Polyurethane Scaffolds Research Articles

Polyurethane Meniscal Scaffold: Does Preoperative Remnant Meniscal Extrusion Have an Influence on Postoperative Extrusion and Knee Function?

Meniscal extrusion (ME) has been identified as a risk factor in the development of knee osteoarthritis. The relevance of this finding when a meniscal scaffold is used has not been extensively studied. The objective of this study was to determine whether preoperative meniscal remnant extrusion (MRE) was correlated with postoperative scaffold extrusion (SE) or with functional outcomes at the 2-year follow-up. Retrospective study included all polyurethane scaffolds implanted with a minimum 2-year follow-up. A magnetic resonance imaging (MRI) was performed preoperatively and postoperatively at 2 years. Extrusion was measured in millimeters in a coronal view. Patients were assigned to either group 1 or 2 depending on the preoperative MRE being either <3 mm (minor extrusion) or 3 mm (major extrusion). Functional outcomes were analyzed by means of the Western Ontario Meniscal Evaluation Tool (WOMET), International Knee Documentation Committee, Kujala and Tegner scores, as well as visual analog scale. Satisfaction was also documented. Sixty-two out of 98 patients were available to undergo an MRI at final follow-up. The mean age was 41.3 years (range, 17-58) and the mean follow-up was 45 months (range, 25-69). The mean preoperative MRE was 2.8 mm (standard deviation [SD] 1.2) and the mean postoperative SE was 3.8 mm (SD 1.8) (p < 0.01). All functional scores improved during the study period. When the correlation (Spearman's rho) between the difference in extrusion between the pre 26 and postoperative periods and their correlation with the different scores was assessed, correlation was only observed in the WOMET (rho 0.61, p = 0.02). The preoperative MRE in Group 1 was 1.85 mm (SD 0.83) and 3.7 mm (SD 2.2) in Group 2 (p < 0.01). At final follow-up, SE was 3.86 mm (SD 0.7) in Group 1, whereas it was 3.98 mm (SD 1) in Group 2 (p = 0.81). No differences were observed in the scores used for these two groups. The SE observed at the 2-year follow-up after the implantation of a polyurethane scaffold did not depend on preoperative MRE (major or minor extrusion). The WOMET score, which was the only meniscal-specific functional scored used, showed some inferior results in the most extruded meniscal scaffolds. This is a retrospective case series. Level of evidence is 4.

In situ synthesized TiO2-polyurethane nanocomposite for bypass graft application: In vitro endothelialization and degradation.

The in vitro endothelial response of human umbilical vein endothelial cells was investigated on a poly (caprolactone)-based polyurethane surface vs an in situ TiO2-polyurethane nanocomposite surface, which has been produced as scaffolds for artificial vascular graft. The in situ synthesis of TiO2 nanoparticles in polyurethane provided surface properties that facilitated cellular adhesion, cell sensing, cell probing and especially cell migration. Cells on the nanocomposite surface have elongated morphology and were able to produce more extracellular matrix. All of these advantages led to an increase in the rate of endothelialization of the nanocomposite scaffold surface vs pure polyurethane. The presence of TiO2 nanoparticles with very good distribution in polyurethane increased the degradability of the scaffolds by increasing the phase separation and hydrophilicity in the nanocomposite film. The results showed that the degradation mechanism of nanocomposite films prompted the interconnectivity of spaces inside structures that probably could give extra chances to improve migration and proliferation of cells, as well as, the delivery of nutrients and metabolites inside the pores of the scaffold. The outcomes revealed that the rate of endothelialization of the nanocomposite scaffold after 7days of in vitro cell culture was 1.5 times and the rate of degradation of the nanocomposite film was 2 times after 8weeks of immersion scaffolds in PBS compared to the polyurethane scaffolds. In addition, the nanocomposite scaffold possessed good mechanical properties. Despite its high modulus, it was flexible with a 500% elongation at break.

