extracellular matrices

Acellular extracellular matrices (aECM) are commonly utilized, both experimentally and clinically, in the regenerative medicine field. However, some disadvantages such as rapid degradation, poor mechanical properties, chronic inflammatory reactions and low antioxidant activity have limited their further application. In this study the feasibility of caffeic acid as a crosslinking agent in fixing small intestinal submucosa (SIS) was evaluated. The ninhydrin assay, swelling ratio and FTIR spectra indicated that caffeic acid can efficiently react with free amino groups to crosslink SIS and the highest crosslinking index reached 21.60 ± 1.37%. Moreover, the shrinkage temperature of SIS remarkably increased from 59 °C to about 80 °C and the degradation rate of CA-SIS was all lower than 6%, demonstrating their improved biostability and hydrothermal stability. Importantly, the antioxidant activity of CA-SIS ranged from 55% to 90%, statistically higher than that of native SIS (37.33 ± 2.94%). Additionally the cytotoxicity test presented that the cytotoxicity grade of CA-SIS was 1 or 0, whilst large numbers of living HUVECs were attached to the surface of the material and exhibited high cell viability. These results indicated their excellent cytocompatibility. The data of subcutaneous implant displayed that the number of inflammatory cells in 2%- and 2.5%CA-SIS groups remained at a low level (below 100 cells/field) while that of the native SIS group continued increasing, finally reaching 142.33 ± 30.92 cells/field. In conclusion, caffeic acid is a promising candidate for modifying aECM and may play a vital role in the design and fabrication of tissue engineering scaffolds.

3D Printing Type 1 Bovine Collagen Scaffolds for Tissue Engineering Applications-Physicochemical Characterization and In Vitro Evaluation.

Collagen, an abundant extracellular matrix protein, has shown hemostatic, chemotactic, and cell adhesive characteristics, making it an attractive choice for the fabrication of tissue engineering scaffolds. The aim of this study was to synthesize a fibrillar colloidal gel from Type 1 bovine collagen, as well as three dimensionally (3D) print scaffolds with engineered pore architectures. 3D-printed scaffolds were also subjected to post-processing through chemical crosslinking (in N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide) and lyophilization. The scaffolds were physicochemically characterized through Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis, Differential Scanning Calorimetry, and mechanical (tensile) testing. In vitro experiments using Presto Blue and Alkaline Phosphatase assays were conducted to assess cellular viability and the scaffolds' ability to promote cellular proliferation and differentiation. Rheological analysis indicated shear thinning capabilities in the collagen gels. Crosslinked and lyophilized 3D-printed scaffolds were thermally stable at 37 °C and did not show signs of denaturation, although crosslinking resulted in poor mechanical strength. PB and ALP assays showed no signs of cytotoxicity as a result of crosslinking. Fibrillar collagen was successfully formulated into a colloidal gel for extrusion through a direct inkjet writing printer. 3D-printed scaffolds promoted cellular attachment and proliferation, making them a promising material for customized, patient-specific tissue regenerative applications.

A novel eco-friendly abrasive media based abrasive flow machining of 3D printed PLA parts using IGWO and ANN

