Laser assisted soldering: effects of hydration on solder-tissue adhesion

Wound stabilization is critical in early wound healing. Other than superficial skin wounds, most tissue repair is exposed to a hydrated environment postoperatively. To simulate the stability of laser-soldered tissue in a wet environment, we studied the effects of hydration on laser soldered rat dermis and baboon articular cartilage. In this in vitro study, we used a solder composed of human serum albumin, sodium hyaluronate, and Indocyanine Green. A 2 μL solder droplet was deposited on each tissue specimen and then the solder was irradiated with a scanning laser beam (808 nm and 27 W/cm2). After photocoagulation, each tissue specimen was cut into two halves dividing the solder. One half was reserved as control while the other half was soaked in saline for a designated period before fixation (1 h, 1, 2, and 7 days). All tissue specimens were prepared for scanning electron microscopy (SEM). SEM examinations revealed nonuniform coagulation across the solder thickness for most of the specimens, likely a result of the temperature gradient generated by laser heating. Closer to the laser beam, the uppermost region of the solder formed a dense coagulum. The solder aggregated into small globules in the region anterior to the solder-tissue interface. All cartilage specimens soaked in saline suffered coagulum detachment from tissue surface. We noted a high concentration of the protein globules in the detached coagulum. These globules were likely responsible for solder detachment from the cartilage surface. Solder adhered better to the dermis than to cartilage. The dermal layer of the skin, composed of collagen matrix, provided a better entrapment of the solder than the smooth surface of articular cartilage. Insufficient laser heating of solder formed protein globules. Unstable solder-tissue fusion was likely a result of these globules being detached from tissue substrate when the specimen was submerged in a hydrated environment. The solder-tissue bonding was compromised as a result of this phenomenon. © 1998 Society of Photo-Optical Instrumentation Engineers.