Biomimetic materials for tissue engineering

An Update on the Use of Alginate in Additive Biofabrication Techniques

BACKGROUND

Solid free forming (SFF) technique also called additive manufacturing process is immensely popular for biofabrication owing to its high accuracy, precision and reproducibility.

METHOD

SFF techniques like stereolithography, selective laser sintering, fused deposition modeling, extrusion printing, and inkjet printing create three dimension (3D) structures by layer by layer processing of the material. To achieve desirable results, selection of the appropriate technique is an important aspect and it is based on the nature of biomaterial or bioink to be processed.

RESULT & CONCLUSION

Alginate is a commonly employed bioink in biofabrication process, attributable to its nontoxic, biodegradable and biocompatible nature; low cost; and tendency to form hydrogel under mild conditions. Furthermore, control on its rheological properties like viscosity and shear thinning, makes this natural anionic polymer an appropriate candidate for many of the SFF techniques. It is endeavoured in the present review to highlight the status of alginate as bioink in various SFF techniques.

Self-Healing Supramolecular Hydrogels for Tissue Engineering Applications

Self-healing supramolecular hydrogels have emerged as a novel class of biomaterials that combine hydrogels with supramolecular chemistry to develop highly functional biomaterials with advantages including native tissue mimicry, biocompatibility, and injectability. These properties are endowed by the reversibly cross-linked polymer network of the hydrogel. These hydrogels have great potential for realizing yet to be clinically translated tissue engineering therapies. This review presents methods of self-healing supramolecular hydrogel formation and their uses in tissue engineering as well as future perspectives.

Biocompatibility studies on cerium oxide nanoparticles - combined study for local effects, systemic toxicity and genotoxicity via implantation route

An implantation study of cerium oxide nanoparticles (CeO2-NP) combined with 28-day systemic toxicity and genotoxicity studies aligned to current regulatory standards was conducted. The results suggested that local tissue reactions caused by CeO2-NP was minimal (implantation irritation index of less than 3) and was better tolerated than most other implant materials tested in our laboratory. Furthermore, CeO2-NP showed virtually no systemic toxicity or in vivo micronucleus induction in bone marrow via implantation route. Chemical analysis showed that CeO2-NP migrated from the implant sites (250 mg per site) in low levels and was deposited predominantly in liver (191.8 ± 35.1 ng g-1 of tissue; P < 0.01), lungs (263.4 ± 30.9 ng g-1 of tissue; P < 0.001), spleen (211.2 ± 6.5 ng g-1 of tissue; P < 0.001) and kidneys (272.8 ± 20.4 ng g-1 of tissue; P < 0.001). These observations provide a base line biocompatibility and toxicity data on CeO2-NP. The current findings will also be useful in defining standards for nanoparticle containing biomaterials and devices.

Fabrication and characterization of silk microfiber-reinforced methacrylated gelatin hydrogel with turnable properties

Despite considerable research effort, the natural hydrogels presently available for tissue engineering suffer from several major drawbacks, one of the significant issue is their poor mechanical strength which are unable to satisfy some mechanical requirements for successful outcomes. Herein, to mimic the composition and structure of the natural extracellular matrix, the micron-sized silk fibers obtained by alkaline hydrolysis were used as a reinforcement phase in a GelMA hydrogel, resulting in a material with significantly greater stiffness than pure GelMA hydrogel alone. In addition, the hydrogel demonstrated tunable compressive strength, swelling capacity, and degradation properties based on the silk fiber length. Experiments with cells indicated that MC3T3-E1 pre-osteoblasts quickly adhered to and proliferated on the surface of the composite hydrogels, as revealed by FDA/PI staining and CCK-8 assays. In addition, various cellular responses, including cell adhesion, changes in cellular morphology and cell proliferation behavior, occurred on the composite hydrogel and varied with fiber length. Overall, this study introduces a series of fiber-reinforced, tunable composite hydrogels that could be useful for various tissue engineering applications.

Osteogenic differentiation of preconditioned bone marrow mesenchymal stem cells with lipopolysaccharide on modified poly-l-lactic-acid nanofibers

Tissue engineering is an interdisciplinary expertise that involves the use of nanoscaffolds for repairing, modifying, and removing tissue defects and formation of new tissues. Mesenchymal stem cells (MSCs) can differentiate into a variety of cell types, and they are attractive candidates for tissue engineering. In the current study, the electrospinning process was used for nanofiber preparation, based on a poly-l-lactic-acid (PLLA) polymer. The surface was treated with O ₂ plasma to enhance hydrophilicity, cell attachment, growth, and differentiation potential. The nanoscaffolds were preconditioned with lipopolysaccharide (LPS) to enhance induction of differentiation. The nanoscaffolds were categorized by contact angle measurements and scanning electron microscopy. The MTT assay was used to analyze the rate of growth and proliferation of cells. Osteogenic differentiation of cultured MSCs was evaluated on nanofibers using common osteogenic markers, such as alkaline phosphatase activity, calcium mineral deposition, quantitative real-time polymerase chain reaction, and immunocytochemical analysis. Based on the in vitro results, primed MSCs with LPS on the PLLA nanoscaffold significantly enhanced the proliferation and osteogenesis of MSCs. Also, the combination of LPS and electrospun nanofibers can provide a new and suitable matrix to support stem cells' differentiation for bone tissue engineering.

Pore size directs bone marrow stromal cell fate and tissue regeneration in nanofibrous macroporous scaffolds by mediating vascularization

In the U.S., 30% of adults suffer joint pain, most commonly in the knee, which severely limits mobility and is often attributed to injury of cartilage and underlying bone in the joint. Current treatment methods such as microfracture result in less resilient fibrocartilage with eventual failure; autografting can cause donor site morbidity and poor integration. To overcome drawbacks in treatment, tissue engineers can design cell-instructive biomimetic scaffolds using biocompatible materials as alternate therapies for osteochondral defects. Nanofibrous poly (l-lactic acid) (PLLA) scaffolds of uniform, spherical, interconnected and well-defined pore sizes that are fabricated using a thermally-induced phase separation and sugar porogen template method create an extracellular matrix-like environment which facilitates cell adhesion and proliferation. Herein we report that chondrogenesis and endochondral ossification of rabbit and human bone marrow stromal cells (BMSCs) can be controlled by scaffold pore architecture, particularly pore size. Small-pore scaffolds support enhanced chondrogenic differentiation in vitro and cartilage formation in vivo compared to large-pore scaffolds. Endochondral ossification is prevented in scaffolds with very small pore sizes; pore interconnectivity is critical to promote capillary ingrowth for mature bone formation. These results provide a novel strategy to control tissue regenerative processes by tunable architecture of macroporous nanofibrous scaffolds. STATEMENT OF SIGNIFICANCE: Progress in understanding the relationship between cell fate and architectural features of tissue engineering scaffolds is critical for engineering physiologically functional tissues. Sugar porogen template scaffolds have uniform, spherical, highly interconnected macropores. Tunable pore-size guides the fate of bone marrow stromal cells (BMSCs) towards chondrogenesis and endochondral ossification, and is a critical design parameter to mediate neotissue vascularization. Preventing vascularization favors a chondrogenic cell fate while allowing vascularization results in endochondral ossification and mineralized bone formation. These results provide a novel strategy to control tissue regenerative processes by tunable architecture of macroporous nanofibrous scaffolds.

