Scaffolds For Tissue Engineering 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.

Development of a bacterial cellulose-gelatin composite as a suitable scaffold for cardiac tissue engineering.

Cardiac tissue engineering is suggested as a promising approach to overcome problems associated with impaired myocardium. This is the first study to investigate the use of BC and gelatin for cardiomyocyte adhesion and growth. Bacterial cellulose (BC) membranes were produced by Komagataeibacter xylinus and coated or mixed with gelatin to make gelatin-coated BC (BCG) or gelatin-mixed BC (mBCG) scaffolds, respectively. BC based-scaffolds were characterized via SEM, FTIR, XRD, and AFM. Neonatal rat-ventricular cardiomyocytes (nr-vCMCs) were cultured on the scaffolds to check the capability of the composites for cardiomyocyte attachment, growth and expansion. The average nanofibrils diameter in all scaffolds was suitable (~ 30-65nm) for nr-vCMCs culture. Pore diameter (≥ 10µm), surface roughness (~ 182nm), elastic modulus (0.075 ± 0.015MPa) in mBCG were in accordance with cardiomyocyte requirements, so that mBCG could better support attachment of nr-vCMCs with high concentration of gelatin, and appropriate surface roughness. Also, it could better support growth and expansion of nr-vCMCs due to submicron scale of nanofibrils and proper elasticity (~ 0.075MPa). The viability of nr-vCMCs on BC and BCG scaffolds was very low even at day 2 of culture (~ ≤ 40%), but, mBCG could promote a metabolic active state of nr-vCMCs until day 7 (~ ≥ 50%). According to our results, mBCG scaffold was the most suitable composite for cardiomyocyte culture, regarding its physicochemical and cell characteristics. It is suggested that improvement in mBCG stability and cell attachment features may provide a convenient scaffold for cardiac tissue engineering.

Decellularization and characterization of camel pericardium as a new scaffold for tissue engineering and regenerative medicine.

Valvular heart diseases (VHDs) have become prevalent in populations due to aging. Application of different biomaterials for cardiac valve regeneration and repair holds a great promise for treatment of VHD. Aortic valve replacement using tissue-engineered xenografts is a considered approach, and the pericardium of different species such as porcine and bovine has been studied over the last few years. It has been suggested that the animal origin can affect the outcomes of replacement. So, herein, we at first decellularized and characterized the camel pericardium (dCP), then characterized dCP with H&E staining, in vitro and in vivo biocompatibility and mechanical tests and compared it with decellularized bovine pericardium (dBP), to describe the potency of dCP as a new xenograft and bio scaffold. The histological assays indicated less decluttering and extracellular matrix damage in dCP after decellularization compared to the dBP also dCP had higher Young Modulus (105.11), and yield stress (1.57 ± 0.45). We observed more blood vessels and also less inflammatory cells in the dCP sections after implantation. In conclusion, the results of this study showed that the dCP has good capabilities not only for use in VHD treatment but also for other applications in tissue engineering and regenerative medicine.

Cadherin Expression is Regulated by Mechanical Phenotypes of Fibroblasts in the Perivascular Matrix.

The influence of mechanical forces generated by stromal cells in the perivascular matrix is thought to be a key regulator in controlling blood vessel growth. Cadherins are mechanosensors that facilitate and maintain cell-cell interactions and blood vessel integrity, but little is known about how stromal cells regulate cadherin signaling in the vasculature. Our objective was to investigate the relationship between mechanical phenotypes of stromal cells with cadherin expression in 3D tissue engineering models of vascular growth. Stromal cell lines were subjected to a bead displacement assay to track matrix distortions and characterize mechanical phenotypes in 3D microtissue models. These cells included human ventricular cardiac (NHCF), dermal (NHDF), lung (NHLF), breast cancer-associated (CAF), and normal breast fibroblasts (NBF). Cells were embedded in a fibrin matrix (10mg/mL) with fluorescent tracker beads; images were collected every 30min. We also studied endothelial cells (ECs) in co-culture with mechanically-active or -inactive stromal cells and quantified N-Cad, OB-Cad, and VE-Cad expression using immunofluorescence. Bead displacement studies identified mechanically-active stromal cells (CAFs, NHCFs, NHDFs) that generate matrix distortions and mechanically-inactive cells (NHLFs, NBFs). Compared to ECs only, CAFs + ECs as well as NBFs + ECs in 3D co-culture significantly decreased expression of VE-Cad; in addition, the Pearson's Correlation Coefficient for N-Cad and VE-Cad showed a strong correlation (>0.7), suggesting cadherin colocalization. Using a microtissue model, we demonstrated that mechanical phenotypes associated with increased matrix deformations correspond to enhanced angiogenic growth. The results could suggest a mechanism to control tight junction regulation in developing vascular beds for tissue engineering scaffolds or understanding vascular growth during developmental processes. Our studies provide novel data for how mechanical phenotype of stromal cells in combination with secreted factor profiles is related to cadherin regulation, localization, and vascularization potential in 3D microtissue models.

