Given the low self-healing capacity of fibrocartilage and hyaline cartilage, tissue engineering holds great promise for the development of new regenerative therapies. However, dedifferentiation of ...cartilage cells during expansion leads to fibrous tissue instead of cartilage. The purpose of our study was to generate 3D microtissues, spheroids, mimicking the characteristics of native fibrocartilage or articular cartilage to use as modular units for implantation in meniscal and articular cartilage lesions, respectively, within the knee joint. A set of parameters was assessed to create spheroids with a geometry compatible with 3D bioprinting for the creation of a biomimetic cartilage construct. Fibrochondrocytes (FC) and articular chondrocytes (AC) spheroids were created using a high-throughput microwell system. Spheroid morphology, viability, proliferation and extracellular matrix were extensively screened. After 2D expansion, FC and AC dedifferentiated, resulting in a loss of cartilage specific extracellular matrix proteins. Spheroid formation did not result in FC redifferentiation, but did lead to redifferentiation of AC, resulting in microtissues displaying collagen II, aggrecan and glycosaminoglycans. This study demonstrates 3D cartilage mimics that could have a potential application in the next generation of Autologous Chondrocyte Implantation procedures. Moreover, spheroids can be used as building blocks to create cartilage constructs by bioprinting in the future.
Hydrogels are interesting as wound dressing for burn wounds to maintain a moist environment. Especially gelatin and alginate based wound dressings show strong potential. Both polymers are modified by ...introducing photocrosslinkable functionalities and combined to hydrogel films (gel‐MA/alg‐MA). In one protocol gel‐MA films are incubated in alg‐MA solutions and crosslinked afterward into double networks. Another protocol involves blending both and subsequent photocrosslinking. The introduction of alginate into the gelatin matrix results in phase separation with polysaccharide microdomains in a protein matrix. Addition of alg(‐MA) to gel‐MA leads to an increased swelling compared to 100% gelatin and similar to the commercial Aquacel Ag dressing. In vitro tests show better cell adhesion for films which have a lower alginate content and also have superior mechanical properties. The hydrogel dressings exhibit good biocompatibility with adaptable cell attachment properties. An adequate gelatin‐alginate ratio should allow application of the materials as wound dressings for several days without tissue ingrowth.
Hydrogels, especially gelatin and alginate are interesting as wound dressing for burn wounds. Both polymers are modified with photocrosslinkable functionalities and combined to hydrogel films by two different protocols. In vitro tests show better cell adhesion for films which have a lower alginate content. The hydrogel dressings exhibit good biocompatibility with adaptable cell attachment properties.
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•The present study aims to investigate the role of enzymatic mineralization on polymeric structures bearing both cationic and anionic groups.•Polyelectrolyte complexes of ulvan and ...chitosan are evaluated as matrices for biomimetic mineralization using ALP.•Successful mineralization by ALP is observed which improved cellular activity.
Polyelectrolyte complexes (PEC) of chitosan and ulvan were fabricated to study alkaline phosphatase (ALP) mediated formation of apatitic minerals. Scaffolds of the PEC were subjected to ALP and successful mineral formation was studied using SEM, Raman and XRD techniques. Investigation of the morphology via SEM shows globular structures of the deposited minerals, which promoted cell attachment, proliferation and extracellular matrix formation. The PEC and their successful calcium phosphate based mineralization offers a greener route of scaffold fabrication towards developing resorbable materials for tissue engineering.
The prominent success of polycaprolactone (PCL) bioengineered fibrous scaffolds has expanded the use of PCL over other polymers in the wide electrospinning literature. Several highly toxic solvent ...systems providing a good PCL solubility-spinability are recurrently applied in the overwhelming majority of studies. One of the current major focuses revolves around the challenging generation of aligned fibers that are very desirable in numerous tissue engineering applications. Moreover, the critical influence of fiber size on cellular performance has led to the use of different solvent systems for the production of specific nano- or micro-sized PCL fibers while neglecting the solvents toxicity. Therefore, our goal is to use the unconventional solvent system acetic acid/formic acid of very low toxicity, recently defined as the system producing ultra-thin PCL fibers, in a trial to outspread the size range and to tackle fiber alignment. After profound analysis of the effect of varying collector motion and collector design on fiber alignment, a novel collector producing highly aligned PCL fibers based on synchronic mechanical and electrical effects is designed. In a subsequent step, the fiber diameter is manipulated by analyzing 3 influential parameters: polymer concentration, tip-to-collector distance and the frequently overlooked parameter humidity. The parameters fine-tuning study has resulted in very broad PCL fiber diameter ranges of 94–1548 nm and 114–1408 nm for random and aligned fibers respectively. PCL fibers properties are also characterized in this study by means of water contact angle (WCA), X-ray photoelectron spectroscopy (XPS) and tensile measurements. Despite the detection of the same surface chemical composition on all fiber conditions, the WCA values tend to decrease with increased fiber diameters, especially for aligned fibers. Moreover, aligning the fibers and decreasing their size is found to lead to considerably enhanced mechanical properties. Overall, it can be concluded that this work represents a picture-perfect reference for the electrospinning of PCL fibers having different orientations, diameters and physico-chemical properties from a benign solvent system.