Polyvinylpyrrolidone (PVP) hydrogel coating for cylindrical polyurethane scaffolds

The presented study describes a method for the preparation and modification of cylindrical polyurethane structures with polyvinylpyrrolidone (PVP) hydrogel coating. The modified polyurethane scaffolds were fabricated using the phase-inversion technique and intended to be used as a vascular prosthesis. The proposed modification method involves a two-step Fenton-type reaction. Physicochemical analysis (Fourier transform infrared spectroscopy, scanning electron microscopy) confirmed the presence of the hydrogel coating. The influence of PVP and polymerization initiator (cumene hydroperoxide) concentrations on hydrogel’s properties were examined. The higher concentrations of reagent were used, the thicker coating was obtained. After modification, the material’s surface becomes more hydrophilic in comparison to pristine polyurethane. Cytotoxicity assay (MTT test) confirmed that PVP-coating is not toxic. The introduction of hydrogel coating resulted in a significant decrease in the fibrinogen adsorbed to the material’s surface as compared to a non-modified polymer. Platelet adhesion assay demonstrated almost no platelet adhesion to the modified surfaces.

Studies of proliferation and chondrogenic differentiation of rat adipose stem cells using an anti-oxidative polyurethane scaffold combined with cyclic compression culture.

The adipose stem cell is a potential candidate for the autologous chondrocytes repairing approach because of the abundance of fat in the animal body and its versatile differentiation capability. In this study, rat adipose stem cells (rASCs) were seeded into anti-oxidative N-acetylcysteine (NAC) grafted polyurethane (PU) scaffold and then combined with short dynamic compressive stimulation (24h) to induce rASCs chondrogenesis differentiation in vitro. The inner pore surface of the PU scaffold was first modified via alginate and type I collagen to promote rASCs adherence. The modified layers crosslinked by genipin showed outstanding stability after ultrasonic treatment, indicating the modified layers were stable and can keep the cells adhesion well during dynamic compressive stimulation. After inner pore surface modification and 10mM NAC grafting, the PU scaffold-A-C-G (graft 10mM NAC) has shown the best proliferation efficiency with homogeneous cell distribution after 72hr static culture. After short term dynamic compressive stimulation, significant gene expression in chondrogenic markers, Sox-9, and Aggrecan, were noted in both PU scaffold-A-C-G and PU scaffold-A-C-G (graft 10mM NAC). Considering the cell proliferation efficiency and gene expression, the anti-oxidative NAC grafted PU scaffold combined with short term dynamic compressive stimulation could be useful for cell culturing in stem cell therapy.

Polyurethane Meniscal Scaffold for the Treatment of Partial Meniscal Deficiency: 5-Year Follow-up Outcomes: A European Multicentric Study

Background: A biodegradable polyurethane scaffold was developed to treat patients with the challenging clinical condition of painful partial meniscal defects. Hypothesis: The use of an acellular polyurethane scaffold in patients with symptomatic partial meniscal defects would result in both midterm pain relief and improved function. Study Design: Case series; Level of evidence, 4. Methods: A total of 155 patients with symptomatic partial meniscal defects (101 medial and 54 lateral) were implanted with a polyurethane scaffold in a prospective, single-arm, multicentric study with a minimum 5-year follow-up. Clinical outcomes were measured with the visual analog scale for pain, International Knee Documentation Committee subjective knee evaluation form, Lysholm knee scale, and Knee injury and Osteoarthritis Outcome Score at baseline and at 2- and 5-year follow-ups. Magnetic resonance imaging (MRI) was used to evaluate the knee joint, meniscal implant, and meniscal extrusion. Kaplan-Meier survival analysis was also performed. Removal of the scaffold, conversion to a meniscal transplant, and unicompartmental/total knee arthroplasty were used as endpoints. Results: Eighteen patients were lost to follow-up (11.6%). The patients who were included in this study showed significant clinical improvement after surgery as indicated by the different outcome measures (P = .01). However, the clinical improvement tended to stabilize between 2 and 5 years of follow-up. MRI scans of the scaffolds in 56 patients showed a smaller-sized implant in the majority of the cases when compared with the native meniscus with an irregular surface at the 5-year follow-up. During the follow-up period, 87.6% of the implants survived in this study. At 5 years of follow-up, 87.9% of the medial scaffolds were still functioning versus 86.9% of the lateral scaffolds. In total, 23 treatments had failed: 10 removed scaffolds because of breakage, 7 conversions to meniscal allograft transplantation, 4 conversions to unicompartmental knee arthroplasty, and 2 conversions to total knee arthroplasty. Conclusion: The polyurethane meniscal implant was able to improve knee joint function and reduce pain in patients with segmental meniscal deficiency over 5 years after implantation. The MRI appearance of this scaffold was different from the original meniscal tissue at the midterm follow-up. The treatment survival rates of 87.9% of the medial scaffolds and 86.9% of the lateral scaffolds in the present study compared favorably with those published concerning meniscal allograft transplantation after total meniscectomy.