Device Design and Advanced Computed Tomography of 3D Printed Radiopaque Composite Scaffolds and Meniscus

Abstract3D‐printed biomaterial implants are revolutionizing personalized medicine for tissue repair, especially in orthopedics. In this study, a radiopaque bismuth oxide (Bi2O3) doped polycaprolactone (PCL) composite is developed and implemented to enable the use of diagnostic X‐ray technologies, especially spectral photon counting X‐ray computed tomography (SPCCT), for comprehensive tissue engineering scaffold (TES) monitoring. PCL filament with homogeneous Bi2O3 nanoparticle (NP) dispersion (0.8 to 11.7 wt%) is first fabricated. TES are then 3D printed with the composite filament, optimizing printing parameters for small features and severely overhung geometries. These composite TES are characterized via micro‐computed tomography (µCT), tensile testing, and a cytocompatibility study, with 2 wt% Bi2O3 NPs providing improved tensile properties, equivalent cytocompatibility to neat PCL, and excellent radiographic distinguishability. Radiographic performance is validated in situ by imaging 4 and 7 wt% Bi2O3 doped PCL TES in a mouse model with µCT, showing excellent agreement with in vitro measurements. Subsequently, CT image‐derived swine menisci are 3D printed with composite filament and re‐implanted in corresponding swine legs ex vivo. Re‐imaging the swine legs via clinical CT allows facile identification of device location and alignment. Finally, the emergent technology of SPCCT unambiguously distinguishes the implanted meniscus in situ via color K‐edge imaging.

Thickening tissue by thinning electrospun scaffolds for skeletal muscle tissue engineering

AbstractElectrospun scaffolds with aligned fiber orientation are widely used in tissue engineering, such as muscle, heart, nerve, tendon, and cartilage, due to their ability to guide cell morphology and induce cellular functions. However, the dense fibrous structure of the scaffolds poses a critical obstacle to engineering highly cellular and thick 3D tissues, as it prevents cell infiltration. While many techniques have been developed to increase the pore size of electrospun scaffolds and improve cell infiltration/migration, it often leads to a decrease in direct cell‐cell contact, compromising cell differentiation and tissue maturation. This study presents an alternative approach by reducing the thickness of scaffolds to the cellular scale and stacking or rolling the cell‐scaffold complex into 3D constructs. We devise a series of novel tools to fabricate, characterize, and manipulate ultra‐thin electrospun scaffolds, which demonstrate high reproducibility, resolution, and cellularity. Our study provides a solution to the cell infiltration issue in muscle tissue engineering and is highly versatile, and can be applied to various fields that require structures with high‐resolution gradients in a layered pattern or complex spatial distribution in a rolled pattern.

Tissue Engineering Scaffolds for Dentin-Pulp Complex Regeneration

Tissue Engineering Scaffolds for Dentin-Pulp Complex Regeneration

A Biomimetic Fibrous Composite Scaffold with Nanotopography-Regulated Mineralization for Bone Defect Repair.

The effective regeneration of large bone defects via bone tissue engineering is challenging due to the difficulty in creating an osteogenic microenvironment. Inspired by the fibrillar architecture of the natural extracellular matrix, we developed a nanoscale bioengineering strategy to produce bone fibril-like composite scaffolds with enhanced osteogenic capability. To activate the surface for biofunctionalization, self-adaptive ridge-like nanolamellae were constructed on poly(ε-caprolactone) (PCL) electrospinning scaffolds via surface-directed epitaxial crystallization. This unique nanotopography with a markedly increased specific surface area offered abundant nucleation sites for Ca2+ recruitment, leading to a 5-fold greater deposition weight of hydroxyapatite than that of the pristine PCL scaffold under stimulated physiological conditions. Bone marrow mesenchymal stem cells (BMSCs) cultured on bone fibril-like scaffolds exhibited enhanced adhesion, proliferation, and osteogenic differentiation in vitro. In a rat calvarial defect model, the bone fibril-like scaffold significantly accelerated bone regeneration, as evidenced by micro-CT, histological histological and immunofluorescence staining. This work provides the way for recapitulating the osteogenic microenvironment in tissue-engineered scaffolds for bone repair.

