Improved Neural Differentiation of Human-induced Pluripotent Stem Cell [hiPSCs] on a Novel Polyurethane-based Scaffold Containing Iron Oxide Nanoparticles [Fe2O3 NPs].

BACKGROUND: Repair of the nervous system in humans has always been complicated and faced difficulties. Cell transplantation approaches using biocompatible scaffolds might be an attractive therapeutic strategy for neuronal regeneration. OBJECTIVE: We designed a cell delivery platform based on polyurethane [PU] and modified it with iron oxide nanoparticles [Fe2O3 NPs] for neural induction of human-induced pluripotent stem cells [hiPSC]. Forskolin, IBMX, and different ratios of FBS were employed to induce neurogenesis of hiPSCs. Neural differentiations were assessed at the level of genes and proteins. METHODS: As was shown by MTT colorimetric assay, the proliferation and viability of SNL 76/7 on PU/ Fe2O3 were superior in comparison with pure PU and Fe2O3. hiPSCs cultured with PU/Fe2O3 exhibited an elevated expression of ß3-tubulin, MAP2, NSE, OLIG2, as compared to controls. Furthermore, Acridine Orange staining assured the survival and viability of hiPSCs after 14 days of differentiation. RESULTS: All in all, our findings pointed out the biocompatibility and positive regulatory effect of PU/Fe2O3 on neural markers. CONCLUSION: We believe this scaffold could be a potential candidate for future nerve differentiation applications.

Bioscaffold Stiffness Mediates Aerosolized Nanoparticle Uptake in Lung Epithelial Cells.

In this study, highly porous, ultrasoft polymeric mats mimicking human tissues were formed from novel polyurethane soft dendritic colloids (PU SDCs). PU SDCs have a unique fibrillar morphology controlled by antisolvent precipitation. When filtered from suspension, PU SDCs form mechanically robust nonwoven mats. The stiffness of the SDC mats can be tuned for physiological relevance. The unique physiochemical characteristics of the PU SDC particles dictate the mechanical properties resulting in tunable elastic moduli ranging from 200 to 800 kPa. The human lung A549 cells cultured on both stiff and soft PU SDC membranes were found to be viable, capable of supporting the air-liquid interface (ALI) cell culture, and maintained barrier integrity. Furthermore, A549 cellular viability and uptake efficiency of aerosolized tannic acid-coated gold nanoparticles (Ta-Au) was found to depend on elastic modulus and culture conditions. Ta-Au nanoparticle uptake was twofold and fourfold greater on soft PU SDCs, when cultured at submerged and ALI conditions, respectively. The significant increase in endocytosed Ta-Au resulted in a 20% decrease in viability, and a 4-fold increase in IL-8 cytokine secretion when cultured on soft PU SDCs at ALI. Common tissue culture materials exhibit super-physiological elastic moduli, a factor found to be critical in analyzing nanomaterial cellular interactions and biological responses.

A biodegradable block polyurethane nerve-guidance scaffold enhancing rapid vascularization and promoting reconstruction of transected sciatic nerve in Sprague-Dawley rats.

Reconstruction of peripheral nerve defects with tissue engineered nerve scaffolds is an exciting field of biomedical research and holds potential for clinical application. However, due to poor neovascularization after the implantation, nerve regeneration is still not satisfactory, especially for large nerve defects. These obstacles hinder the investigation of basic neurobiological principles and development of a wide range of treatments for peripheral nerve diseases. Herein, we designed an amphiphilic alternating block polyurethane (abbreviated as PU) copolymer-based nerve guidance scaffold, which has good Schwann cell compatibility, and more importantly, a rapid vascularization of the scaffold in vivo. In the sciatic nerve transection model of SD rats, vascularized PU nerve guidance scaffolds induced rapid regeneration of nerve fibers and axons along the scaffold. Through the analysis of nerve electrophysiology, sciatic nerve functional index, histology, and immunofluorescence related to angiogenesis, we determined that PU with rapid vascularization function enhances recovery and re-obtains nerve conduction function. Our study points out a new strategy of using nerve tissue engineering scaffolds to treat large nerve defects.

Highly Sensitive Bacteria-Responsive Membranes Consisting of Core-Shell Polyurethane Polyvinylpyrrolidone Electrospun Nanofibers for In Situ Detection of Bacterial Infections.