Biomaterials of PVA and PVP in medical and pharmaceutical applications: Perspectives and challenges

Poly(vinyl alcohol) (PVA) has attracted considerable research interest and is recognized among the largest volume of synthetic polymers that have been produced worldwide for almost one century. This is due to its exceptional properties which dictated its extensive use in a wide variety of applications, especially in medical and pharmaceutical fields. However, studies revealed that PVA-based biomaterials present some limitations that can restrict their use or performances. To overcome these limitations, various methods have been reported, among which blending with poly(vinylpyrrolidone) (PVP) showed promising results. Thus, our aim was to offer a systematic overview on the current state concerning the preparation, properties and various applications of biomaterials based on synergistic effect of mixtures between PVA and PVP. Future trends towards where the biomaterials research is headed were discussed, showing the promising opportunities that PVA and PVP can offer.

Facile fabrication of electrospun regenerated cellulose nanofiber scaffold for potential bone-tissue engineering application

In this study, cellulose acetate (CA) solutions (9-15% w/v) prepared in acetone-water (80:20 & 90:10 v/v) system were subjected to electrospinning for fabricating non-woven nanofibrous CA scaffolds (CAS) with average fiber diameters from 300 to 600 nm. Further, regenerated cellulose scaffold (RCS) was obtained by deacetylation of electrospun CAS in alkaline media for varying time periods to find the ideal time required for complete deacetylation. Following deacetylation, RCS was subjected to varying temperatures (60 °C, 80 °C) to observe the possible positive effect of heat treatment on the improvement of mechanical strength. The RCS was characterized using ATR FTIR, SEM for studying its surface chemistry and morphology along with other physio-chemical characterizations such as micro-tensile strength, swelling property, porosity, degradation rate in acidic conditions. The results were analyzed and co-related with variation of composition in solvent system, deacetylation time and heat treatment temperatures to determine the optimal fabricating conditions for RCS. In vitro studies using MC3T3-E1 osteoblast cells were also conducted on the selected RCS samples to evaluate cell adhesion and cell proliferation using SEM and MTT assay analysis. The primary results indicate positive outcome regarding the viability of RCS as potential biomaterial for bone-tissue engineering.

Macroporous nanofibrous vascular scaffold with improved biodegradability and smooth muscle cells infiltration prepared by dual phase separation technique

INTRODUCTION

The fast degradation of vascular graft and the infiltration of smooth muscle cells (SMCs) into the vascular graft are considered to be critical for the regeneration of functional neo-vessels. In our previous study, a novel dual phase separation technique was developed to one-pot prepare macroporous nanofibrous poly(L-lactic acid) (PLLA)/poly(ε-caprolactone) (PCL) vascular scaffold by phase separating the immiscible polymer blend. However, the slow degradation of PLLA/PCL limited cell infiltration. Herein, we hypothesized that poly(lactic-co-glycolic acid) (PLGA) would be miscible with PLLA but immiscible with PCL. Then, PLGA can be introduced into the PLLA/PCL blend to fabricate macroporous nanofibrous scaffold with improved biodegradability by using dual phase separation technique.

MATERIALS AND METHODS

The miscibility of PLGA with PLLA and PCL was evaluated. Then, the PLLA/PLGA/PCL scaffold was prepared by dual phase separation technique. The prepared scaffolds were characterized in terms of the morphology, in vitro degradation, mechanical properties, and cells' infiltration and viability for human vascular SMCs (HVSMCs). Finally, platelet-derived growth factor-BB (PDGF-BB) was immobilized on the scaffold and its effect on the bioactivity of HVSMCs was studied.

RESULTS

PLGA is miscible with PLLA but immiscible with PCL as hypothesized. The addition of PLGA enlarged the pore size and improved the biodegradability of composite scaffold. Notably, PLLA/PLGA/PCL scaffold with the blend ratio of 30:40:30 possessed improved pore interconnectivity for cells' infiltration and enough mechanical properties. Moreover, HVSMCs could grow and infiltrate into this scaffold, and surface modification with PDGF-BB on the nanofibrous scaffold enhanced HVSMCs migration and proliferation.

CONCLUSION

This study provides a strategy to expand dual phase separation technique into utilizing ternary even multinary polymer blend to fabricate macroporous nanofibrous scaffold with improved physicochemical properties. The prepared PLLA/PLGA/PCL scaffold would be promising for the regeneration of functional tunica media in vascular tissue engineering.

Nanofibrous Spongy Microspheres To Distinctly Release miRNA and Growth Factors To Enrich Regulatory T Cells and Rescue Periodontal Bone Loss

In addition to T cells' roles in immune response and autoimmune diseases, certain types of T cells, called regulatory T cells (Tregs), play important roles in microenvironment modulation for resolution and tissue regeneration. However, there are currently few options available other than introducing more Tregs or immunosuppressive drugs to locally enrich Tregs. Herein, poly(l-lactic acid) (PLLA) nanofibrous spongy microspheres (NF-SMS), PLLA/polyethylene glycol (PEG) co-functionalized mesoporous silica nanoparticles (MSN), and poly(lactic acid- co-glycolic acid) microspheres (PLGA MS) are integrated into one multibiologic delivery vehicle for in situ Treg manipulation, where the MSNs and PLGA MS were utilized to distinctly release IL-2/TGF-β and miR-10a to locally recruit T cells and stimulate their differentiation into Tregs, while PLLA NF-SMS serve as an injectable scaffold for the adhesion and proliferation of these Tregs. In a mouse model of periodontitis, the injectable and biomolecule-delivering PLLA NF-SMS lead to Treg enrichment, expansion, and Treg-mediated immune therapy against bone loss. This system can potentially be utilized in a wide variety of other immune and regenerative therapies.