Chitosan-incorporated Bioceramic-based Nanomaterials for Localized Release of Therapeutics and Bone Regeneration: An Overview of Recent Advances and Progresses

Abstract: The usage of nanoparticles in tissue engineering applications has increased significantly in the last several years. Functional tissues are developed by regulating cell proliferation, differentiation, and migration on nanostructured scaffolds containing cells. These scaffolds provide an environment that is more structurally supportive than the microarchitecture of natural bone. Given its exceptional properties, such as its osteogenic potential, biocompatibility, and biodegradability, chitosan is a good and promising biomaterial. Unfortunately, chitosan's low mechanical strength makes it unsuitable for load-bearing applications. By mixing chitosan with other biomaterials, this drawback might be mitigated. Bone tissue engineering uses both bioresorbable materials like tricalcium phosphate and bioactive materials like hydroxyapatite and bioglass. Alumina and titanium are examples of bioinert materials that are part of these bioceramics. When produced at nanoscale scales, these materials have a larger surface area and better cell adhesion. This review paper will go into great detail on the bioinert, bioresorbable, and bioactive nanoceramics-reinforced chitosan scaffolds for bone tissue engineering.

Engineering Cell Instructive Microenvironments for In Vitro Replication of Functional Barrier Organs.

Multicellular organisms exhibit synergistic effects among their components, giving rise to emergent properties crucial for their genesis and overall functionality and survival. Morphogenesis involves and relies upon intricate and biunivocal interactions among cells and their environment, that is, the extracellular matrix (ECM). Cells secrete their own ECM, which in turn, regulates their morphogenetic program by controlling time and space presentation of matricellular signals. The ECM, once considered passive, is now recognized as an informative space where both biochemical and biophysical signals are tightly orchestrated. Replicating this sophisticated and highly interconnected informative media in a synthetic scaffold for tissue engineering is unattainable with current technology and this limits the capability to engineer functional human organs in vitro and in vivo. This review explores current limitations to in vitro organ morphogenesis, emphasizing the interplay of gene regulatory networks, mechanical factors, and tissue microenvironment cues. In vitro efforts to replicate biological processes for barrier organs such as the lung and intestine, are examined. The importance of maintaining cells within their native microenvironmental context is highlighted to accurately replicate organ-specific properties. The review underscores the necessity for microphysiological systems that faithfully reproduce cell-native interactions, for advancing the understanding of developmental disorders and disease progression.

Scaffold-based microsphere in drug delivery system

Microspheres are free-flowing powders having a synthetic and natural polymer. A targeted drug delivery system can overcome some of the problems of conventional therapy and enhance the therapeutic efficacy of the drug. This is a biodegradable and non-biodegradable efficacy of a given drug. There are various approaches to delivering a therapeutic substance to the target site in a sustained controlled release fashion. One approach is a scaffold-based microsphere for drug delivery, where the target site is very specific if modified, and the proper concentration is maintained at the site of interest without causing toxic effects. Microspheres received much attention not only for control release but also in drug targeting for example in anticancer therapy. Moreover, the joining of medications (i.e., incendiary inhibitors and additionally anti-microbial) into platforms might be utilized to forestall contamination after medical procedures and other infections for the longer term. The framework additionally can be utilized to give sufficient signs to the cells, to initiate and keep them in their coveted separation organization, and to keep up their survival and development. The present survey gives an itemized record of the requirement for the advancement of frameworks alongside the materials utilized and systems embraced to fabricate platforms for tissue designing and delay. The present review gives a detailed account of the need for the development of scaffolds along with the materials used and techniques adopted to manufacture scaffolds for tissue engineering and microspheres for drug delivery systems.

Quantitative Evaluation of the Pore and Window Sizes of Tissue Engineering Scaffolds on Scanning Electron Microscope Images Using Deep Learning

Quantitative Evaluation of the Pore and Window Sizes of Tissue Engineering Scaffolds on Scanning Electron Microscope Images Using Deep Learning

Can self-powered piezoelectric materials be used to treat disc degeneration by means of electrical stimulation?

