Microplastic contamination in biological systems is becoming a significant concern in environmental and biomedical studies. Recent findings indicate that inhaled airborne microplastics may penetrate deep into the respiratory tract, where they may accumulate inside tissues and cells.
Determining the localization and chemical identity of these particles is crucial for assessing their potential biological effects and possible correlation with pathological conditions.
This article demonstrates the capability of Raman microscopy to identify intracellular microplastics within respiratory cells using the Thermo Scientific™ DXR3xi Raman Imaging Microscope.
To accurately characterize intracellular microplastics in biological samples, every experimental parameter must be carefully controlled, including the laser power delivered during Raman analysis.
Since laser exposure may trigger morphological or biochemical alterations, maintaining well-defined and repeatable irradiation conditions is essential for producing dependable data and establishing meaningful correlations between microplastic accumulation and possible biological damage.
The Thermo Scientific DXR3xi Raman Imaging Microscope tackles this issue with its laser power regulator technology, an active feedback system that continuously controls and maintains the absolute laser power delivered to the sample.
This ability reduces the likelihood of laser-induced artifacts and increases confidence in the interpretation of experimental findings.
Experimental Concept
The study involved exposing animal models to fluorescent polystyrene microplastic particles with a mean diameter of 1 μm. Fluorescent labeling facilitated preliminary localization of the particles inside respiratory cells via fluorescence microscopy.
Cell preparation, fixation, and stabilization were carried out by the collaborating research lab. The prepared cells were placed onto microscope slides and maintained in a liquid environment to retain cellular integrity throughout Raman evaluations.
Raman Analysis with the DXR3xi Raman Imaging Microscope
Raman analysis was conducted with the Thermo Scientific DXR3xi Raman Imaging Microscope, fitted with a 60x water immersion objective.
Using water immersion optics offered two significant benefits:
- Enhanced visualization of cellular structures
- Minimized thermal stress and cellular degradation during laser exposure
Analysis was conducted on both intracellular and extracellular microplastic particles to confirm spectral consistency and verify the chemical identity of the detected material.
Laser power was precisely optimized using the system’s adjustable laser control capabilities, ensuring that the cellular membrane was not damaged or altered by analytical conditions during measurements.
Figure 1. Reference polystyrene microplastic particles. Image Credit: Thermo Fisher Scientific - Vibrational Spectroscopy
Figure 2. (A) Extracellular polystyrene particle. (B) Corresponding Raman spectrum with spectral library identification. Image Credit: Thermo Fisher Scientific - Vibrational Spectroscopy
Spectral Identification
Raman spectra collected from particles located both inside and outside the cells exhibited spectral characteristics consistent with polystyrene.
The DXR3xi spectral search functionality allowed for swift verification of polymer identity by matching the collected spectra with reference polystyrene spectra stored in the spectral database.
The findings highlighted several critical aspects of the analysis:
- Intracellular microplastics can be effectively identified using Raman microscopy
- Raman analysis can be conducted without observable cellular damage* under optimized conditions
- Spectral matching enables accurate chemical confirmation of the identified particles
*Cellular integrity assessment was carried out by the client using suitable biological validation models.
Figure 3. (A) Intracellular polystyrene particle. (B) At higher magnification. (C) Raman spectrum and spectral library identification. Image Credit: Thermo Fisher Scientific - Vibrational Spectroscopy
Figure 4. Raman spectral map of the entire cell showing the intracellular polystyrene particle. Image Credit: Thermo Fisher Scientific - Vibrational Spectroscopy
Significance
This study showcases the practicality of Raman microscopy for investigating microplastics within biological cellular environments.
The strategy provides novel opportunities for studying microplastic presence and distribution in human tissues and biological systems. Through collaboration with biomedical scientists and pathologists, these analytical capabilities may support future research into potential correlations between microplastic accumulation and diseases, including cancer and other pathological conditions.
Conclusions
The Thermo Scientific DXR3xi Raman Imaging Microscope showcased its analytical performance and capabilities in a biological environment by enabling:
- Identification of intracellular microplastics within respiratory cells
- Preservation of cellular morphology through optimized low-power Raman conditions
- Chemical confirmation of polymer identity via Raman spectral analysis
- Support for advanced biomedical research involving microplastic contamination in biological tissues
These findings emphasize the potential of Raman microscopy as a robust analytical instrument for future research at the interface of environmental science, toxicology, and biomedical studies.
Acknowledgments
Produced from materials originally authored by Barbara Bravo and Angelo Traina from Thermo Fisher Scientific.
This information has been sourced, reviewed, and adapted from materials provided by Thermo Fisher Scientific - Vibrational Spectroscopy.
For more information on this source, please visit Thermo Fisher Scientific - Vibrational Spectroscopy.