Piotr Kurcok

Study of Aliphatic-Aromatic Copolyester Degradation in Sandy Soil and Its Ecotoxicological Impact

Degradation of poly[(1,4-butylene terephthalate)-co-(1,4-butylene adipate)] (Ecoflex, BTA) monofilaments (rods) in standardized sandy soil was investigated. Changes in the microstructure and chemical composition distribution of the degraded BTA samples were evaluated and changes in the pH and salinity of postdegradation soil, as well as the soil phytotoxicity impact of the degradation products, are reported. A macroscopic and microscopic evaluation of the surface of BTA rod samples after specified periods of incubation in standardized soil indicated erosion of the surface of BTA rods starting from the fourth month of their incubation, with almost total disintegration of the incubated BTA material observed after 22 months. However, the weight loss after this period of time was about 50% and only a minor change in the M(w) of the investigated BTA samples was observed, along with a slight increase in the dispersity (from an initial 2.75 up to 4.00 after 22 months of sample incubation). The multidetector SEC and ESI-MS analysis indicated retention of aromatic chain fragments in the low molar mass fraction of the incubated sample. Phytotoxicity studies revealed no visible damage, such as necrosis and chlorosis, or other inhibitory effects, in the following plants: radish, cres, and monocotyledonous oat, indicating that the degradation products of the investigated BTA copolyester are harmless to the tested plants.

Synthesis and antiproliferative properties of ibuprofen-oligo(3-hydroxybutyrate) conjugates

Synthesis of novel conjugates of the non-steroidal anti-inflammatory drug - ibuprofen with nontoxic oligo(3-hydroxybutyrate) (OHB) is described. Presented results indicate that anionic ring-opening polymerization of (R,S)-beta-butyrolactone initiated with an alkali metal salt of (S)-(+)-2-(4-isobutylphenyl)propionic acid (ibuprofen) may constitute a convenient method of conjugation of selected drugs with biodegradable OHB. Furthermore using the MTT cell proliferation assay we demonstrated that ibuprofen conjugated with OHB exhibited significantly increased, as compared to free ibuprofen, potential to inhibit proliferation of HT-29 and HCT 116 colon cancer cells. However, the conjugates of ibuprofen and OHB are less toxic as was shown in oral acute toxicity test in rats. Although the mechanism of antiproliferative activity of ibuprofen-OHB conjugates (Ibu-OHB) has to be established, we suggest that partially it can be related to more effective cellular uptake of the conjugate than the free drug. This assumption is based on the observation of much more efficient accumulation of a marker compound - OHB conjugated with fluorescein, in contrast to fluorescein sodium salt, which entered cells inefficiently. Further characterization of biological properties of the ibuprofen-OHB conjugates would provide insight into the mechanism of their antiproliferative effect and assess the potential relevance of their anticancer activity.

Polyhydroxybutyrate targets mammalian mitochondria and increases permeability of plasmalemmal and mitochondrial membranes.

Poly(3-hydroxybutyrate) (PHB) is a polyester of 3-hydroxybutyric acid (HB) that is ubiquitously present in all organisms. In higher eukaryotes PHB is found in the length of 10 to 100 HB units and can be present in free form as well as in association with proteins and inorganic polyphosphate. It has been proposed that PHB can mediate ion transport across lipid bilayer membranes. We investigated the ability of PHB to interact with living cells and isolated mitochondria and the effects of these interactions on membrane ion transport. We performed experiments using a fluorescein derivative of PHB (fluo-PHB). We found that fluo-PHB preferentially accumulated inside the mitochondria of HeLa cells. Accumulation of fluo-PHB induced mitochondrial membrane depolarization. This membrane depolarization was significantly delayed by the inhibitor of the mitochondrial permeability transition pore - Cyclosporin A. Further experiments using intact cells as well as isolated mitochondria confirmed that the effects of PHB directly linked to its ability to facilitate ion transport, including calcium, across the membranes. We conclude that PHB demonstrates ionophoretic properties in biological membranes and this effect is most profound in mitochondria due to the selective accumulation of the polymer in this organelle.

