Miroslawa El Fray

Biocompatibility studies of new multiblock poly(ester-ester)s composed of poly(butylene terephthalate) and dimerized fatty acid

This study was undertaken to evaluate the biocompatibility of new multiblock poly(ester-ester)s proposed as an alternative to Hunter silastic prosthesis used in a two-stage tendon reconstruction. Methanol-extracted polymeric material retained its weight, demonstrating the absence of leachable particles (e.g. low-molecular weight oligomers). Implantation tests indicated that the observed tissue changes were similar to those obtained with silicone, no evidence of contact necrosis being observed. The unchanged morphology of rat liver hepatocytes and the lack of parenchymal necrosis also indicated that exposure to the investigated polymers did not cause any cytotoxic reactions.

A nanostructured carbon-reinforced polyisobutylene-based thermoplastic elastomer

This paper presents the synthesis and characterization of a polyisobutylene (PIB)-based nanostructured carbon-reinforced thermoplastic elastomer. This thermoplastic elastomer is based on a self-assembling block copolymer having a branched PIB core carrying -OH functional groups at each branch point, flanked by blocks of poly(isobutylene-co-para-methylstyrene). The block copolymer has thermolabile physical crosslinks and can be processed as a plastic, yet retains its rubbery properties at room temperature. The carbon-reinforced thermoplastic elastomer had more than twice the tensile strength of the neat polymer, exceeding the strength of medical grade silicone rubber, while remaining significantly softer. The carbon-reinforced thermoplastic elastomer displayed a high T(g) of 126 degrees C, rendering the material steam-sterilizable. The carbon also acted as a free radical trap, increasing the onset temperature of thermal decomposition in the neat polymer from 256.6 degrees C to 327.7 degrees C. The carbon-reinforced thermoplastic elastomer had the lowest water contact angle at 82 degrees and surface nano-topography. After 180 days of implantation into rabbit soft tissues, the carbon-reinforced thermoplastic elastomer had the thinnest tissue capsule around the microdumbbell specimens, with no eosinophiles present. The material also showed excellent integration into bones.

Novel “soft” biodegradable nanoparticles prepared from aliphatic based monomers as a potential drug delivery system

The search for new biomaterials intended for biomedical applications has considerably intensified in recent years. Herein, the synthesis and characterization of a new aliphatic biodegradable copolyester named PBS/PBDL (poly(butylene succinate-co-butylene dilinoleate)) is reported. Surfactant-free, narrowly distributed, nanosized spherical particles (RH < 60 nm) have been produced from the biodegradable material by applying a single-step nanoprecipitation protocol. Their structure was characterized in detail by employing a variety of scattering techniques and transmission electron microscopy (TEM). Combined SLS and DLS measurements suggested that the nanoparticles comprise a porous core conferring a non-compact characteristic. Their porosity enables water to be entrapped which is responsible for their pronounced stability and relatively fast degradation as followed by size exclusion chromatography (SEC). The polymeric nanoparticles could be loaded with the hydrophobic model drug paclitaxel (PTX) with an encapsulation efficiency of ∼95% and drug loading content of ∼6–7% wdrug/wpolymer. The drug release was followed by HPLC and scattering measurements (DLS, SLS and SAXS). The drug encapsulation and release modifies the inner structure of the nanoparticles, which holds a large amount of entrapped water in the drug-free condition. PTX encapsulation leads to replacement of the entrapped water by the hydrophobic model drug and to shrinking of the nanoparticles, probably due to favorable drug–polymer hydrophobic interactions. Cell viability experiments demonstrated that the nanoparticles are biocompatible and non-toxic, making them potentially useful for applications in nanomedicine.

Modification of bacterial cellulose through exposure to the rotating magnetic field

The aim of the study was to assess the influence of rotating magnetic field (RMF) on production rate and quality parameters of bacterial cellulose synthetized by Glucanacetobacter xylinus. Bacterial cultures were exposed to RMF (frequency f=50Hz, magnetic induction B=34mT) for 72h at 28°C. The study revealed that cellulose obtained under RMF influence displayed higher water absorption, lower density and less interassociated microfibrils comparing to unexposed control. The application of RMF significantly increased the amount of obtained wet cellulose pellicles but decreased the weight and thickness of dry cellulose. Summarizing, the exposure of cellulose-synthesizing G. xylinus to RMF alters cellulose biogenesis and may offer a new biotechnological tool to control this process. As RMF-modified cellulose displays better absorbing properties comparing to non-modified cellulose, our finding, if developed, may find application in the production of dressings for highly exudative wounds.

Synthesis and thermal properties of poly(ester-siloxane) multiblock copolymers

The goal of this research was the synthesis and thermal characterization of poly(ester-siloxane) multiblock copolymers. Poly(butylene terephthalate) (PBT) was the polyester block. α, ω-Diamino-terminated poly(dimethylsiloxane) (PDMS) was reacted with an excess of dimerized fatty acid to form a dicarboxy-terminated oligomer containing stable amide links. Multiblock copolymers were obtained in a three-stage process: oligomer preparation, transesterification, and polycondensation from the melt. A magnesium-titanate catalyst was used for transesterification and polymer formation (polycondensation). The synthesized oligomer was considered to be the soft segment and its content ranged from 20 to 45% by weight. Multiblock copolymers showed microphase separation as determined by differential scanning calorimetry (DSC). Their morphology was studied by optical microscopy (OM) and showed spherulitic ordering.The goal of this research was the synthesis and thermal characterization of poly(ester-siloxane) multiblock copolymers. Poly(butylene terephthalate) (PBT) was the polyester block. α, ω-Diamino-terminated poly(dimethylsiloxane) (PDMS) was reacted with an excess of dimerized fatty acid to form a dicarboxy-terminated oligomer containing stable amide links. Multiblock copolymers were obtained in a three-stage process: oligomer preparation, transesterification, and polycondensation from the melt. A magnesium-titanate catalyst was used for transesterification and polymer formation (polycondensation). The synthesized oligomer was considered to be the soft segment and its content ranged from 20 to 45% by weight. Multiblock copolymers showed microphase separation as determined by differential scanning calorimetry (DSC). Their morphology was studied by optical microscopy (OM) and showed spherulitic ordering.