Optimizing Anisotropic Polyurethane Scaffolds to Mechanically Match with Native Myocardium.

Biodegradable cardiac patch is desirable to possess mechanical properties mimicking native myocardium for heart infarction treatment. We fabricated a series of anisotropic and biodegradable polyurethane porous scaffolds via thermally induced phase separation (TIPS) and tailored their mechanical properties by using various polyurethanes with different soft segments and varying polymer concentrations. The uniaxial mechanical properties, suture retention strength, ball-burst strength, and biaxial mechanical properties of the anisotropic porous scaffolds were optimized to mechanically match native myocardium. The optimal anisotropic scaffold had a ball burst strength (20.7 ± 1.5 N) comparable to that of native porcine myocardium (20.4 ± 6.0 N) and showed anisotropic behavior close to biaxial stretching behavior of the native porcine myocardium. Furthermore, the optimized porous scaffold was combined with a porcine myocardium-derived hydrogel to form a biohybrid scaffold. The biohybrid scaffold showed morphologies similar to the decellularized porcine myocardial matrix. This combination did not affect the mechanical properties of the synthetic scaffold alone. After in vivo rat subcutaneous implantation, the biohybrid scaffolds showed minimal immune response and exhibited higher cell penetration than the polyurethane scaffold alone. This biohybrid scaffold with biomimetic mechanics and good tissue compatibility would have great potential to be applied as a biodegradable acellular cardiac patch for myocardial infarction treatment.

Effect of corrugated structure on the collapsing of the small-diameter vascular scaffolds.

Major barriers to the development of a desirable small-diameter vascular scaffold are the compliance mismatch between natural and artificial vessels and low long-term patency. In the present study, the electrospinning technique was performed to fabricate three different structures, i.e. non-corrugated, radial corrugated, and axial corrugated, for small-diameter vascular graft. The compliance measurement shows that the value of dynamic compliance for the crimping structures is lower than that of the simple structure and decreases in the order: non-corrugated structure &gt; radial corrugated structure &gt; axial corrugated structure. The crimping in the axial direction decreases the more than requirement compliance of Thermoplastic polyurethane (TPU) scaffolds. The scaffolds should maintain its tubular shape during the grafting to avoid any collapsing, hence, the setup for measuring the resistance of scaffold against radial compression was designed and the result was reported as the dimensionless collapse coefficient. For non-corrugated, radial corrugated, and axial corrugated structures at constant intraluminal pressure, the required external pressure corresponding to the collapse coefficients equal to 0.5 were 140.92 ± 3.43, 136.51 ± 2.53, and 152.26 ± 3.08 mmHg, respectively. The reinforcing role of the axial crimping shifts the collapsing threshold to higher external pressure. Besides, the fabricated scaffolds provided the burst strength very close to those of the native blood vessels.

Polyurethane Composite Scaffolds Modified with the Mixture of Gelatin and Hydroxyapatite Characterized by Improved Calcium Deposition.

