Localisation and identification of polystyrene particles in tissue sections using Raman spectroscopic imaging

Jasmin Kniese; Sven Ritschar; Lina Bünger; Heike Feldhaar; Christian Laforsch; Andreas Römpp; Heinar Schmidt

doi:10.1016/j.impact.2023.100465

Localisation and identification of polystyrene particles in tissue sections using Raman spectroscopic imaging

NanoImpact. 2023 Apr:30:100465. doi: 10.1016/j.impact.2023.100465. Epub 2023 Apr 28.

Authors

Jasmin Kniese¹, Sven Ritschar², Lina Bünger¹, Heike Feldhaar³, Christian Laforsch³, Andreas Römpp⁴, Heinar Schmidt⁵

Affiliations

¹ Bioanalytical Sciences and Food Analysis, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
² Animal Ecology I, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
³ Animal Ecology I, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany; Bayreuth Center for Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany.
⁴ Bioanalytical Sciences and Food Analysis, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany. Electronic address: andreas.roempp@uni-bayreuth.de.
⁵ Bioanalytical Sciences and Food Analysis, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany. Electronic address: heinar.schmidt@uni-bayreuth.de.

PMID: 37119946
DOI: 10.1016/j.impact.2023.100465

Abstract

The uptake of microplastic particles (MPP) by organisms is frequently described and poses a potential risk for these organisms and ultimately for humans either through direct uptake or trophic transfer. Currently, the in-situ detection of MPP in organisms is typically based on histological examination of tissue sections after uptake of fluorescently-labelled MPP and is thus not feasible for environmental samples. The alternative approach is purification of MPP from whole organisms or organs by chemical digestion and subsequent spectroscopic detection (FT-IR or Raman). While this approach is feasible for un-labelled particles it goes along with loss of any spatial information related to the location in the tissue. In our study we aimed at providing a workflow for the localisation and identification of non-fluorescent and fluorescent polystyrene (PS) particles (fragments, size range 2-130 μm) in tissue sections of the model organism Eisenia fetida with Raman spectroscopic imaging (RSI). We provide methodological approaches for the preparation of the samples, technical parameters for the RSI measurements and data analysis for PS differentiation in tissue sections. The developed approaches were combined in a workflow for the in-situ analysis of MPP in tissue sections. The spectroscopic analysis requires differentiation of spectra of MPP and interfering compounds, which is challenging given the complexity of tissue. Therefore, a classification algorithm was developed to differentiate PS particles from haem, intestinal contents and surrounding tissue. It allows the differentiation of PS particles from protein in the tissue of E. fetida with an accuracy of 95%. The smallest PS particle detected in the tissue was 2 μm in diameter. We show that it is possible to localise and identify non-fluorescent and fluorescent ingested PS particles directly in tissue sections of E. fetida in the gut lumen and the adjacent tissue.

Keywords: Classification; Intestinal tract; Non-fluorescent and fluorescent microplastics; Polystyrene; Raman spectroscopy.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Humans
Microplastics
Plastics* / analysis
Polystyrenes* / analysis
Spectroscopy, Fourier Transform Infrared
Spectrum Analysis, Raman

Substances

Polystyrenes
Plastics
Microplastics