In vitro and in vivo tissue repair with laser-activated chitosan adhesive

Background and Objectives: Sutures are currently the gold standard for wound closure but they are still unable to seal tissue and may induce scarring or inflammation. Biocompatible glues, based on polysaccharides such as chitosan, are a possible alternative to conventional wound closure. In this study, the adhesion of laser-activated chitosan films is investigated in vitro and in vivo. In particular we examine the effect of varying the laser power, as well as adding a natural cross-linker (genipin) to the adhesive composition. Study Design/Materials and Methods: Flexible and insoluble strips of chitosan films (surface area ∼34 mm², thickness ∼20 μm) were bonded to sheep intestine using several laser powers (0, 80, 120, and 160 mW) at 808-nm wavelength. The strength of repaired tissue was tested by a calibrated tensiometer to select the best power. A natural cross-linker (genipin) was also added to the film and the tissue repair strength compared with the strength of plain films. The adhesive was also bonded in vivo to the sciatic nerve of rats and the thermal damage induced by the laser assessed 4 days post-operatively. Results: Chitosan adhesives successfully repaired intestine tissue, attaining a maximum repair strength of 14.7 ± 4.3 kPa (n = 30) at the laser power of 120 mW. The chitosan-genipin films achieved lower repair strength (9.1 ± 2.9 kPa). The laser caused partial demyelination of axons at the site of operation, but the myelinated axons retained a normal morphology proximally and distally. Conclusions: The chitosan adhesive effectively bonded to tissue causing only localized thermal damage in vivo, when the appropriate laser parameters were selected.