Tailoring lactide/caprolactone co-oligomers as tissue adhesives

This article introduces novel biocompatible tissue adhesives that do not involve any chemical or biochemical reactions, during their application in vivo. The use of these new adhesives is based exclusively on their temperature-dependent rheological properties. Since biocompatibility and biodegradability are additional crucial attributes of tissue adhesives, the polymers were tailored so that they as well as their degradation products are non-toxic. Branched oligomers consisting of a core molecule and biodegradable chains bound to it were synthesized and the relationship between their composition and their adhesive properties under in vitro conditions, was investigated. The oligomers comprised trimethylolpropane as the trifunctional central molecule, while lactoyl and caprolactone units formed the biodegradable segments. Oligomers with glass transition temperatures in the 20–25°C range, were found to perform better. A strong connection was found between the length of the PLA blocks, the glass transition temperature (Tg) of the different materials and their Adhesive Failure Strength (AFS) at 37°C. The remarkable flexibilizing effect of the caprolactone units incorporated along the PLA blocks, allowed to generate longer biodegradable chains and to improve, therefore, the adhesive strength of the oligomers, while keeping their Tg within the appropriate temperature interval. The TMP(LA16–CL2–LA16–CL2–LA16)3 oligomer attained especially high AFS values under in vitro conditions.