Gold Nanorod-Collagen Nanocomposites as Photothermal Nanosolders for Laser Welding of Ruptured Porcine Intestines

Surgical site infection and postoperative leakage are complications that may develop following colorectal surgery and result in fatal consequences. Rapid, fluid-tight wound closure through laser tissue welding (LTW) can reduce postoperative leakage and thus decrease infection. Laser tissue welding involves generation of localized heat by exposing an exogenous chromophore to near-infrared (NIR) irradiation in order to seal wounds. In this study, we generated gold nanorod (GNR)-collagen nanocomposites (NCs) for laser-facilitated welding of ruptured intestinal tissue. The fluid content, stiffness, elasticity, and laser-induced temperature response of these nanocomposites were modulated to optimize laser-induced tissue fusion and minimize tissue damage. In addition, the effect of laser operating parameters including power density, femtosecond pulsed wave (PW) or continuous wave (CW) laser, and exposure duration were all studied. Laser power density and treatment duration significantly affected the temperatures reached during welding, as well as tissue weld strength and burst pressure. CW laser was found to induce significantly higher temperatures of the nanocomposites during treatment than PW laser, but the differences in weld strength and burst pressure for the two laser types were insignificant. This suggests that PW lasers can result in robust welds while minimizing potential thermal damage compared to CW lasers. The ultimate tensile strength of welded ruptured tissue was returned to as high as 68% of the native tissue strength through laser treatment, and laser treatment with these nanocomposites restored up to 64% of native tissue leak pressure and 42% of burst pressure. To the best of our knowledge, the laser power densities used (≤2.50 W/cm<sup>2</sup>) are among the lowest reported for laser tissue welding, and the laser configuration and use require very little surgical skill. Our results indicate that GNR-collagen nanocomposites are promising photothermal biomaterials in laser tissue welding applications.