The skeleton is a crucial element of the motion system in the human body, whose main function is to support and protect the soft tissues. Furthermore, the elements of the skeleton act as a storage place for minerals and participate in the production of red blood cells. The bone tissue includes the craniomaxillofacial bones, ribs, and spine. There are abundant reports in the literature indicating that the amount of treatments related to bone fractures increases year by year. Nowadays, the regeneration of the bone tissue is performed by using autografts or allografts, but this treatment method possesses a few disadvantages. Therefore, new and promising methods of bone tissue regeneration are constantly being sought. They often include the implantation of tissue scaffolds, which exhibit proper mechanical and osteoconductive properties. In this paper, the preparation of polyurethane (PUR) scaffolds modified by gelatin as the reinforcing factor and hydroxyapatite as the bioactive agent was described. The unmodified and modified scaffolds were tested for their mechanical properties; morphological assessments using optical microscopy were also conducted, as was the ability for calcification using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Moreover, each type of scaffold was subjected to a degradation process in 5M NaOH and 2M HCl aqueous solutions. It was noticed that the best properties promoting the calcium phosphate deposition were obtained for scaffolds modified with 2% gelatin solution containing 5% of hydroxyapatite.

The effect of oxygen plasma pretreatment on the properties of mussel-inspired polydopamine-decorated polyurethane nanofibers

AbstractIn this study, polyurethane (PU) scaffolds were fabricated by electrospinning technology and modified through the deposition of polydopamine (PDA) on the activated surface under oxygen plasma treatment. Herein, the effect of the modification process on the homogeneous surface coating and the changes in the physicochemical and biological properties were evaluated. Morphological observations demonstrated decoration of the nanofibrous microstructure with PDA, while the uniformity and homogeneity of the deposited layer increased after plasma oxygen treatment. Hydrophilicity measurements and swelling ratio indicated a remarkable improvement in the interaction of scaffolds with water molecules when the PDA coating is applied on the surface of the treated nanofibers. The biomineralization of the samples was characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) images. It was found that PDA has the capability for mineralization, and the amount of deposited hydroxyapatite increased as a function of PDA content. Thein vitroevaluation of constructs indicated great improvement in cell-scaffold interactions, biocompatibility, and alkaline phosphatase activity after coating the PDA on the plasma-modified matrix. These results suggest that PDA coating, especially after oxygen plasma treatment, improves the physicochemical andin vitroproperties of PU scaffolds for bone tissue engineering application.

Construction and Biocompatibility of Three-Dimensional Composite Polyurethane Scaffolds in Liquid Crystal State.

Liquid crystal (LC), a characteristic substance of biofilms, has been reported to positively affect cell affinity. To better combine and utilize the properties of an LC and the advantages of polyurethane (PU) elastomers, the three-dimensional printing (3DP) molding technology and the simple soaking-swelling blending technology were used to construct PU/LC 3D composite scaffolds, and the compressive strength, porosity, hydrophilicity, and in vitro cell experiments of the scaffolds were initially discussed. The results indicated that the newly developed PU/LC 3D composite scaffolds exhibited an LC state; the addition of an LC did not change the porosity after swelling while maintaining a high porosity; the compressive strength of the composite scaffolds decreased while still maintaining high mechanical properties and enhancing hydrophilicity. At the same time, it could improve the cell affinity on the surface of the material, which was beneficial to increase the cell adhesion rate and cell activity, promote the osteogenic differentiation of human mesenchymal stem cells grown on the materials, and improve the alkaline phosphatase activity, calcium nodules, and the expression of related osteogenic genes and proteins. These results demonstrated potential applications of PU/LC composite scaffolds in repairing or regeneration of bone tissue engineering.

Functional cell phenotype induction with TGF-β1 and collagen-polyurethane scaffold for annulus fibrosus rupture repair.

