Methods and systems for endoscopic suturing of biological tissue are disclosed. Endoscopic instruments are described which serve to position a suture material at an anastomotic site and deliver laser radiation to the suture material to effect fusion. The suture material includes a structure adapted for positioning at an anastomotic site and has at least a portion of the structure formed by a photoreactive crosslinking agent, such that upon irradiation of the structure the crosslinking agent adheres to the biological material. In one embodiment, the suture material can also include a high tensile strength element which is coated with a laser activatable crosslinking agent or glue. Upon activation, the suture material creates a desired closure or joinder of the biological material and is left in place while the endoscope is advanced to another target site or removed.