Doina Macocinschi

Segmented biopolyurethanes for medical applications

Polyurethanes are one of the most popular groups of biomaterials applied for medical devices. Their segmented block copolymeric character endows them a wide range of versatility in terms of tailoring their physical properties, blood and tissue compatibility. Polyester- and polyether-urethanes have been modified with hydroxypropyl cellulose aiming the change of their surface and bulk characteristics to confer them biomaterial qualities. In this respect, dynamic contact angle measurements, dynamic mechanical analyses accompanied by mechanical testing have been done. Platelet adhesion test has been carried out in vitro and the use of hydroxypropyl cellulose in the polyurethane matrix reduces the platelet adhesion and therefore recommends them as candidates for biocompatible materials.

Aromatic polysulfones for flame retardancy

Abstract A poly(ether sulfone) and a copoly(ester sulfone) were synthesized and characterized using elemental analyses, IR, 1H-NMR spectrometry, GPC, thermogravimetric analyses. These polysulfones which show good thermal stability and flame retardancy were applied on textile materials and measurements for the evaluation of the flame retardant effect were carried out.

Surface characterization of biopolyurethanes based on cellulose derivatives.

Surface tension parameters and surface morphology of biopolyurethanes based on cellulose derivatives thin films, before and after HF cold plasma treatment has been investigated. Calculations are based on the geometric mean approach of Owens and Wendt, Rabel and Kälble, on the Lifshitz-van der Waals acid/base approach of van Oss and co-workers and on the theoretical methods involving quantitative structure-property relationship. For all the investigated samples the polar component contributes significantly to the total surface tensions, as due to the large electron donor interactions. HF cold plasma treatment modifies the surface energy of biopolyurethanes by changing their surface polarity and hydrophilicity. The hydrophilic/hydrophobic balance was studied by means of the free energy of hydration between the biomaterial film and water. The protein adsorption tests of fibrinogen were effected to evaluate the applicability of these biopolyurethanes as biomedical thromboresistant devices.

Thermal, dynamic mechanical, and dielectric analyses of some polyurethane biocomposites

Polymer biocomposites based on segmented poly(ester urethane) and extracellular matrix components have been prepared for the development of tissue engineering applications with improved biological characteristics of the materials in contact with blood and tissues for long periods. Thermal, dynamical, and dielectrical analyses were employed to study the molecular dynamics of these materials and the influence of changing the physical network morphology and hydrogen bond interactions accompanied by phase transitions, interfacial effects, and polarization or conductivity. All phenomena that concur in the tested materials are evaluated by cross-examination of the dynamic mechanical characteristic properties (storage modulus, loss modulus, and loss factor) and dielectric properties (relative permittivity, relative loss factor, and loss tangent) as a function of temperature. Comparative aspects were elucidated by calculating the apparent activation energies of multiplex experiments.

Biomaterials based on new polyurethane and hydrolyzed collagen, k-elastin, hyaluronic acid and chondroitin sulfate.

In this paper biomaterials based on various polyurethane formulations have been physically characterized by FT-IR spectroscopy, contact angle measurements, DSC, TG/DTG and SEM methods. It has been established that the transition temperatures of soft and hard segments of polyurethane (glass transition or melting) depend on the blend composition. The melting temperature varies from 54.2 to 81.9°C for soft segments, and from 220 to 235°C for hard segments. FT-IR spectrometry allows identifying the functional groups involved in interactions and consequently the changes in polymer chain mobility. From SEM images, is evident that polyurethanic film is porous and spongious. By adding of the others components such as hydrolyzed collagen, elastin, chondroitin sulfate or hyaluronic acid, a reduction of porosity of films was obtained.

Evaluation of polyurethane based on cellulose derivative-ketoprofen biosystem for implant biomedical devices.

A polyether-urethane based on polytetrahydrofuran containing hydroxypropyl cellulose for biomedical applications was tested for its biocompatibility. Ketoprofen was incorporated (3% and 6%) in the polyurethane matrix as an anti-inflammatory drug. Dynamic vapour sorption method was employed for testing the water sorption/desorption behaviour of these materials with the determination of the surface isotherms, surface parameters and the kinetic curves of sorption/desorption processes. Cytotoxicity testing in vitro for quantifying cell proliferation was employed, and the results evidence noncytotoxicity for the studied polyurethane-drug systems. In vivo biocompatibility study was performed on 200 g weight male rats. It was found that after implantation of the polyether-urethane samples a reduced acute inflammation occurred, especially for polyurethane samples with added ketoprofen.