PurposeThree-dimensional (3D) printed parts usually have poor surface quality due to layer manufacturing’s “stair casing/stair-stepping”. So post-processing is typically needed to enhance its capabilities to be used in closed tolerance applications. This study aims to examine abrasive flow finishing for 3D printed polylactic acid (PLA) parts.Design/methodology/approachA new eco-friendly abrasive flow machining media (EFAFM) was developed, using paper pulp as a base material, waste vegetable oil as a liquid synthesizer and natural additives such as glycine to finish 3D printed parts. Characterization of the media was conducted through thermogravimetric analysis and Fourier transform infrared spectroscopy. PLA crescent prism parts were produced via fused deposition modelling (FDM) and finished using AFM, with experiments designed using central composite design (CCD). The impact of process parameters, including media viscosity, extrusion pressure, layer thickness and finishing time, on percentage improvement in surface roughness (%ΔRa) and material removal rate were analysed. Artificial neural network (ANN) and improved grey wolf optimizer (IGWO) were used for data modelling and optimization, respectively.FindingsThe abrasive media developed was effective for finishing FDM printed parts using AFM, with SEM images and 3D surface profile showing a significant improvement in surface topography. Optimal solutions were obtained using the ANN-IGWO approach. EFAFM was found to be a promising method for improving finishing quality on FDM 3D printed parts.Research limitations/implicationsThe present study is focused on finishing FDM printed crescent prism parts using AFM. Future research may be done on more complex shapes and could explore the impact of different materials, such as thermoplastics and composites for different applications. Also, implication of other techniques, such as chemical vapour smoothing, mechanical polishing may be explored.Practical implicationsIn the biomedical field, the use of 3D printing has revolutionized the way in which medical devices, implants and prosthetics are designed and manufactured. The biodegradable and biocompatible properties of PLA make it an ideal material for use in biomedical applications, such as the fabrication of surgical guides, dental models and tissue engineering scaffolds. The ability to finish PLA 3D printed parts using AFM can improve their biocompatibility, making them more suitable for use in the human body. The improved surface quality of 3D printed parts can also facilitate their sterilization, which is critical in the biomedical field.Social implicationsThe use of eco-friendly abrasive flow finishing for 3D printed parts can have a positive impact on the environment by reducing waste and promoting sustainable manufacturing practices. Additionally, it can improve the quality and functionality of 3D printed products, leading to better performance and longer lifespans. This can have broader economic and societal benefits.Originality/valueThis AFM media constituents are paper pulp, waste vegetable oil, silicon carbide as abrasive and the mixture of “Aloe Barbadensis Mill” – “Cyamopsis Tetragonoloba” powder and glycine. This media was then used to finish 3D printed PLA crescent prism parts. The study also used an IGWO to optimize experimental data that had been modelled using an ANN.

Magnesium-Rich Calcium Phosphate Derived from Tilapia Bone Has Superior Osteogenic Potential.

We extracted magnesium-rich calcium phosphate bioceramics from tilapia bone using a gradient thermal treatment approach and investigated their chemical and physicochemical properties. X-ray diffraction showed that tilapia fish bone-derived hydroxyapatite (FHA) was generated through the first stage of thermal processing at 600-800 °C. Using FHA as a precursor, fish bone biphasic calcium phosphate (FBCP) was produced after the second stage of thermal processing at 900-1200 °C. The beta-tricalcium phosphate content in the FBCP increased with an increasing calcination temperature. The fact that the lattice spacing of the FHA and FBCP was smaller than that of commercial hydroxyapatite (CHA) suggests that Mg-substituted calcium phosphate was produced via the gradient thermal treatment. Both the FHA and FBCP contained considerable quantities of magnesium, with the FHA having a higher concentration. In addition, the FHA and FBCP, particularly the FBCP, degraded faster than the CHA. After one day of degradation, both the FHA and FBCP released Mg2+, with cumulative amounts of 4.38 mg/L and 0.58 mg/L, respectively. Furthermore, the FHA and FBCP demonstrated superior bone-like apatite formation; they are non-toxic and exhibit better osteoconductive activity than the CHA. In light of our findings, bioceramics originating from tilapia bone appear to be promising in biomedical applications such as fabricating tissue engineering scaffolds.

3D Bioprinting of a Bioactive Composite Scaffold for Cell Delivery in Periodontal Tissue Regeneration.

