Tissue adhesives in surgery spans more than 50 years. Although fibrin glues have been used the most extensively and for the widest variety of applications, the cyanoacrylates, gelatin-resorcinol-formaldehyde, mussel adhesive proteins, and others could be used for similar purposes if fully exploited. In addition to the traditional uses as adhesives, sealants, and hemostatic agents, researchers have explored the use of tissue adhesives as coatings for implants, as regenerative scaffolds for wound healing, and as drug delivery systems. The various applications of tissue adhesives each have different design requirements for optimal effectiveness.

Interest has mostly been on the use of tissue adhesives as drug delivery systems and scaffolds for wound healing. For wound healing, the optimal tissue adhesive serves as a scaffold to facilitate the healing response. The ability to degrade at an appropriate rate is a critical feature for tissue adhesives. If the adhesive degrades too rapidly, presumably sufficient strength could be lost so that the adhesive fails and the tissues separate prematurely. If it degrades too slowly, it could impede the regeneration process. The ultimate design, therefore, would be a system where the regenerative process controls the degradation. This would allow the system to automatically take into account patient-to-patient variability in healing rate; to adjust the healing rate continually rather than just approximate the overall rate; and to be used in different tissues with different healing rates.

Because a tissue adhesive is often applied to an injured area, it becomes an attractive vehicle for providing healing substances directly to the site of injury. In this case, the risk of giving a systemic drug is minimized because the medication is applied topically in a smaller dose to a particular area of the body. Furthermore, a tissue adhesive can be designed to release a medication over a period of time to obviate the need for repeated doses. If the release of medication is tied to the degradation rate of the tissue adhesive, it can be said to have biofeedback-controlled release of the therapeutic agent. Identifying appropriate therapeutic agents to incorporate into a biodegradable tissue adhesive depends on the application. For applications in which enhanced wound healing is desired, such as wound closure and skin grafting, growth factors and other biological response modifiers can be used. An angiogenic agent is an excellent choice for enhancing wound healing, because new capillaries are required to supply nutrients and remove waste products for the cells involved in healing

• Investigators: J. Thompson, A. Tipton, S. Sullivan, D. Kilpadi
• Students: J. Bowman, and T. Thomas