Polyurethane-extracellular matrix/silver bionanocomposites for urinary catheters

Polyurethane–extracellular matrix membranes with bionanocomposites or coatings containing a small amount of biocompatible polymers such as hydrolyzed collagen, elastin, hyaluronic acid or chondroitin sulfate, and silver were obtained by solvent casting or electrospinning/electrospraying of the polyurethane–extracellular matrix–Ag formulations onto pure polyurethane membrane in order to achieve improved antibacterial biomaterials for urinary catheters. Using Fourier transform infrared spectroscopy, the interaction of the incorporated silver nanoparticles with polyurethane–extracellular matrix was found, while X-ray photoelectron spectroscopy and X-ray diffraction analyses ws used to determine the presence of metallic Ag for polyurethane membrane and Ag only in oxidized state for polyurethane–extracellular matrix membranes due to the stabilizing effect of polymeric components. The in vitro antimicrobial tests against Escherichia coli, Salmonella typhymurium, and Listeria monocytogenes were used for the evaluation of the antimicrobial efficiency.

New polyurethane materials from renewable resources: synthesis and characterization

Abstract In the present study new types of polyurethane-cellulose derivative biomaterials based on urethane prepolymers functionalized with hydroxypropylcellulose are presented. The aim of the present study is to obtain materials with better haemocompatibility, biocompatibility and amphiphilic microphase-separated domain structures. The outcome of remarkable chemical versatility characteristic to polyurethane materials combined with polymers derived from nature like cellulose derivatives resulting in bulk and surface properties is evidenced by means of different techniques like DSC, TGA, FT-IR, AFM and mechanical tensile tests. The influence of various factors on the developed morphologies and the microstructural changes is investigated. Both polyester and polyether macrodiols have been used to prepare these polyurethanes. The aim of this study is to find also alternative methods for improving biostability while maintaining the excellent biocompatibility and other properties.

Influence of Hard Segments to Specific Refractive Index Increments of Segmented Poly(Ester Urethane)s

Abstract The segmented poly(ester urethane)s were obtained from 4,4′-methylene diphenylene diisocyanate and 2,4-tolylene dissocyanate with thiodiglycol, diethylene glycol, or 4,4′-dihidroxydiethoxydiphenyl sulfone as chain extender, and poly(ethylene glycol)adipate using a multistep polyaddition process. Specific refractive index increments of these segmented copolymers in N,N-dimethyl-formamide have been determined by the Lorenz–Lorentz and Gladstone–Dale equations and the corresponding group contributions to the molar refraction and to the molar volume. The results are compared with the experimental values. Also, for studied samples we can observe the contribution of composition of hard segments to the refractive index and specific refractive index increment.

Effect of silver nanoparticles on the dispersion, rheological properties and morphological aspect of solvent cast polyurethane/biopolymers bionanocomposite membranes

Abstract Nanocomposite dispersions from polyester-type polyurethane and mixtures of the polyurethane with various biopolymers such as hydrolysed collagen, k-elastin, chondroitin sulphate or hyaluronic acid containing different concentrations of in situ generated silver nanoparticles (Ag NPs) were prepared and studied for application as antimicrobial materials or coatings. The influence of Ag NPs presence and of the dispersion composition on the rheological properties, microstructure of polyurethane/biopolymers-based dispersions and on the morphology of the solvent cast membranes obtained was investigated. The rheological measurements performed emphasizing on crossover point changes and relaxation time spectra investigation showed an increased restriction of chain movements in polyurethane as a consequence of increasing Ag NPs content and the complex viscoelastic response determined by chain rearrangements within macromolecules under flow disturbances with significantly modified relaxation times due to the presence of biopolymers. The Ag NPs distribution within polymeric dispersions was studied by TEM. It was found an ordered distribution of the spherical Ag NPs within PU-based matrix and formation of aggregates in both PU-biopolymers dispersions containing either chondroitin sulphate or hyaluronic acid, well-correlated with the rheology results. The morphology study by scanning electron microscopy evidenced the influence of Ag NPs dispersion degree and of natural compounds in composition on the aspect of the casted nanocomposite membranes.