Poly(ester urethane)s with polycaprolactone soft segments: A morphological study

Biocompatibility studies of polyurethane electrospun membranes based on arginine as chain extender

Electrospun polymers are an example of multi-functional biomaterials that improve the material-cellular interaction and aimed at enhancing wound healing. The main objective of this work is to fabricate electrospun polyurethane membranes using arginine as chain extender (PUUR) in order to test the fibroblasts affinity and adhesion on the material and the polymer toxicity. Polyurethane membranes were prepared in two steps: (i) the polyurethane synthesis, and ii) the electrospinning process. The membranes were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry techniques. The evaluation of PUUR as a scaffolding biomaterial for growing and developing of cells on the material was realized by LIVE/DEAD staining. The results show that the fluorescent surface area of human fibroblasts (hFB), was greater in control dense membranes made from Tecoflex than in electrospun and dense PUUR. From SEM analysis, the electrospun membranes show relatively uniform attachment of cells with a well-spread shape, while Tecoflex dense membranes show a non-proliferating round shape, which is attributed to the fiber's structure in electrospun membranes. The cell morphology and the cell attachment assay results reveal the well spreading of hFB cells on the surface of electrospun PUUR membranes which indicates a good response related to cell adhesion.

Assessment of the Efficacy of Tributylammonium Alginate Surface-Modified Polyurethane as an Antibacterial Elastomeric Wound Dressing for both Noninfected and Infected Full-Thickness Wounds

Risk factors of nonhealing wounds include persistent bacterial infections and rapid onset of dehydration; therefore, wound dressings should be used to accelerate the healing process by helping to disinfect the wound bed and provide moisture. Herein, we introduce a transparent tributylammonium alginate surface-modified cationic polyurethane (CPU) wound dressing, which is appropriate for full-thickness wounds. We studied the physicochemical properties of the dressing using Fourier transform infrared, ¹H NMR, and ¹³C NMR spectroscopies and scanning electron microscopy, energy-dispersive X-ray, and thermomechanical analyses. The surface-modified polyurethane demonstrated improved hydrophilicity and tensile Young's modulus that approximated natural skin, which was in the range of 1.5-3 MPa. Cell viability and in vitro wound closure, assessed by MTS and the scratch assay, confirmed that the dressing was cytocompatible and possessed fibroblast migratory-promoting activity. The surface-modified CPU had up to 100% antibacterial activity against Staphylococcus aureus and Escherichia coli as Gram-positive and Gram-negative bacteria, respectively. In vivo assessments of both noninfected and infected wounds revealed that the surface-modified CPU dressing resulted in a faster healing rate because it reduced the persistent inflammatory phase, enhanced collagen deposition, and improved the formation of mature blood vessels when compared with CPU and commercial Tegaderm wound dressing.

Investigation of the effects of polycaprolactone molecular weight and graphene content on crystallinity, mechanical properties and shape memory behavior of polyurethane/graphene nanocomposites

In the following work, different shape memory polyurethanes (SMPUs) were synthesized using polycaprolactone (PCL) with various molecular weights, hexamethylene diisocyanate (HDI), and 1,4-butanediol (BDO). Afterward, polyurethane (PU)-based nanocomposites were prepared with different graphene nanosheets contents via solution casting method. Hydrogen nuclear magnetic resonance (¹H-NMR) was used to confirm the chemical structure of PCLs and calculate their actual molecular weights. The chemical structure and hydrogen bonding content of PUs and their nanocomposites were investigated by Fourier-transform infrared spectroscopy (FTIR). According to the results, the hydrogen bonding contents of nanocomposites were reduced by graphene nanosheets inhibition from the formation of hydrogen bonds between polyurethane chains. Thermal properties and crystalline morphology of samples were studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results indicated that the transition temperature and crystallinity of samples were changed by variation of the molecular weight of the PCL component and of the concentration of the graphene nanosheets. Graphene nanosheets dispersion in polyurethane matrix was investigated using the field emission scanning electron microscope (FE-SEM). The mechanical and shape memory properties of different PUs and their nanocomposites were determined at both 75 °C and room temperature. It can be deduced from the results that the modulus of the samples increased due to the rigidity of nanosheets. Furthermore, the restricted mobility of PCL chains, due to the presence of nanosheets, led to higher shape fixity ratio. Moreover, the nanosheets prevented the stress transfer on the hard segments which increased the shape recovery ratio.

Waterborne polyurethanes based on macrocyclic thiacalix[4]arenes as novel emulsifiers: synthesis, characterization and anti-corrosion properties

1,3-alternate derivatives of thiacalix[4]arenes were employed as new macrocyclic emulsifiers to synthesize waterborne polyurethanes as environmental friendly anti-corrosive coatings for mild steel.