Bacteria responsive color-changing wound dressings offer a valuable platform for continuous monitoring of the wound bed facilitating early detection of bacterial infections. In this study, we present a highly sensitive electrospun nanofibrous polyurethane wound dressing incorporating a hemicyanine-based chromogenic probe with a labile ester linkage that can be enzymatically cleaved by bacterial lipase released from clinically relevant strains, such as Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA). A rapid chromogenic response was achieved by localizing the dye at the surface of core-shell fibers, resulting in a 5x faster response relative to conventional nanofibers. By incorporating polyvinylpyrrolidone (PVP) dopant in the shell, the sensitivity was boosted to enable detection of bacteria at clinically relevant concentrations after 2 h exposure: 2.5 × 105 CFU/cm2 P. aeruginosa and 1.0 × 106 CFU/cm2 MRSA. Introduction of PVP in the shell also boosted the degree of hydrolysis of the chromogenic probe by a factor of 1.2× after a 3 h exposure to a low concentration of P. aeruginosa (105 CFU/cm2). PVP was also found to improve the discernibility of the color change at high bacterial concentrations. The co-operativity between the chromogenic probe, fiber structure, and polymer composition is well-suited for timely in situ detection of wound infection.

Improved tissue integration of a new elastic intraperitoneal stoma mesh prosthesis.

Parastomal herniation is a frequent complication in colorectal surgery, occurring with a prevalence of 30-80%. The aim of the study was to create a new intraperitoneal colostoma mesh prosthesis (IPST) with enhanced elastic properties made with thermoplastic polyurethane (TPU) monofilaments. We performed open terminal sigmoid colostomies reinforced with either a 10 cm by 10 cm polyvinylidene fluoride (PVDF) or a new TPU/PVDF composite mesh in a total of 10 minipigs. Colostoma was placed paramedian in the left lower abdomen and IPST meshes were fixed intraperitoneal. After 8 weeks, the animals were euthanized after laparoscopic exploration and specimen were explanted for histological investigations. Implantation of a new IPST-mesh with enhanced elastic properties was feasible in a minipig model within an observation period of 8 weeks. Immunohistochemically, Collagen I/III ratio as a marker of tissue integration was significantly higher in TPU-group versus PVDF group (9.4 ± 0.5 vs. 8.1 ± 0.5, p = 0.002) with a significantly lower inflammatory reaction measured by a smaller inner granuloma at mesh-colon interface (17.6 ± 3.3 µm vs. 23 ± 5 µm, p < 0.001). A new TPU/PVDF composite mesh with enhanced elastic properties as IPST was created. Stoma surgery and especially the evaluation of the new stoma mesh prosthesis are feasible with reproducible results in an animal model. Tissue integration expressed by Collagen I/III ratio seems to be improved in comparison to standard-elastic PVDF-IPST meshes.

Biological acellular pericardial mesh regulated tissue integration and remodeling in a rat model of breast prosthetic implantation.

The use of biological meshes has proven beneficial in surgical restriction and periprosthetic capsular contracture following breast prosthetic-reconstruction. Three different types (smooth, texturized, and polyurethane) of silicone round mini prostheses were implanted under rat skin with or without two different bovine acellular pericardial biological meshes (APMs, BioRipar, and Tutomesh). One hundred eighty-six female rats were divided into 12 groups, sacrificed after 3, 6, and 24 weeks and tissue samples investigated by histology and immunohistochemistry. Implantation of both APMs, with or without prostheses, reduced capsular α-SMA expression and CD3+ inflammatory cell infiltration, increasing capillary density and cell proliferation, with some differences. In particular, Tutomesh was associated with higher peri-APM CD3+ inflammation, prosthetic capsular dermal α-SMA expression and less CD31+ vessels and cell proliferation compared with BioRipar. None differences were observed in tissue integration and remodeling following the APM + prostheses implantation; the different prostheses did not influence tissue remodeling. The aim of our study was to investigate if/how the use of different APMs, with peculiar intrinsic characteristics, may influence tissue integration. The structure of APMs critically influenced tissue remodeling after implantation. Further studies are needed to develop new APMs able to optimize tissue integration and neoangiogenesis minimizing periprosthetic inflammation and fibrosis.

Targeting microplastic particles in the void of diluted suspensions.