Intervertebral disc degeneration (IDD) due to multiple causes is one of the major causes of low back pain (LBP). A variety of traditional treatments and biologic therapies are currently used to delay or even reverse IDD; however, these treatments still have some limitations. Finding safer and more effective treatments is urgent for LBP patients. With increasing reports it has been found that the intervertebral disc (IVD) can convert pressure loads from the spine into electrical stimulation in a variety of ways, and that this electrical stimulation is of great importance in modulating cell behavior, the immune microenvironment and promoting tissue repair. However, when intervertebral disc degeneration occurs, the normal structures within the IVD are destroyed. This eventually leads to a weakening or loss of self-powered. Currently various piezoelectric materials with unique crystal structures can mimic the piezoelectric effect of normal tissues. Based on this, tissue-engineered scaffolds prepared using piezoelectric materials have been widely used for regenerative repair of various types of tissues, however, there are no reports of their use for the treatment of IDD. For this reason, we propose to utilize tissue-engineered scaffolds prepared from piezoelectric biomaterials with excellent biocompatibility and self-powered properties to be implanted into degenerated IVD to help restore cell type and number, restore extracellular matrix, and modulate immune responses. It provides a feasible and novel therapeutic approach for the clinical treatment of IDD.

Low-Temperature Deposited Amorphous Poly(aryl ether ketone) Hierarchically Porous Scaffolds with Strontium-Doped Mineralized Coating for Bone Defect Repair.

In recent years, the demand for clinical bone grafting has increased. As a new solution for orthopedic implants, polyether ether ketone (PEEK, crystalline PAEK) has excellent comprehensive performance and has been practically applied in clinic. In this research, a noteworthy elevated scheme to enhance the performance of PEEK scaffolds was presented. The amorphous aggregated poly (aryl ether ketone) (PAEK) resin was prepared as the matrix material, which maintained high mechanical strength and could be processed through solution. So, the tissue engineering scaffolds with multilevel pores could be printed by low-temperature deposited manufacturing (LDM) to improve biologically inert scaffolds with smooth surfaces. Also, the feature of PAEK's solution processing is profitable to uniformly add the functional components for bone repair. Ultimately, A system of orthopedic implantable PAEK material based on intermolecular interactions, surface topology, and surface modification was established. The specific steps include synthesizing PAEK that contain polar carboxyl structures, preparing bioinks and fabricating scaffolds by LDM, preparation of scaffolds with strontium-doped mineralized coatings, evaluation of their osteogenic properties in vitro and in vivo, and investigation on the effect and mechanism of scaffolds in promoting osteogenic differentiation. This work provides an upgraded system of PAEK implantable materials for clinical application. This article is protected by copyright. All rights reserved.

Challenges in Application: Gelation Strategies of DAT-Based Hydrogel Scaffolds.

Decellularized adipose tissue (DAT) has great clinical applicability, owing to its abundant source material, natural extracellular matrix microenvironment, and nonimmunogenic attributes, rendering it a versatile resource in the realm of tissue engineering. However, practical implementations are confronted with multifarious limitations. Among these, the selection of an appropriate gelation strategy serves as the foundation for adapting to diverse clinical contexts. The cross-linking strategies under varying physical or chemical conditions exert profound influences on the ultimate morphology and therapeutic efficacy of DAT. This review sums up the processes of DAT decellularization and subsequent gelation, with a specific emphasis on the diverse gelation strategies employed in recent experimental applications of DAT. The review expounds upon methodologies, underlying principles, and clinical implications of different gelation strategies, aiming to offer insights and inspiration for the application of DAT in tissue engineering and advance research for tissue engineering scaffold development.

Periapical lesion-derived decellularized extracellular matrix as a potential solution for regenerative endodontics

Abstract Pulp regeneration remains a crucial target in the preservation of natural dentition. Using decellularized extracellular matrix is an appropriate approach to mimic natural microenvironment and facilitate tissue regeneration. In this study, we attempted to obtain decellularized extracellular matrix from periapical lesions (PL-dECM) and evaluate its bioactive effects. The decellularization process yielded translucent and viscous PL-dECM, meeting the standard requirements for decellularization efficiency. Proteomic sequencing revealed that the PL-dECM retained essential extracellular matrix components and numerous bioactive factors. The PL-dECM conditioned medium could enhance the proliferation and migration ability of periapical lesion-derived stem cells (PLDSCs) in a dose-dependent manner. Culturing PLDSCs on PL-dECM slices improved odontogenic/angiogenic ability compared to the type I collagen group. In vivo, the PL-dECM demonstrated a sustained supportive effect on PLDSCs and promoted odontogenic/angiogenic differentiation. Both in vitro and in vivo studies demonstrated that PL-dECM served as an effective scaffold for pulp tissue engineering, providing valuable insights into PLDSCs differentiation. These findings pave avenues for the clinical application of dECM's in situ transplantation for regenerative endodontics.

A Pump-Free Strategy for the Controllable Generation of Alginate Microgels as Cellular Microcarriers.

