Poly(urethane-dimethylsiloxane) copolymers displaying a range of soft segment contents, noncytotoxic chemistry, and nonadherent properties toward endothelial cells.

Polyurethane copolymers based on α,ω-dihydroxypropyl poly(dimethylsiloxane) (PDMS) with a range of soft segment contents were prepared by two-stage polymerization, and their microstructures, thermal, thermomechanical, and surface properties, as well as in vitro hemo- and cytocompatibility were evaluated. All utilized characterization methods confirmed the existence of moderately microphase separated structures with the appearance of some microphase mixing between segments as the PDMS (i.e., soft segment) content increased. Copolymers showed higher crystallinity, storage moduli, surface roughness, and surface free energy, but less hydrophobicity with decreasing PDMS content. Biocompatibility of copolymers was evaluated using an endothelial EA.hy926 cell line by direct contact, an extraction method and after pretreatment of copolymers with multicomponent protein mixture, as well as by a competitive protein adsorption assay. Copolymers showed no toxic effect to endothelial cells and all copolymers, except that with the lowest PDMS content, exhibited resistance to endothelial cell adhesion, suggesting their unsuitability for long-term biomedical devices which particularly require re-endothelialization. All copolymers exhibited excellent resistance to fibrinogen adsorption and adsorbed more albumin than fibrinogen in the competitive adsorption assay, suggesting their good hemocompatibility. The noncytotoxic chemistry of these synthesized materials, combined with their nonadherent properties which are inhospitable to cell attachment and growth, underlie the need for further investigations to clarify their potential for use in short-term biomedical devices.

Synergistic anti-biofouling effect of Ag-exchanged zeolite and D-Tyrosine on PVC composite against the clinical isolate of Acinetobacter baumannii.

Due to their susceptibility to bacterial biofilm formation, commercial tubes for medical use are one of the main sources of hospital infections with Acinetobacter baumannii. The anti-biofouling activity of novel composites against the clinical isolate of the multi-drug resistant A. baumannii is reported here. The composites were prepared by addition of micronised silver-exchanged natural zeolite (Ag-NZ) into poly(vinyl chloride) (PVC), followed by coating of the composites with D-Tyrosine (D-Tyr). The Ag-NZ composites (containing 1-15 wt% of Ag-NZ) coated with D-Tyr (Ag-NZ-Tyr) showed a bactericidal effect (100% or a 6.9 log CFU reduction) towards immobilised bacterial cells. The uncoated Ag-NZ composites showed a reduction of up to 70% (4.4 log CFU) of immobilised bacteria in comparison with the original PVC. Rheological testing of the composites revealed that the addition of Ag-NZ slightly affected processability and formability of the PVC and increased the elasticity of the polymer matrix.

Structure and properties of thermoplastic polyurethanes based on poly(dimethylsiloxane): assessment of biocompatibility.

Properties and biocompatibility of a series of thermoplastic poly(urethane-siloxane)s (TPUSs) based on α,ω-dihydroxy ethoxy propyl poly(dimethylsiloxane) (PDMS) for potential biomedical application were studied. Thin films of TPUSs with a different PDMS soft segment content were characterized by (1) H NMR, quantitative (13) C NMR, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), contact angle, and water absorption measurements. Different techniques (FTIR, AFM, and DMA) showed that decrease of PDMS content promotes microphase separation in TPUSs. Samples with a higher PDMS content have more hydrophobic surface and better waterproof performances, but lower degree of crystallinity. Biocompatibility of TPUSs was examined after attachment of endothelial cells to the untreated copolymer surface or surface pretreated with multicomponent protein mixture, and by using competitive protein adsorption assay. TPUSs did not exhibit any cytotoxicity toward endothelial cells, as measured by lactate dehydrogenase and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assays. The untreated and proteins preadsorbed TPUS samples favored endothelial cells adhesion and growth, indicating good biocompatibility. All TPUSs adsorbed more albumin than fibrinogen in competitive protein adsorption experiment, which is feature regarded as beneficial for biocompatibility. The results indicate that TPUSs have good surface, thermo-mechanical, and biocompatible properties, which can be tailored for biomedical application requirements by adequate selection of the soft/hard segments ratio of the copolymers.

Release behaviour of carbamazepine-loaded poly(ε-caprolactone)/poly(ethylene oxide) microspheres.

Poly(ε-caprolactone) (PCL), a biodegradable and biocompatible aliphatic polyester has a great potential as a drug carrying material in controlled drug delivery/release systems. The most simple and economical way to tailor the release profile of active substances from biodegradable polymer matrix is by the addition of the second polymeric component in the polymer matrix, i.e. by blending. This study describes the preparation and characterization of a carbamazepine-loaded microspheres by the use of PCL blended with poly(ethylene oxide) as a drug carrying material. By the use of two-component hydrophilic/hydrophobic polymer blend as a microspheres' matrix material, release profile of the drug can be modified and dictated. The microspheres prepared by classical oil-in-water emulsion solvent evaporation technique were characterized with respect to particle size and morphology, polymer matrix composition, encapsulation efficiency, physical state of the drug and in vitro release behaviour. It was presented that the release profile can be modified by the presence and the amount of hydrophilic component in the starting formulation of microspheres.

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.

Application of Electrostatic Extrusion - Flavour Encapsulation and Controlled Release.

The subject of this study was the development of flavour alginate formulationsaimed for thermally processed foods. Ethyl vanilline was used as the model flavourcompound. Electrostatic extrusion was applied for the encapsulation of ethyl vanilline inalginate gel microbeads. The obtained microbeads with approx. 10 % w/w of ethylvanilline encapsulated in about 2 % w/w alginate were uniformly sized spheres of about450 µm. Chemical characterization by H-NMR spectroscopy revealed that the alginateused in this study had a high content (67 %) of guluronic residues and was rich in GG diadblocks (FGG = 55%) and thus presented a high-quality immobilisation matrix. The thermalbehaviour of alginate beads encapsulating ethyl vanilline was investigated bythermogravimetric (TG) and differential scanning calorimetry measurements (TG-DSC)under heating conditions which mimicked usual food processing to provide informationabout thermal decomposition of alginate matrix and kinetics of aroma release. Two wellresolved weight losses were observed. The first one was in the 50-150 °C temperaturerange with the maximum at approx. 112 °C, corresponding to the dehydration of thepolymer network. The second loss in the 220-325 °C temperature range, with a maximumat ~ 247 °C corresponded to the release of vanilline. The obtained results indicate that up to230 °C most of the vanilline remained intacta, while prolonged heating at elevatedtemperatures led to the entire loss of the aroma compound.