Accumulation of microplastic in the environment and food chain will be a grand challenge for our society. Polyurethanes are widely used synthetic polymers in medical (e.g. catheters) and industrial products (especially as foams). Polyurethane is not abundant in nature and only a few microbial strains (fungi and bacteria) and enzymes (polyurethaneases and cutinases) have been reported to efficiently degrade polyurethane. Notably, in nature a long period of time (from 50 to >100 years depending on the literature) is required for degradation of plastics. Material binding peptides (e.g. anchor peptides) bind strongly to polymers such as polypropylene, polyethylene terephthalate, and polyurethane and can target specifically polymers. In this study we report the fusion of the anchor peptide Tachystatin A2 to the bacterial cutinase Tcur1278 which accelerated the degradation of polyester-polyurethane nanoparticles by a factor of 6.6 in comparison to wild-type Tcur1278. Additionally, degradation half-lives of polyester-polyurethane nanoparticles were reduced from 41.8 h to 6.2 h (6.7-fold) in a diluted polyester-polyurethane suspension (0.04% w/v).

Temporal trends and developmental patterns of plasma polybrominated diphenyl ether concentrations over a 15-year period between 1998 and 2013.

Polybrominated diphenyl ethers (PBDEs) were used extensively as flame retardants in furniture containing polyurethane foam until they were phased out of use, beginning in 2004. We examined temporal changes in plasma PBDE concentrations from 1998 to 2013 and characterized patterns of exposure over the early lifecourse among 334 children (903 samples) between birth and 9 years. We examined time trends by regressing PBDE concentration on year of sample collection in age-adjusted models and characterized developmental trajectories using latent class growth analysis (LCGA). Controlling for age, BDE-47 concentrations decreased 5% (95% confidence interval (CI): -9, -2) per year between 1998 and 2013. When considering only postnatal samples, this reduction strengthened to 13% (95% CI: -19, -9). Findings for BDE-99, 100 and 153 were similar, except that BDE-153 decreased to a lesser extent when both prenatal and postnatal samples were considered (-2%, 95% CI: -7, 0). These findings suggest that, on average, pentaBDE body burdens have decreased since the 2004 phase-out of these chemicals. When examining developmental period, PBDE concentrations peaked during toddler years for the majority of children, however, our observation of several unique trajectories suggests that a single measure may not accurately reflect exposure to PBDEs throughout early life.

Improved Chondrogenic Differentiation of rAAV SOX9-Modified Human MSCs Seeded in Fibrin-Polyurethane Scaffolds in a Hydrodynamic Environment.

The repair of focal articular cartilage defects remains a problem. Combining gene therapy with tissue engineering approaches using bone marrow-derived mesenchymal stem cells (MSCs) may allow the development of improved options for cartilage repair. Here, we examined whether a three-dimensional fibrin-polyurethane scaffold provides a favorable environment for the effective chondrogenic differentiation of human MSCs (hMSCs) overexpressing the cartilage-specific SOX9 transcription factor via recombinant adeno-associated virus (rAAV) -mediated gene transfer cultured in a hydrodynamic environment in vitro. Sustained SOX9 expression was noted in the constructs for at least 21 days, the longest time point evaluated. Such spatially defined SOX9 overexpression enhanced proliferative, metabolic, and chondrogenic activities compared with control (reporter lacZ gene transfer) treatment. Of further note, administration of the SOX9 vector was also capable of delaying premature hypertrophic and osteogenic differentiation in the constructs. This enhancement of chondrogenesis by spatially defined overexpression of human SOX9 demonstrate the potential benefits of using rAAV-modified hMSCs seeded in fibrin-polyurethane scaffolds as a promising approach for implantation in focal cartilage lesions to improve cartilage repair.

Development of high-performance biodegradable rigid polyurethane foams using all bioresource-based polyols: Lignin and soy oil-derived polyols.