Si-H functional polysilanes via a homogeneous reductive coupling reaction

A polysilane copolymer with reactive Si-H side groups was obtained through a homogeeous coupling reaction of dichlorodiphenylsilane with dichloromethylsilane. The reaction was carried out in a tetrahydrofuran (THF) solution of a sodium-potasium alloy complex with 18-crown-6 with a well defined composition of alkali metal ion pairs (Mt + /crown ether, Mt ― ) at -75°C. The product was characterized using 1 H NMR, 13 C NMR, FT-IR and UV/Visible spectroscopies and gel permeation chromatography. The result were compared with those obtained by the heterogeneous coupling reaction of the same monomers.

Polymerization of β-butyrolactone initiated with Al(OiPr)3

Polymerization of β-butyrolactone has been studied in toluene with Al(O i Pr) 3 as an initiator. The ring-opening polyaddition proceeds through a coordination-insertion mechanism at a very low rate. Well defined α-isopropylester, ω-hydroxy poly(β-butyrolactone)s (PBL) are formed with a narrow molecular weight distribution at low monomer-to-initiator molar ratios, When this ratio is higher (ca. 170), a competition occurs between propagation and side reactions, i.e. elimination, inter- and intra-molecular transesterifications and thermal degradation, which is responsible for a loss of control of the PBL molecular characteristics. The addition of a Lewis base (1 equivalent of nicotine/Al) to the Al-alkoxide initiator has no significant effect on the polymerization rate, although the chain microstructure is deeply affected since predominantly syndiotactic PBL chains are formed (63% syndio-diads) in contrast to a completely atactic polymer in the absence of nicotine.

Degradability of Poly(β-Hydroxybutyrate)s. Correlation with Chemical Microstructure

Abstract Poly(β-hydroxybutyrate)s (PHB) of different microstructures were synthesized via anionic polymerization of β-butyrolactone initiated by two initiators: 1) supramolecular complexes of alkali metals with asymmetric induction agents, and 2) alkali metal alkoxides. The relationships between chemical microstructure and hydrolytic as well as thermal degradation properties of synthetic and natural PHB are discussed.

Synthesis of Potentially Biodegradable Polymers

Abstract Homopolymers of β-butyrolactone, L-lactide, δ-valerolactone, and methyl methacrylate, as well as their block copolymers, were prepared with simple initiator systems based on alkali metal alkoxides and alkali metal supramolecular complexes. The goal was to synthesize polymeric materials with potential biodegradability.

Polymerization of β-Lactones Initiated by Alkali Metal Naphthalenides. A Convenient Route to Telechelic Polymers

Abstract The polymerization of β-lactones initiated by potassium naphtha-lenide and its mechanism are discussed on the basis of 1H NMR 300 MHz measurement, GC-MS experiments, and model reactions. It was demonstrated that the initiator was not incorporated into the polymer chains, but unsaturated groups were formed as the dead endgroups of the polymer chains due to proton abstraction from the monomer. The salts of unsaturated acids, formed at the initiation step, are responsible for the growth of polymer chains at the propagation step.

Oligo-3-hydroxybutyrate functionalised pyrroles for preparation of biodegradable conductive polymers

We report the synthesis and characterization of a novel polypyrrole material grafted with biodegradable oligo-3-hydroxybutyrate pendants. The polymer was prepared in a two-step process. Firstly, the potassium salt 1–(2-carboxyethyl)pyrrole was reacted with β-butyrolactone affording N-substituted macromonomer. Secondly, the macromonomer was oxidatively polymerised with FeCl3 Lewis acid. The reaction was carried out in solvents of assorted polarity: dimethylsulphoxide, acetonitrile, dimethylformamide and water. Obtained polymers have been characterised comprehensively using a suite of spectral techniques. The material was found to combine the well-known merits of 3-hydroxybutyrate polymers with the electrical conductivity imparted by polypyrrole units.

Oxidative degradation of poly(3-hydroxybutyrate). A new method of synthesis for the malic acid copolymers

The thermal stability of poly(3-hydroxybutyrate) (PHB) in an oxidation environment was investigated in bulk at temperatures ranging from 100 °C to 140 °C. The process carried out in pure oxygen resulted in PHB backbone degradation with resulting non-volatile products typical for regular PHB thermal degradation while thermal treatment of PHB in an oxygen/ozone mixture resulted in increased rate of polymer backbone scission. The non-volatile degradation product contained macromolecules with several types of terminal groups but also a part of the 3-hydroxybutyrate repeating units was transformed into 3-malic acid units. NMR and multi-stage MS characterization revealed the random distribution of 3-malic acid units in the oligomeric products as well as the content of the malic acid units being dependent on oxidation conditions.