Diffusion of Hydrogen Peroxide Through Medical Grade Poly(Ether)urethane: Analyzing Mechanisms of Sorption and Transport to Support Sterilization With Vapor Phase Hydrogen Peroxide

Abstract

The United States Food and Drug Administration (FDA) recently announced an update to their 510(k) medical device sterility guidance to include vapor phase hydrogen peroxide (VH2O2) as an established ‘Category A’ sterilization process. This places VH2O2 in the same category as ethylene oxide (EO or EtO), which has demonstrated user and patient safety as well as microbiocidal effectiveness through scientific literature and FDA-recognized consensus standards. For some implantable medical devices, the sterilant chemistry must diffuse through the polymers of construction to access sealed parts of the finished assembly to achieve an appropriate sterility assurance level. Diffusion of EO through materials has been well established over decades of successful use. However, the ability of VH2O2 to diffuse through materials of construction has not been demonstrated. In this work, we measured the diffusivity and permeability of VH2O2 for a series of increasing durometer poly(ether)urethanes (PEUs) commonly used in the construction of single-use medical devices. The diffusion coefficients were 1 × 10⁻⁸ cm²/s for PEU75D, 2 × 10⁻⁸ cm²/s for PEU55D, and 5 × 10⁻⁸ cm²/s for PEU80A. The permeabilities were calculated to be 4.7 × 10⁻⁶ cm²/s and 1.3 × 10⁻⁵ cm²/s for PEU55D and PEU80A, respectively. For a typical cardiac or neuromodulation lead, the PEU80A wall thickness is on the order of 0.013 cm, resulting in penetration of hydrogen peroxide into the sealed construction in less than 10 min, a timeframe that is a fraction of the total sterilization cycle time.