Fraunhofer Institute for Ceramic Technologies and Systems IKTS
Detection of Micro- and Nanoplastics in Plants Using Coherent Raman Spectroscopy
Current research
Fig. 1: CRS instrument with two detection geometries (forward and epi) for MNP detection.
Fig. 2: Top: SRS/CARS composite image in 2D. Bottom: SRSI CARS composite image in 3D. PS MNPs are shown in red.
Fig. 3: Chemical identification of PS particles in plant tissue by SRS based on a characteristic Raman peak of PS (marked with an asterisk).
The accumulation of micro- and nanoplastics (MNPs) in edible plants poses risks to food safety and human health. In addition, MNPs can promote the uptake of soil contaminants such as pesticides and endocrine-active chemicals, further increasing their toxicity.
Coherent Raman scattering microscopy (CRS) using a tunable near-infrared (NIR) excitation laser has become established as a label-free molecular fingerprinting method for detecting MNPs in biological matrices with strong autofluorescence. Fig. 1 shows the setup for CRS measurements (Leica Stellaris 8) on microtome sections (approximately 40 μm thick) of wheat roots that were exposed to polystyrene (PS) particles during growth. The instrument supports both forward detection (transmission) and epidetection (reflection) configurations and enables acquisition of stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) signals. Fig. 3 shows typical SRS spectra from plant tissue and embedded PS particles.
After identifying a PS-specific vibrational mode, large-area SRS scans are performed to locate and count the PS particles taken up by the wheat roots. CARS scans are then acquired to provide contrast to the plant tissue, while remaining non-resonant for PS detection.
Fig. 2 shows 2D (top) and 3D (bottom) composite images combining SRS and CARS channels. In the 2D overlay, both a micrometer-sized and a nanometer-sized PS particle (circled) can be seen on the cellular structure of the root. In the 3D reconstruction, consecutive optical sections are combined to visualize the spatial distribution of PS particles within the root. This allows the uptake pathway in plants to be assessed and enables the acquisition of statistically more relevant data.
The work demonstrates that Fraunhofer IKTS in Forchheim combines extensive sample preparation with advanced analytical techniques and deep-learning-based segmentation to detect and characterize particles in different matrices. This enables precise and fully automated data analysis.
Services offered
- Sample preparation, multimodal analytics, automated particle segmentation and correlative data analysis
- Label-free coherent Raman scattering microscopy
- High-resolution 2D/3D imaging workflows
Supported by
