Open Access Conference Proceedings

The antioxidant activity assessed using the ABTS assay can serve as an indirect marker of moderate oxidative stress, specific to adaptive physiological responses. This study aimed to evaluate the influence of copper nanoparticles (CuNPs), copper oxide nanoparticles (CuONPs), zinc oxide nanoparticles (ZnONPs), and titanium dioxide nanoparticles (TiO2NPs) on the antioxidant activity of the cyanobacterium Arthrospira platensis (spirulina), using the ABTS method. The cyanobacterium was cultivated in mineral medium supplemented with two concentration ranges of nanoparticle: low (0.01–0.5 mg/L) and high (1.0–20 mg/L). Antioxidant activity was measured in both aqueous and ethanolic extracts of the resulting biomass. The results revealed that aqueous extracts exhibited a significant increase in antioxidant activity (77.6–95.3% ABTS inhibition) at higher concentrations of CuNPs, CuONPs, and ZnONPs, following a clear concentration-dependent trend. In ethanolic extracts, the response was more variable: CuNPs induced a moderate increase in antioxidant activity, while CuONPs caused a decrease. TiO2NPs showed relatively stable antioxidant values across all tested concentrations, with minimal variation between solvents. The study demonstrates that metal-based nanoparticles modulate the antioxidant mechanisms of Arthrospira platensis, triggering adaptive responses to oxidative stress, with effects depending on the nanoparticle type, dose, and type of extract. Extracts obtained from exposed biomass may be considered valuable functional products with biotechnological potential.

Keywords: Arthrospira platensis, nanoparticles, hydric extract, ethanolic extract, antioxidant activity

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