Shape-Dependent Toxicity of Gold Nanoparticles in Microalgae: Distinct Cellular and Molecular Responses

Area of Science:

• Ecotoxicology
• Environmental Nanotechnology
• Aquatic Biology

Background:

• Engineered nanoparticles (NPs) pose ecotoxicological risks in aquatic environments.
• NP effects depend on size, composition, and morphology.
• Shape-dependent interactions with primary producers like algae are poorly understood.

Purpose of the Study:

• To investigate the cellular and molecular responses of freshwater algae (Chlamydomonas reinhardtii) to silica-coated gold nanospheres (AuNP) and nanostars (AuNS).
• To compare the toxicity of different NP morphologies at equivalent concentrations.

Main Methods:

• Exposure of Chlamydomonas reinhardtii to 100 nm AuNP and AuNS at various concentrations.
• Assessment of algal growth, photosynthetic activity, and cellular structure.
• Confocal imaging to determine NP internalization patterns.
• RNA sequencing to identify differentially expressed genes (DEGs).

Main Results:

• Nanostars (AuNS) at 10 mg/L caused greater growth inhibition and photosynthetic impairment than nanospheres (AuNP).
• AuNS induced more severe structural damage and distinct internalization patterns compared to AuNP.
• AuNP exposure affected photosynthesis and energy storage pathways (PSBS1/ELI3).
• AuNS exposure impacted membrane integrity and nitrogen metabolism pathways (NIT1/AMT1/A0A2K3CRU5).

Conclusions:

• Nanoparticle morphology is a critical determinant of ecotoxicological effects in algae.
• Different NP shapes trigger distinct cellular and molecular toxicity mechanisms.
• Environmental risk assessments must consider NP morphology for accurate hazard evaluation.
• Safer nanomaterial design should account for shape-dependent interactions with aquatic organisms.