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•PCL fibers are electrospun using benign solvents: formic acid/acetic acid.•A new collector engendering electro-mechanical effects led to highly aligned fibers.•Electrospun fibers of 94–1548 nm (random) and 114–1408 nm (aligned) are developed.•Mechanical properties increase with decreasing the diameter and aligning the fibers.
This work describes the surface modification of 300PEO-PEOT/PBT 55/45 thin films using a medium pressure dielectric barrier discharge system operated in argon, helium, nitrogen or dry air to improve ...cell-surface interactions of this established biomaterial. The first part of the paper describes the optimization of the plasma processing parameters using water contact angle goniometry. The optimized samples are then characterized for changes in surface topography and surface chemical composition using atomic force microscopy (AFM) and X-ray fluorescence spectroscopy (XPS) respectively. For all plasma treatments, a pronounced increase in surface wettability was observed, of which the extent is dependent on the used plasma discharge gas. Except for dry air, only minor changes in surface topography were noted, while XPS confirmed that the changes in wettability were mainly chemical in nature with the incorporation of 5-10% of extra oxygen as a variety of polar groups. Similarly, for the nitrogen plasma, 3.8% of nitrogen polar groups were additionally incorporated. Human foreskin fibroblast (HFF) in vitro analysis showed that within the first 24 h after cell seeding, the effects on cell-surface interactivity were highly dependent on the used discharge gas, nitrogen plasma treatment being the most efficient. Differences between untreated and plasma-treated samples were less pronounced compared to other biodegradable materials, but a positive influence on cell adhesion and proliferation was still observed.
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•Pectin-BG composite hydrogels were prepared by a relatively simple mixing technique.•BG particles delivers Ca2+ ions for internal pectin crosslinking.•Composite hydrogels exhibited ...strong antibacterial activity against MRSA.•Mineralization process of composite hydrogels occurred upon incubation in SBF.•Composite hydrogels were cytocompatible with MC3T3-E1 osteoblastic cells.
The present work focuses on the development of novel injectable, self-gelling composite hydrogels based on two types of low esterified amidated pectins from citrus peels and apple pomace. Sol-gel-derived, calcium-rich bioactive glass (BG) fillers in a particle form are applied as delivery vehicles for the release of Ca2+ ions to induce internal gelation of pectins. Composites were prepared by a relatively simple mixing technique, using 20% w/v BG particles of two different sizes (2.5 and <45 μm). Smaller particles accelerated pectin gelation slightly faster than bigger ones, which appears to result from the higher rate of Ca2+ ion release. μCT showed inhomogeneous distribution of the BG particles within the hydrogels. All composite hydrogels exhibited strong antibacterial activity against methicilin-resistant Staphylococcus aureus. The mineralization process of pectin-BG composite hydrogels occurred upon incubation in simulated body fluid for 28 days. In vitro studies demonstrated cytocompatibility of composite hydrogels with MC3T3-E1 osteoblastic cells.
Biomimetic matrices offer a great advantage to understand several biological processes including regeneration. The study involves the development of a hybrid biomimetic scaffold and the uniqueness ...lies in the use of mucin, as a constituent protein. Through this study, the role of the protein in bone regeneration is deciphered through its development as a 3D model. As a first step towards understanding the protein, the interactions of mucin and collagen are determined by in silico studies considering that collagen is the most abundant protein in the bone microenvironment. Both proteins are reported to be involved in bone biology though the exact role of mucin is a topic of investigation. The in silico studies of collagen–mucin suggest to have a proper affinity toward each other, forming a strong basis for 3D scaffold development. The developed 3D scaffold is a double network system comprising of mucin and collagen and vinyl end functionalized polyethylene glycol. In situ deposition of mineral crystals has been performed enzymatically. Biological evaluation of these mineral deposited scaffolds is done in terms of their bone regeneration potential and a comparison of the two systems with and without mineral deposition is presented.
Mucin and collagen are covalently conjugated to form a scaffold. The scaffold has water retention capacity and demonstrated mineralization ability upon enzymatic stimulation. The mineral deposition can be confirmed using Raman spectroscopy. Different ratios of the protein lead to scaffolds with different mechanical property and mineralization capability. The protein matrix promotes cell proliferation and mineral deposition.