Development of biodegradable polyurethane materials is the most promising in the wider context of the "greening" of industrial chemistry. To tackle this challenge, a novel biodegradable polyurethane foam from all bioresource-based polyols (lignin and soy oil-derived polyols) and polymeric methyldiphenyl diisocyanate (pMDI) have been synthesized via a one-pot and self-rising process. All these foam samples have the internal cellular morphology and microstructure. FTIR result exhibits characteristic peaks of polyurethane, and indicates covalent bonds between soy-based polyurethane and lignin, and the lignin powders can react with pMDI via active -H and -CNO. In addition, hydrogen bonding also plays an important role in forming the 3D structures. These interactions and chemical bonds made the prepared foam samples form the 3D macromolecular structure with improved mechanical, thermal, and biodegradable properties. The reaction process is time-saving and cost-effective as it requires no blowing agent and minimum processing steps, while exploring the potential of using the higher content of nature bioresource constituents.

Fibronectin adsorption on surface-modified polyetherurethanes and their differentiated effect on specific blood elements related to inflammatory and clotting processes.

After the introduction of a medical device into the body, adhesive proteins such as fibronectin (Fn) will adsorb to the surface of the biomaterial. Monocytes (MCs) will interact with these adsorbed proteins, and adopt either a proinflammatory and/or prowound healing phenotype, thereby influencing many blood interaction events including thrombogenesis. In this work, Fn adsorption as well as subsequent MC response and thrombus formation were investigated on two surfaces-modified polyetherurethanes (PEUs) using different surface modifiers: an anionic/dihydroxyl oligomeric (ADO) additive, known to enable cell adhesion, and a fluorinated polypropylene oxide oligomer (PPO), known to reduce platelet adhesion. Results indicated that at 24 h of MC culture, PEU-ADO and PEU-PPO promoted an anti-inflammatory character relative to the base PEU. Longer clotting times, based on a free hemoglobin assay, were also found on the two surface-modified PEUs relative to the native one, suggesting their potential for the reduction of thrombus formation. In presence of a Fn monolayer, the surface-modified PEUs conserved a lower thrombogenic character than the base PEU, and was however significantly decreased when compared to prior protein adsorption. Furthermore, Fn coatings increased the MC production levels of tumor necrosis factor-α and interleukin-10 at 24 h, while not affecting the anti-inflammatory effect of the modifications relative to the base PEU. This finding was most prominent on PEU-PPO, suggesting that the interaction of the adsorbed Fn with blood cells was different for the two additives. Hence, the results highlighted differentiating effects of Fn adsorption on specific blood activating processes related to inflammatory and thrombotic responses.

Electroactive biodegradable polyurethane significantly enhanced Schwann cells myelin gene expression and neurotrophin secretion for peripheral nerve tissue engineering.

Myelination of Schwann cells (SCs) is critical for the success of peripheral nerve regeneration, and biomaterials that can promote SCs' neurotrophin secretion as scaffolds are beneficial for nerve repair. Here we present a biomaterials-approach, specifically, a highly tunable conductive biodegradable flexible polyurethane by polycondensation of poly(glycerol sebacate) and aniline pentamer, to significantly enhance SCs' myelin gene expression and neurotrophin secretion for peripheral nerve tissue engineering. SCs are cultured on these conductive polymer films, and the biocompatibility of these films and their ability to enhance myelin gene expressions and sustained neurotrophin secretion are successfully demonstrated. The mechanism of SCs' neurotrophin secretion on conductive films is demonstrated by investigating the relationship between intracellular Ca(2+) level and SCs' myelination. Furthermore, the neurite growth and elongation of PC12 cells are induced by adding the neurotrophin medium suspension produced from SCs-laden conductive films. These data suggest that these conductive degradable polyurethanes that enhance SCs' myelin gene expressions and sustained neurotrophin secretion perform great potential for nerve regeneration applications.

Study of Biological Degradation of New Poly(Ether-Urethane-Urea)s Containing Cyclopeptide Moiety and PEG by Bacillus amyloliquefaciens Isolated from Soil.

The present work for the first time investigates the effect of Bacillus amyloliquefaciens, M3, on a new poly(ether-urethane-urea) (PEUU). PEUU was synthesized via reaction of 4,4'-methylenebis(4-phenylisocyanate) (MDI), L-leucine anhydride cyclopeptide (LACP) as a degradable monomer and polyethylene glycol with molecular weight of 1000 (PEG-1000). Biodegradation of the synthesized PEUU as the only source for carbon and nitrogen for M3 was studied. The co-metabolism biodegradation of the polymer by this organism was also investigated by adding mannitol or nutrient broth to the basic media. Biodegradation of the synthesized polymer was followed by SEM, FT-IR, TGA, and XRD techniques. It was shown that incubation of PEUU with M3 resulted in a 30-44 % reduction in polymer's weight after 1 month. This study indicates that the chemical structure of PEUU significantly changes after exposure to M3 due to hydrolytic and enzymatic degradation of polymer chains. The results of this work supports the idea that this poly(ether-urethane) is used as a sole carbon source by M3 and this bacterium has a good capability for degradation of poly(ether-urethane)s.

