Bonding of human meniscal and articular cartilage with photoactive 1, 8-naphthalimide dyes

This study focused on meniscal cartilage repair by using the laser-activated photoactive 1,8- naphthalimide dye N,N'-bis-{6-[2-(2-(2- aminoethoxy)ethoxy)ethoxyethyl]amino-1H-benz (de)isoquinolin-1,3(2H)-dion-2- yl}-1,11-diamino-3,6,9-trioxaundecane. Harvested cadaveric human menisci were debrided and carved into strips 1 mm thick, 10 mm long, and 3 mm wide. Each strip was divided into two flaps, the surface painted with photoactive dye, the painted surfaces overlapped, the sample wrapped in Saran film, and the composite sandwiched between two glass slides at a pressure of approximately 3 kg/cm ². The sample then was transilluminated by argon ion laser light of 457.9-nm wavelength at a power density of 200 mW/cm ² with exposure times up to 5 h (3902 J/cm ² energy density). Essentially, the same procedures were performed for human femoral articular cartilage samples. Control experiments were conducted with laser irradiation alone and with dye alone. All the specimens were stored in isotonic saline solution for 2 h after irradiation to ensure hydration. The bond shear-strength was then tested and samples prepared for optical and electron transmission microscopy. Shear strength values of up to 1.8 kg/cm ² for meniscal tissues and 1.2 kg/cm ² for articular cartilaginous tissues were obtained for exposures of 3902 J/cm ². Shear strength values of approximately 0.9 kg/cm ² and 0.4 kg/cm ², respectively, for meniscus and cartilage were obtained with 459 J/cm ² exposure. Dye- and light-only controls exhibited 0 kg/cm ² shear strength values. Microscopy revealed close contact at the bonded surface in the laser-activated, dye-treated-specimens. This study shows that the laser-activated photoactive dyes have the capability of athermally bonding the meniscal and articular cartilage surfaces.