|
|
Literature Abstracts from PubMed: Hildebrandt et al., Immobilisiertes Heparin als inkrustierungsresistente Beschichtung auf urologischen Implantaten, Biomed. Technik 42 (1997) 123-124 [Immobilized
heparin as an incrustation-resistant layer on urologic implants] [Article in German] Zentralinstitut für Biomedizinische Technik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Deutschland. Die kovalente Immobilisierung des makromolekularen Inhibitors Heparin über Spacer an Festkörperoberflächen hat sich in vitro als erfolgreiches Konzept zur sicheren und langzeitstabilen Inhibition von Inkrustierung erwiesen. An heparinbeschichteten Proben ließen sich zu keinem Zeitpunkt kristalline Ablagerungen nachweisen. Für eine Anwendung ist von besonderer Bedeutung, daß sich durch Auswahl eines angepaßten Spacers eine Vielzahl von Werkstoffen mit Heparin beschichten läßt. Basierend auf dem dargestellten neuartigen Konzept wurde zwischenzeitlich ein Prostata-Stent für die Behandlung benigner Prostatahyperplasie entwickelt. Erste klinische Versuche mit diesem System stehen in Vorbereitung. PMID: 9517077 [PubMed - indexed for MEDLINE] Hildebrandt et al., Prevention of surface encrustation of urological implants by coating with inhibitors, Biomaterials 22 (2001) 503-507 Prevention
of surface encrustation of urological implants by coating with inhibitors. Department
of Biomedical Engineering, Friedrich-Alexander-University Erlangen-Nuremberg,
The encrustation of materials used for urological implants is as yet an unresolved problem. The crystallisation-inhibiting effect of the glycosaminoglycan heparin was used to reduce encrustation. Heparin was covalently bound to the surface of slotted-tube stents of tantalum and stainless steel using a spacer molecule. To verify the inhibition of crystallisation processes, reproducible in vitro tests and in vivo tests using the rat as animal model were carried out. The in vitro and in vivo experiments showed that the heparin coating has a significant influence on the encrustation of the surface. After 7 days in vitro and 120 days in vivo, heparin coated stents were free of encrustation, whereas the uncoated reference stents were extensively covered. PMID: 11214762 [PubMed - indexed for MEDLINE] Hildebrandt, Glycosaminoglycans – all round talents in coating technology, Biomed. Technik 47 (2002) 476-478 Glycosaminoglycans - all
round talents in coating technology. UroNova GmbH
Medizinische Implantate, The use of glycosaminoglycans for coating of medical implants had it's beginning in heparin coating of coronary stents and catheters to improve their haemocompatibility. Until now glycosaminoglycans proved as very potent in a variety of medical applications. Glycosaminoglycans not only show anticoagulant properties, also their crystal growth inhibiting effects in urology, inhibition of bacterial adherence and influence on the proliferation behaviour of human cells could be demonstrated. Beside an overview over the development of glycosaminoglycan coatings so far, recent outcomes of a bacteriological and a cell proliferation study with coated surfaces are presented. PMID: 12451898 [PubMed - indexed for MEDLINE] Riedl et al., Heparin coating reduces encrustation of ureteral stents: a preliminary report, Internat. J. of Antimicrobial Agents 19 (2002) 507-510 Heparin
coating reduces encrustation of ureteral stents: a preliminary report. Department
of Urology, The present study evaluated the inhibition of ureteral stent encrustation by heparin coating. In contrast to uncoated polyurethane stents, heparin coated ureteral stents did not show any organic (biofilms) or anorganic (crystals) deposits after being in situ for up to 6 weeks and effectively inhibited the encrustation process. PMID: 12135841 [PubMed - indexed for MEDLINE] Tenke et al., Bacterial biofilm formation on urologic devices and heparin coating as preventive strategy, Internat. J. of Antimicrobial Agents 23 (2004) 67-74 Bacterial
biofilm formation on urologic devices and heparin coating as preventive
strategy. Department
of Urology, In the process of endourological development a variety of foreign bodies have been invented besides urinary catheters, on which biofilm can be formed. Bacteria in the biofilm are less susceptible to antibiotics. An additional problem of medical biomaterials in the urinary tract environment is the development of encrustation and consecutive obstruction. The most promising prevention strategy for bacterial biofilms is the production of materials with anti-adhesive surfaces such as heparin. Although heparin-coated ureteral stents are expensive, they justify their cost. Our studies show that such devices are protected against incrustation and biofilm formation for a longer period of time: 6-12 months, both in vitro and in vivo. PMID: 15037330 [PubMed - indexed for MEDLINE]
Heparin coating on ureteral Double J stents prevents encrustations: an
in vivo case study
Dipartimento
di Nefrourologia, S.S.C.V.D. per il trattamento integrato della calcolosi
urinaria, Ospedale Maggiore S. Giovanni Battista, PURPOSE: To
evaluate the ability of heparin coating to inhibit Double J stent
encrustation and compare it with the classic polyurethane Double J stent.
