Jadwiga Laska

Processable conducting polymers obtained via protonation of polyaniline with phosphoric acid esters

Abstract The protonation of polyemeraldine base (PANI) by diesters of phosphoric acid was studied. Three esters were investigated, namely bis(2-methylpropyl) hydrogen phosphate (DiBHP), bis(2-ethylhexyl) hydrogen phosphate (DiOHP) and its non-branched analogue, bis(n-octyl) hydrogen phosphate (DnOHP). It has been found that DiOHP, in addition to protonation, plasticizes PANI at very low ester contents i.e. for y ≥0.25 in PANI(DiOHP) y . In PANI(DnOHP) y and PANI(DiBHP) y the plastification starts at y =0.50 and y =0.65 respectively. It is clear that the long and branched substituents facilitate plastification. PANI protonated with DiOHP is soluble in common organic solvents such as toluene, chloroform, THF etc. The soluble fraction is enriched in DiOHP as compared with the parent protonated polymer. The existence of the anions originating from the ester in the soluble part of the polymer was confirmed by FT i.r. and 31 P n.m.r. studies of the soluble fraction. Free-standing films with a conductivity of 10 S cm −1 can be produced by hot pressing PANI(DiOHP) y at temperatures of 80–140°C. At higher temperatures partial degradation of the complex occurs resulting in a decrease of conductivity with a simultaneous increase of Youngs modulus and tensile strength. Blends of DiOHP-plasticized PANI and dioctyl phthalate-plasticized PVC, of excellent mechanical properties, can be prepared by hot pressing at 160°C.

Polyurethane/polylactide-based biomaterials combined with rat olfactory bulb-derived glial cells and adipose-derived mesenchymal stromal cells for neural regenerative medicine applications

Research concerning the elaboration and application of biomaterial which may support the nerve tissue regeneration is currently one of the most promising directions. Biocompatible polymer devices are noteworthy group among the numerous types of potentially attractive biomaterials for regenerative medicine application. Polylactides and polyurethanes may be utilized for developing devices for supporting the nerve regeneration, like nerve guide conduits or bridges connecting the endings of broken nerve tracts. Moreover, the combination of these biomaterial devices with regenerative cell populations, like stem or precursor cells should significantly improve the final therapeutic effect. Therefore, the composition and structure of final device should support the proper adhesion and growth of cells destined for clinical application. In current research, the three polymer mats elaborated for connecting the broken nerve tracts, made from polylactide, polyurethane and their blend were evaluated both for physical properties and in vitro, using the olfactory-bulb glial cells and mesenchymal stem cells. The evaluation of Youngs modulus, wettability and roughness of obtained materials showed the differences between analyzed samples. The analysis of cell adhesion, proliferation and morphology showed that the polyurethane-polylactide blend was the most neutral for cells in culture, while in the pure polymer samples there were significant alterations observed. Our results indicated that polyurethane-polylactide blend is an optimal composition for culturing and delivery of glial and mesenchymal stem cells.

Rheological behavior of plasticized polyaniline

In this article, rheological properties of polyaniline (PANI) doped with diisooctyl phosphate (DIOHP) are described. Rheological properties of this material depend strongly on the content of the dopant. For low concentrations, the material is rather stiff but becomes a Bingham or St. Venant body for higher contents of the dopant. Rheological parameters for samples containing various molar ratios of PANI to DIOHP were determined.

Characterization of Olfactory Ensheathing Glial Cells Cultured on Polyurethane/Polylactide Electrospun Nonwovens

The aim of this research was to evaluate novel biomaterials for neural regeneration. The investigated materials were composed of polyurethane (PU) and polylactide (PLDL) blended at three different w/w ratios, that is, 5/5, 6/4, and 8/2 of PU/PLDL. Ultrathin fibrous scaffolds were prepared using electrospinning. The scaffolds were investigated for their applicability for nerve regeneration by culturing rat olfactory ensheathing glial cells. Cells were cultured on the materials for seven days, during which cellular morphology, phenotype, and metabolic activity were analysed. SEM analysis of the fabricated fibrous scaffolds showed fibers of a diameter mainly lower than 600 μm with unimportant volume of protrusions situated along the fibers, with nonsignificant differences between all analysed materials. Cells cultured on the materials showed differences in their morphology and metabolic activity, depending on the blend composition. The most proper morphology, with numerous p75

Assessment of in vivo behavior of polymer tube nerve grafts simultaneously with the peripheral nerve regeneration process using scanning electron microscopy technique.

In this study, scanning electron microscopy (SEM) has been applied for instantaneous assessment of processes occurring at the site of regenerating nerve. The technique proved to be especially useful when an artificial implant should have been observed but have not yet been extensively investigated before for assessment of nerve tissue. For in vivo studies, evaluation of implants morphology and its neuroregenerative properties is of great importance when new prototype is developed. However, the usually applied histological techniques require separate and differently prepared samples, and therefore, the results are never a 100% comparable. In our research, we found SEM as a technique providing detailed data both on an implant behavior and the nerve regeneration process inside the implant. Observations were carried out during 12-week period on rat sciatic nerve injury model reconstructed with nerve autografts and different tube nerve grafts. Samples were analyzed with haematoxylin-eosin (HE), immunocytochemical staining for neurofillament and S-100 protein, SEM, TEM, and the results were compared. SEM studies enabled to obtain characteristic pictures of the regeneration process similarly to TEM and histological studies. Schwann cell transformation and communication as well as axonal outgrowth were identified, newly created and matured axons could be recognized. Concurrent analysis of biomaterial changes in the implant (degradation, collapsing of the tube wall, migration of alginate gel) was possible. This study provides the groundwork for further use of the described technique in the nerve regeneration studies.

