Understanding nanoplastic toxicity and their interaction with engineered cationic nanopolymers in microalgae by physiological and proteomic approaches

The amount of plastics produced per year is in constant growth alongside their use in different sectors like the textile industry, agriculture or, more recently, in nanotechnology. Under certain environmental conditions, plastics break down into smaller pieces. Those plastics in the nanosize range are the most difficult to identify, quantify and remove and therefore probably prevail in aquatic ecosystems. Likewise, nanomaterial production has been increasing exponentially and therefore their potential release to the environment poses a threat. There is a lack of knowledge regarding the combined effects of co-occurring nanopolymers on biota. In this work, we have studied the individual toxicity of polystyrene nanoplastics (PS-NPs) as well as their combined effect with generation 7 PAMAM dendrimers (G7) on the filamentous cyanobacterium Anabaena sp. PCC7120, a relevant aquatic primary producer. Exposure to PS-NPs induced the overproduction of reactive oxygen species, lipid peroxidation, membrane disruptions, intracellular acidification and a decrease in photosynthetic activity. Internalization of the nanoplastics was also observed. Combined exposure to PS-NPs and G7 lowered PS-NP toxicity and precluded their internalization. This antagonistic interaction was due to the formation of heteroaggregates. Molecular biomarkers (differentially expressed proteins, DEPs) of the toxic effect of nanoplastics, G7 and their binary mixture were identified for the first time. These molecular biomarkers may be envisaged as a molecular signature of the toxic effect of the nanopolymers and could be predictors of cellular damage caused by exposure to nanopolymers.

Automated summary

The study suggests that nanosize plastics in aquatic ecosystems are difficult to identify and remove, and their toxic effects can be alleviated through combined exposure with other nanomaterials. Additionally, molecular biomarkers can be used to predict cellular damage caused by exposure to nanopolymers and other materials.