Hydrogels have been widely applied to the fabrication of tissue engineering scaffolds via three-dimensional (3D) bioprinting because of their extracellular matrix-like properties, capacity for living cell encapsulation, and shapeable customization depending on the defect shape. However, the current hydrogel scaffolds show limited regeneration activity, especially in the application of periodontal tissue regeneration. In this study, we attempted to develop a novel multi-component hydrogel that possesses good biological activity, can wrap living cells for 3D bioprinting and can regenerate periodontal soft and hard tissue. The multi-component hydrogel consisted of gelatin methacryloyl (GelMA), sodium alginate (SA) and bioactive glass microsphere (BGM), which was first processed into hydrogel scaffolds by cell-free 3D printing to evaluate its printability and in vitro biological performances. The cell-free 3D-printed scaffolds showed uniform porous structures and good swelling capability. The BGM-loaded scaffold exhibited good biocompatibility, enhanced osteogenic differentiation, apatite formation abilities and desired mechanical strength. The composite hydrogel was further applied as a bio-ink to load with mouse bone marrow mesenchymal stem cells (mBMSCs) and growth factors (BMP2 and PDGF) for the fabrication of a scaffold for periodontal tissue regeneration. The cell wrapped in the hydrogel still maintained good cellular vitality after 3D bioprinting and showed enhanced osteogenic differentiation and soft tissue repair capabilities in BMP2- and PDGF-loaded scaffolds. It was noted that after transplantation of the cell- and growth factor-laden scaffolds in Beagle dog periodontal defects, significant regeneration of gingival tissue, periodontal ligament, and alveolar bone was detected. Importantly, a reconstructed periodontal structure was established in the treatment group eight weeks post-transplantation of the scaffolds containing the cell and growth factors. In conclusion, we developed a bioactive composite bio-ink for the fabrication of scaffolds applicable for the reconstruction and regeneration of periodontal tissue defects.

3D Printed Hierarchical Porous Poly(ε-caprolactone) Scaffolds from Pickering High Internal Phase Emulsion Templating.

In the realm of biomaterials, particularly bone tissue engineering, there has been a great increase in interest in scaffolds with hierarchical porosity and customizable multifunctionality. Recently, the three-dimensional (3D) printing of biopolymer-based inks (solutions or emulsions) has gained high popularity for fabricating tissue engineering scaffolds, which optimally satisfies the desired properties and performances. Herein, therefore, we explore the fabrication of 3D printed hierarchical porous scaffolds of poly(ε-caprolactone) (PCL) using the water-in-oil (w/o) Pickering PCL high internal phase emulsions (HIPEs) as the ink in 3D printer. The Pickering PCL HIPEs stabilized using hydrophobically modified nanoclay comprised of aqueous poly(vinyl alcohol) (PVA) as the dispersed phase. Rheological measurements suggested the shear thinning behavior of Pickering HIPEs having a dispersed droplet diameter of 3-25 μm. The pore morphology resembling the natural extracellular matrix and the mechanical properties of scaffolds were customized by tuning the emulsion composition and 3D printing parameters. In vitro biomineralization and drug release studies proved the scaffolds' potential in developing the apatite-rich bioactive interphase and controlled drug delivery, respectively. During in vitro osteoblast (MG63) growth experiments for up to 7 days, good adhesion and proliferation on PCL scaffolds confirmed their cytocompatibility, assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) analysis. This study suggests that the assembly of HIPE templates and 3D printing is a promising approach to creating hierarchical porous scaffolds potentially suitable for bone tissue engineering and can be stretched to other biopolymers as well.

Current Concepts and Methods in Tissue Interface Scaffold Fabrication.

Damage caused by disease or trauma often leads to multi-tissue damage which is both painful and expensive for the patient. Despite the common occurrence of such injuries, reconstruction can be incredibly challenging and often may focus on a single tissue, which has been damaged to a greater extent, rather than the environment as a whole. Tissue engineering offers an approach to encourage repair, replacement, and regeneration using scaffolds, biomaterials and bioactive factors. However, there are many advantages to creating a combined scaffold fabrication method approach that incorporates the treatment and regeneration of multiple tissue types simultaneously. This review provides a guide to combining multiple tissue-engineered scaffold fabrication methods to span several tissue types concurrently. Briefly, a background in the healing and composition of typical tissues targeted in scaffold fabrication is provided. Then, common tissue-engineered scaffold fabrication methods are highlighted, specifically focusing on porosity, mechanical integrity, and practicality for clinical application. Finally, an overview of commonly used scaffold biomaterials and additives is provided, and current research in combining multiple scaffold fabrication techniques is discussed. Overall, this review will serve to bridge the critical gap in knowledge pertaining to combining different fabrication methods for tissue regeneration without disrupting structural integrity and biomaterial properties.