Influence of calcium alginate on peripheral nerve regeneration: In vivo study

Recently, we described the influence of sodium alginate on the inflammatory infiltrate during neuroregeneration in tube nerve grafts. It was noticeable that there was the coexistence of inflammatory cells, including neutrophils, plasma cells, and macrophages with Schwann cells and axons. This may indicate a beneficial interaction between alginates and the infiltrate and the additional beneficial effect of the cells on the neuroregeneration process in the inflammatory infiltrates. In this study, we have performed in vivo evaluation of our novel tubular implant prepared by a polyurethane/polylactide blend filled with alginate fibers. The influence of filling the lumen of the tubes with sodium and calcium alginates on the regeneration process of the rat sciatic nerve was investigated. The neuroregeneration process was assessed by detailed histomorphometric studies, axon counting, and calculating the regenerative indexes. It was observed that calcium alginate had a supportive effect on nerve regeneration similar to nerve autotransplant.

Polyurethane/Polylactide-Blend Films Doped with Zinc Ions for the Growth and Expansion of Human Olfactory Ensheathing Cells (OECs) and Adipose-Derived Mesenchymal Stromal Stem Cells (ASCs) for Regenerative Medicine Applications

Polymeric biomaterials based on polyurethane and polylactide blends are promising candidates for regenerative medicine applications as biocompatible, bioresorbable carriers. In current research we showed that 80/20 polyurethane/polylactide blends (PU/PLDL) with confirmed biological properties in vitro may be further improved by the addition of ZnO nanoparticles for the delivery of bioactive zinc oxide for cells. The PU/PLDL blends were doped with different concentrations of ZnO (0.001%, 0.01%, 0.05%) and undertaken for in vitro biological evaluation using human adipose stromal stem cells (ASCs) and olfactory ensheathing cells (OECs). The addition of 0.001% of ZnO to the biomaterials positively influenced the morphology, proliferation, and phenotype of cells cultured on the scaffolds. Moreover, the analysis of oxidative stress markers revealed that 0.001% of ZnO added to the material decreased the stress level in both cell lines. In addition, the levels of neural-specific genes were upregulated in OECs when cultured on sample 0.001 ZnO, while the apoptosis-related genes were downregulated in OECs and ASCs in the same group. Therefore, we showed that PU/PLDL blends doped with 0.001% of ZnO exert beneficial influence on ASCs and OECs in vitro and they may be considered for future applications in the field of regenerative medicine.

The influence of sterilization on properties of polyurethane/polylactide blend

The biodegradable polyurethane/polylactide blend was treated with low temperature hydrogen peroxide plasma, ethylene oxide and immersing in ethanol combined with ultraviolet radiation. The samples sterilized by hydrogen peroxide and ethylene oxide stood practically unaffected, while UV/EtOH caused distinct changes in their mechanical properties. For example the significant reduction of tensile strength occurred, elongation at break became twice lower, while the Young’s modulus increased by 23%. The XPS measurements showed that after all types of treatment atomic carbon and nitrogen concentrations in the surface layer was slightly lower than in the bulk. Instead the surface layer was more enriched with oxygen. Ethylene oxide sterilization caused that both surfaces became more hydrophobic i.e. the contact angle increased about 15% for the top surface and 8% for the bottom surface, respectively. Sterilization with ethanol and UV radiation changed the nature of surface into more hydrophilic, the contact angle of the top surface was reduced about 6% and the bottom about 24%. The FT-IR spectra of all sterilized samples were recorded and discussed. From all used sterilization methods only hydrogen peroxide plasma is fully suitable for biodegradable PU/PLA blend.

Engineering polymers with high mechanical and thermal resistance for electric motors

The aim of the research was to select and evaluate polymers that could be used as rotor insulation in electric motors based on Halbach array system. Which have specific material properties, such as high mechanical strength, high thermal resistance and, especially, high thermal conductivity, also at room and at elevated temperatures. Three high performance polymers were selected for the research: polyetheretherketone (PEEK), polyamideimide (PAI) and poly(p-phenylene sulphide) (PPS). Polymers were evaluated for mechanical strength, thermal conductivity, thermal diffusivity, specific heat capacity, linear thermal expansion and also differential scanning calorimetry (DSC) and thermal gravimetry (TG) analyses were carried out. Analyses proved that all materials have appropriate properties for advanced electric motor insulator.

Polyurethane/polylactide-based electrospun nonwovens as carriers for human adipose derived stromal stem cells and chondrogenic progenitor cells

ABSTRACT Articular cartilage dysfunctions are major cause of pain and disability and lead to serious health complications. Cell-based therapies are proposed as treatment methods for cartilage regeneration. In this study, we proposed polyurethane/poly(L-lactide-co-D, L-lactide)-based electrospun nonwovens as carriers for the delivery of human adipose-derived stromal stem cells. We found that 6:4 and 8:2 polyurethane/poly(L-lactide-co-D, L-lactide) initially enhance proliferative rate of human adipose-derived stromal stem cells, shorten their population doubling time, promote creation of functional chondrogenic nodules during chondrogenic differentiation, improve the collagen-2-to-collagen-1 protein ratio, and upregulate the expression of collagen-2 and aggrecan genes. GRAPHICAL ABSTRACT