Electron beam sterilization of cyclo olefin polymer leads to polymer degradation and production of alkyl radicals

Abstract

We investigated the effects of electron-beam (EB) sterilization on syringe barrels manufactured from cyclo olefin polymer (COP). The chemical structure of the polymer was determined by interpreting the 13 C NMR and DEPT-135 spectra of the COP resin. The antioxidants in the resin were identified by analyzing the liquid chromatography-photo diode array-mass spectrometry (LC-PDA-MS) data for the methanol extract of the resin and the gas chromatography-mass spectrometry (GC-MS) data for the supercritical methanol degradation products of the extract. NMR and LC-PDA-MS analyses revealed that EB sterilization produces degradation products in the COP main chain and reduces the quantity of the antioxidants in the COP resin. ESR spectra of the EB-sterilized syringe barrels indicated the presence and location of alkyl radicals, which were generated in the COP main chain by EB sterilization. ESR analyses also indicated that the quantity of alkyl radicals decreased over time.

Carbon radicals generated by solid polymers: Electron spin resonance spectroscopy for detection of species in water

“…(1)], resulting in the generation of ·OH radicals. As another route, the carbon radicals form peroxide by reacting with oxygen in water. The peroxide reacts with water/·CH and decomposes to ·OH [eq.…”

“…Recently, PFSs composed of plastic (polymer) barrels (P‐PFS) have been explored and applied practically to mitigate the problems associated with glass (e.g., shock resistance, delamination, silicone oil, and elution of tungsten oxide). Cyclic olefin polymers (COPs), cyclic olefin copolymers, and polypropylene have been used for this purpose . Although the P‐PFS was put to practical use to mitigate the demerits of a glass syringe, a carbon radical species is reportedly produced in the barrel polymer because of γ‐rays or EB irradiation during sterilization.…”

“…Although the P‐PFS was put to practical use to mitigate the demerits of a glass syringe, a carbon radical species is reportedly produced in the barrel polymer because of γ‐rays or EB irradiation during sterilization. This radical, which is absent in the case of glass, persists for a relatively long time . For PFSs made of COP, protein drugs have been reported to be susceptible to oxidation when in contact with the irradiated barrel .…”

“…A mechanism of drug oxidation is proposed hypothetically as follows. The carbon radicals in a polymer solid phase generate a new radical species in the drug solution (liquid phase); that is, migration of radicals from the solid phase to the liquid phase occurs . To the best of our knowledge, no direct evidence of the generation of radical species in the liquid phase owing to a radical species in the solid phase (migration of radicals) has been provided.…”