MgNd2 alloy in contact with nasal mucosa: an in vivo and in vitro approach.

Biodegradable and biocompatible magnesium alloys appear to be very promising not only for temporary clinical application but also for developing deformable and degradable medical implants. This study analyzes the in vivo degradation behavior and the impact on the paranasal sinuses of the highly ductile Mg-2 wt%Nd alloy (MgNd2) in order to provide a basis for a satisfying stent system for the therapy of a chronic sinusitis. Moreover, in vitro tests were carried out on primary porcine nasal epithelial cells (PNEC). For the in vivo tests, cylindrical MgNd2 specimens were implanted into the sinus' mucosa of minipigs. During and after a total period of 180 days the long-term biodegradation and biocompatibility properties after direct contact with the physiological tissue were analyzed. Biodegradation was investigated by measuring the mass and volume losses of the MgNd2 specimens as well as by performing element analyses to obtain information about the degradation layer. The influence on the surrounding tissue of paranasal sinuses was evaluated by endoscopic and histopathological examinations of the mucosa. Here, only a locally unspecific chronic infection was found. The degradation rate showed a maximum after 45 days postsurgery and was determined to decrease subsequently. In vitro experiments using PNEC showed adequate biocompatibility of MgNd2. This study demonstrates a good in vivo biocompatibility for MgNd2 in the system of paranasal sinuses and underlines the promising properties of alloy MgNd2 for biodegradable nasal stent applications.