Microgels are advanced scaffolds for tissue engineering due to their proper biodegradability, good biocompatibility, and high specific surface area for effective oxygen and nutrient transfer. However, most of the current monodispersed microgel fabrication systems rely heavily on various precision pumps, which highly increase the cost and complexity of their downstream application. In this work, we developed a simple and facile system for the controllable generation of uniform alginate microgels by integrating a gas-shearing strategy into a glass microfluidic device. Importantly, the cell-laden microgels can be rapidly prepared in a pump-free manner under an all-aqueous environment. The three-dimensional cultured green fluorescent protein-human A549 cells in alginate microgels exhibited enhanced stemness and drug resistance compared to those under two-dimensional conditions. The pancreatic cancer organoids in alginate microgels exhibited some of the key features of pancreatic cancer. The proposed microgels showed decent monodispersity, biocompatibility, and versatility, providing great opportunities in various biomedical applications such as microcarrier fabricating, organoid engineering, and high-throughput drug screening.

CT-Visible Microspheres Enable Whole-Body In Vivo Tracking of Injectable Tissue Engineering Scaffolds.

Targeted delivery and retention are essential requirements for implantable tissue-engineered products. Non-invasive imaging methods that can confirm location, retention, and biodistribution of transplanted cells attached to implanted tissue engineering scaffolds will be invaluable for the optimization and enhancement of regenerative therapies. To address this need, an injectable tissue engineering scaffold consisting of highly porous microspheres compatible with transplantation of cells is modified to contain the computed tomography (CT) contrast agent barium sulphate (BaSO4). The trackable microspheres show high x-ray absorption, with contrast permitting whole-body tracking. The microspheres are cellularized with GFP+ Luciferase+ mesenchymal stem cells and show in vitro biocompatibility. In vivo, cellularized BaSO4-loaded microspheres are delivered into the hindlimb of mice where they remain viable for 14 days. Co-registration of 3D-bioluminescent imagingand µCT reconstructions enable the assessment of scaffold material and cell co-localization. The trackable microspheres are also compatible with minimally-invasive delivery by ultrasound-guided transthoracic intramyocardial injections in rats. These findings suggest that BaSO4-loaded microspheres can be used as a novel tool for optimizing delivery techniques and tracking persistence and distribution of implanted scaffold materials. Additionally, the microspheres can be cellularized and have the potential to be developed into an injectable tissue-engineered combination product for cardiac regeneration.

Dimensional and Structural Instability of Electrospun Polylactic Acid Membranes in Liquid Environments: Role of Water, Ethanol, and Temperature

AbstractElectrospun nanofibres of polylactic acid (PLA) are suggested for a variety of uses, including scaffolds for tissue engineering, components of drug delivery devices, sustainable packaging materials and membranes for liquid filtration/purification. For all these applications, it is critical to consider the stability of the PLA electrospun materials once in operation. Exposure to certain liquids and temperatures can modify their dimensions, shape, surface topography and mechanical response and compromise their performance. In this study, electrospun PLA mats were exposed to water and ethanol solutions, at different temperatures and for defined time periods, and changes in their properties were analysed. It was found that the impact of water on area shrinkage and fibre arrangement strongly depended on temperature, particularly if the treatment was performed at the glass transition temperature of PLA. Ethanol, instead, induced significant alterations in the size, morphology, and elastic modulus of the electrospun mats, even at room temperature and determined the formation of crimped structures. This work provides insights into the conditions that can critically affect the properties of PLA electrospun fibres and, hence, impact on their usage.

Physical cues of scaffolds promote peripheral nerve regeneration

The effective treatment of long-gap peripheral nerve injury (PNI) remains a challenge in clinical settings. The autograft, the gold standard for the long-gap PNI therapy, has several limitations, including a limited supply of donor nerve, size mismatch between the donor and recipient sites, functional loss at the donor site, neuroma formation, and the requirement for two operations. With the increasing abundance of biocompatible materials with adjustable structures and properties, tissue engineering provides a promising avenue for bridging peripheral nerve gaps and addressing the above issues of autograft. The physical cues provided by tissue engineering scaffolds, essential for regulating the neural cell fate and microenvironments, have received considerable research attention. This review elaborates on three major physical cues of tissue engineering scaffolds for peripheral nerve regeneration: topological structure, mechanical support, and electrical stimulation. These three aspects are analogs to Lego bricks, wherein different combinations result in diverse functions. Innovative and more effective bricks, along with multi-level and all-around integration, are expected to provide new advances in tissue engineering for peripheral nerve generation.