Morphology-dependent biotoxic effects and cellular damage mechanisms of silver nanoparticles on Chlorella vulgaris and Scenedesmus obliquus

Abstract

The widespread application of silver nanoparticles (AgNPs) leads to their inevitable release into freshwater ecosystems, raising ecological concerns. The present study involved the synthesis of silver nanospheres (AgNSs), nanocubes (AgNCs), and nanoplates (AgPLs) through chemical synthesis methods. It also investigates the morphological-dependent biotoxicity of AgNPs at two distinct concentrations (0–5 mg L⁻¹ and 0–5000 ng L⁻¹) on two species of algae, C. vulgaris and S. obliquus. The results demonstrated that AgPLs exhibited the strongest inhibitory growth, with 0.5 mg L⁻¹ AgPLs inhibiting C. vulgaris growth by 58% (2.5–2.7-fold higher than AgNSs/AgNCs) and 5 mg L⁻¹ AgPLs inhibiting S. obliquus by 76%. Transmission electron microscopy (TEM) showed AgPLs caused cell content leakage, AgNCs induced starch granule accumulation, and AgNSs only damaged cell walls. Low-concentration (ng L⁻¹) AgNPs triggered a “low-dose stimulation, high-dose inhibition” hormesis on S. obliquus chlorophyll a. AgPLs had the highest colloidal stability (zeta potential: −23.07 mV), and cell-associated Ag accumulation was morphology- and species-dependent, with S. obliquus more sensitive than C. vulgaris. These findings provide toxicity data for AgNPs, supporting ecological risk assessments by incorporating morphology and species specificity.