Bioanalytical approaches for the detection, characterization, and risk assessment of micro/nanoplastics in agriculture and food systems

In-situ detection of microplastics in the aquatic environment: A systematic literature review

Microplastics are ubiquitous in the aquatic environment and have emerged as a significant environmental issue due to their potential impacts on human health and the ecosystem. Current laboratory-based microplastic detection methods suffer from various drawbacks, including a lack of standardisation, limited spatial and temporal coverage, high costs, and time-consuming procedures. Consequently, there is a need for the development of in-situ techniques to detect and monitor microplastics to effectively identify and understand their sources, pathways, and behaviours. Herein, we adopt a systematic literature review method to assess the development and application of experimental and field technologies designed for the in-situ detection and monitoring of aquatic microplastics, without the need for sample preparation. Four scientific databases were searched in March 2023, resulting in a review of 62 relevant studies. These studies were classified into seven sensor categories and their working principles were discussed. The sensor classes include optical devices, digital holography, Raman spectroscopy, other spectroscopy, hyperspectral imaging, remote sensing, and other methods. We also looked at how data from these technologies are integrated with machine learning models to develop classifiers capable of accurately characterising the physical and chemical properties of microplastics and discriminating them from other particles. This review concluded that in-situ detection of microplastics in aquatic environments is feasible and can be achieved with high accuracy, even though the methods are still in the early stages of development. Nonetheless, further research is still needed to enhance the in-situ detection of microplastics. This includes exploring the possibility of combining various detection methods and developing robust machine-learning classifiers. Additionally, there is a recommendation for in-situ implementation of the reviewed methods to assess their effectiveness in detecting microplastics and identify their limitations.

Effects of partial reduction of polystyrene micro-nanoplastics on the immunity, gut microbiota and metabolome of mice

Microplastic (MP) and nanoplastic (NP) could cause gut microbiota alterations. Although micro/nanoplastic (MNP) degradation is attracting increasing scientific interest, the evaluation of MNP reduction in gut needs to be further investigated. This study aimed to determine whether partial reduction of polystyrene MNP in gut could affect the immunity, gut microbiota and metabolome of mice. Serum eotaxin/CCL11 was at a lower level in the mice exposed to 200 μg and 500 μg NP (i.e., 2NP and 5NP groups, respectively) compared to those exposed to 500 μg MP (i.e., 5 MP group), while serum IL-2 and IL-4 were both greater in the 5NP group compared to the 5 MP group. The gut bacterial alpha diversity, fungal diversity and evenness were all similar among the MNP and control groups. However, the gut fungal richness was greater in both the 5NP and 5 MP groups compared to the control group. The gut bacterial and fungal compositions were both different between the MNP and control groups. Multiple gut bacteria and fungi showed different levels between the 2NP and 5NP groups, as well as between the 2NP and 5 MP groups. Increased Staphylococcus and decreased Glomus were determined in the 2NP group compared to both the 5NP and 5 MP groups. A Lactobacillus phylotype was found as the sole gatekeeper in the bacterial network of the 2NP group, while a Bifidobacterium phylotype contributed most to the stability of the bacterial networks of both the 5NP and 5 MP groups. Multiple differential gut metabolic pathways were found between the 2NP and 5NP/5 MP groups, and mTOR signaling pathway was largely upregulated in the 2NP group compared to both the 5NP and 5 MP groups. The relevant results could help with the evaluation of partial reduction of MNP in gut.

A colorimetric detection of polystyrene nanoplastics with gold nanoparticles in the aqueous phase

Nanoplastics has become a growing environmental concern because these tiny particles can easily penetrate biological tissues and have possible toxic effects. FT-IR and Raman spectroscopy methods are currently used to analyze microplastics (5 mm or less), but they encounter difficulty when the particles are below 1 μm. On the other hand, thermoanalysis of nanoplastics does not provide the size information. Therefore, herein, we proposed the colorimetric detection method with gold nanoparticles (AuNPs) to measure the concentration of polystyrene nanoplastics (PSNPs, size = 350 and 880 nm) through a color change that is obvious to the naked eye. A mixed dispersion of PSNPs and AuNPs was added with acetone, a good solvent for polystyrene. In this colorimetric detection, acetone acted as a key component to enhance or hinder the aggregation of AuNPs around PSNPs. Namely, acetone itself promoted AuNPs aggregation, but it was dissolved partially PS chains from PSNSs to act as inhibitor of aggregation of AuNPs. These two contradictory feature of acetone to AuNPs and PSNPs affect the aggregation and color of AuNPs (dispersed = red, aggregated = blue). Finally, the heat-map between PSNSs and acetone was prepared to use for estimation of concentration of PSNPs in the aqueous solution with naked eye. To the best of our knowledge, this is the first attempt to measure nanoplastics by colorimetry.