Preparation of dissolvable albumin stents for vascular anastomosis with a 1.9μm laser and in vitro mechanical strength assessments

Introduction 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 1.9μm 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. Materials and Methods The axial tensile strength and burst pressure of 3.75±0.3mm inner-diameter vessels soldered with varied swath width (1-7mm), laser power (430-610mW), 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 25kGy gamma-irradiation, and stents with varied diameter and wall thickness. Results Optimized soldering parameters yielded tensile strengths of 4.4±1.2N and burst pressures of 400±90mm Hg with stay sutures. Differences in stent solubility in blood and PBS were not statistically significant (p=0.99). Sterilization by 25kGy gamma-irradiation did not cause significant changes (p>0.6) in stent solubility, which was primarily volume-dependent. Under simulated intravascular flow conditions, 3mm stents dissolved completely with 2.7±0.7ml/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.