Cell toxicity in vitro analysis of PVC tubes consecutively submitted to gamma-rays and ethylene oxide sterilization / Análise in vitro da toxicidade celular de tubos de PVC esterilizados consecutivamente em raios gama e óxido de etileno

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

In 1967, a letter sent to the British Medical Journal reported that the re-sterilization with Ethylene Oxide (EtO) of previously irradiated Polyvinyl Chloride (PVC) formed large amounts of ethylene chlorohydrin, a highly toxic compound. Even though it did not present measured data, this letter initiated a controversy that still divide the opinion of researchers to date. To solve this doubt is relevant, as PVC products submitted to gamma radiation are usually re-sterilized with EtO, when the sterilization validity has expired, which is determined by the manufacturer. The present study aimed at assessing the toxicity of PVC tubes through the cytotoxicity test, using the NCTC clone 929 cell culture agar diffusion test. Four experimental groups were created with 81 analysis units: G1, consisting of tubes in natura; G2, consisting of tubes submitted to gamma radiation; G3, consisting of tubes submitted to EtO sterilization and G4, consisting of tubes submitted to gamma-radiation and re-sterilized with EtO. The tests were carried out in triplicate and each tube was tested in order to represent its internal and external surfaces, as well as its mass. After the measurement of the colorless halo, the analysis units were graded according to the degrees of biological reactivity described in the ISO 10993-5:2009. Only the analysis units that were considered grade 3 and above were considered cytotoxic. The results showed evidence of cell toxicity only in G3, which disclosed plaques that presented death of all cells, a fact that necessitated repetition of the experiment, according to the adopted methodology. The first repetition showed the persistence of the analysis units to cause the death of all cells in the plaque. At the second repetition, none of the analysis units was classified as being cytotoxic. It was inferred that there were failures in the process of aeration in group G3 and in the first repetition. The results of the gas chromatography of groups G3 and G4 demonstrated that the materials from both groups would be safe for use. The maximum value of residues found in both groups was identical, in disagreement with the cytotoxicity test results. It was concluded that, according to the conditions of this experiment, the PVC materials submitted to gamma-radiation and consecutively sterilized by EtO are not cytotoxic and that the gas chromatography, when used alone, can yield debatable results regarding the safety of materials sterilized with EtO.

ASSUNTO(S)

radiação gama ethylene oxide pvc pvc nursing in material and sterilization center Óxido de etileno gamma-radiation esterilização sterilization enfermagem em centro de material e esterilização cytotoxicity citotoxicidade

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