Ethylene oxide sterilization of acoustic transmitters for surgical implantation

Surgically implanted acoustic transmitters have provided substantial insight into aquatic wildlife ecology. While there is debate over the necessity of transmitter sterilization prior to implantation, some investigators and regulatory bodies may require it. Methods of sterilizing acoustic transmitters have not been well described. Sterilizing such transmitters by autoclave is not recommended due to the associated high temperature and pressure, which may cause physical damage. However, gas sterilization methods that occur at ambient temperature and atmospheric pressure may be considered. In this study, INNOVASEA V13 (n = 8) and V16 (n = 16) acoustic transmitters were exposed to an ethylene oxide gas sterilization cycle. Transmitters did not include temperature, pressure, depth, acceleration, nor predation sensors. Appropriate gas exposure was confirmed by biological, chemical, and packaging color indicators, allowing inference of transmitter sterility, but transmitters were not directly tested for sterility by microbiological methods. All transmitters functioned properly after gas sterilization as confirmed by hydrophone detection of their correct identification number. There was no external evidence of transmitter damage, and no adverse events were noted during the sterilization cycle. While not attempting to resolve the debate about the necessity of acoustic transmitter sterilization, the present study provides a potential option for sterilization should it be required. Microbiological, analytical chemical, and materials science studies are indicated to further assess the safety and efficacy of transmitter sterilization methods. Additional study is also needed regarding sterilization of transmitters bearing temperature, pressure, depth, acceleration, predation, or other sensors, as these were not investigated in this study.