Experimental study on laser assisted vascular repair and anastomosis with ICG-infused chitosan films

Laser-based approach for suturing biological tissues is emerging as a valid alternative to conventional techniques, because of its widely demonstrated advantages, such as immediate watertight closure of the wound, minimal inflammatory response and scar formation, and reduced wound healing time. Moreover the laser based techniques may provide suturing in hardly accessible sites (e.g. in microsurgery, endoscopic and minimally invasive surgery) or in thin tissues that are impossible to treat with staples and/or stitches (e.g. the lens capsule bag). Usually, the biological tissue is stained with a liquid or semisolid preparation of organic chromophores (indocyanine green - ICG): a near infrared laser light is locally absorbed and converted into a photothermal effect, thus inducing welding of the wound. Some limitations are ascribed to the use of organic chromophores, such as their poor photochemical stability, excessive diffusiveness in the biological matrices and inadequate stability when stored in an aqueous solution or dispersed in a physiological environment. To overcome these problems we proposed the use of chitosan matrices, properly stained with conventional chromophores (ICG). The Indocyanine Green (ICG) is included into the chitosan matrices: the matrix enwraps the chromophore particles, thus enhancing their stability, durability and effectiveness. The final product has thus the necessary optical and mechanical characteristics to design a safe and standard laser-based tissue closuring procedure. The ICG infused chitosan patches were used to perform Laser Assisted Vasular Repair (LAVR) and Anastomosis (LAVA) in an in vivo experimental study in carotid rabbits. An ICG-infused chitosan patch was used to wrap the artery in the lesion area. A diode laser emitting at 810 nm, equipped with a 300 °m diameter optical fiber was used to weld the patch onto the artery wall, by delivering single laser spots to induce local patch/tissue adhesion. The result is an imm- - ediate closure of the wound, with no bleeding at clamps release. The animals were observed during follow-up. All the anastomosis were patent, no bleeding signs were documented. The carotid samples underwent histological examinations. The advantages of the proposed technique are: simplification of the surgical procedure and shortening of the operative time; decreased foreign-body reaction; reduced inflammatory response and improved vascular healing process.