The Organization for Economic Cooperation and Development (OECD) has published for comment a draft study report entitled “Applicability of the key event based TG 442D for in vitro skin sensitisation testing of nanomaterials.” Switzerland conducted experimental work with selected nanomaterials using OECD Test Guideline (TG) 442D (KeratinoSens^TM) and made a basic in vitro to in vivo correlation to outline the potential relevance of the results for prediction of skin sensitisation of nanomaterials. According to the draft report, a limited number of relevant nanomaterials for testing within this project, as well as limited availability of in vivo skin sensitisation data for nanomaterials, led Switzerland, in discussion with experts and the OECD secretariat, “to the final conclusion that a study report was the most appropriate way of documenting the outcome of this project and to make it available by publication in the Series on Testing and Assessment for any interested parties carrying out further work related to nanomaterials in the area of skin sensitisation.” The test materials included:

• Two qualities of titanium dioxide nanoparticles and a nickel (II) oxide particle preparation. All three materials showed negative results in the KeratinoSens^TM At least partial cytotoxicity at the top concentration indicated that there was cellular exposure.

• Silver and gold were obtained in dispersion form and tested directly without further processing. Both silver and gold gave a clear, dose-dependent luciferase induction in KeratinoSens^TM Cytotoxicity was measured in parallel, and the positive result occurred at non-cytotoxic levels, indicating a final positive rating according to the standard prediction model.

• Three tattoo inks were tested as tattoo inks have been discussed in regard to the potential induction of skin sensitisation. Both qualities of black tattoo inks were negative in the KeratinoSens^TM assay, while a preparation with pigment red tattoo ink gave a clearly positive result at non-cytotoxic concentrations.

• Polyethylenglycoldiacrylate nanotubes (PEGDA 575) made from organic polymers tested negative in KeratinoSens^TM.

Comments are due November 7, 2022. Instructions for commenting are available on the OECD website.