title: Preparation of dissolvable albumin stents for vascular anastomosis with a 1.9 µm laser and in vitro mechanical strength assessments.
abstract: BACKGROUND
  We present a clinically relevant method for producing and sterilizing dissolvable albumin stents to provide intraluminal support during vascular anastomosis, and a method for photothermally soldering vessels using a 1.9 µm diode laser with a 200-µm spot size, albumin solder, and water as the chromophore. Our aim in this study was to assess the mechanical integrity of soldered vessels, and to determine if gamma-irradiation affected the solubility of the stents.
  
  
  METHODS
  The axial tensile strength and burst pressure of 3.75 ± 0.3 mm inner-diameter vessels soldered with varied swath width (1-7 mm), laser power (430-610 mW), solder concentration (22-46%w/w), and solder layering (1-3 layers) was tested in vitro. Stent dissolution was monitored by weight in blood, and with UV absorbance measurements in phosphate buffered saline (PBS). Solubility was measured for stents sterilized by 25 kGy gamma-irradiation, and stents with varied diameter and wall thickness.
  
  
  RESULTS
  Optimized soldering parameters yielded tensile strengths of 4.4 ± 1.2 N and burst pressures of 400 ± 90 mm Hg with stay sutures. Differences in stent solubility in blood and PBS were not statistically significant (p = 0.99). Sterilization by 25 kGy gamma-irradiation did not cause significant changes (p > 0.6) in stent solubility, which was primarily volume-dependent. Under simulated intravascular flow conditions, 3 mm stents dissolved completely with 2.7 ± 0.7 ml/mg.
  
  
  CONCLUSIONS
  The results show that fast-dissolving stents can be produced reliably using the extrusion technique, and sterilized by gamma-irradiation. Without stay sutures, soldered vessels exhibited low tensile strength, but burst pressures comparable to sutured vessels. It was concluded that stay sutures would be necessary in vivo due to degradation of the tensile strength of soldered vessels with exposure to moisture.
authors.affiliation: Department of Electrical and Computer Engineering, PO Box 751, Portland State University, Portland, OR 97207, USA. rmccar@cecs.pdx.edu
authors.forename: Reid
authors.initials: R
authors.lastname: McCargar
authors.forename: Kari
authors.initials: K
authors.lastname: Jenson
authors.forename: Amanda
authors.initials: A
authors.lastname: Dayton
authors.forename: Katrina
authors.initials: K
authors.lastname: Murphy
authors.forename: Hua
authors.initials: H
authors.lastname: Xie
authors.forename: Scott A
authors.initials: SA
authors.lastname: Prahl
mesh_terms: D000418:Albumins; D000714:Anastomosis, Surgical; D000818:Animals; D001672:Biocompatible Materials; D002339:Carotid Arteries / Q000502:physiology / Q000601:surgery; D006801:Humans; D066298:In Vitro Techniques; D054023:Lasers, Semiconductor; D011312:Pressure; D015607:Stents; D013242:Sterilization; D013552:Swine; D013718:Tensile Strength; D058017:Vascular Grafting / Q000295:instrumentation* / Q000379:methods
chemical_list: D000418:Albumins; D001672:Biocompatible Materials