title: Tissue adhesion to bioactive glass-coated silicone tubing in a rat model of peritoneal dialysis catheters and catheter tunnels.
abstract: BACKGROUND
  Silicone peritoneal dialysis catheters do not develop tissue ingrowth, lack a mechanical barrier to periluminal bacterial migration and need cuffs for anchorage. We hypothesized that a bioactive glass coating composed of silicon, calcium, sodium and phosphorous oxides would cause a beneficial tissue reaction causing catheter adhesion, and tested this in a rat model.
  
  
  METHODS
  A hexane solvent-based method of coating silicone tubes with Bioglass powder was used, which maintained flexibility, and then the ultrastructure was confirmed with scanning electron microscopy (EM). Segments 2.5 cm were implanted subcutaneously in 8 Sprague-Dawley rats, with uncoated tubes as a contralateral control, and histology was done at 2, 4 and 6 weeks, including special stains and EM.
  
  
  RESULTS
  The uncoated segments grossly had no adherence to surrounding tissue, and were physically separate from a thin fibrous capsule of approximately 50 micro width. Trichrome stains demonstrated the capsule was rich in collagen. There was minimal adjacent tissue reaction. In contrast, the coated tubes were palpably fixed to the soft tissues, and sections demonstrated an adjacent prominent layer of macrophages and multinucleated giant cells. Small numbers of lymphocytes were noted. This cellular reaction increased over the 6-week implant duration, and was also associated with neovascularization of the tissue adjacent to the segments (33 vessels in coated vs. 20 in controls per x 200 field, P < 0.0001). Many refractile silicone particles and prominent multinucleated giant cells were present, with small numbers of lymphocytes and macrophages. Stains showed scattered discontinuous calcific deposits. These findings are consistent with reports that the Bioglass(R) silicon oxide leads to the formation of a layer of hydroxyapatite, which binds to collagen and induces a tissue cellular reaction.
  
  
  CONCLUSIONS
  In summary, bioactive glass coatings can improve the tissue retention of silicone tubing by promoting adhesion by collagen and cell proliferation, and are promising for future studies of peritoneal dialysis catheters.
authors.affiliation: Division of Nephrology, Hypertension & Transplantation, Department of Materials Science, University of Florida and Veterans Affairs Medical Center, Gainesville, Florida 32610, USA. Rossea@medicine.ufl.edu
authors.forename: Edward A
authors.initials: EA
authors.lastname: Ross
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Batich
authors.forename: William L
authors.initials: WL
authors.lastname: Clapp
authors.forename: Judith E
authors.initials: JE
authors.lastname: Sallustio
authors.forename: Nadeen C
authors.initials: NC
authors.lastname: Lee
mesh_terms: D000818:Animals; D002408:Catheters, Indwelling; D002448:Cell Adhesion; D002455:Cell Division; D002516:Ceramics; D020099:Coated Materials, Biocompatible; D003094:Collagen / Q000378:metabolism; D004867:Equipment Design; D005898:Glass; D008297:Male; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D018919:Neovascularization, Physiologic; D010530:Peritoneal Dialysis / Q000295:instrumentation*; D010537:Peritoneum / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D020099:Coated Materials, Biocompatible; C425330:bioactive glass 45S5; D003094:Collagen