Overview - ISO/TS 5094:2023 (Nanotechnologies, peroxidase-like activity)
ISO/TS 5094:2023 specifies a standardized spectrophotometric method to assess the peroxidase‑like activity of metal and metal‑oxide nanoparticles (NPs). The technical specification defines the measurement principle, required physicochemical characterization, solution and reagent preparation, instrument conditions, data analysis and reporting. It is intended as a reference protocol for measuring nanoparticle catalytic activity that mimics horseradish peroxidase (HRP).
Key topics and technical requirements
- Principle: Catalysis of chromogenic substrates (commonly TMB - 3,3',5,5'‑tetramethylbenzidine) by nanoparticles in the presence of H2O2 generates an oxidized product with an absorption peak at ≈650 nm; the initial linear rate of absorbance change is used to quantify activity.
- Measurement conditions: Record absorbance vs time at (37 ± 1) °C, within the linear phase of the reaction. Applicable pH range is 3.5–5.5 (TMB solubility and NP activity considerations).
- Calculation: Use the Lambert–Beer relationship and the measured initial slope (∆A/∆t) corrected for reagent blank to compute activity in katal (kat). Specific catalytic activity is reported per unit mass of metal/metal‑oxide in the sample (document provides formulas and examples). The molar attenuation coefficient for the TMB derivative is provided in the specification.
- Controls and uncertainties: Include reagent blanks, positive controls, and additional controls to account for ion dissolution under acidic conditions. The specification outlines uncertainty evaluation and reporting requirements.
- Characterization prerequisites: Prior characterization of nanoparticle size, shape, composition, surface chemistry and crystal structure is required because peroxidase‑like activity depends strongly on these parameters.
- Apparatus/reagents: Calibrated spectrophotometer (visible range), temperature control, TMB, buffer solutions, nanoparticle dispersions and standard reagents are specified.
Applications and who uses this standard
- Biosensor and assay developers: Validate and compare nanoparticle‑based colorimetric or chemiluminescent assays and immunoassays.
- Nanomaterials researchers: Quantify enzyme‑mimicking catalytic activity (e.g., iron oxide, CoO, CuO, Au, Pt NPs) and relate activity to size, surface chemistry and structure.
- Biomedical and environmental labs: Assess potential applications (biosensing, antibacterial/antitumour strategies, contaminant degradation) and study safety/impact related to catalytic activity.
- Metrology institutes and regulatory bodies: Provide traceable, comparable measurements for reporting and conformity assessment.
Related standards and references
- ISO 18153:2003 - metrological traceability for catalytic concentration of enzymes.
- ISO/TS 80004‑2 - nanotechnologies vocabulary (nano‑objects).
- Prepared by ISO/TC 229 (Nanotechnologies); includes annexes with mass measurement and example calculations.
Keywords: ISO/TS 5094:2023, peroxidase‑like activity, metal nanoparticles, metal oxide nanoparticles, spectrophotometry, TMB assay, nanoparticle catalytic activity, nanotechnologies.