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Developing an In vitro Alternative for Dermal Sensitisation

The possibility for in vitro assays to replace animal-based tests is growing, as culture methods, models and techniques continue to improve and more accurately predict in vivo results. In terms of medical device testing, ISO 10993-10, which currently requires the guinea pig maximisation test, the Buehler test, or murine local lymph node assay, is one such regulation that may be amenable to non-animal alternatives. The SenCeeTox® assay has already proven its utility in assessing sensitisation potential through reporting cell viability, protein reactivity and stimulation of genes transactivated by the Nrf2 pathway, all of which are indicative of sensitisation response. In a paper co-authored with Medtronic (Coleman et al., 2015), we sought to explore if SenCeeTox® could provide an in vitro alternative method to ISO 10993-10.

For this study, a group of 10 known sensitisers were selected, six of which were incorporated into medical device silicone at a 10% final concentration and extracted into polar and non-polar solvents in accordance with ISO 10993-12:2012. The remaining four sensitising test articles were spiked into extracts of plain silicone, resulting in a total of 20 test solutions. Assays controls were prepared directly in saline (polar) and sesame oil (non-polar) prior to exposure to MatTek EpiDerm™ tissues for 24 hours. Following the exposure period, tissue viability was evaluated via LDH release, and genes controlled by Nrf2/ARE were assessed using qRT-PCR. Reactivity with glutathione was also measured. Of the 10 sensitisers, eight were accurately identified as either negative (non-sensitiser or weak sensitiser) or positive (moderate/strong/extreme sensitiser) in at least two extracts. Furthermore, 40% of the potencies of the extracts were correctly identified. Further studies and validation are required before this method can be confirmed as an alternative to ISO 10993-10 animal testing, but these results offer a strong indication that SenCeeTox® may be a suitable in vitro replacement to animal methods.

This paper won the Best Published Paper award in the Society of Toxicology Medical Device Specialty Section in 2016.

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