Fig. 4
Representative detection and validation of polyethylene (PE), and polystyrene (PS) particles in FFPE human colon tissue using OPTIR spectroscopy. (a) Visible image of region II (muscularis) in sample 1 showing the area where PE particles (~ 4 μm) are identified. Bright spots are observed in the corresponding chemical ratio image for PE (wavenumber ratio 2855/1660 cm− 1), whereas the ratio image for PS (wavenumber ratio 1455/1660 cm− 1) serves as a negative control; subsequent full spectral analysis at the detected points revealed a strong correlation with the characteristic PE bands, observed at wavenumbers 2923 cm− 1, 2855 cm− 1 and 1467 cm− 1 of a native PE reference sample. (b) Analysis of region I (mucosa) of sample 2, similar to Fig. 4a. Identification of a single PS particle using vibrational bands indicative for PS (correlation with native sample spectrum at characteristic wavenumbers 1602 cm− 1, 1495 cm− 1 and 1455 cm− 1) and amide (notably at 1660 cm⁻¹ and 1545 cm⁻¹), supporting the particle’s localization within biological tissue. The spectral signature shown here for PE and PS particles, mixed with characteristic amide bands confirm the presence of embedded plastic material.