Advanced smart biomaterials and constructs for hard tissue engineering and regeneration

Hard tissue repair and regeneration cost hundreds of billions of dollars annually worldwide, and the need has substantially increased as the population has aged. Hard tissues include bone and tooth structures that contain calcium phosphate minerals. Smart biomaterial-based tissue engineering and regenerative medicine methods have the exciting potential to meet this urgent need. Smart biomaterials and constructs refer to biomaterials and constructs that possess instructive/inductive or triggering/stimulating effects on cells and tissues by engineering the material's responsiveness to internal or external stimuli or have intelligently tailored properties and functions that can promote tissue repair and regeneration. The smart material-based approaches include smart scaffolds and stem cell constructs for bone tissue engineering; smart drug delivery systems to enhance bone regeneration; smart dental resins that respond to pH to protect tooth structures; smart pH-sensitive dental materials to selectively inhibit acid-producing bacteria; smart polymers to modulate biofilm species away from a pathogenic composition and shift towards a healthy composition; and smart materials to suppress biofilms and avoid drug resistance. These smart biomaterials can not only deliver and guide stem cells to improve tissue regeneration and deliver drugs and bioactive agents with spatially and temporarily controlled releases but can also modulate/suppress biofilms and combat infections in wound sites. The new generation of smart biomaterials provides exciting potential and is a promising opportunity to substantially enhance hard tissue engineering and regenerative medicine efficacy.

Ether-Oxygen Containing Electrospun Microfibrous and Sub-Microfibrous Scaffolds Based on Poly(butylene 1,4-cyclohexanedicarboxylate) for Skeletal Muscle Tissue Engineering

We report the study of novel biodegradable electrospun scaffolds from poly(butylene 1,4-cyclohexandicarboxylate-co-triethylene cyclohexanedicarboxylate) (P(BCE-co-TECE)) as support for in vitro and in vivo muscle tissue regeneration. We demonstrate that chemical composition, i.e., the amount of TECE co-units (constituted of polyethylene glycol-like moieties), and fibre morphology, i.e., aligned microfibrous or sub-microfibrous scaffolds, are crucial in determining the material biocompatibility. Indeed, the presence of ether linkages influences surface wettability, mechanical properties, hydrolytic degradation rate, and density of cell anchoring points of the studied materials. On the other hand, electrospun scaffolds improve cell adhesion, proliferation, and differentiation by favouring cell alignment along fibre direction (fibre morphology), also allowing for better cell infiltration and oxygen and nutrient diffusion (fibre size). Overall, C2C12 myogenic cells highly differentiated into mature myotubes when cultured on microfibres realised with the copolymer richest in TECE co-units (micro-P73 mat). Lastly, when transplanted in the tibialis anterior muscles of healthy, injured, or dystrophic mice, micro-P73 mat appeared highly vascularised, colonised by murine cells and perfectly integrated with host muscles, thus confirming the suitability of P(BCE-co-TECE) scaffolds as substrates for skeletal muscle tissue engineering.

Fabrication of heterogeneous porous bilayered nanofibrous vascular grafts by two-step phase separation technique

Innterconnected porous architecture is critical for tissue engineering scaffold as well as biomimetic nanofibrous structure. In addition, a paradigm shift is recently taking place in the scaffold design from homogeneous porous scaffold to heterogeneous porous scaffold for the complex tissues. In this study, a versatile and simple one-pot method, dual phase separation, is developed to fabricate macroporous nanofibrous scaffold by phase separating the mixture solutions of immiscible polymer blends without using porogens. The macropores in the scaffold are interconnected, and their size can be tuned by the polymer blend ratio. Moreover, benefiting from the easy operation of dual phase separation technique, an innovative, versatile and facile two-step phase separation method is developed to fabricate heterogeneous porous layered nanofibrous scaffolds with different shapes, such as bilayered tubular scaffold and tri-layered cylindrical scaffold. The bilayered tubular nanofibrous scaffold composed of poly(l-lactic acid) (PLLA)/poly(l-lactide-co-ε-caprolactone) (PLCL) microporous inner layer and PLLA/poly(ε-caprolactone) (PCL) macroporous outer layer matches simultaneously the functional growth of endothelial cells (ECs) and smooth muscle cells (SMCs), and shows the favorable performance for potential small diameter blood vessel application. Therefore, this study provides the novel and facile strategies to fabricate macroporous nanofibrous scaffold and heterogeneous porous layered nanofibrous scaffold for tissue engineering applications.

STATEMENT OF SIGNIFICANCE

The fabrication of porous tissue engineering scaffold made of non-water-soluble polymer commonly requires the use of porogen materials. This is complex and time-consuming, resulting in greater difficulty to prepare heterogeneous porous layered scaffold for multifunctional tissues repair, such as blood vessel and osteochondral tissue. Herein, a novel, versatile and simple one-pot dual phase separation technique is developed for the first time to fabricate porous scaffold without using porogens. Simultaneously, it also endows the resultant scaffold with the biomimetic nanofibrous architecture. Based on the easy operation of this dual phase separation technique, a facile two-step phase separation method is also put forward for the first time and applied in fabricating heterogeneous porous layered nanofibrous scaffold for tissue engineering applications.

[Scaffold-based Bone Tissue Engineering]

Tissue engineering provides the possibility of regenerating damaged or lost osseous structures without the need for permanent implants. Within this context, biodegradable and bioresorbable scaffolds can provide structural and biomechanical stability until the body's own tissue can take over their function. Additive biomanufacturing makes it possible to design the scaffold's architectural characteristics to specifically guide tissue formation and regeneration. Its nano-, micro-, and macro-architectural properties can be tailored to ensure vascularization, oxygenation, nutrient supply, waste exchange, and eventually ossification not only in its periphery but also in its center, which is not in direct contact with osteogenic elements of the surrounding healthy tissue. In this article we provide an overview about our conceptual design and process of the clinical translation of scaffold-based bone tissue engineering applications.

Influence of liquid pore precursors on morphology and mechanical properties of 3D scaffolds obtained by dry inversion phase method

Polyester 3D scaffolds were obtained by dry inversion phase method. The influence of a polymer and liquid pore precursor type on the 3D scaffolds morphology, porosity and mechanical properties was tested. Polymers and precursors forming a porous structure were identified. It was found that 3D scaffolds having the most preferable structure for cell cultures were obtained from polylactide with the addition of n-butanol as the liquid pore precursor. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1079-1087, 2019.

