Binding of indocyanine green in polycaprolactone fibers using blend electrospinning for in vivo laser-assisted vascular anastomosis.

BACKGROUND AND OBJECTIVE: The clinical application of laser-assisted vascular anastomosis is afflicted by unreliable and low bonding strengths as well as tedious handling during microvascular surgery. The challenge to be met arises from the flow-off of the chromophore during soldering that changes the absorption and stains the surrounding tissue, leading to an uncontrollable thermal damage zone. In this study, we investigated the feasibility to produce an indocyanine green (ICG)-loaded patch by electrospinning and tested its applicability to both in vitro and in vivo microvascular laser soldering. MATERIALS AND METHODS: A blend of polycaprolactone and ICG was electrospun to produce a pliable patch. Prior to soldering, the patch was soaked in 40% wt. bovine serum albumin solution. The solder patch was wrapped in vitro around blood vessel stumps of rabbit aortas. An intraluminal balloon catheter enabled an easy alignment and held the setup in place. The soldering energy was delivered via a diffusor fiber from the vessel lumen using a diode laser at 810 nm. During the procedure, the surface temperature was observed with an infrared camera. Afterward, samples were embedded in methylmethacrylate and epon to study thermal damage. The quality of the fusion was assessed by measuring the tensile strength. After in vitro tests with rabbit aortas, eight large white pigs were subjected to an acute in vivo experiment, and the artery of the latissimus dorsi flap was anastomosed to the distal femoral artery. RESULTS: The ICG-loaded patch, produced by electrospinning, has a thickness of 279 ± 62 µm, a fiber diameter of 1.20 ± 0.19 µm, and an attenuation coefficient of 1,119 ± 183 cm-1 at a wavelength of 790 nm. The patch was pliable and easy to handle during surgery. No leakage of the chromophore was observed. Thermal damage was restricted to the Tunica adventitia and Tunica media and the area of the vessel wall that was covered with the patch. Six pigs were successfully treated, without any bleeding and with a continuous blood flow. The in vivo flap model yielded a similar tensile strength compared to in vitro laser-assisted vascular anastomoses (138 ± 52 vs. 117 ± 30 mN/mm2 ). CONCLUSION: Our study demonstrated the applicability of the ICG-loaded patch for laser-assisted vascular anastomosis. By using electrospinning, ICG could be bound to polymer fibers, avoiding its flow-off and the staining of the surrounding tissue. This patch demonstrated several advantages over liquid solder as it was easier to apply, ensured a high and reliable bonding strength while maintaining a constant concentration of ICG concentration during the surgery. Lasers Surg. Med. 49:928-939, 2017. © 2017 Wiley Periodicals, Inc.

Endoluminal laser-assisted vascular anastomosis-an in vivo study in a pig model.

Microvascular surgery is time consuming and requires high expertise. Laser-assisted vascular anastomosis (LAVA) is a promising sutureless technique that has the potential to facilitate this procedure. In this study, we evaluate the handling of our soldering material and the 1-week patency rate in a porcine model. Six pigs were subjected to LAVA. For each pig, the saphenous artery on one side was transected while the contralateral side was used as control. A porous polycaprolactone scaffold soaked in 40% (w/w) bovine serum albumin solution in combination with 0.1% (w/w) indocyanine green was wrapped at the anastomosis site and at the control site. Both sides were then soldered with a diode laser coupled into a light diffuser fiber emitting radiation with a wavelength of 808 nm and a power of 2-2.2 W. Vessels were successfully soldered with a 100% immediate patency rate. The 1-week patency rate was 83% for the anastomoses versus 67% for the control side. Vessels irradiated for 80 to 90 s tended to maintain the highest patency rate. Macroscopically, there was no difference between the two sides. The patch was easy to handle provided that the environment could be kept dry. This study shows the potential and the limitations of endoluminal LAVA as a one-step procedure without the use of stay sutures. Further studies are needed to improve the soldering material, the long-term patency rate, and standardized irradiation parameters. The long-term effects of laser soldering on the vessel wall remain to be determined.

Electrospinning of highly concentrated albumin patches by using auxiliary polymers for laser-assisted vascular anastomosis.

BACKGROUND AND OBJECTIVE: Electrospun meshes have been extensively investigated for tissue engineering and drug delivery. The application of this technology is of interest for laser-assisted vascular anastomosis (LAVA) due to the possibility to bind and stabilize macromolecules in fibers. MATERIALS AND METHODS: We prepared bovine serum albumin (BSA) blend microfibers from the auxiliary proteins polyethylene oxide (PEO), polycaprolactone (PCL), polyvinyl alcohol (PVA) and gelatin. The thickness and weight of the resulting patches were measured and the morphological characteristics were observed by scanning electron microscopy. Thereafter, layered patches were prepared by spinning the BSA/polymer layer on top of a light absorbing layer made of indocyanine green and PCL. The effect of the material composition of the electrospun patches on the behavior during LAVA, the bonding strength and the resulting thermal damage were investigated. RESULTS: The bonding strength of the tissue fusion increased with higher BSA amounts in the patch. By using PEO, a ratio of 85/15 (w/w) of BSA/PEO was stable during electrospinning, leading to a shear strength that was similar to patches that were soaked in liquid BSA (20.7 ± 4.1 mN mm-2 and 20.3 ± 4.1 mN mm-2, respectively). The handling during LAVA was however drastically improved by using a layered patch made from BSA/PEO. Thermal damage was similar compared to previous solder materials. CONCLUSION: This study investigated the maximum amount of BSA possible in electrospun polymer fibers made from PEO, PCL, PVA and gelatin. Both, the process of electrospinning and the performance during ex vivo LAVA, makes the BSA/PEO blend a promising material for LAVA.