Sterilization Effects on Nitric Oxide-Releasing Glucose Sensors

Nitric oxide (NO) release from S-nitrosothiol-modified mesoporous silica nanoparticles imbedded in the diffusion limiting layer of a glucose sensor has been demonstrated as an effective strategy for mitigating the foreign body response common to sensor implantation, resulting in improved analytical performance. With respect to potential clinical translation of this approach, the effects of sterilization on NO-releasing biosensors require careful evaluation, as NO donor chemistry is sensitive to temperature and environment. Herein, we evaluated the influence of multiple sterilization methods on 1) sterilization success; 2) NO payload; and 3) sensor performance to establish the commercialization potential of NO-releasing glucose sensors. Sensors were treated with ethylene oxide gas, the most common sterilization method for intricate medical devices, which led to undesirable (i.e., premature) release of NO. To reduce NO loss, alternative sterilization methods that were studied included exposure to ultraviolet (UV) light and immersion in 70% ethanol (EtOH). Sterilization cycle times required to reach a 10^-6 sterility assurance level were determined for both UV light and 70% EtOH against Gram-negative and -positive bacteria. The longest sterilization cycle times (258 s and 628 s for 70% EtOH and UV light, respectively) resulted in a negligible impact on benchtop sensor performance. However, sterilization with 70% ethanol resulted in a reduced NO-release duration. Ultraviolet light exposure for ~10 min proved successful at eliminating bacteria without compromising NO payloads or durations and presents as the most promising method for sterilization of these sensors. In addition, storage of NO-releasing sensor membranes at -20 and -80°C resulted in preservation of NO release for 6 and 12 months, respectively.