Control of hyperbranched structure of polycaprolactone/poly(ethylene glycol) polyurethane block copolymers by glycerol and their hydrogels for potential cell delivery

A series of biodegradable amphiphilic polyurethane block copolymers with hyperbranched structure were synthesized by copolymerizing poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) together with glycerol. The copolymers were characterized, and their composition and branch length were varied with the feeding ratio between PCL, PEG, and glycerol used. Hydrogels were formed from these copolymers by swelling of water at low polymer concentrations. The hydrogels were thixotropic, and their dynamic viscoelastic properties were dependent on the copolymer composition, branch length, and polymer concentration. Hydrolytic degradation of the hydrogels was evaluated by mass loss and changes in molecular structures. The porous morphology of the hydrogels provided good permeability for gas and nutrition. Together with the tunable rheological properties, the hydrogels were found to be suitable for 3D living cell encapsulation and delivery. The morphology of the solid copolymers was semicrystalline, while the hydrogels were totally amorphous without crystallinity, providing a mild aqueous environment for living cells. When the encapsulated cells were recovered from the hydrogels followed by subculture, they showed good cell viability and proliferation ability. The results indicate that the hyperbranched copolymers hydrogels developed in this work may be promising candidates for potential injectable cell delivery application.

Design of triple-shape memory polyurethane with photo-cross-linking of cinnamon groups

A triple-shape memory polyurethane (TSMPU) with poly(ε-caprolactone) -diols (PCL-diols) as the soft segments and diphenyl methane diisocyanate (MDI), N,N-bis (2-hydroxyethyl) cinnamamide (BHECA) as the hard segments was synthesized via simple photo-crosslinking of cinnamon groups irradiated under λ > 280 nm ultraviolet (UV) light. Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance ((1)H-NMR) and ultraviolet-visible absorption spectrum (UV-vis) confirmed the chemical structure of the material. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) results demonstrated that the photo-crosslinked polymer possessed two transition temperatures, one is due to the melting point of the soft segment PCL-diols, and the other is due to the glass transition temperature. All these contributed to the cross-linked structure of the hard segments and resulted in an excellent triple-shape memory effect. Alamar blue assay showed that the material has good non-cytotoxicity and can be potentially used in biomaterial devices.

In vitro biocompatibility evaluation of novel urethane-siloxane co-polymers based on poly(ϵ-caprolactone)-block-poly(dimethylsiloxane)-block-poly(ϵ-caprolactone)

Novel polyurethane co-polymers (TPUs), based on poly(ϵ-caprolactone)-block-poly(dimethylsiloxane)-block-poly(ϵ-caprolactone) (PCL-PDMS-PCL) as soft segment and 4,4'-methylenediphenyl diisocyanate (MDI) and 1,4-butanediol (BD) as hard segment, were synthesized and evaluated for biomedical applications. The content of hard segments (HS) in the polymer chains was varied from 9 to 63 wt%. The influence of the content and length of the HS on the thermal, surface, mechanical properties and biocompatibility was investigated. The structure, composition and HS length were examined using (1)H- and quantitative (13)C-NMR spectroscopy. DSC results implied that the synthesized TPUs were semicrystalline polymers in which both the hard MDI/BD and soft PCL-PDMS-PCL segments participated. It was found that an increase in the average HS length (from 1.2 to 14.4 MDI/BD units) was accompanied by an increase in the crystallinity of the hard segments, storage moduli, hydrophilicity and degree of microphase separation of the co-polymers. Depending on the HS content, a gradual variation in surface properties of co-polymers was revealed by FT-IR, AFM and static water contact angle measurements. The in vitro biocompatibility of co-polymers was evaluated using the endothelial EA.hy926 cell line and protein adsorption on the polyurethane films. All synthesized TPUs adsorbed more albumin than fibrinogen from multicomponent protein mixture, which may indicate biocompatibility. The polyurethane films with high HS content and/or high roughness coefficient exhibit good surface properties and biocompatible behavior, which was confirmed by non-toxic effects to cells and good cell adhesion. Therefore, the non-cytotoxic chemistry of the co-polymers makes them good candidates for further development as biomedical implants.

Correlação entre propriedades mecânicas e parâmetros estruturais de poliuretanos à base de poli(épsilon-caprolactona)

No presente trabalho foram preparados poliuretanos (PUs) segmentados. Primeiramente foi obtido um pré-polímero (PP) a partir da reação de 2,4 e 2,6 - diisocianato de tolileno (TDI) e poli(épsilon-caprolactona) diol (PCL). A PCL é um poliéster biodegradável que constituiu o segmento flexível do PU. O segmento rígido foi constituído por unidades uretânicas provenientes da ligação entre as extremidades isocianato do PP e as hidroxilas do extensor de cadeia: 1,4 - butanodiol (BDO), ou sacarose (SAC), ou glicose (GLY). Foram avaliadas as propriedades mecânicas e dinâmico-mecânicas dos poliuretanos obtidos e estas foram correlacionadas com os parâmetros estruturais. Os resultados foram justificados com base na intensidade das interações de hidrogênio, na mistura de fases, no volume dos extensores cíclicos e na presença de ligações cruzadas. Estes PUs estão sendo estudados com vistas à preparação de materiais biodegradáveis com propriedades mecânicas úteis.