Strategies for the in vitro testing of in situ polymers

In situ polymers are used by mixing two or more compounds that are then placed directly in tissues to form a unique product. This type of reaction can generate heat, reactive oxygen species, free radicals, and other by-products of unknown toxicities, but the polymer itself is biocompatible. Many regulatory agencies require in vitro testing, however, standard guidelines (ASTM, ISO, AAMI) test polymers in a final form prior to use as a medical device. To better estimate the cytotoxicity of these in situ polymers, various means of introducing the reacting material to cells in culture were explored. Coating the material on a sterile glass cover slip then adding the cover slip to the in vitro test system immediately provided reasonable cytotoxicity data that reflected actual use conditions. For in situ polymeric devices that are more viscous, such as dental materials and bone cements, a mold was used that was placed directly into cell culture. This approach in testing in situ polymers generated in vitro toxicity data that reflects the actual use of the material.