Micro- and Nano- Plastics

The Rising Concern of Micro- and Nano- Plastics

Microplastics and nanoplastics (MNPs) are tiny plastic particles less than 5 mm in size. They are pervasive, from the ocean depths to the air we breathe [1], and even within human organs and tissues [2]. Nowadays they have raised significant concerns. However, their small size, complex nature, and diverse polymeric makeup make the identification and quantification of MNPs a challenging task [3].

Innovative Detection with Fluorescence Lifetime Analysis

Fluorescence Lifetime Analysis (FLA) – an innovative method that utilizes the autofluorescence of plastics. Combined with a microscope, known as FLIM, it measures the decay rate of light emitted from excited plastic particles. This decay rate, or fluorescence lifetime, is unique to different components and serves as a fingerprint for MNPs [4]. Phasor analysis further enhances this method by providing a two-dimensional representation of these unique fingerprints, enabling quick and label-free mapping and identification of MNPs in samples [5].

FLIM LABS’ Portable Solution

At FLIM LABS, we have developed a portable, USB-powered FLA system that does not require a microscope. In collaboration with the University of La Sapienza, we’ve tailored this system specifically for MNP detection.

FLA system tailored for MNPs detection

It is based on FLIM Starter Kit and involves exciting MNP samples with a 445 nm pulsed laser. The emitted photons are detected over time by the single-photon SPAD detector, and the FLIM Data Acquisition card record the time delay between the laser pulse and the arrival of the emitted photons, allowing the reconstruction of TCSPC histogram. Then our software uses phasor analysis to transform the resulting data into phasor fingerprints. Notably, the phasor fingerprints of the same type aligned on a single line, shift towards the origin as the concentration decreases. 

Working principle of FLIM LABS’ FLA system

Proven Performance

Our FLA system successfully detected polystyrene (PS) particles – a common plastic type in everyday use – across various sizes and concentrations. It demonstrates remarkable sensitivity in detecting unmodified PS micro- and nano- particles, which are representative of environmental MNPs. Being portable, our FLA system offers a promising solution for on-site investigation. Achieving detection limits as low as 0.01 mg/mL for PS MNPs, our system holds great potential for monitoring and assessing MNP pollution.

TCSPC histograms of various PS particles and their corresponding phasor fingerprints when excited at 445 nm

Gratitude and Recognition

This work was supported by the Italian Minister for University and Research (MUR) for the research project “PON Ricerca e Innovazione” – Progetti DM 1062 del 10/08/2021.

Bibliography

[1] Sangkham, S., Faikhaw, O., Munkong, N., Sakunkoo, P., Arunlertaree, C., Chavali, M., … & Tiwari, A. (2022). A review on microplastics and nanoplastics in the environment: Their occurrence, exposure routes, toxic studies, and potential effects on human health. Marine pollution bulletin, 181, 113832.

[2] Li, P., & Liu, J. (2024). Micro (nano) plastics in the Human Body: Sources, Occurrences, Fates, and Health Risks. Environmental Science & Technology.

[3] Cai, H., Xu, E. G., Du, F., Li, R., Liu, J., & Shi, H. (2021). Analysis of environmental nanoplastics: Progress and challenges. Chemical Engineering Journal, 410, 128208.

[4] Monteleone, A., Wenzel, F., Langhals, H., & Dietrich, D. (2021). New application for the identification and differentiation of microplastics based on fluorescence lifetime imaging microscopy (FLIM). Journal of Environmental Chemical Engineering, 9(1), 104769.

[5] Monteleone, A., Schary, W., Wenzel, F., Langhals, H., & Dietrich, D. R. (2021). Label-free identification and differentiation of different microplastics using phasor analysis of fluorescence lifetime imaging microscopy (FLIM)-generated data. Chemico-Biological Interactions, 342, 109466.

[6] Xiao, S., Filippini, A., Casadei, M., Caracciolo, G., Digiacomo, L., & Rossetta, A. (2024). Fast and portable fluorescence lifetime analysis for early warning detection of micro-and nanoplastics in water. Environmental Research, 244, 117936.