Overview
ISO/TS 21633:2021 specifies a methodology for using label-free impedance technology to assess the toxicity of nanomaterials in vitro. The Technical Specification covers non‑invasive, real‑time electrochemical impedance approaches for monitoring cell‑based assays with both eukaryotic and prokaryotic cells. It positions impedance-based sensing as an alternative to optical assays (absorbance, fluorescence, luminescence) that can be compromised by nanomaterial (NM) optical and surface interactions.
Key topics
- Scope and definitions: clear terminology for nanomaterials, nano‑objects, cell index (CI), electrochemical impedance (EIS), and related terms.
- Principles of operation: fundamentals of electrochemical impedance and how cell attachment, morphology and membrane properties alter impedance signals.
- Instrument types: overview of impedance platforms referenced in the document, including ECIS/RTCA‑style systems, impedance‑based flow cytometry (IFC), electrochemical impedance spectroscopy (EIS) and electrical impedance tomography (EIT).
- Signal metrics: use of Cell Index (CI) and Normalized Cell Index (NCI) as dimensionless readouts for viability, proliferation and cytotoxic response.
- Application guidance: recommended workflows for non‑invasive, real‑time monitoring of nanomaterial toxicity; guidance to avoid interference issues typical of optical readouts.
- Technical limitations: documented constraints and considerations when applying impedance methods to different cell types and nanomaterials.
- Practical annexes: informative annexes with example procedures and case studies (e.g., an xCELLigence system SOP and cell model examples).
- References: normative references to related ISO/TS documents on nanotechnology vocabulary and biological evaluation.
Applications
ISO/TS 21633:2021 is intended for use where reliable in vitro nanotoxicity data are required without artefacts from optical interference. Common applications include:
- Nanotoxicology research - kinetic, label‑free monitoring of cytotoxicity, proliferation and morphological changes.
- Preclinical safety screening - high‑temporal‑resolution assays for NM hazard assessment.
- Assay development and validation - comparison or replacement of optical assays when NM optical properties cause bias.
- Instrument manufacturers and labs - implementing impedance‑based workflows (ECIS/RTCA, EIS, IFC, EIT) for standardized testing.
Who will use it: nanomaterial researchers, toxicologists, in vitro assay developers, contract testing laboratories, academic labs, instrument vendors and regulatory scientists.
Related standards
For implementation or to obtain the full text, consult ISO or your national standards body for ISO/TS 21633:2021.
