Chitosan adhesive for laser tissue repair: In vitro characterization

Background and Objectives: Laser tissue repair usually relies on hemoderivate protein solders, based on serum albumin. These solders have intrinsic limitations that impair their widespread use, such as limited tensile strength of repaired tissue, poor solder solubility, and brittleness prior to laser denaturation. Furthermore, the required activation temperature of albumin solders (between 65 and 70°C) can induce significant thermal damage to tissue. In this study, we report on the design of a new polysaccharide adhesive for tissue repair that overcomes some of the shortcomings of traditional solders. Study Design/Materials and Methods: Flexible and insoluble strips of chitosan adhesive (elastic modulus ∼6.8 Mpa, surface area ∼34 mm ², thickness ∼20 μm) were bonded onto rectangular sections of sheep intestine using a diode laser (continuous mode, 120 ± 10 mW, λ = 808 nm) through a multimode optical fiber with an irradiance of ∼15 W/cm². The adhesive was based on chitosan and also included indocyanin green dye (IG). The temperature between tissue and adhesive was measured using a small thermocouple (diameter ∼0.25 mm) during laser irradiation. The repaired tissue was tested for tensile strength by a calibrated tensiometer. Murine fibroblasts were cultured in extracted media from chitosan adhesive to assess cytotoxicity via cell growth inhibition in a 48 hours period. Results: Chitosan adhesive successfully repaired intestine tissue, achieving a tensile strength of 14.7 ± 4.7 kPa (mean ± SD, n = 30) at a temperature of 60-65°C. Media extracted from chitosan adhesive showed negligible toxicity to fibroblast cells under the culture conditions examined here. Conclusion: A novel chitosan-based adhesive has been developed, which is insoluble, flexible, and adheres firmly to tissue upon infrared laser activation.