Bioinspired liver scaffold design criteria

Maintaining hepatic functional characteristics in-vitro is considered one of the main challenges in engineering liver tissue. As hepatocytes cultured ex-vivo are deprived of their native extracellular matrix (ECM) milieu, developing scaffolds that mimic the biomechanical and physicochemical properties of the native ECM is thought to be a promising approach for successful tissue engineering and regenerative medicine applications. On the basis that the decellularized liver matrix represents the ideal design template for engineering bioinspired hepatic scaffolds, to derive quantitative descriptors of liver ECM architecture, we characterised decellularised liver matrices in terms of their biochemical, viscoelastic and structural features along with porosity, permeability and wettability. Together, these data provide a unique set of quantitative design criteria which can be used to generate guidelines for fabricating biomaterial scaffolds for liver tissue engineering. As proof-of-concept, we investigated hepatic cell response to substrate viscoelasticity. On collagen hydrogels mimicking decellularised liver mechanics, cells showed superior morphology, higher viability and albumin secretion than on stiffer and less viscous substrates. Although scaffold properties are generally inspired by those of native tissues, our results indicate significant differences between the mechano-structural characteristics of untreated and decellularised hepatic tissue. Therefore, we suggest that design rules - such as mechanical properties and swelling behaviour - for engineering biomimetic scaffolds be re-examined through further studies on substrates matching the features of decellularized liver matrices.

Biomimetic delivery of signals for bone tissue engineering

Bone tissue engineering is an exciting approach to directly repair bone defects or engineer bone tissue for transplantation. Biomaterials play a pivotal role in providing a template and extracellular environment to support regenerative cells and promote tissue regeneration. A variety of signaling cues have been identified to regulate cellular activity, tissue development, and the healing process. Numerous studies and trials have shown the promise of tissue engineering, but successful translations of bone tissue engineering research into clinical applications have been limited, due in part to a lack of optimal delivery systems for these signals. Biomedical engineers are therefore highly motivated to develop biomimetic drug delivery systems, which benefit from mimicking signaling molecule release or presentation by the native extracellular matrix during development or the natural healing process. Engineered biomimetic drug delivery systems aim to provide control over the location, timing, and release kinetics of the signal molecules according to the drug's physiochemical properties and specific biological mechanisms. This article reviews biomimetic strategies in signaling delivery for bone tissue engineering, with a focus on delivery systems rather than specific molecules. Both fundamental considerations and specific design strategies are discussed with examples of recent research progress, demonstrating the significance and potential of biomimetic delivery systems for bone tissue engineering.

Nanoscale and Macroscale Scaffolds with Controlled-Release Polymeric Systems for Dental Craniomaxillofacial Tissue Engineering

Tremendous progress in stem cell biology has resulted in a major current focus on effective modalities to promote directed cellular behavior for clinical therapy. The fundamental principles of tissue engineering are aimed at providing soluble and insoluble biological cues to promote these directed biological responses. Better understanding of extracellular matrix functions is ensuring optimal adhesive substrates to promote cell mobility and a suitable physical niche to direct stem cell responses. Further, appreciation of the roles of matrix constituents as morphogen cues, termed matrikines or matricryptins, are also now being directly exploited in biomaterial design. These insoluble topological cues can be presented at both micro- and nanoscales with specific fabrication techniques. Progress in development and molecular biology has described key roles for a range of biological molecules, such as proteins, lipids, and nucleic acids, to serve as morphogens promoting directed behavior in stem cells. Controlled-release systems involving encapsulation of bioactive agents within polymeric carriers are enabling utilization of soluble cues. Using our efforts at dental craniofacial tissue engineering, this narrative review focuses on outlining specific biomaterial fabrication techniques, such as electrospinning, gas foaming, and 3D printing used in combination with polymeric nano- or microspheres. These avenues are providing unprecedented therapeutic opportunities for precision bioengineering for regenerative applications.

Biopolymers for Antitumor Implantable Drug Delivery Systems: Recent Advances and Future Outlook

In spite of remarkable improvements in cancer treatments and survivorship, cancer still remains as one of the major causes of death worldwide. Although current standards of care provide encouraging results, they still cause severe systemic toxicity and also fail in preventing recurrence of the disease. In order to address these issues, biomaterial-based implantable drug delivery systems (DDSs) have emerged as promising therapeutic platforms, which allow local administration of drugs directly to the tumor site. Owing to the unique properties of biopolymers, they have been used in a variety of ways to institute biodegradable implantable DDSs that exert precise spatiotemporal control over the release of therapeutic drug. Here, the most recent advances in biopolymer-based DDSs for suppressing tumor growth and preventing tumor recurrence are reviewed. Novel emerging biopolymers as well as cutting-edge polymeric microdevices deployed as implantable antitumor DDSs are discussed. Finally, a review of a new therapeutic modality within the field, which is based on implantable biopolymeric DDSs, is given.

Suppressing mesenchymal stem cell hypertrophy and endochondral ossification in 3D cartilage regeneration with nanofibrous poly(l-lactic acid) scaffold and matrilin-3

Articular cartilage has a very limited ability to self-heal after injury or degeneration due to its low cellularity, poor proliferative activity, and avascular nature. Current clinical options are able to alleviate patient suffering, but cannot sufficiently regenerate the lost tissue. Biomimetic scaffolds that recapitulate the important features of the extracellular matrix (ECM) of cartilage are hypothesized to be advantageous in supporting cell growth, chondrogenic differentiation, and integration of regenerated cartilage with native cartilage, ultimately restoring the injured tissue to its normal function. It remains a challenge to support and maintain articular cartilage regenerated by bone marrow-derived mesenchymal stem cells (BMSCs), which are prone to hypertrophy and endochondral ossification after implantation in vivo. In the present work, a nanofibrous poly(l-lactic acid) (NF PLLA) scaffold developed by our group was utilized because of the desired highly porous structure, high interconnectivity, and collagen-like NF architecture to support rabbit BMSCs for articular cartilage regeneration. We further hypothesized that matrilin-3 (MATN3), a non-collagenous, cartilage-specific ECM protein, would enhance the microenvironment of the NF PLLA scaffold for cartilage regeneration and maintain the cartilage property. To test this hypothesis, we seeded BMSCs on the NF PLLA scaffold with or without MATN3. We found that MATN3 suppresses hypertrophy in this 3D culture system in vitro. Subcutaneous implantation of the chondrogenic cell/scaffold constructs in a nude mouse model showed that pretreatment with MATN3 was able to maintain chondrogenesis and prevent hypertrophy and endochondral ossification in vivo. These results demonstrate that the porous NF PLLA scaffold treated with MATN3 represents an advantageous 3D microenvironment for cartilage regeneration and phenotype maintenance, and is a promising strategy for articular cartilage repair.