Synergistic effect of type and concentration of surfactant and diluting solvent on the morphology of emulsion templated matrices developed as tissue engineering scaffolds

Emulsion templating is an advantageous route for the fabrication of tissue engineering scaffolds. Emulsions are mostly stabilised using surfactants, and the performances of the surfactants depend on various parameters such as emulsification temperature and the presence of the electrolytes. In this study, we suggest that diluting solvent type also has a dramatic impact on the efficiency of the surfactant and morphology of the polymerised emulsions. For this, morphologies of polycaprolactone methacrylate-based polymerised emulsions, which are designed for tissue engineering applications and in vitro biocompatibilities, were shown by our group, prepared using four different surfactants, and three different solvents were investigated. Results showed that the diluting solvent used in the emulsion composition has a strong impact on the performance of the surfactant and consequently on the morphology of polymerised emulsions. Increasing surfactant concentration and diluting solvent volume have an opposite impact on the characteristics of emulsions. Scaffolds with average pore sizes changing from 10 to 78 μm could be fabricated. Establishing these relations enables us to have control over the overall morphology of polymerised emulsions and precisely engineer them for specific tissue engineering applications by tuning solvent and surfactant type and concentration.

3D Printing GelMA/PVA Interpenetrating Polymer Networks Scaffolds Mediated with CuO Nanoparticles for Angiogenesis.

Biocompatible hydrogels have been considered one of the most well-known and promising in various materials used in the fabrication of tissue-engineering scaffolds. Although considerable progress has been made in recent decades, many limitations remain, such as poor mechanical and degradation properties of biomaterials. In addition, vascularization of tissue-engineering scaffold is an enduring challenge, which limited the fabrication and application of scaffold with clinically relevant dimension. To cover these challenges, in this work, a novel nanocomposite interpenetrating polymer networks (IPN) hydrogel scaffold consists of methacrylated gelatin (GelMA), poly(vinyl alcohol) (PVA), and copper oxide nanoparticles (CuONPs) is fabricated by extrusion-based 3D printing. A series of physiochemical and biological characterizations of the nanocomposite GelMA/PVA scaffolds are performed. Results showed that the mechanical and degradation properties of the nanocomposite GelMA/PVA scaffolds are obviously improved compared to GelMA scaffolds with single network. In vitro cell experiments and chick embryo angiogenesis (CEA) assay confirmed good cytocompatibility of the fabricated scaffold and its potential to promote cell migration and angiogenesis. In conclusion, altogether the results demonstrated that GelMA/PVA IPN scaffolds modified with CuONPs have great potential for fabrication of volumetric scaffolds and promote angiogenesis during tissue growth and repair.

Microenvironmentally optimized 3D-printed TGFβ-functionalized scaffolds facilitate endogenous cartilage regeneration in sheep

