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At least 865 records · Page 48Linked to original sources
PubMed1993

[Treatment of postoperative incisional hernias by a composite prosthesis (polyester-polyglactin 910). Clinical and experimental study].

Because of complications resulting from the use of intraperitoneal prosthetic materials, the authors studied a new double Layered composite mesh (formed by a Dacron mesh, and a polyglactin 910 mesh). The experimental study (40 rats) compared the composite mesh with Dacron mesh. Statistical analysis demonstrated the following conclusions. At 6 months, the poor fibroblastic activity with the composite mesh, indicated the absence of replacement of the polyglactin 910 mesh by a neo-tissue. The Dacron mesh remained in contact the abdominal viscera and contracted with them as many adhesions as when Dacron mesh was used alone. The composite mesh showed poor biological tolerance, lower than that of Dacron mesh. The clinical study concerned 24 patients, 3 recurrences were observed. In one case, we observed migration of the mesh in the small bowel. The unfavorable results of the experimentation, and the risk of visceral migration lead us to avoid the use of composite mesh in intraperitoneal sites.

Animals↗
PubMed1996

Assessment of DNA adducts and the frequency of 6-thioguanine resistant T-lymphocytes in F344 rats fed 2,4-toluenediamine or implanted with a toluenediisocyanate-containing polyester polyurethane foam.

Toluenediamines have been of toxicological concern because of their industrial use as intermediates in polyurethane synthesis and because of the potential of their release from degradation of the Microthane polyesterurethane covering of some breast implants. In this study, we have assessed the extent of DNA damage in rats treated with a carcinogenic toluenediamine isomer, 2,4-toluenediamine (2,4-TDA), under conditions that result in tumor induction, and in rats implanted with Microthane polyesterurethane foam. Time and dose-dependent formation of adducts was observed in DNA from the liver and mammary gland of rats fed 10, 40, 80 and 180 ppm 2,4-TDA for up to 6 weeks. In assays conducted 1 to 32 weeks after the start of treatment, no adducts were detected in the DNA of T-lymphocytes isolated from the spleens of animals fed 40 or 180 ppm 2,4-TDA, nor was there an increase in mutations at the hprt locus in these lymphocytes. In rats fed 40 or 180 ppm, 2,4-TDA for 6 weeks, adducts were detectable in DNA isolated from liver and mammary gland for 26 to 43 weeks after termination of the treatment. No DNA damage, as assessed by both DNA adduct measurement and induction of T-lymphocyte hprt mutations, was observed in rats up to 42 weeks after receiving subcutaneous implants of polyesterurethane foam (67 or 267 mg/kg). Although 2,4-TDA is clearly capable of damaging DNA, the results of this study are consistent with the conclusion that Microthane foam-containing implants present a minimal risk of genotoxicity through release and subsequent metabolic activation of 2,4-TDA. The study also indicates that DNA adduct formation and mutation induction in lymphocytes are inadequate biomonitors for measuring exposure to toluenediamines.

Animals↗
PubMed1996

[Bio-absorbable synthetic polyesters and tissue regeneration. A study of three-dimensional proliferation of ovine chondrocytes and osteoblasts].

The tissue engineering area henceforth calls more and more for bioabsorbable substrata made of biopolymers (collagen, laminin...) or polymers (PLA, PLGA, PGA...) to realize the three-dimensional culture of tissue equivalents. The poly (beta-hydroxybutyrate-beta-hydroxyvalerate), a biopolymer considered as being biodegradable and biocompatible, has been recently introduced for orthopaedic biomaterials and regeneration purposes. In our study, a PHB/9% HV polymer was transformed into 3D foams, then applied to the culture 3D of ovine chondrocytes (fibrous rings & growth plates) and osteoblasts (periostum). Sponges made of bovine type I collagen were used as references. Orthopaedic cells were isolated, prepared and sown by simple injection to the geometrical center of the substrata, then incubated from 0 to 35 days by changing the culture medium all 4 days. Maximal densities were reached after 21 days: 18-24.10(6) cells/g for the chondrocytes, 8-10.10(6) cells/g for the osteoblasts. The cellular proliferation was more marked, with highest cell densities, for the collagen sponges. Laser confocal microscopy shows that the cellular diffusion take place throughout the entire volume of the porous artificial substrata. Future studies will allow to apply the porous bioabsorbable substrata to high-density cell cultures, to the tissue engineering and regeneration, for example for orthopaedic tissues: cartilage, fibrocartilage and bone.