STATEMENT OF SIGNIFICANCE

Articular cartilage defects, caused by trauma, inflammation, or joint instability, may ultimately lead to debilitating pain and disability. Bone marrow-derived mesenchymal stem cells (BMSCs) are an attractive cell source for articular cartilage tissue engineering. However, chondrogenic induction of BMSCs is often accompanied by undesired hypertrophy, which can lead to calcification and ultimately damage the cartilage. Therefore, a therapy to prevent hypertrophy and endochondral ossification is of paramount importance to adequately regenerate articular cartilage. We hypothesized that MATN3 (a non-collagenous ECM protein expressed exclusively in cartilage) may improve regeneration of articular cartilage with BMSCs by maintaining chondrogenesis and preventing hypertrophic transition in an ECM mimicking nanofibrous scaffold. Our results showed that the administration of MATN3 to the cell/nanofibrous scaffold constructs favorably maintained chondrogenesis and prevented hypertrophy/endochondral ossification in the chondrogenic constructs in vitro and in vivo. The combination of nanofibrous PLLA scaffolds and MATN3 treatment provides a very promising strategy to generate chondrogenic grafts with phenotypic stability for articular cartilage repair.

Preparation of poly(lactic acid)/sintered hydroxyapatite composite biomaterial by supercritical CO2

Based on a kind of sintered hydroxyapatite (HA) with a good cytocompatibility, a series of polylactic acid (PLA) and PLA/HA with the various PLA:HA weight ratio (5:5, 4:6, 3:7, 2:8, 1:9) were fabricated by supercritical CO2. The physical and chemical properties were evaluated by pH, degradation, water absorption, porosity, density, mechanical property, and cytotoxicity respectively. With the increase of HA content, the pH value and porosity increased gradually, while weight loss rate and the density showed a gradual downward trend. Existence of HA can drastically improve the hydroscopicity of PLA scaffolds. The compression strength values slightly increased (p>0.05) from 39.96 MPa of PLA to 45.00 MPa of PLA/HA with the ratio of 7:3, subsequently, the values decreased (p<0.05) from 43.29 MPa (8:2) to 19.00 MPa (9:1). While the modulus of elasticity decreased (p<0.05) from 5.89 to 1.84 GPa with increasing HA content. The PLA/HA (8:2) promoted cell proliferation more significantly than any of other groups (p<0.05). Based on the results, the overall properties of porous scaffolds are the optimal when the weight ratio of PLA/HA is 8:2. Its pH, porosity, density, compression strength, and elasticity modulus are 7.39, 83.0%, 0.60g/cm-3, 34.1 MPa and 2.63 GPa, respectively. SEM observation presented a homogeneous distribution of HA in PLA matrix and a foam-like structure comprising interconnected pores.

Micropatterned cell sheets as structural building blocks for biomimetic vascular patches

To successfully develop a functional tissue-engineered vascular patch, recapitulating the hierarchical structure of vessel is critical to mimic mechanical properties. Here, we use a cell sheet engineering strategy with micropatterning technique to control structural organization of bovine aortic vascular smooth muscle cell (VSMC) sheets. Actin filament staining and image analysis showed clear cellular alignment of VSMC sheets cultured on patterned substrates. Viability of harvested VSMC sheets was confirmed by Live/Dead^® cell viability assay after 24 and 48 h of transfer. VSMC sheets stacked to generate bilayer VSMC patches exhibited strong inter-layer bonding as shown by lap shear test. Uniaxial tensile testing of monolayer VSMC sheets and bilayer VSMC patches displayed nonlinear, anisotropic stress-stretch response similar to the biomechanical characteristic of a native arterial wall. Collagen content and structure were characterized to determine the effects of patterning and stacking on extracellular matrix of VSMC sheets. Using finite-element modeling to simulate uniaxial tensile testing of bilayer VSMC patches, we found the stress-stretch response of bilayer patterned VSMC patches under uniaxial tension to be predicted using an anisotropic hyperelastic constitutive model. Thus, our cell sheet harvesting system combined with biomechanical modeling is a promising approach to generate building blocks for tissue-engineered vascular patches with structure and mechanical behavior mimicking native tissue.

Tailored Biodegradable and Electroactive Poly(Hydroxybutyrate-Co-Hydroxyvalerate) Based Morphologies for Tissue Engineering Applications

Polymer-based piezoelectric biomaterials have already proven their relevance for tissue engineering applications. Furthermore, the morphology of the scaffolds plays also an important role in cell proliferation and differentiation. The present work reports on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), a biocompatible, biodegradable, and piezoelectric biopolymer that has been processed in different morphologies, including films, fibers, microspheres, and 3D scaffolds. The corresponding magnetically active PHBV-based composites were also produced. The effect of the morphology on physico-chemical, thermal, magnetic, and mechanical properties of pristine and composite samples was evaluated, as well as their cytotoxicity. It was observed that the morphology does not strongly affect the properties of the pristine samples but the introduction of cobalt ferrites induces changes in the degree of crystallinity that could affect the applicability of prepared biomaterials. Young’s modulus is dependent of the morphology and also increases with the addition of cobalt ferrites. Both pristine and PHBV/cobalt ferrite composite samples are not cytotoxic, indicating their suitability for tissue engineering applications.

Silsesquioxane polymer as a potential scaffold for laryngeal reconstruction

Cancer, disease and trauma to the larynx and their treatment can lead to permanent loss of structures critical to voice, breathing and swallowing. Engineered partial or total laryngeal replacements would need to match the ambitious specifications of replicating functionality, outer biocompatibility, and permissiveness for an inner mucosal lining. Here we present porous polyhedral oligomeric silsesquioxane-poly(carbonate urea) urethane (POSS-PCUU) as a potential scaffold for engineering laryngeal tissue. Specifically, we employ a precipitation and porogen leaching technique for manufacturing the polymer. The polymer is chemically consistent across all sample types and produces a foam-like scaffold with two distinct topographies and an internal structure composed of nano- and micro-pores. While the highly porous internal structure of the scaffold contributes to the complex tensile behaviour of the polymer, the surface of the scaffold remains largely non-porous. The low number of pores minimise access for cells, although primary fibroblasts and epithelial cells do attach and proliferate on the polymer surface. Our data show that with a change in manufacturing protocol to produce porous polymer surfaces, POSS-PCUU may be a potential candidate for overcoming some of the limitations associated with laryngeal reconstruction and regeneration.