Structure-property relationships and biocompatibility of carbohydrate crosslinked polyurethanes.

Biocompatible and biodegradable polyurethanes (PUs) based on castor oil and polypropylene glycols (PPGs) were prepared using various carbohydrate crosslinkers: monosaccharide (glucose), disaccharide (sucrose) and polysaccharides (starch and cellulose). The mechanical and thermal properties were investigated and interpreted on the basis of SEM study. The advantage of incorporating various carbohydrates is to have tunable mechanical properties and biodegradability due to variety in their structure. The glass transition temperature and sorption behavior were dominated by the type of polyol than by the type of crosslinker. All the PUs were observed to be biodegradable as well as non-cytotoxic as revealed by MTT assay in normal lung cell line L132. The study supports the suitability of carbohydrates as important components of biocompatible PUs for development of biomedical devices.

Heat-transfer resistance measurement method (HTM)-based cell detection at trace levels using a progressive enrichment approach with highly selective cell-binding surface imprints.

Surface-imprinted polymers allow for specific cell detection based on simultaneous recognition of the cell shape, cell size, and cell membrane functionalities by macromolecular cell imprints. In this study, the specificity of detection and the detection sensitivity for target cells within a pool of non-target cells were analyzed for a cell-specific surface-imprinted polymer combined with a heat-transfer-based read-out technique (HTM). A modified Chinese hamster ovarian cell line (CHO-ldlD) was used as a model system on which the transmembrane protein mucin-1 (MUC1) could be excessively expressed and for which the occurrence of MUC1 glycosylation could be controlled. In specific cancer cells, the overexpressed MUC1 protein typically shows an aberrant apical distribution and glycosylation. We show that surface-imprinted polymers discriminate between cell types that (1) only differ in the expression of a specific membrane protein (MUC1) or (2) only differ in the membrane protein being glycosylated or not. Moreover, surface-imprinted polymers of cells carrying different glycoforms of the same membrane protein do target both types of cells. These findings illustrate the high specificity of cell detection that can be reached by the structural imprinting of cells in polymer layers. Competitiveness between target and non-target cells was proven to negatively affect the detection sensitivity of target cells. Furthermore, we show that the detection sensitivity can be increased significantly by repetitively exposing the surface to the sample and eliminating non-specifically bound cells by flushing between consecutive cell exposures.

Glutathione-responsive biodegradable poly(urea-urethane)s containing L-cystine-based chain extender.

A series of glutathione-responsive biodegradable poly(urea-urethane)s were synthesized from poly(ethylene glycol) as the soft segment and 1,6-hexamelthylene diisocyanate incorporating cystine-based chain extender as the hard segment. Structure and thermal properties of the poly(urea-urethane)s were characterized with attenuated total reflectance Fourier transform infrared, (1)H NMR, gel permeation chromatography, differential scanning calorimeter and thermogravimetric analyses. In vitro degradation test was carried out under physiological conditions in the presence of glutathione and the degradability of poly(urea-urethane)s were evaluated by the decrease in their molecular weight (M w), on which the degradation rate constants were calculated and kinetic equations were established. PU[Cys] had the highest degradation rate and it remained only 30% of the original M w in eight days. All the poly(urea-urethane)s were testified with noncytotoxicity and good biocompatibility.

A review of adaptive mechanisms in cell responses towards oxidative stress caused by dental resin monomers.

