Chitosan adhesive for laser tissue repair

Background. Laser tissue repair usually relies on haemoderivate solders, based on serum albumin. These solders have intrinsic limitations that impair their widespread use, such as limited repair strength, high solubility, brittleness and viral transmission. Furthermore, the solder activation temperature (65-70°C) can induce significant damage to tissue. In this study, a new laser-activated biomaterial for tissue repair was developed and tested in vitro and in vivo to overcome some of the shortcomings of traditional solders. Materials and Methods. Flexible and insoluble strips of chitosan adhesive (surface area ∼34 mm², thickness ∼20 μm) were developed and bonded on sheep intestine with a laser fluence and irradiance of 52 ± 2 J/cm² and ∼15 W/cm² respectively. The temperature between tissue and adhesive was measured using small thermocouples. The strength of repaired tissue was tested by a calibrated tensiometer. The adhesive was also bonded in vivo to the sciatic nerve of rats to assess the thermal damage induced by the laser (fluence = 65 ± 11 J/cm², irradiance = 15 W/cm²) four days post-operatively. Results. Chitosan adhesives successfully repaired intestine tissue, achieving a repair strength of 0.50 ± 0.15 N (shear stress = 14.7 ± 4.7 KPa, n=30) at a temperature of 60-65°C. The laser caused demyelination of axons at the operated site; nevertheless, the myelinated axons retained their normal morphology proximally and distally.