Appropriate cell sources, bioactive factors and biomaterials for generation of functional and integrated annulus fibrosus (AF) tissue analogues are still an unmet need. In the present study, the AF cell markers, collagen type I, cluster of differentiation 146 (CD146), mohawk (MKX) and smooth muscle protein 22α (SM22α) were found to be suitable indicators of functional AF cell induction. In vitro 2D culture of human AF cells showed that transforming growth factor β1 (TGF-β1) upregulated the expression of the functional AF markers and increased cell contractility, indicating that TGF-β1-pre-treated AF cells were an appropriate cell source for AF tissue regeneration. Furthermore, a tissue engineered construct, composed of polyurethane (PU) scaffold with a TGF-β1-supplemented collagen type I hydrogel and human AF cells, was evaluated with in vitro 3D culture and ex vivo preclinical bioreactor-loaded organ culture models. The collagen type I hydrogel helped maintaining the AF functional phenotype. TGF-β1 supplement within the collagen I hydrogel further promoted cell proliferation and matrix production of AF cells within in vitro 3D culture. In the ex vivo IVD organ culture model with physiologically relevant mechanical loading, TGF-β1 supplement in the transplanted constructs induced the functional AF cell phenotype and enhanced collagen matrix synthesis. In conclusion, TGF-β1-containing collagen-PU constructs could induce the functional cell phenotype of human AF cells in vitro and in situ. This combined cellular, biomaterial and bioactive agent therapy has a great potential for AF tissue regeneration and rupture repair.

Novel electrospun polyurethane scaffolds containing bioactive glass nanoparticles

In the present study, polyurethane (PU) nanocomposite scaffolds containing bioactive glass nanoparticles (BG-NPs) were successfully fabricated through the electrospinning process. The BG-NPs were synthesized through the sol–gel method. PU solutions (10% w/v) containing different weight percentages of the BG-NPs (5, 10 and 15 wt.%) in dimethylformamide/tetrahydrofuran were prepared. To determine both the size of BG-NPs and the diameter of the nanofibers, transmission electron microscopy and scanning electron microscopy were carried out. The surface morphology, mechanical properties, bioactivity and degradation rate of the scaffolds were studied. Fourier transform infrared spectroscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy confirmed the presence of BG within the scaffolds. The tensile strength of nanocomposite scaffolds was in the range 5–8 MPa, which is in good agreement with the tensile strength of cancellous bone tissue. MG63 cells attached to and proliferated well within the scaffolds; therefore, cellular growth was also improved in the nanocomposite scaffolds. Based on the results, the novel PU/BG-NP (10 wt.%) nanocomposite scaffold has a great potential to be applied in cancellous bone tissue engineering.

Electrospun novel nanocomposite comprising polyurethane integrated with ayurveda amla oil for bone tissue engineering.

Ayurveda oil contains numerous source of biological constituents which plays an important role in reducing the pain relief caused during bone fracture. The aim of the study is to fabricate the polyurethane (PU) scaffold for bone tissue engineering added with ayurveda amla oil using electrospinning technique. Scanning Electron Microscopy (SEM) analysis showed that the fabricated nanocomposites showed reduced fiber diameter (758 ± 185.46 nm) than the pristine PU (890 ± 116.91 nm). Fourier Infrared Analysis (FTIR) revealed the existence of amla oil in the PU matrix by hydrogen bond formation. The contact angle results revealed the decreased wettability (116° ± 1.528) of the prepared nanocomposites compared to the pure PU (100° ± 0.5774). The incorporation of amla oil into the PU matrix improved the surface roughness. Further, the coagulation assay indicated that the addition of amla oil into PU delayed the blood clotting times and exhibited less toxic to red blood cells. Hence, the fabricated nanocomposites showed enhanced physicochemical and better blood compatibility parameters which may serve as a potential candidate for bone tissue engineering.

Functionalization of 3-D porous thermoplastic polyurethane scaffolds by two-stage polydopamine/hydroxyapatite composite nanoparticles

Functionalization of 3-D porous thermoplastic polyurethane scaffolds by two-stage polydopamine/hydroxyapatite composite nanoparticles

Preparation and characterization of aliphatic polyurethane and modified hydroxyapatite composites for bone tissue engineering

