Preparation of surgical indocyanine green-dyed gauze using an autoclave and its near-infrared fluorescence properties

A near-infrared (NIR)-fluorescent gauze dyed with indocyanine green (ICG) was newly developed using an autoclave to prevent gauze remnants and serve as a landmark for rapid identification of the target area during surgery. The gauze samples were dyed with an aqueous ICG solution at variable concentrations at high temperatures of 121 − 132 °C and high water vapor pressures of 0.21 − 0.29 MPa to enhance NIR fluorescence (FL) and increase dyeability and fastness. The gauze dyed with an ICG concentration of 1.5 × 10 –4 mol L –1 at 132 °C for 10–15 min exhibited the brightest FL, with a quantum yield of 3.9%. Although the color of the dyed gauze was nearly identical to that of undyed gauze, as estimated by optical density and K/S value, the FL intensity further increased after post-sterilization (PS) at 132 °C for 8 min. This enhancement was attributed to the dissolution of ICG aggregates and improved fixation on the cotton fibers. Furthermore, the high-temperature dyeing technique followed by PS effectively suppressed ICG leakage from the gauze when soaked in artificial body fluid. The NIR-FL emitted from the gauze was clearly observed through human tissue, approximately 10 mm or more in thickness.