Investigation of the Biocompatibility of Parylene-based Encpasulations for Medical Implants

The polymer family of Parylene is a promising candidate for the realization of smart systems due to its unique combination of excellent properties. These particularly include compatibility to most established microtechnologies, but also barrier properties enabling its use as encapsulation layer. Additionally, some Parylene types are classified to be biocompatible according ISO 10993, so that they can be used for medical applications such as medical implants. The presented paper aims to investigate the biocompatibility of Parylene F, which is not certified to be biocompatible but of high interest for technical use due to its better thermal stability compared to the more common Parylene C. Furthermore, the literature reports the diffusion of toxic metal ions through Parylene C. With respect to the use of Parylene as a biocompatible encapsulation layer for medical implants, this paper investigates, whether Parylene C is suitable to encapsulate a cytotoxic copper layer and avoid diffusion, particularly for the combination of Parylene C with inorganic metal oxide layers to form an ultrabarrier. For both investigations, cytotoxicity tests according to ISO 10993-5 were performed. The results prove the same cell behavior of Parylene F compared to the biocompatible certified Parylene C as well as the suppression of the diffusion of toxic metal ions through Parylene C and Parylene based ultrabarriers.