Surfaces of nano-hydroxyapatite (n-HA) particles were modified by grafting of etidronic acid (ETD, 0.1 M) and were reinforced into polyurethane scaffolds prepared by foaming method to develop porous modified nano-hydroxyapatite/polyurethane (m-HA/PU) nanocomposite scaffolds for bone tissue engineering. Particle size and morphology of nanoparticles were studied using X-ray diffraction, transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. TEM and SEM results revealed that the surface of obtained modified hydroxyapatite (m-HA) particles was completely changed from grain- to plate-type structure with the size of 40 nm. Chemical structure, mechanical properties and biomedical application were studied using Fourier transform infrared spectroscopy (FTIR), universal testing machine and in vitro studies. In FTIR spectra, disappearance of peak around 2270 cm−1 confirmed the formation of polyurethane nanocomposite scaffolds and bands in the spectral range of 1400 and 800–900 correspond to the presence of calcium and phosphate groups due to hydroxyapatite. As the concentration of m-HA increased from 0 to 30 wt%, the compressive strength of the resulting PU/m-HA nanocomposites increased from 0.094 to 22.4 MPa. In vitro study with simulated body fluid (SBF) for 4 weeks indicated that surface was partially hydrolysed. Cell culture study showed that m-HA/PU nanocomposite scaffold is well suited for application in bone tissue engineering.

Paracrine signalling from monocytes enables desirable extracellular matrix accumulation and temporally appropriate phenotype of vascular smooth muscle cell-like cells derived from adipose stromal cells

In vascular tissue engineering, the ability to obtain a robust and safe vascular tissue cell source (e.g. vascular smooth muscle cells (VSMCs)) and to promote vascular tissue-specific extracellular matrix (ECM) protein production is critically important. Mature blood vessel-derived VSMCs are not practical for in vitro vascular tissue regeneration. The authors have conceived a strategy to differentiate adipose derived stromal cells (ASCs) into VSMC-like cells (ASC-VSMCs) that were similar to mature umbilical artery VSMCs at the transcriptional, protein and contraction function levels. Monocytes/macrophages are known as important regulators of the inflammation and regeneration processes within different tissue types of the body. However, our understanding of the potential interactions between specific tissue-like cells differentiated from stem/stromal cells (e.g. ASC-VSMCs) and monocytes/macrophages (cued by specific biomaterial scaffolds) is still limited. In this study, indirect and direct ASC-VSMC-monocyte co-cultures were constructed within a porous polyurethane scaffold (D-PHI) previously shown to have an immunomodulatory character. The effects of monocytes/macrophages on the cellularity (cell number detected with DNA quantification assay), ECM (glycosaminoglycan (GAG), collagen, and elastin) accumulation as well as the maintenance of contractile VSMC markers (calponin and smoothelin) of the ASC-VSMCs after a month of co-culture were investigated. It was found that monocyte paracrine signalling in D-PHI positively affected the cellularity and ECM accumulation of ASC-VSMCs in co-culture. Cause-effect relationships were also identified between the release of pro-inflammatory/anti-inflammatory factors (i.e. IL6, TGF-β1) in co-culture and the expression of contractile proteins (calponin and smoothelin) by ASC-VSMCs. This study demonstrated the importance of combining an immune cell strategy with stromal cell derived VSMCs (i.e. ASC-VSMCs) to achieve a practical vascular tissue engineering outcome. Statement of significanceAdipose stromal cell derived-vascular smooth muscle cells (ASC-VSMCs) are a promising cell source for vascular tissue engineering. Monocytes/monocyte derived macrophages can be harnessed as an immune-assisted strategy to promote vascular tissue regeneration. This study demonstrated that the co-culture of human ASC-VSMCs with monocytes significantly enhanced the cellularity and extracellular matrix (ECM) accumulation within anionic polyurethane (D-PHI) scaffolds, partially mediated by monocyte paracrine signalling mechanisms. In addition, specific VSMC contractile markers (calponin and smoothelin) were still present in ASC-VSMCs when the cells were exposed to monocytes for a month in vitro. This study corroborated the potential selection of ASC-VSMCs for in vitro engineering of vascular tissue in an immunomodulatory biomaterial scaffold (e.g. D-PHI) based co-culture system containing monocytes.

