Effective inhibition of the early copper ion burst release with ultra-fine grained copper and single crystal copper for intrauterine device application

To solve the main problems of existing coarse grained copper (CG Cu) intrauterine devices (IUD)—namely burst release and a low transfer efficiency of the cupric ions during usage—ultra-fine grained copper (UFG Cu) and single crystal copper (SC Cu) have been investigated as potential substitutes. Their corrosion properties with CG Cu as a control have been studied in simulated uterine fluid (SUF) under different conditions using electrochemical measurement methods. Long-term immersion of UFG Cu, SC Cu and CG Cu samples in SUF at 37 °C have been studied for 300 days. A lower copper ion burst release and a higher efficiency release of cupric ions were observed for UFG Cu and SC Cu compared with CG Cu in the first month of immersion and 2 months later. The respective corrosion mechanisms for UFG Cu, SC Cu and CG Cu in SUF are proposed. In vitro biocompatibility tests show a better cellular response to UFG Cu and SC Cu than CG Cu. In terms of instantaneous corrosion behavior, long-term corrosion performance and in vitro biocompatibility, the three pure copper materials follow the order: UFG Cu > SC Cu > CG Cu, which indicates that UFG Cu could be the most suitable candidate material for intrauterine devices.