Overcoming the problem of vascularization remains the main challenge in the field of tissue engineering. As three-dimensional (3D) bioprinting is the rising technique for the fabrication of large ...tissue constructs, small prevascularized building blocks were generated that can be incorporated throughout a printed construct, answering the need for a microvasculature within the small micron range (<10 m). Uniform spheroids with an ideal geometry and diameter for bioprinting were formed, using a high-throughput non-adhesive agarose microwell system. Since monoculture spheroids of endothelial cells were unable to remain stable, coculture spheroids combining endothelial cells with fibroblasts and/or adipose tissue derived mesenchymal stem cells (ADSC) as supporting cells, were created. When applying the favorable coculture ratio, viable spheroids were obtained and endothelial cells spontaneously formed a capillary-like network and lumina, as shown by immunohistochemistry and transmission electron microscopy. Especially the presence of ADSC led to a higher vascularization and extracellular matrix production of the microtissue. Moreover, spheroids were able to assemble at random in suspension and in a hydrogel, creating a macrotissue. During at random assembly, cells reorganized, creating a branched capillary-network throughout the entire fused construct by inoculating with capillaries of adjacent spheroids. Combining the advantage of this natural capacity of microtissues to self-assemble and the controlled organization by bioprinting technologies, these prevascularized spheroids can be useful as building blocks for the engineering of large vascularized 3D tissues.
Scaffold architecture and composition are crucial parameters determining the initial cell spatial distribution and consequently bone tissue formation. Three-dimensional poly-ε-caprolactone (PCL) ...scaffolds with a 0/90° lay-down pattern were plotted and subjected to (1) an oxygen plasma (PCL O) or (2) a postargon plasma modification with gelatin and fibronectin (PCL Fn). These scaffolds with an open pore structure were compared with more compact scaffolds fabricated by conventional processing techniques: oxidized polylactic acid (LA O) and collagen (COL) scaffolds. Human adipose tissue-derived stem cell/scaffold interactions were studied. The study revealed that the biomimetic surface modification of plotted scaffolds did not increase the seeding efficiency. The proliferation and colonization was superior for PCL Fn in comparison with PCL O. The plotted PCL Fn was completely colonized throughout the scaffold, whereas conventional scaffolds only at the edge. Protein-based scaffolds (PCL Fn and COL) enhanced the differentiation, although plotted scaffolds showed a delay in their differentiation compared with compact scaffolds. In conclusion, protein modification of plotted PCL scaffolds enhances uniform tissue formation, but shows a delayed differentiation in comparison with compact scaffolds. The present study demonstrates that biomimetic PCL scaffolds could serve as a guiding template to obtain a uniform bone tissue formation in vivo.
To date, the treatment of articular cartilage lesions remains challenging. A promising strategy for the development of new regenerative therapies is hybrid bioprinting, combining the principles of ...developmental biology, biomaterial science, and 3D bioprinting. In this approach, scaffold-free cartilage microtissues with small diameters are used as building blocks, combined with a photo-crosslinkable hydrogel and subsequently bioprinted. Spheroids of human bone marrow-derived mesenchymal stem cells (hBM-MSC) are created using a high-throughput microwell system and chondrogenic differentiation is induced during 42 days by applying chondrogenic culture medium and low oxygen tension (5%). Stable and homogeneous cartilage spheroids with a mean diameter of 116 ± 2.80 μm, which is compatible with bioprinting, were created after 14 days of culture and a glycosaminoglycans (GAG)- and collagen II-positive extracellular matrix (ECM) was observed. Spheroids were able to assemble at random into a macrotissue, driven by developmental biology tissue fusion processes, and after 72 h of culture, a compact macrotissue was formed. In a directed assembly approach, spheroids were assembled with high spatial control using the bio-ink based extrusion bioprinting approach. Therefore, 14-day spheroids were combined with a photo-crosslinkable methacrylamide-modified gelatin (gelMA) as viscous printing medium to ensure shape fidelity of the printed construct. The photo-initiators Irgacure 2959 and Li-TPO-L were evaluated by assessing their effect on bio-ink properties and the chondrogenic phenotype. The encapsulation in gelMA resulted in further chondrogenic maturation observed by an increased production of GAG and a reduction of collagen I. Moreover, the use of Li-TPO-L lead to constructs with lower stiffness which induced a decrease of collagen I and an increase in GAG and collagen II production. After 3D bioprinting, spheroids remained viable and the cartilage phenotype was maintained. Our findings demonstrate that hBM-MSC spheroids are able to differentiate into cartilage microtissues and display a geometry compatible with 3D bioprinting. Furthermore, for hybrid bioprinting of these spheroids, gelMA is a promising material as it exhibits favorable properties in terms of printability and it supports the viability and chondrogenic phenotype of hBM-MSC microtissues. Moreover, it was shown that a lower hydrogel stiffness enhances further chondrogenic maturation after bioprinting.
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