Infrared spectroscopy as a tool to monitor interactions between nanoplastics and microalgae
Résumé
The unicellular photosynthetic organisms known as microalgae are becoming one of the most important models for aquatic
system studies. Among them, Chlamydomonas reinhardtii is widely used as a bioindicator of pollution or of different changes in
the environment. Numerous pollutants are present in aquatic environments, particularly plastics and nanoplastics. Physiological
variations after an environmental change highlight variation in the macromolecular composition of microalgae (proteins, nucleic
acids, lipids and carbohydrates). Recently, Fourier transform infrared vibrational spectroscopy has been described as a reliable
tool, sensitive and allowing rapid measurement of macromolecular composition of microalgae. Coupled with preprocessing and
principal component analysis, it is well adapted to monitoring the effect of environmental stress on biochemical composition. In
this study, infrared spectroscopy, combinedwithmultivariate analysis, has been tested first on known environmental stresses such
as light intensity variation and nitrogen limitation. Then, this technique has been applied to monitor the interaction and potential
impacts of polystyrene nanoparticles on microalgae. The results showed slight variations on protein and carbohydrates bands in
the presence of nanoplastics, suggesting that their presence led to modifications in the biochemical composition of the
microalgae. To confirm the interaction between microalgae and nanoplastics, visualization by confocal microscopy and cytotoxicity
measurement has been carried out. Results showed that polystyrene nanoparticles seemed to adsorb on microalgae
surface, leading to a loss of plasma membrane integrity. The resulting chemical modifications, even if moderate, could be
detected by infrared spectroscopy‚ showing that this tool could be very helpful in the understanding of nanoparticlemicroalgae
interaction mechanisms.