Assessing the molecular mechanisms behind nanoparticle toxicity towards microalgae – ANATOMIC

The originality of the approach relies on a combination of tools and methodologies from microbiology, physico-chemistry and biophysics that allow to identify and establish links between toxicity mechanisms measured at different scales. in particular, the use of atomic force microscopy, still under-used to answer ecotoxicological questions, allow to quantify interactions between cells and nanoparticles from their first second of contact and to visualize their effects with a very good spatial resolution.

At mid-course, our main results show that:
- Morphological features, mechanical properties and chemical composition of the algal cell-wall are very dependent on the cell’s growth-phase and can be modulated by enzymatic treatments. These findings could have an impact for industrial applications such as algal lipid extraction for biofuel production.
- Adhesion of nanoparticles to the algal cell-wall, in terms of nanoparticles amount and sorption kinetics, is very dependent on the nanoparticles charge and pH of the surrounding media. These parameters lead to important differences in the nanoparticles behavior towards the algal and influence cellular viability.
- Finally, interactions between proteins involved in the detoxification mechanisms of the algae subjected to stress (such as nanoparticle exposure) have been highlighted, allowing for a better understanding of their anti-oxidative action.

The main prospect of the project is to establish scenarios for nanoparticles toxicity towards microalgae, and this, according to their respective bio-physico-chemical properties. To reach this objective, the goal is to establish connections between the dynamic of nanoparticle partitioning (i.e. the distribution between the particles adsorbed at the algal surface, the internalized ones and those which remain in solution).

One paper is under review in Algal Research on the effect of the growth phase and enzymatic treatment on the physico-chemical properties of the microalgal cell-wall.
One paper has been published in Nanoscale Horizons on the interactions between redox intracellular enzymes. This paper has been selected to illustrate the journal cover and has been elected ‘paper of the month’ by the French Society of Biochemistry and Molecular Biology.

Ecotoxicological effects that nanoparticles (NPs) produce on microorganisms are the consequence of underlying dynamic molecular processes taking place well beforehand their observed repercussion. ANATOMIC shall establish mechanistic relationships between NPs physicochemical properties and their biological effects to better understand toxicity processes. Initial molecular interactions between Quantum Dots and the green algae Chlorella vulgaris, as well as their intracellular stress-response will be assessed by advanced in-situ multiparametric atomic force microscopy (AFM), combined to confocal microscopy. Characterization of the mechanisms at the nanometric scale will be linked to adverse effects measured at the population scale. This project aims to decipher the molecular mechanism behind NPs-induced toxicity toward microalgae. It will also contribute to establish AFM-based nanoscopy as an innovative analytical tool in the ecotoxicology research area.