Clinically, microfracture is the most commonly applied surgical technique for cartilage defects. However, an increasing number of studies have shown that the clinical improvement remains questionable, and the reason remains unclear. Notably, recent discoveries revealed that signals from regenerated niches play a critical role in determining mesenchymal stem cell fate specification and differentiation. We speculate that a microenvironmentally optimized scaffold that directs mesenchymal stem cell fate will be a good therapeutic strategy for cartilage repair. Therefore, we first explored the deficiency of microfractures in cartilage repair. The microfracture not only induced inflammatory cell aggregation in blood clots but also consisted of loose granulation tissue with increased levels of proteins related to fibrogenesis. We then fabricated a functional cartilage scaffold using two strong bioactive cues, transforming growth factor-β3 and decellularized cartilage extracellular matrix, to modulate the cell fate of mesenchymal stem cells. Additionally, poly(ε-caprolactone) was also coprinted with extracellular matrix-based bioinks to provide early mechanical support. The in vitro studies showed that microenvironmentally optimized scaffolds exert powerful effects on modulating the mesenchymal stem cell fate, such as promoting cell migration, proliferation and chondrogenesis. Importantly, this strategy achieved superior regeneration in sheep via scaffolds with biomechanics (restored well-organized collagen orientation) and antiapoptotic properties (cell death-related genes were also downregulated). In summary, this study provides evidence that microenvironmentally optimized scaffolds improve cartilage regeneration in situ by regulating the microenvironment and support further translation in human cartilage repair. Statement of significanceAlthough microfracture (MF)-based treatment for chondral defects has been commonly used, critical gaps exist in understanding the biochemistry of MF-induced repaired tissue. More importantly, the clinically unsatisfactory effects of MF treatment have prompted researchers to focus on tissue engineering scaffolds that may have sufficient therapeutic efficacy. In this manuscript, a 3D printing ink containing cartilage tissue-specific extracellular matrix (ECM), methacrylate gelatin (GelMA), and transforming growth factor-β3 (TGF-β3)-embedded polylactic-coglycolic acid (PLGA) microspheres was coprinted with poly(ε-caprolactone) (PCL) to fabricate tissue engineering scaffolds for chondral defect repair. The sustained release of TGF-β3 from scaffolds successfully directed endogenous stem/progenitor cell migration and differentiation. This microenvironmentally optimized scaffold produced improved tissue repair outcomes in the sheep animal model, explicitly guiding more organized neotissue formation and therefore recapitulating the anisotropic structure of native articular cartilage. We hypothesized that the cell-free scaffolds might improve the clinical applicability and become a new therapeutic option for chondral defect repair.

Tissue engineered scaffold fabrication methods for medical applications

Donor shortage for organ transplantations is a major clinical challenge worldwide. Potential risks inevitably encountered with traditional methods include complications, secondary injuries, and, most importantly, limited donor sources. Today, researchers from multiple disciplinary areas, including biomaterials, biology, and nanotechnology in tissue engineering, attempt to bio-fabricate virtually every human tissue or organ. Tissue engineering techniques generally require the use of a porous scaffold, which serves as a three-dimensional template for initial cell attachment and subsequent tissue formation both in vitro and in vivo. The scaffold provides the necessary support for cells to attach, grow, proliferate, and maintain their differentiated function. This article represents a concise summary of different procedures for fabricating sponge-like and fibrous scaffolds using a variety of technologies. First, we will discuss different approaches that allow us to create fibers, which have long been recognized as the primary constituent in 3D scaffolds. These methods include electrospinning and microfluidic-based methods, among others. Following that, the various techniques for fabricating 3D scaffolds, ranging from simple to complex structures, as well as evaluating their advantages and disadvantages, will be explored.

A Review: Textile Technologies for Single and Multi‐Layer Tubular Soft Tissue Engineering

AbstractIn cell‐free scaffold tissue engineering (TE), an essential prerequisite is the scaffold design to promote cellular activities and tissue formation. The success is greatly dependent upon the nature of the scaffold including the composition, topography, and mechanical performance. Recent TE approaches use textile technologies to create biomimetic and functional scaffolds similar to the extracellular matrix (ECM). The hierarchical architecture of fiber to yarn to fabric allows precise size‐to‐scale design. Moreover, textile technologies offer a high degree of manufacturing precision, reproducibility, and potential industrial scalability. Although research in industry and academia has increased significantly over the past years, current fibrous scaffold designs don't fully exploit the potential and diversity of yarn and fabric structures. This review emphasizes hollow tubular textile‐based scaffolds that aim to replace vasculature and respiratory tissues. The different techniques, that is, electrospinning, weaving, knitting, and braiding are discussed and the effect of the fiber, yarn, and fabric assembly is highlighted. The design of multi‐layer hybrid structures, combining conventional textile techniques and electrospinning can address current challenges. Prospects of structural design in TE scaffold fabrication can anticipate profiled fibers, and complex pattern designs to fully exploit the potential of textile technologies for tissue‐engineered scaffolds.

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.