Label-free nano- and microplastics detection and identification in vivo using dark-field hyperspectral microscopy

, Fakhrullin Rawil, Nigamatzyanova Läysän.

Microscale and nanoscale polymer particle pollution is among most serious ecological threats, severely affecting environments, live organisms and human well-being. To tackle nano- and microplastics pollution one needs a powerful methodology to visualise and identify small polymer particles in cells, tissues, organisms and environmental specimens (e.g. water, soil, sediments, etc). We have developed a novel methodology to visualise and identify synthetic polymer nanoscale (down to 100 nm) and microscale particles utilising hyperspectral dark-field microscopy in 400-1000 nm wavelength range (visible-near infrared). To demonstrate the feasibility of our technique we have used polystyrene particles with diameters between 100 nm – 1 µm, polymethacrylate 1 µm and melamine formaldehyde 2 µm microspheres. These nano- and micro particles in pure and mixed suspensions were effectively imaged and identified chemically using the libraries of spectral signatures and image-assisted analysis. We also succeeded in imaging and hyperspectral identification of pure and mixed nano- and microplastics in Caenorhabditis elegans nematodes in vivo, to demonstrate the ingestion and distribution of nano- and microplastics in tissues. We found that dark-field hyperspectral microscopy can be successfully applied for differentiating between chemically-different microplastics confined within live invertebrates. This simple optical technology allows for quantitative identification of microplastics taken up by live nematodes. This label-free non-destructive methodology will find applications in environmental nano- and microplastics detection and quantification, studies of microplastics biodistribution in tissues and organs and nanotoxicology. The authors acknowledge funding by Russian Federation presidential grant MD-2153.2020.3.

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