PATIENTS AND METHODS: The study involved five patients with bilateral
obstructions, who required bilateral ureteral Double J stent placement. Every
patient received a heparin-coated Double J stent and a traditional
polyurethane Double J stent for 1 month. After removal, the stents were
analyzed using field emission scanning electron microscopy (FESEM), energy
dispersive spectroscopy (EDS), and micro-infrared spectrophotometry
(Micro-IR). These same techniques were used to analyze the heparin-coated and
uncoated stents before insertion. The thickness, extension, and composition
of encrustation of the coated and uncoated stents were compared. Moreover,
two heparin-coated stents were analyzed with the same techniques after they
had been in place for 10 and 12 months. RESULTS: FESEM analysis showed that
the difference in encrustation thickness and extension between the two groups
was significant. EDS and Micro-IR confirmed that in the heparinized stents
the encrustations were not as uniform and compact as those in the uncoated
stents. The stents that were left in place long-term were free of
encrustations and had no changes in the heparin layer. CONCLUSIONS: Heparin
coating reduces stent encrustation. Moreover, as no changes were seen in the
heparin layer, we concluded that covalent heparin bonding enhances its
adhesion to the polyurethane surface and ensures its stability for long
periods. The heparin-coated stent appears to be a useful tool for long-term
urinary drainage. PMID: 18307380 [PubMed - indexed for MEDLINE] Farnbacher et al., Does heparin coating reduce occlusion in biliray
plastic endoprostheses?, P1533, 16th United European Gastroenterology Week,
18 – 22 October 2008, Vienna, Austria Does heparin coating reduce occlusion in biliary plastic endoprostheses? Innere Medizin, Klinikum Fürth, Akademisches Lehrkrankenhaus der Friedrich-Alexander-Universität Erlangen-Nürnberg, Fürth, Germany INTRODUCTION: Biliary stenting using plastic endoprostheses is limited by early occlusion. The resulting scheduled stent exchange is expensive and uncomfortable. In urological endoprostheses covalent binding of glycosaminoglycanes to polyurethane stents proved to reduce incrustation. Since development of urological and biliary stent occlusion shows parallels, the aim of the study was to evaluate the efficacy of heparin coating of biliary endoprostheses to prevent stent occlusion. AIMS & METHODS: Study design was prospective, randomised, single centre, cross over. All stents used were Amsterdam type (10Fr, 9cm, polyethylene). The covalent heparin coating was performed by UroNova GmbH, GERMANY. Before implantation, weight of all stents was determined. Due to randomisation, coated or standard stents were then implanted in jaundiced patients suffering from malignant biliary obstruction. Scheduled stent exchange was performed after 90 days implanting new coated or standard stents according to the cross over design for the same duration. After explantation, stents were stored at -18°C. Immediately before analysis stents were dried at 50°C for 24 hours, then weighed and finally longitudinally opened to visualize incrustation and discolouration. Occlusion was measured by the increase of stent dry weight. Statistical analysis was done using the Wilcoxon-Test. RESULTS: In total 32 patients were randomized. Twenty-two patients dropped out due to short duration of stent implantation or missing cross over. In 10 patients (3 male/7 female, 58-79 yrs.) study was completed. Premature stent removal was necessary in 3/10 standard stents, because of new jaundice or cholangitis, but in none of the coated stents. After longitudinal incision, all three stents showed total or partial occlusion. Altogether, coated stents showed less visible occlusion and discolouration than standard stents. On average the weight of standard stents was twice as high as of coated stents (standard: 32±12 (16-56)mg; coated: 15±4 (9-24)mg), although the duration of stent implantation was not significantly different between both groups (standard: 80±21(30-106) days; coated: 87±13(56-101)days). In total, the weight of removed coated stents was lower than the weight of the standard stents in 9/10 patients. CONCLUSION: With respect to development of stent occlusion, heparin-coated plastic biliary endoprostheses are significantly superior to standard polyethylene stents. Further studies have to show whether this effect allows the stent to remain in situ for a longer period of time to reduce the frequency of scheduled stent exchange.
|