Canine Placenta Recellularized Using Yolk Sac Cells with Vascular Endothelial Growth Factor

Regenerative medicine has been growing because of the emergent need for tissues/organs for transplants and restorative surgeries. Biological scaffolds are important tools to try to solve this problem. The one used in this reserach was developed by an acellular biological scaffold from canine placenta with a rich source of cellular matrix. After decellularization, the cellular matrix demonstrated structural preservation with the presence of important functional proteins such as collagen, fibronectin, and laminin. We used cells transduced with vascular endothelial growth factor (VEGF) to recellularize this scaffold. It was succeeded by seeding the cells in nonadherent plaques in the presence of the sterelized placenta scaffold. Cells were adhered to the scaffold when analyzed by immunocytochemistry and scanning electron microscopy, both showing sprouting of yolk sac VEGF (YSVEGF) cells. This recellularized scaffold is a promissory biomaterial for repairing injured areas where neovascularization is required.

Evaluation of osteoblast differentiation and function when cultured on mesoporous bioactive glass adsorbed with testosterone

Mesoporous bioactive glass (MBG), a kind of porous materials with great osteoconductive and osteoinductive ability, shows promising application in bone tissue engineering due to its high specific surface area, orderly channel structure, and large pore volume. Here we reported that the proliferation, differentiation, and mineralization were promoted in MC3T3-E1 cells cultured on MBG which adsorbed with testosterone (MBG/T). We found that transcriptional activity of Runx2 which is a critical transcription factor is increased in MC3T3-E1 cells cultured on MBG/T. Intriguingly, we observed that ERK phosphorylation was enhanced in MC3T3-E1 cells cultured on MBG/T. We showed that activated Runx2 in MC3T3-E1 cells cultured on MBG/T is through Erk1/2 phosphorylation. Consistent with this result, we also found that the expression of osteoblastic marker genes were increased. Therefore, we concluded that osteoblast differentiation and mineralization was enhanced after cells cultured on MBG/T through Erk1/2-activated Runx2 pathway. Our findings provided that MBG/T is a potential material in the process of bone repair.

Outcomes of necrotic immature open-apex central incisors treated by MTA apexification using poly(ε-caprolactone) fiber mesh as an apical barrier

BACKGROUND/PURPOSE

Although unset mineral trioxide aggregate (MTA) has some cytotoxicity, MTA is still a biocompatible material suitable for doing apexification. This study assessed the outcomes for 8 necrotic immature open-apex permanent maxillary central incisors treated by MTA apexification using poly(ε-caprolactone) fiber mesh (PCL-FM) as an apical barrier (so-called PCL-FM/MTA apexification) to prevent extrusion of MTA materials into the periapical tissues of open-apex teeth.

METHODS

Eight necrotic immature open-apex permanent maxillary central incisors with the open apices measuring 2.5 mm-3.5 mm in diameter in 8 patients (6 boys and 2 girls; age range, 8-10 years) were first cleaned using ultrasonic activated irrigation with 2.5% sodium hypochlorite solution and then treated by PCL-FM/MTA apexification procedure.

RESULTS

All the 8 permanent maxillary central incisors showed successful outcomes after PCL-FM/MTA apexification procedure. The mean duration for apical hard tissue barrier formation of the 8 incisors was 6.8 ± 0.5 weeks (range 6-7 weeks). The mean increased root length was 1.8 ± 0.7 mm (range 1-3 mm) at 7 weeks and 3.1 ± 0.6 mm (range 2-4 mm) at 3 months. The mean increased dentinal wall thickness at the most apical portion of the root was 1.3 ± 0.5 mm (range 1-2 mm) at 7 weeks and 2.4 ± 0.6 mm (range 1.5-3 mm) at 3 months. None of the teeth treated by PCL-FM/MTA apexification showed tooth discoloration after a follow-up period of 3 months.

CONCLUSION

PCL-FM/MTA apexification is an excellent technique for treatment of necrotic immature open-apex permanent maxillary central incisors.

Conducting Polymers for Tissue Engineering

Electrically conducting polymers such as polyaniline, polypyrrole, polythiophene, and their derivatives (mainly aniline oligomer and poly(3,4-ethylenedioxythiophene)) with good biocompatibility find wide applications in biomedical fields including bioactuators, biosensors, neural implants, drug delivery systems, and tissue engineering scaffolds. This review focuses on these conductive polymers for tissue engineering applications. Conductive polymers exhibit promising conductivity as bioactive scaffolds for tissue regeneration, and their conductive nature allows cells or tissue cultured on them to be stimulated by electrical signals. However, their mechanical brittleness and poor processability restrict their application. Therefore, conductive polymeric composites based on conductive polymers and biocompatible biodegradable polymers (natural or synthetic) were developed. The major objective of this review is to summarize the conductive biomaterials used in tissue engineering including conductive composite films, conductive nanofibers, conductive hydrogels, and conductive composite scaffolds fabricated by various methods such as electrospinning, coating, or deposition by in situ polymerization. Furthermore, recent progress in tissue engineering applications using these conductive biomaterials including bone tissue engineering, muscle tissue engineering, nerve tissue engineering, cardiac tissue engineering, and wound healing application are discussed in detail.

Electroactive polymers for tissue regeneration: Developments and perspectives

Human body motion can generate a biological electric field and a current, creating a voltage gradient of -10 to -90 mV across cell membranes. In turn, this gradient triggers cells to transmit signals that alter cell proliferation and differentiation. Several cell types, counting osteoblasts, neurons and cardiomyocytes, are relatively sensitive to electrical signal stimulation. Employment of electrical signals in modulating cell proliferation and differentiation inspires us to use the electroactive polymers to achieve electrical stimulation for repairing impaired tissues. Electroactive polymers have found numerous applications in biomedicine due to their capability in effectively delivering electrical signals to the seeded cells, such as biosensing, tissue regeneration, drug delivery, and biomedical implants. Here we will summarize the electrical characteristics of electroactive polymers, which enables them to electrically influence cellular function and behavior, including conducting polymers, piezoelectric polymers, and polyelectrolyte gels. We will also discuss the biological response to these electroactive polymers under electrical stimulation. In particular, we focus this review on their applications in regenerating different tissues, including bone, nerve, heart muscle, cartilage and skin. Additionally, we discuss the challenges in tissue regeneration applications of electroactive polymers. We conclude that electroactive polymers have a great potential as regenerative biomaterials, due to their ability to stimulate desirable outcomes in various electrically responsive cells.

