Tox21 Assays

Tox21 researchers work on a variety of different assays.


Nominate an Assay

Tox21 currently is accepting assay proposals from investigators in all areas, both within and outside NIH and the federal government. Follow the instructions provided below to nominate an assay.

Proposed assays should be compatible with the qHTS guidelines in NCATS’ assay guidance criteria.

For questions regarding nominating an assay, please email: Menghang Xia, Ph.D .

Tox 21 Assay Nomination Form


Assay Evaluation and Development Process


Researchers from academia, private institutions and government/non-government organizations may nominate assays.


The Tox21 Pathways/Assays Working Group (with representatives from each of the Tox21 partners) reviews submitted assays on an ongoing basis. Tox21 leadership provides final approval. Assays are selected based on their biological and toxicological relevance and adaptability to miniaturization and qHTS screening.

Optimization and Miniaturization

Tox21 staff optimize and miniaturize selected assays into the qHTS screening platform.

Validation and Screening

In robotic online validation, the assay is screened in triplicate against a validation library. Tox21 experts evaluate validation data for reproducibility and positive control consistency before submission to the Pathways/Assays Working Group for approval.

Data Analysis and Dissemination

Tox21 staff analyze the resulting information and send raw data and/or summary tables to Tox21 partners on a regular basis. All results are made publicly available.