Eco-corona formation and associated ecotoxicological impacts of nanoplastics in the environment

Nanoplastics (NPs, diameter < 100 nm), are ubiquitously found in the environment including water, atmosphere, and soil because of their widespread applications and degradation resistant nature. Similarly, large quantities of natural organic matter (NOM) are present in the environment, in the form of extracellular polymeric substances (DNA, proteins, carbohydrates, etc.) and humic substances (humic acid, fulvic acid, humin, etc.), respectively released by organisms and degradation products of organic matter. These biomolecules interact with NPs and encapsulate to form a unique layered structure termed as eco-corona, which can alter the physicochemical characteristics, interaction, fate, and effects of plastic particles in the environment. The current study collated and reviewed recent findings emphasizing the progress of ecological (eco)-corona formation on NPs and affiliated toxicological effects in freshwater, marine water, and terrestrial ecosystems. The eco-corona layer formed around NPs may vary in sizes and biochemical composition, attributed mainly to the abundance, properties and physicochemical nature of both biomolecules and plastic particles, as well as medium properties and source of NOM in the ecosystem. Besides, most of the reviewed literature showed that eco-corona can reduces the toxicity of NPs with few exceptions, which demonstrates that eco-corona may enhance the NPs toxicity through the Trojan horse effect and longer retention time in biological system. Overall, this review also highlights future research perspectives for a better understanding of NPs toxicity modified by eco-corona, which is crucial to realizing the complex nature of interactions among plastic particles and NOM in a natural ecosystem.