Fibrous Topography-Potentiated Canonical Wnt Signaling Directs the Odontoblastic Differentiation of Dental Pulp-Derived Stem Cells

Nanofibrous engineered matrices have significant potential in cellular differentiation and tissue regeneration. Stem cells require specific extracellular signals that lead to the induction of different lineages. However, the mechanisms by which the nanofibrous matrix promotes mesenchymal stem cell (MSC) differentiation are largely unknown. Here, we investigated the mechanisms that underlie nanofibrous matrix-induced odontoblastic differentiation of human dental pulp MSCs (DP-MSCs). An electrospun polystyrene nanofibrous (PSF) matrix was prepared, and the cell responses to the PSF matrix were assessed in comparison with those on conventional tissue culture dishes. The PSF matrix promoted the expression of Wnt3a, Wnt5a, Wnt10a, BMP2, BMP4, and BMP7 in the DP-MSCs, concomitant with the induction of odontoblast/osteoblast differentiation markers, dentin sialophosphoprotein (DSPP), osteocalcin, and bone sialoprotein, whose levels were further enhanced by treatment with recombinant Wnt3a. The DP-MSCs cultured on the PSF matrix also exhibited a high alkaline phosphatase activity and intense Alizarin Red staining, indicating that the PSF matrix promotes odontoblast differentiation. Besides inducing the expression of Wnt3a, the PSF matrix maintained high levels of β-catenin protein and enhanced its translocation to the nucleus, leading to its transcriptional activity. Forced expression of LEF1 or treatments with LiCl further enhanced the DSPP expression. Blocking the Wnt3a-initiated signaling abrogated the PSF-induced DSPP expression. Furthermore, the cells on the PSF matrix increased the DSPP promoter activity. The β-catenin complex was bound to the conserved motifs on the DSPP promoter dictating its transcription. Transplantations of the preodontoblast-seeded PSF matrix to the subcutaneous tissues of nude mice confirmed the association of the PSF matrix with the Wnt3a and DSPP expressions in vivo. Taken together, these results demonstrate the nanofibrous engineered matrix strongly supports odontoblastic differentiation of DP-MSCs by enhancing Wnt/β-catenin signaling.

Synthesis of bioinspired collagen/alginate/fibrin based hydrogels for soft tissue engineering

Hydrogels based on natural polymers offer a range of properties to mimic the native extracellular matrix, and provide microenvironments to preserve cellular function and encourage tissue formation. A tri-component hydrogel using collagen, alginate and fibrin (CAF) was developed and investigated at three collagen concentrations for application as a functional extracellular matrix analogue. Physical-chemical characterization of CAF hydrogels demonstrated a thermo-responsive crosslinking capacity at physiological conditions with stiffness similar to native soft tissues. CAF hydrogels were also assessed for cytocompatibility using L929 murine fibroblasts, pancreatic MIN6 β-cells and human mesenchymal stem cells (hMSCs); and demonstrated good cell viability, proliferation and metabolic activity after 7 days of in vitro culture. CAF hydrogels, especially with 2.5% w/v collagen, increased alkaline phosphatase production in hMSCs indicating potential for the promotion of osteogenic activity. Moreover, CAF hydrogels also increased metabolic activity of MIN6 β-cells and promoted the reconstitution of spherical pseudoislets with sizes ranging between 50 and 150 μm at day 7, demonstrating potential in diabetic therapeutic applications.

Subpopulations of dermal skin fibroblasts secrete distinct extracellular matrix: implications for using skin substitutes in the clinic

Background

While several commercial dermoepidermal scaffolds can promote wound healing of the skin, the achievement of complete skin regeneration still represents a major challenge.

Objectives

To perform biological characterization of self‐assembled extracellular matrices (ECMs) from three different subpopulations of fibroblasts found in human skin: papillary fibroblasts (Pfi), reticular fibroblasts (Rfi) and dermal papilla fibroblasts (DPfi).

Methods

Fibroblast subpopulations were cultured with ascorbic acid to promote cell‐assembled matrix production for 10 days. Subsequently, cells were removed and the remaining matrices characterized. Additionally, in another experiment, keratinocytes were seeded on the top of cell‐depleted ECMs to generate epidermal‐only skin constructs.

Results

We found that the ECM self‐assembled by Pfi exhibited randomly oriented fibres associated with the highest interfibrillar space, reflecting ECM characteristics that are physiologically present within the papillary dermis. Mass spectrometry followed by validation with immunofluorescence analysis showed that thrombospondin 1 is preferentially expressed within the DPfi‐derived matrix. Moreover, we observed that epidermal constructs grown on DPfi or Pfi matrices exhibited normal basement membrane formation, whereas Rfi matrices were unable to support membrane formation.

Conclusions

We argue that inspiration can be taken from these different ECMs, to improve the design of therapeutic biomaterials in skin engineering applications.

What's already known about this topic?

There are several types of skin fibroblasts within the dermis that can be defined by their spatial location: papillary fibroblasts (Pfi), reticular fibroblasts (Rfi) and dermal papilla fibroblasts (DPfi).

Extracellular matrix (ECM) composition is distinct with regard to composition and architecture within the papillary, reticular and hair follicle dermis in vivo.

When skin is injured, dermal replacement substitutes used for tissue repair do not reflect the heterogeneity observed within the skin dermis.

What does this study add?

Self‐assembled ECMs from different subpopulations of skin fibroblasts can be generated in vitro.

Cell‐assembled ECMs made in vitro from Pfi, Rfi and DPfi reflect dermal heterogeneity seen in vivo and are morphologically, functionally and compositionally distinct from one another.

Inspiration should be taken from cell‐assembled ECMs from distinct fibroblast subpopulations, to improve the design of therapeutic biomaterials in skin engineering applications.

What is the translational message?

Cell‐assembled ECMs from DPfi and Pfi, but not Rfi, can support formation of a basement membrane in adjacent keratinocytes in vitro.

Inspiration should be taken from cell‐assembled ECMs from distinct fibroblast subpopulations, to improve the design of therapeutic biomaterials in skin engineering applications.

Linked Comment: https://doi.org/10.1111/bjd.16773.

https://doi.org/10.1111/bjd.16946 available online

https://goo.gl/Uqv3dl

Reconstruction of structure and function in tissue engineering of solid organs: Toward simulation of natural development based on decellularization

Failure of solid organs, such as the heart, liver, and kidney, remains a major cause of the world's mortality due to critical shortage of donor organs. Tissue engineering, which uses elements including cells, scaffolds, and growth factors to fabricate functional organs in vitro, is a promising strategy to mitigate the scarcity of transplantable organs. Within recent years, different construction strategies that guide the combination of tissue engineering elements have been applied in solid organ tissue engineering and have achieved much progress. Most attractively, construction strategy based on whole-organ decellularization has become a popular and promising approach, because the overall structure of extracellular matrix can be well preserved. However, despite the preservation of whole structure, the current constructs derived from decellularization-based strategy still perform partial functions of solid organs, due to several challenges, including preservation of functional extracellular matrix structure, implementation of functional recellularization, formation of functional vascular network, and realization of long-term functional integration. This review overviews the status quo of solid organ tissue engineering, including both advances and challenges. We have also put forward a few techniques with potential to solve the challenges, mainly focusing on decellularization-based construction strategy. We propose that the primary concept for constructing tissue-engineered solid organs is fabricating functional organs based on intact structure via simulating the natural development and regeneration processes.

