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Microplastics (MPs), defined as plastic particles smaller than 5 mm, have garnered considerable attention owing to their potential biological impact on human health. These particles exhibit a range of physicochemical properties, including size, shape, and surface oxidation. Nile Red is a prominent tool for detecting microplastics, enabling staining for dynamic analyses within biological systems. However, the efficacy of Nile Red staining for surface-oxidized MPs remains unclear. Therefore, we applied Nile Red dye to stain surface-oxidized polyethylene and polyvinyl chloride and observed that both materials were effectively stained, although the fluorescence intensity varied according to different hydrophobic dynamics. Imaging analysis revealed a correlation between the fluorescence intensity score and the degree of surface oxidation, as determined using the carbonyl index calculated from attenuated total reflection-Fourier transform infrared spectroscopy data. Collectively, these findings offer novel analytical approaches for investigating environmental MPs, enhancing our understanding of their behavior and impact.
Idehara et al. (Thu,) studied this question.