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In accordance with ISO 10993-10, the guinea pig maximization test, Buehler test, or murine local lymph node assay are used to assess the dermal sensitization potential of medical devices. The goal of our study was to determine if the in vitro SenCeeTox Ò assay could be an acceptable alternative. The SenCeeTox assay has previously been shown to accurately predict sensitization by monitoring viability, reactivity, and specific genes known to be crucial in dermal sensitization. Here, 10 known sensitizers were evaluated. Six were incorporated into medical device silicone (10% final concentration) and extracted in polar (physiological saline) and nonpolar (sesame oil) solvents in accordance with ISO 10993-12:2012. The four remaining compounds were added to extracts of plain silicone. This resulted in 20 test solutions (10 compounds in both saline and sesame oil). The assay controls were prepared directly in saline and sesame oil before exposure. EpiDermÔ tissues were exposed for 24 hours and tissue viability was assessed by LDH release. Expression of multiple genes controlled by Nrf2/ARE was assessed by qRT-PCR. The test solutions were also assessed for reactivity with glutathione. Eight of the 10 test samples (80%) were correctly identified as negative (nonsensitizers or weak sensitizers) or positive (moderate/strong/extreme sensitizers) in at least one of the two extracts, and 40% of the potencies were correctly identified. Our results indicate that the SenCeeTox assay combined with EpiDerm tissues can detect the presence of sensitizers in medical device extracts. If these findings are confirmed by further studies, then this model may be a suitable replacement for the animal methods currently used to evaluate medical device biocompatibility.

A round robin study using reconstructed human epidermis (RhE) tissues was conducted to test medical device polymer extracts for skin irritation potential. Test samples were four irritant and three non-irritant medical device polymers. Five of these polymer samples were developed and two were obtained commercially. The three non-irritant samples were comprised of 100% 80A polyurethane, one-part silicone, and polyvinyl chloride (PVC). The polyurethane samples were made using a hot-melt process, while the silicone samples were created by mixing and casting. The PVC samples were commercially produced sheets. The four irritant samples were comprised of one-part silicone and 25% heptanoic acid (HA), two-part silicone and 15% sodium dodecyl sulfate (SDS), PVC and 4% Genapol® X-100, and PVC and 5.8% Genapol® X-080. The HA, SDS, and Genapol® X-100 samples were produced using the mixing and casting method, while the Genapol® X-080 sheet samples were obtained commercially. During development, irritant polymer samples were extracted using polar and non-polar solvents that were subsequently analyzed chemically. Samples with sufficient levels of extracted irritants were tested on RhE tissues to confirm their irritation potential. Polymers that passed this screening test were used in the round robin study described elsewhere in this special edition.

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