Laser-activated solid protein solder for nerve repair: In vitro studies of tensile strength and solder/tissue temperature

Laser-activated solid protein solder strips have been developed for peripheral nerve repair. Indocyanine green dye added to the solder strongly absorbs diode wavelengths (~ 800 nm) and causes localised heating and coagulation of the albumin protein solder. The protein strengthens the tissue join, particularly during the acute healing phase postoperative, while shielding the underlying axons from excessive thermal damage. In this investigation of the solid protein solder technique for nerve repair, the effect of laser irradiance on weld strength and solder and tissue temperature were studied. The tensile strength of repaired nerves rose steadily with increased irradiance reaching a maximum of 105 ± 10 N/cm² at 12.7 W/cm². At higher irradiances, tensile strength fell. The maximum temperature reached at the solder surface and at the solder/nerve interface, measured using a non-contact fibre optic radiometer and thermocouple, respectively, also rose steadily with laser irradiance. At 12.7 W/cm², the temperatures reached at the surface and at the interface were 88 ± 5°C and 71 ± 4°C, respectively. This in vitro investigation demonstrates the feasibility of the laser-activated solid protein solder strips for peripheral nerve repair. The laser irradiance and the corresponding solder surface temperature for optimal tensile strength have been identified.