Dental composite resins are biomaterials commonly used to aesthetically restore the structure and function of teeth impaired by caries, erosion, or fracture. Residual monomers released from resin restorations as a result of incomplete polymerization processes interact with living oral tissues. Monomers like triethylene glycol dimethacrylate (TEGDMA) or 2-hydroxylethyl methacrylate (HEMA) are cytotoxic via apoptosis, induce genotoxic effects, and delay the cell cycle. Monomers also influence the response of cells of the innate immune system, inhibit specific odontoblast cell functions, or delay the odontogenic differentiation and mineralization processes in pulp-derived cells including stem cells. These observations indicate that resin monomers act as environmental stressors which inevitably disturb regulatory cellular networks through interference with signal transduction pathways. We hypothesize that an understanding of the cellular mechanisms underlying these phenomena will provide a better estimation of the consequences associated with dental therapy using composite materials, and lead to innovative therapeutic strategies and improved materials being used at tissue interfaces within the oral cavity. Current findings strongly suggest that monomers enhance the formation of reactive oxygen species (ROS), which is most likely the cause of biological reactions activated by dental composites and resin monomers. The aim of the present review manuscript is to discuss adaptive cell responses to oxidative stress caused by monomers. The particular significance of a tightly controlled network of non-enzymatic as well as enzymatic antioxidants for the regulation of cellular redox homeostasis and antioxidant defense in monomer-exposed cells will be addressed. The expression of ROS-metabolizing antioxidant enzymes like superoxide dismutase (SOD1), glutathione peroxidase (GPx1/2), and catalase in cells exposed to monomers will be discussed with particular emphasis on the role of glutathione (GSH), which is the major non-enzymatic antioxidant. The causal relationship between vital cell functions like the regulation of cell survival or cell death in monomer-treated cell cultures and the availability of GSH will be highlighted. We will also consider the influence of monomer-induced oxidative stress on central signal transduction pathways including mitogen-activated protein kinases (MAPK) ERK1/2, p38, and JNK as well as the stress-activated transcription factors downstream Elk-1, ATF-2, ATF-3, and cJun. Finally, we address signaling pathways originating from monomer-induced DNA damage including the activation of ATM (ataxia-telangiectasia mutated), Chk2, p53, p21, and H2AX. The understanding of the mechanisms underlying adaptive cell responses will stimulate a constructive debate on the development of smart dental restorative materials which come into contact with oral tissues and effective strategies in dental therapy.

Polymers for the cell-specific immobilisation of megakaryocytic cell lines.

Primary human megakaryocytes, the precursor cells of platelets, are difficult to collect and cultivate. Polymers that enrich these cells without affecting their regulation or function are of interest for basic research as well as for cord blood transplantation purposes since co-transplantation of enriched megakaryocyte concentrates increase the success of stem cell therapy. Herein, polymer microarrays were used for the discovery of substrates for MEG-01 cells, with five polymers identified which selectively bound cells of the megakaryocytic lineage. Flow cytometry and miRNA profiling revealed that immobilisation had only a minor effect on the cellular maturation status, making the identified substrates potential candidates for concentrating megakaryocytes from patients prior to transplantation.

Degradable segmented polyurethane elastomers for bone tissue engineering: effect of polycaprolactone content.

Segmented polyurethanes (PURs), consisting of degradable poly(a-hydroxy ester) soft segments and aminoacid-derived chain extenders, are biocompatible elastomers with tunable mechanical and degradative properties suitable for a variety of tissue-engineering applications. In this study, a family of linear PURs synthesized from poly(ϵ-caprolactone) (PCL) diol, 1,4-diisocyanobutane and tyramine with theoretical PCL contents of 65-80 wt% were processed into porous foam scaffolds and evaluated for their ability to support osteoblastic differentiation in vitro. Differential scanning calorimetry and mechanical testing of the foams indicated increasing polymer crystallinity and compressive modulus with increasing PCL content. Next, bone marrow stromal cells (BMSCs) were seeded into PUR scaffolds, as well as poly(lactic-co-glycolic acid) (PLGA) scaffolds, and maintained under osteogenic conditions for 14 and 21 days. Analysis of cell number indicated a systematic decrease in cell density with increasing PUR stiffness at both 14 and 21 days in culture. However, at these same time points the relative mRNA expression for the bone-specific proteins osteocalcin and the growth factors bone morphogenetic protein-2 and vascular endothelial growth factor gene expression were similar among the PURs. Finally, prostaglandin E2 production, alkaline phosphatase activity and osteopontin mRNA expression were highly elevated on the most-crystalline PUR scaffold as compared to the PLGA and PUR scaffolds. These results suggest that both the modulus and crystallinity of the PUR scaffolds influence cell proliferation and the expression of osteoblastic proteins.