Selective photothermal tissue interaction using 805-nm laser and indocyanine green in tissue welding

Abstract

Laser tissue welding has the potential to become an effective method for wound closure and healing without sutures and staples. Laser light has the ability to control the volume of tissue being exposed. It can also cause selective tissue fusion by activating light-absorbing dye in the target tissue without significantly affecting the surrounding normal tissue. Temperature is a crucial factor in tissue welding. Too high a temperature causes irreversible tissue damage, while too low a temperature fails to form a strong tissue bond. To effectively control tissue temperature, an 805-nm laser was used in conjunction with in situ application of indocyanine green (ICG) as the light-absorbing dye. In vivo laser tissue welding using rat skin was performed with the laser-dye combination. Using different power densities, ranging from 0.4 W/cm $^2$ to 1.2 W/cm $^2$ , the skin temperature could be increased from body temperature to a range of 40°C to 72°C, with the enhancement of ICG solution. The long-term effect of laser welding was studied by measuring the tensile strength of the welded tissue at different times after the welding, in comparison with that of the tissue closure using conventional suturing. Our results showed that the welded tissue provided a stronger tissue holding power at the early stage than the sutured tissue and provided almost the same strength as the sutured tissue 30 days after the welding.