In vitro assays for assessment of the skin sensitization hazard and potency of isobornyl acrylate

Presented at SOT 2023

In vitro assays for assessment of the skin sensitization hazard and potency of isobornyl acrylate

Rose-Marie Jenvert1, Olivia Larne1, Ulrika Mattson1, Robin Gradin1, Kelly P Coleman2 and Andy Forreryd1  1SenzaGen, Lund, Sweden, 2Medtronic, Minneapolis, USA


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The GARDskin Medical Device assay can be used

  • with the extraction vehicles saline and oil as described 
    in ISO 10993. 
  • to detect low concentrations of skin sensitizers in a mixture and have the potential to replace in vivo tests 
    for risk assessment of skin sensitizers in medical devices. 
  • as risk assessment tool in combination with the 
    GARDskin Dose-Reponse assay during development of medical devices containing acrylates. 


Acrylates have a wide range of applications for medical devices as they can bring several advantages  such as transparency, super-absorbency and hardness in combination with flexibility. The manufacturing of acrylic materials typically involves using at least one monomer of either acrylate or methacrylate which react to form a polymer. Several methodologies can be used for polymerization and the degree of polymerization of the final material can vary, hence some products can contain more residual monomers than others, and human exposure to these well-known skin sensitizers may increase the risk of developing the adverse immunological response, allergic contact dermatitis.

In 2020, the acrylate monomer, isobornyl acrylate (IBOA; CAS 5888-33-5), was named allergen of the year by American Contact Dermatitis Society due to the increased number of patients that were sensitized to IBOA found in glucose sensors and glucose pumps. IBOA is also present in other medical devices as plastic materials, coatings, sealants, glues, adhesives and inks. As a result, it is important to find alternatives to the animal methods used today to assess skin sensitization to properly identify the skin sensitizing potential of IBOA in medical devices and avoid the risk of sensitizing more individuals to this chemical.

The GARDskin (OECD TG 442E) assay, initially developed for hazard identification of a wide range of skin sensitizers, has been adapted for use with polar and non-polar solvents as described in ISO 10993-12:2021 and can be applied to assess the skin sensitization of medical devices. Further development of the GARDskin protocol has also enabled the prediction of skin sensitization potency by using a dose-response measurements. The cDV0 value derived from the assay corresponds to the lowest concentration required to exceed a binary classification threshold in GARDskin, and this concentration correlates significantly with LLNA EC3 and human NOEL values.  Linear regression models have been established to exploit these relationships for potency predictions.

In this study, we explored the ability of GARDskin Medical Device assay to detect the skin sensitizing potential of IBOA in a mixture of chemicals extracted from a silicone material (Nunsil MED-2000) in both saline and oil extract. Additionally, the skin sensitizing potency of IBOA was also investigated using the novel GARDskin Dose-Response assay. The acrylate monomer, IBOA, was correctly classified as a skin sensitizer in extracts of the silicon material spiked with IBOA using the GARDskin Medical Device assay. The correct classification of IBOA as a skin sensitizer provides evidence that the GARDskin Medical Device assay is sensitive enough to detect low concentrations of device-related skin sensitizers in a mixture of extracted chemicals and hence has the potential to replace in vivo tests for risk assessment of medical devices. Furthermore, IBOA was classified as a strong to moderate skin sensitizer (HP 2) with a predicted LLNA EC3 value of 0.848% and human NOEL value of 230 µg/cm2 using the GARDskin Does-Response assay. These predictions agree with existing human data and information from the ECHA registration dossier, illustrating the potential of the GARDskin Dose-Response assay to replace in vivo tests for quantitative potency assessment of potential skin sensitizers.