Consistent with the present invention, tissue
adhesive compositions and an associated
laser exposure system are provided for bonding or sealing biological tissues. The compositions are comprised of chemically derivatized soluble collagen which is formulated to concentrations
ranging from 300 mg / ml (30%) to 800 mg / ml (80%) collagen
protein. In particular,
Type I collagen, for example, is first prepared by extraction from bovine or porcine hide and purified. The collagen preparations are then chemically derivatized with sulfhydryl reagents to improve
cohesive strength and with secondary derivatizing agents, such as carboxyl groups, to improve the
adhesive strength of the solder to the tissue. The compositions are then formed into viscous solutions, gels or
solid films, which when exposed to energy generated from an
infrared laser, for example, undergo thermally induced phase transitions.
Solid or semi-
solid protein compositions become less viscous enabling the
high concentration protein to penetrate the interstices of treated
biological tissue or to fill voids in tissue. As
thermal energy is released into the surrounding environment, the protein compositions again become
solid or semi-solid, adhering to the treated tissue or
tissue space.