“The approach using O-PTIR spectroscopy has several advantages, including significantly less time for sample preparation compared to destructive techniques and less data collection time as only 2–3 wavenumbers can be utilized for contaminant screening. Furthermore, the location of MPs within tissue samples can be investigated using this technique, which can aid in improved understanding of adverse health effects.”
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Reporting in Analyst (Royal Society of Chemistry), researchers at Temple University, Philadelphia, together with collaborators at Cedars-Sinai Medical Center and Thomas Jefferson University, have developed a novel method to detect and identify microplastics (MPs) in non-digested histological tissue sections using optical photothermal infrared (O-PTIR) microspectroscopy. Conventional microplastic analysis relies on enzymatic or chemical tissue digestion — a process that can lead to MP loss and prevents knowledge of the precise anatomical location of contaminants within the tissue, which is critical for understanding their potential health impacts.
The team first validated the approach using gelatin-based tissue phantoms embedded with common MPs — including polyamide (PA), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polytetrafluoroethylene (PTFE). Five distinct O-PTIR spectral imaging strategies, based on overlays of single wavenumber (SWN) images, were employed to detect and distinguish MPs within the phantom matrix. MPs ranging from 3 to 85 µm in diameter were successfully detected and characterized. Notably, a PP particle as small as 7 µm was clearly visualized using a seven-SWN image overlay approach.
The method was subsequently applied to non-digested human lung tissue sections. Using polarized light microscopy (PLM) to identify birefringent candidate regions, followed by O-PTIR spectral acquisition and database matching, the team identified breakdown products consistent with nylon 11 degradation (matched to 11-(diethylamino) undecanoic acid, 84.9% match) and a composite of diphenylphosphinic acid and oxamide — compounds associated with plastic polymer degradation — in one lung sample (90.63% match). Cellulose particles were also detected in lung tissue with database confirmation (64.3% match) and corroborated against standard O-PTIR reference spectra.
The O-PTIR technique demonstrated clear advantages over conventional µFTIR spectroscopy, including sub-micron spatial resolution (~500 nm versus ~3–6 µm for µFTIR), a shallower sampling depth of approximately 1 µm that minimizes matrix contributions, and the ability to collect spectra directly from contaminants embedded within intact tissue — without digestion. The authors note that only 2–3 wavenumbers are needed for contaminant screening, substantially reducing data collection time, and that spatial localization of MPs within tissue is preserved throughout, supporting more meaningful assessment of potential health effects.
Authors:
Azita HassanMazandarani, John M. Masterson, William Querido, Andrzej Steplewski, Yi Zhang, Carissa Huynh, Maurice M. Garcia, Andrzej Fertala, and Nancy Pleshko
Department of Bioengineering, Temple University, Philadelphia, PA, USA