Polymer-Graphene Nanocomposite Materials for Electrochemical Biosensing.

Biosensing is an important and rapidly developing field, with numerous potential applications in health care, food processing, and environmental control. Polymer-graphene nanocomposites aim to leverage the unique, attractive properties of graphene by combining them with those of a polymer matrix. Molecular imprinted polymers, in particular, offer the promise of artificial biorecognition elements. A variety of polymers, including intrinsically conducting polymers (polyaniline, polypyrrole), bio-based polymers (chitosan, polycatechols), and polycationic polymers (poly(diallyldimethylammonium chloride), polyethyleneimine), have been utilized as matrices for graphene-based nanofillers, yielding sensitive biosensors for various biomolecules, such as proteins, nucleic acids, and small molecules.

Determination of mechanical and hydraulic properties of PVA hydrogels.

In this paper the identification of mechanical and hydraulic parameters of poly(vinyl alcohol) (PVA) hydrogels is described. The identification method follows the solution of inverse problem using experimental data from the unconfined compression test and the poroelastic creep model. The sensitivity analysis of the model shows significant dependence of the creep curves on investigated parameters. The hydrogels containing 22% PVA and 25% PVA were tested giving: the drained Youngs modulus of 0.71 and 0.9MPa; the drained Poissons ratio of 0.18 and 0.31; and the permeability of 3.64·10(-15) and 3.29·10(15)m(4)/Ns, respectively. The values of undrained Youngs modulus were determined by measuring short period deformation of samples in the unconfined tests. A discussion on obtained results is presented.

Cardiac catheterization: consequences for the endothelium and potential for nanomedicine

Cardiac catheterization results in interactions between the catheter and surfaces and the artery lumen, which is lined by the endothelium. These interactions can range from minor rubbing to severe mechanical injury. Further, in the case of radial access, even atraumatic interactions have consequences ranging from clinical complications, such as radial spasm and radial occlusion, to lasting endothelial cell dysfunction. These consequences may be underappreciated; however, endothelial cells play a central role in maintaining vascular homeostasis via nitric oxide production. Existing treatment paradigms do not address endothelial dysfunction or damage and, thus, novel therapeutic approaches are needed. Nanomedicine, in particular, offers great potential in the form of targeted drug delivery, via functionalized coatings or nanocarriers, aimed at increased nitric oxide bioavailability or reduced inflammation.

Enzymatic synthesis of an electrospinnable poly(butylene succinate-co-dilinoleic succinate) thermoplastic elastomer

Candida antarctica lipase B was successfully employed for the first time as a biocatalyst to obtain high molecular weight poly(butylene succinate-co-dilinoleic succinate) (PBS : DLS) copolyester via a two-stage method in a diphenyl ether solution from diethyl succinate, 1,4-butanediol, and dimer linoleic diol. The final hard to soft segments were close to the initial feed ratio as confirmed by 1H NMR and FTIR measurements. Thermal analysis revealed the presence of two transitions typical for thermoplastic elastomers: a low temperature glass transition and high temperature melting point. In addition, the optimized synthetic protocol ensured high reaction yield (>74%) and molecular weight (Mw > 34 × 103 g mol−1) high enough to process the copolymer into electrospun mats without defects. The enzymatically synthesized PBS : DLS was able to be processed at 20–25 w/v% concentrations into fibres and depending on the type of solvent, the fibre diameter was controlled in the range of 0.3 to 0.6 μm.

Multiblock terephthalate copolymer as impact modifier for poly(propylene)/poly(butylene terephthalate) blends

The melt polycondensation method was investigated for the synthesis of a multiblock copolymer. The copolymer consisted of hard segments of poly(butylene terephthalate) (PBT) and soft segments of dimerised fatty acid. This multiblock copolymer was characterised by 1H and 13C NMR and FTIR spectroscopies and differential scanning calorimetry. The 1H NMR method was used for estimating quantitatively the amount of the hard/soft segments. The polymer morphology was characterised using light microscopy and transmission electron microscopy. The investigated polymer was used in a small amount as an additive to poly(propylene)/PBT blends in order to evaluate its influence on the morphology and impact properties of these blends. Die Synthese eines Multiblock-Copolymeren durch Polykondensation in der Schmelze wurde untersucht. Das Copolymere, bestehend aus harten Poly(butylenterephthalat)-Segmenten und weichen Segmenten aus dimerisierter Fettsauren, wurde mit 1H- und 13C-NMR-Spektroskopie, FTIR-Spektroskopie und DSC untersucht. Aus dem 1H-NMR-Spektrum wurde die Konzentration der harten und weichen Segmente bestimmt. Die Polymermorphologie wurde mittels Lichtmikroskopie und Transmissionselektronenmikroskopie charakterisiert. Die untersuchten Copolymeren wurden in kleinen Mengen als Additive in Polypropylen/PBT-Blends eingemischt, um deren Einflus auf die Morphologie und Impact-Eigenschaften der Blends zu untersuchen.