Nanofiber technology in the ex vivo expansion of cord blood-derived hematopoietic stem cells

Umbilical cord blood (CB) can be used as an alternative source of hematopoietic stem cells (HSCs) for transplantation in hematological and non-hematological disorders. Despite several recognized advantages the limited cell number in CB one unit still restricts its clinical use. The success of transplantation greatly depends on the levels of total nucleated cell and CD34+ cell counts. Thus, many ex vivo strategies have been developed within the last decade in order to solve this obstacle, with more or less success, mainly determined by the degree of difficulty related with maintaining HSCs self-renewal and stemness properties after long-term expansion. Different research groups have developed very promising and diverse CB-derived HSC expansion strategies using nanofiber scaffolds. Here we review the state-of-the-art of nanofiber technology-based CB-derived HSC expansion.

Chitosan/gelatin scaffolds support bone regeneration

Chitosan/Gelatin (CS:Gel) scaffolds were fabricated by chemical crosslinking with glutaraldehyde or genipin by freeze drying. Both crosslinked CS:Gel scaffold types with a mass ratio of 40:60% form a gel-like structure with interconnected pores. Dynamic rheological measurements provided similar values for the storage modulus and the loss modulus of the CS:Gel scaffolds when crosslinked with the same concentration of glutaraldehyde vs. genipin. Compared to genipin, the glutaraldehyde-crosslinked scaffolds supported strong adhesion and infiltration of pre-osteoblasts within the pores as well as survival and proliferation of both MC3T3-E1 pre-osteoblastic cells after 7 days in culture, and human bone marrow mesenchymal stem cells (BM-MSCs) after 14 days in culture. The levels of collagen secreted into the extracellular matrix by the pre-osteoblasts cultured for 4 and 7 days on the CS:Gel scaffolds, significantly increased when compared to the tissue culture polystyrene (TCPS) control surface. Human BM-MSCs attached and infiltrated within the pores of the CS:Gel scaffolds allowing for a significant increase of the osteogenic gene expression of RUNX2, ALP, and OSC. Histological data following implantation of a CS:Gel scaffold into a mouse femur demonstrated that the scaffolds support the formation of extracellular matrix, while fibroblasts surrounding the porous scaffold produce collagen with minimal inflammatory reaction. These results show the potential of CS:Gel scaffolds to support new tissue formation and thus provide a promising strategy for bone tissue engineering.

Human Neural Stem/Progenitor Cells Derived From Epileptic Human Brain in a Self-Assembling Peptide Nanoscaffold Improve Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) is a disruption in the brain functions following a head trauma. Cell therapy may provide a promising treatment for TBI. Among different cell types, human neural stem cells cultured in self-assembling peptide scaffolds have been suggested as a potential novel method for cell replacement treatment after TBI. In the present study, we accessed the effects of human neural stem/progenitor cells (hNS/PCs) derived from epileptic human brain and human adipose-derived stromal/stem cells (hADSCs) seeded in PuraMatrix hydrogel (PM) on brain function after TBI in an animal model of brain injury. hNS/PCs were isolated from patients with medically intractable epilepsy undergone epilepsy surgery. hNS/PCs and hADSCs have the potential for proliferation and differentiation into both neuronal and glial lineages. Assessment of the growth characteristics of hNS/PCs and hADSCs revealed that the hNS/PCs doubling time was significantly longer and the growth rate was lower than hADSCs. Transplantation of hNS/PCs and hADSCs seeded in PM improved functional recovery, decreased lesion volume, inhibited neuroinflammation, and reduced the reactive gliosis at the injury site. The data suggest the transplantation of hNS/PCs or hADSCs cultured in PM as a promising treatment option for cell replacement therapy in TBI.

Nano-Graphene Oxide Functionalized Bioactive Poly(lactic acid) and Poly(ε-caprolactone) Nanofibrous Scaffolds

A versatile and convenient way to produce bioactive poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) electrospun nanofibrous scaffolds is described. PLA and PCL are extensively used as biocompatible scaffold materials for tissue engineering. Here, biobased nano graphene oxide dots (nGO) are incorporated in PLA or PCL electrospun scaffolds during the electrospinning process aiming to enhance the mechanical properties and endorse osteo-bioactivity. nGO was found to tightly attach to the fibers through secondary interactions. It also improved the electrospinnability and fiber quality. The prepared nanofibrous scaffolds exhibited enhanced mechanical properties, increased hydrophilicity, good cytocompatibility and osteo-bioactivity. Therefore, immense potential for bone tissue engineering applications is anticipated.

Accelerated Angiogenic Induction and Vascular Integration in a Novel Synthetic Scaffolding Matrix for Tissue Replacement

Purpose

Reduced or delayed neovascularization is a major obstacle with regard to tissue-engineered constructs. The aim of this study was to evaluate the early microvascular response to a novel degradable ε-caprolactone terpolymer matrix.

Methods

ε-caprolactone terpolymer matrices (Suprathel Plus®; Institute of Textile and Process Engineering, Denkendorf, Germany) were implanted into dorsal skinfold chambers of balb/c mice (n=10). Microcirculatory changes were observed by intravital fluorescence microscopy. Scaffolding matrices from PEGT/PBT copolymer were used as controls (n=10).

Results

The formation of de novo vascular networks within both scaffolding matrices was noted throughout the experiment. A vascular ingrowth of perfused microvessels into the matrices up to 600 μm apart from the edge was noted within 10 days of implantation. The earliest signs of neoangiogenesis were visible in ε-caprolactone terpolymer matrices on day 1. In both scaffolds the new developed vessels extended centripetally from the border of the matrices towards the center and anastomosed to form a perfused microvascular network. There was significantly earlier onset of vascularization, increased vascularized area and higher vessel density in ε-caprolactone terpolymer matrices compared to PEGT/PBT copolymer matrices were observed.

Conclusions

The scaffolding matrix from ε-caprolactone terpolymer allowed for an earlier and more intense induction of angiogenesis and displayed the tendency to vascularize more rapidly within a shorter period of time after transplantation compared to PEGT/PBT copolymer scaffolds, thus indicating its potential application for tissue engineering purposes.