Rapid and reusable detection of hydrogen peroxide using polyurethane scaffold incorporated with cerium oxide nanoparticles

We report a novel approach to using a polyurethane scaffold incorporated with cerium oxide nanoparticles as an alternative to the natural enzyme horseradish peroxidase for rapid and reusable detection of hydrogen peroxide. After the preparation of polyurethane from soybean oil and malic acid, cerium or iron oxide nanoparticles were synthesized and incorporated into the polyurethane scaffold by ultrasonic treatment. Formation of nanoparticles was characterized using Fourier transform infrared, transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. Iron oxide nanoparticles (FeONPs) with an average size of 50 nm were not uniformly integrated; however, spherical cerium oxide nanoparticles (CeONPs) with an average size of 14 nm were easily incorporated into the polyurethane scaffold. The CeONP-incorporated polyurethane scaffold was highly responsive (<10 s) to H2O2, with a limit of detection of 3.18 µM, and was reusable for at least ten cycles without significant loss of detection activity. However, the response time of CeONP solution was more than 5 min. Both FeONP solution and FeONP incorporated polyurethane scaffold were poor at detecting H2O2.

Effects of ceramic particle size on cell attachment and viability in polyurethane-based bone adhesive composites

Millions of people require bone injury treatment and there have been many methods suggested for the stabilization of bone fractures. The need for the development of new methods is obvious since current stabilization methods are inadequate. Here, we described the development of polyurethane-based bone adhesives composites containing β-tricalcium phosphate ceramics in different sizes and ratios. To characterize the proposed materials, Fourier transform infrared spectroscopy, hydrogen-nuclear magnetic resonance, differential scanning calorimetry analyses together with scanning electron microscopy observations, and micro-computerized tomography imaging were examined. Furthermore, in vitro performance of the produced materials was tested by using MG63 human osteosarcoma cell line, and an ex vivo modeling study was conducted to test the mechanical performance of resulting materials using bovine rib bone. All materials were exhibited high porosity (above 90%) and homogeneous distribution of ceramic particles. Polyurethane scaffolds containing 40% (w/w) 1–2 mm β-tricalcium phosphate were shown the highest compressive strength as 1.34 ± 0.10 MPa. In addition, 85.75% cell viability was recorded according to the cytotoxicity analysis and also the cell proliferation was found highest in the same group. Taken into account the obtained results, the prepared polyurethane-based bone adhesive materials containing ceramics has a great potential to transform into a final product and meet a clinically significant medical need.

Resveratrol-loaded polyurethane nanofibrous scaffold: viability of endothelial and smooth muscle cells

Acellular small-caliber tissue-engineered vascular grafts (SCTEVGs) have low patency rate due to complications including thrombosis and intimal hyperplasia. Rapid endothelialization, antithrombosis and antiproliferation approaches are suitable for dispelling these complications. Nevertheless, common antithrombosis and antiproliferation techniques are usually incompatible with rapid endothelialization on vascular grafts. To overcome these obstacles, we developed nanofibrous polyurethane scaffolds loaded with resveratrol drug, which is a natural compound extracted from plants and shows multifaceted effects in cardiovascular protection. It was found that the tensile strength and Young’s modulus in modified scaffolds were significantly increased by resveratrol loading into membranes. The tensile strengths and breaking strains of resveratrol-loaded scaffolds were close to that of native vessels. The resveratrol release profile from the nanofibrous scaffolds occurred in a sustained manner. The anti-thrombogenicity of resveratrol-loaded nanofibers increased compared to polyurethane alone, with the result that prolonged human blood clotting time and lower hemolysis were detected on these scaffolds. The viability of human umbilical vein endothelial cells and smooth muscle cells on resveratrol-loaded scaffolds was evaluated. Our findings demonstrated that resveratrol-loaded nanofibers resulted in not only appropriate antithrombotic properties, but the formation of a monolayer of endothelial cells on the scaffold surface and lower smooth muscle cell growth. These resveratrol-loaded nanofibers are suggested as potential scaffolds for SCTEVGs.