Animals↗
PubMed1997

Microencapsulation of antigens using biodegradable polyesters: facts and phantasies.

New vaccination approaches and new delivery systems have been subject of intensive research activities recently. Controlled release vaccine delivery systems depend on the microencapsulation of antigens into biodegradable polymers, yielding small spherical polymeric particles, in the size range of 1-100 microns. By manipulating the micromorphology of the microparticles and degradation properties of the polymer either continuous or pulsatile release patterns can be adjusted. As biodegradable polymers mainly copolymers of lactic- and glycolic acid have been utilized, since these materials are known to be biocompatible and non-toxic. Apart from modulation of antigen release, an improvement of the adjuvant effect and an increase of in vitro (shelf-life) and in vivo stability of the antigen are issues of general interest with respect to parenteral vaccine delivery systems. Using different microparticles that release antigens in a pulsatile pattern at predetermined timepoints one hopes to induce protective immunity by a single administration of the vaccine delivery system. Using tetanus toxoid (TT) as a model antigen we have examined the stability during preparation, in vitro release and storage of TT microparticles. TT is a complex protein mixture sensitive to changes in pH conditions (pH < 5) and to thermal stress. TT microparticles can be prepared by a W/O/W double emulsion technique with satisfactory encapsulation efficiencies in good yields. In accordance with other investigators we observe an adjuvant effect of TT microspheres in mice upon sc administration leading to a long-lasting antibody response. In challenge experiments we could demonstrate a protective effect. The issue of an ideal release pattern remains open, since a boosting of the antibody titers during the bioerosion of the TT microspheres was not observed, possibly due to desactivation of TT in the degrading microspheres.

Animals↗
PubMed1999

Failure mechanisms of polyester fiber anterior cruciate ligament implants: A human retrieval and laboratory study.

It has been hypothesized that ACL implant failure is often caused by bone impingement in knee extension following malplacement of the tibial tunnel. This study examined polyethylene terephtalate fiber ACL implants retrieved from a clinical study, and, to confirm the hypothesis, also set up a laboratory study intended to duplicate the failure mechanism. SEM and TEM examination of 25 ruptured implants gave details of fiber failure morphology, with shearing into longitudinal fibrils, followed by rupture, when the fibrils burst apart. Cadaver joints were run in a knee simulator, with deliberately impinging ACL implants. SEM examination of implants abraded in the knee in vitro showed identical fiber damage patterns, thus confirming the impingement hypothesis.

Anterior Cruciate Ligament↗
PubMed2006

Biodegradable cationic polyester as an efficient carrier for gene delivery to neonatal cardiomyocytes.

Viral-mediated gene delivery has been explored for the treatment and protection of cardiomyocytes, but so far there is only one report using cationic polymer for gene delivery to cardiomyocytes in spite of many advantages of polymer-mediated gene delivery. In this study, a cationic poly(beta-amino ester) (PDMA) with a degradable backbone and cleavable side chains was synthesized by Michael addition reaction. The toxicity of PDMA to neonatal mouse cardiomyocytes (NMCMs) was significantly lower than that of polyethyleneimine (PEI). PDMA formed stable polyplexes with pEGFP. The dissociation of the polyplexes could be triggered by PDMA degradation, and the dissociation time was tunable via the polymer/pEGFP ratio. In vitro transfection showed that PDMA was an effective and low toxic gene delivery carrier for NMCMs. The PDMA/pEGFP polyplexes transfected EGFP gene to NMCMs with about 28% efficiency and caused little death. In contrast, a significant portion of cardiomyocytes cultured with PEI/pEGFP died.

Acrylamides↗