Genetically engineered Pseudomonas: a factory of new bioplastics with broad applications.

New bioplastics containing aromatic or mixtures of aliphatic and aromatic monomers have been obtained using genetically engineered strains of Pseudomonas putida. The mutation (-) or deletion (Delta) of some of the genes involved in the beta-oxidation pathway (fadA(-), fadB(-) Delta fadA or Delta fad BA mutants) elicits a strong intracellular accumulation of unusual homo- or co-polymers that dramatically alter the morphology of these bacteria, as more than 90% of the cytoplasm is occupied by these macromolecules. The introduction of a blockade in the beta-oxidation pathway, or in other related catabolic routes, has allowed the synthesis of polymers other than those accumulated in the wild type (with regard to both monomer size and relative percentage), the accumulation of certain intermediates that are rapidly catabolized in the wild type and the accumulation in the culture broths of end catabolites that, as in the case of phenylacetic acid, phenylbutyric acid, trans-cinnamic acid or their derivatives, have important medical or pharmaceutical applications (antitumoral, analgesic, radiopotentiators, chemopreventive or antihelmintic). Furthermore, using one of these polyesters (poly 3-hydroxy-6-phenylhexanoate), we obtained polymeric microspheres that could be used as drug vehicles.

Hydrophilic hybrid IPNs of segmented polyurethanes and copolymers of vinylpyrrolidone for applications in medicine.

The preparation and biocompatibility properties of thermoplastic apparent interpenetrating polymer networks (T-IPNs) of a segmented polyurethaneurea, Biospan (BS), and vinylpyrrolidone-dimethylacrylamide (VP-DMAm) copolymers, are described. The biological interaction between the obtained materials and blood was studied by in vitro methods. The addition of the VP-DMAm copolymers to form T-IPNs with BS substantially increased the equilibrium water uptake and water diffusion coefficients. Investigation of the proteins adsorption, platelet adhesion, thrombus formation and factor XII activation is presented. Investigations of the proteins adsorption of the BS/VP-DMAm T-IPNs surfaces show that the segmented polyurethane (BS) containing VP-DMAm copolymers with higher VP content adsorb more albumin than fibrinogen and gamma-globulin. The platelets adhesion, thrombus formation and factor XII activation are effectively suppressed with respect to the segmented polyurethane when VP-DMAm copolymers with high VP contents are incorporated into BS as T-IPNs.

Vinylpyrrolidone-N,N'-dimethylacrylamide water-soluble copolymers: synthesis, physical-chemical properties and proteic interactions.

The radical copolymerization of N-vinyl-2-pyrrolidone (NVP) with N,N'-dimethylacrylamide (DMAm) has been studied. The copolymer compositions were determined from 1H-NMR. The radical reactivity ratios for DMAm (M1) and VP (M2) were found to be r1 = 2.232 and r2 = 0.186. An analysis of the water vapor absorption isotherms as a function of the lactam content in the copolymer is reported. It was observed that the water vapor absorption decreases with increasing VP content in the copolymer and show anomalous diffusion behavior with increasing temperature due to the coupling of diffusion and polymer relaxation mechanisms. From the water vapor sorption data the Arrhenius activation parameter (ED) and enthalpy of sorption (deltaH S) were determined. The activation parameters are found to follow the conventional trend. The poly(DMAm-co-VP) copolymers exhibited a decreased critical solution temperature (LCST) in proportion to their lactam content. Contact angle data were evaluated for the determination of surface free energy components (gamma d SV, gamma P SV and gamma SV) of the synthesized polymers. The dispersion force component (gamma d SV) of copolymers increased only slightly with the VP content whereas the polar force component (gamma P SV) decreased with the lactam content. No dependence was observed between the surface free energy (gamma SV) and copolymer compositions. The complex formation between bovine serum albumin (BSA) and the VP-DMAm copolymers in water was studied by fluorescence spectroscopy. It was found that the copolymers bind to BSA non-specifically on the surface. Phase separation was not observed after addition of copolymers to BSA solutions at pH higher or lower than isoelectric point of BSA.

Recombinant growth hormone delivery systems based on vinylpyrrolidone-hydroxyethyl methacrylate copolymer matrices: monitoring optimization by capillary zone electrophoresis.

Experimental conditions for the fabrication of two new polymeric devices (i.e. films and slabs) useful for the controlled release of recombinant growth hormone (GH) are given. The release rate is controlled by the resorption profile of the vinylpyrrolidone-hydroxyethyl methacrylate (VP-HEMA) tested systems which is related to the copolymer composition. The suitability of capillary electrophoresis (CE) for following the complete preparation of the different VP-HEMA devices is shown. Moreover, CE allows simultaneous monitoring of the controlled release of GH and dissolved polymer during in vitro experiments. From these results, guidelines are given for the fabrication of polymeric devices containing protein as active drug as well as for the correct selection of conditions during in vitro experiments.

Hemocompatible properties of polymeric derivative of paracetamol.

Copolymerization of N,N-dimethylacrylamide (DMAA) and p-acryloyloxiacetanilide (AOA) was carried out at different mole ratios of the monomers to obtain copolymers of varying compositions. DMAA contents were very near to the corresponding monomer feed and varied between 0.20 and 0.80. Investigation of the protein adsorption of these polymer surfaces showed that copolymers with higher DMAA content adsorbed more albumin than fibrinogen. The scanning electron micrographs of the polymer-coated coverslips after contact with blood showed an antithrombogenic behaviour of these surfaces.

Stereotypic culture systems for liver and bone marrow: evidence for the development of functional tissue in vitro and following implantation in vivo.

Stromal cell-associated liver cell and bone marrow (BM) culture on three-dimensional nylon screen or polyglycolic acid (PGA) felt templates conveys certain functional advantages to the parenchyma of these tissues. Hepatic parenchymal cells (PC) manifest long-term ( approximately 2 month) expression of liver-specific activities including cytochrome P450 enzyme activity and the synthesis of albumin, fibrinogen, transferrin, and other proteins. PC also undergo proliferation in association with stromal cells that were pre-established on these templates. PC mitoses are directly proportional to available space within the template for their expansion indication that geometric or sterotypic parameters influence the growth of these cells in vitro. BM cultured on a similar template exhibits long-term multilineage hematopoietic expression and limited expansion of progenitor cell numbers. Progenitor cell concentration within the cultures can be substantially enhanced if these cells are liberated from co-culture and reseeded onto a template containing fresh stromal cells. BM and liver cel cultures established on felt composed of bioresorbable PGA filaments was grafted into various sites in rats. Liver co-cultures generated sinusoids and other liver-like structures in situ; active hematopoietic blasts were observed at sites of BM co-culture grafts. Biodegradable polymer constructs may prove useful for certain clinical applications as vehicles for the delivery of tissues that were engineered in culture.