Establishment of a Spontaneous Stromal Microenvironment from Cord Blood Supports Human Dynamic Erythropoietic Temporal Maturation in Long-Term Serum- and Cytokine-Free 3D Cultures and Reveals a Distinct CD44hi Population

Dynamic cultures which can represent physiologic erythropoiesis in vitro require a three-dimensional (3D) architecture with a supportive microenvironment and addition of erythropoietin (EPO). We have previously reported on a 3D bone marrow (BM) biomimicry using polyurethane scaffolds to expand cord blood mononuclear cells (CBMNCs) in a serum- and cytokine-free environment, without addition of dexamethasone, for 28 days (D). CBMNCs were seeded (4x106 cells/scaffold), supplemented with 10ng/mL stem cell factor (SCF; D0-D28) and 100mU/mL EPO (D7-D28), with medium exchange every 3D and exposed to a hypoxia (5%)/normoxia (20%) schedule to mimic BM oxygen gradients. Hypoxia induced rapid erythroid commitment and established an early erythroid progenitor population in the absence of EPO. Normoxia and EPO was required at later maturational stages and enhanced the γ-globin to β-globin switch. We identified D7-D14 as crucial for endogenous cytokine production. Herein, we extended cultures to D48 using two high-dose EPO-stimulation cycles (1U/mL; D20 and D44) to enhance erythropoiesis and further define the microenvironment. Proliferation was higher after EPO pulses (p&lt;0.05) but did not result in enhanced erythropoiesis, suggesting the absence of erythroid precursors. An allogeneic CB unit was added to "recharge" the cultured scaffolds at D39 and a new cycle of erythropoietic differentiation was initiated. Cell proliferation was 4.5-fold higher at D68, compared with that at D28. From D53-D68, CD71+CD235a+ cells were constantly produced (25-54%), corresponding with the presence of erythroid precursors supporting CFU-E and BFU-E. Erythroblastic islands were identified and maturing and enucleated reticulocytes/RBCs were abundant (19±2%; 1±0.3x106 cells) with expression of γ- and β-globin, band 3 and 4.1R RBC membrane proteins. To further evaluate the relative contributions of each CB unit to the "recharge" culture, seeded scaffolds were subjected to irradiation (or not) 48h prior to recharge. By D65, &gt;30% of supernatant cells were CD71+/modCD235a+ and supported BFU-E and CFU-E. Proliferation in long-term cultures was attributed to the second CB unit, regardless of irradiation, as shown by HLA-typing of D68 cells; the first CBMNCs only contributed to establishment of the microenvironment. To further characterize erythroid differentiation dynamics, expression of CD44 vs CD235a was used to identify and sort three erythroid populations. Progenitors in CD44-/modCD235a- populations evolved to CD44modCD235amod, and then to CD44-/modCD235a+ cells, which constitute the most mature erythroid phenotype; CD44modCD235amod erythroid precursors supported mainly BFU-E and CFU-E. A unique CD44hiCD71mod population increased during culture, displayed myeloid progenitor morphology and only supported CFU-GM. This population did not express CD34, CD33 or CD14 but expressed c-KIT, which suggests a hematopoietic population that provides essential culture support. Further characterization of the spontaneously created microenvironment by in situ quantitative analysis of scaffold mid-sections during the 68-day culture showed varying and high dynamic expression of Nestin, STRO-1, CD146, CD68 and CD169 in separate cell populations as well as expression of RUNX2 and Osx. Osteopontin was not detected. In summary, a BM biomimicry composed of diverse stromal populations was spontaneously created in the 3D in vitro scaffold system. This microenvironment proved to effectively induce and sustain erythropoiesis to enucleation to at least D68 when supplied with a second source of CBMNCs, without addition of stroma-specific factors. A unique CD44hi immature monocyte/macrophage population was identified, which contributes to the inductive microenvironment, and distinct stages of human erythroid maturation could be identified using CD44 and CD235a. This work presents a novel and dynamic ex vivo model that can (1) recapitulate physiologic human erythropoiesis in steady-state and stress conditions, (2) capture the fetal to adult hemoglobin transition, (3) explore the direct role of oxygen on erythropoiesis, (4) assess the microenvironment relevant to erythropoiesis in the absence of serum and exogenous factors, (5) sustain long-term erythropoiesis with terminal maturation and, (6) explore the different stromal niche environments spontaneously created for the support of erythropoiesis. Disclosures Brito Dos Santos: GE Healthcare: Employment.