A Rapid Method for Detecting Microplastics Based on Fluorescence Lifetime Imaging Technology (FLIM)

Exploring the trophic transfer and effects of microplastics in freshwater ecosystems: A focus on Bellamya aeruginosa to Mylopharyngodon piceus

Microplastics (MPs) can enter aquatic food webs through direct ingestion from the environment or indirectly via trophic transfer, but their fate and biological effects within local freshwater food chains remain largely unexplored. In this study, we conducted the first investigation on the trophic transfer and impacts of fluorescently labeled polystyrene microplastics (PS-MPs) (100-nm and 10-μm) in a model freshwater food chain consisting of the snail Bellamya aeruginosa and the commercially important fish Mylopharyngodon piceus, both prevalent in Chinese freshwater ecosystems. Quantitative analysis revealed substantial accumulation of MPs in B. aeruginosa, reaching an equilibrium state within 12 h of exposure. While steady-state was not observed, a pronounced time-dependent bioaccumulation of MPs was evident in M. piceus over a five-week period following dietary exposure through the consumption of contaminated B. aeruginosa. Notably, MPs of both sizes underwent translocation from the gastrointestinal tract to the muscle tissue in M. piceus. High-throughput sequencing of the gut microbiota revealed that exposure to 100-nm MPs significantly altered the microbial community composition in M. piceus, and both particle sizes led to increased relative abundance of potentially pathogenic bacterial genera. Our findings provide novel insights into the trophic transfer, tissue accumulation, and biological impacts of MPs in a model freshwater food chain, highlighting the need for further research to assess the ecological and food safety risks associated with microplastic pollution in freshwater environments.

Size- and shape-dependent ingestion and acute toxicity of fragmented and spherical microplastics in the absence and presence of prey on two marine zooplankton

As microplastics (MPs) are particulate pollutants, their size and shape, and the presence of prey in the media can affect their toxicity. However, the size- and shape-dependent toxicities of MPs and their prey-dependent ingestion patterns in marine zooplankton are not well understood. Thus, we investigated the ingestion and egestion patterns, and toxicity of different shapes and sizes of MPs on two marine zooplankton, Brachionus koreanus and Diaphanosoma celebensis, under different prey conditions. The ingestion assay showed that smaller MPs were ingested more frequently, regardless of their shape. However, fragmented MPs showed higher toxicity than spherical MPs of comparable size. Prey in the media reduced the uptake and toxicity of MPs in both species depending on the taxa's feeding strategy. Our findings demonstrate that the size and shape of MPs are important factors in determining toxicity and that the presence of prey should also be considered when assessing MP toxicity.

Experimental detection of marine plastic litter in surface waters by 405 nm LD-based fluorescence lidar

Plastic pollution has become a global challenge, affecting water quality and health. Plastics including polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET), and high-density polyethylene (HDPE), are significant contributors to environmental pollution. With the growing need for investigation and detection of plastics found in natural waters, we propose the use of a portable laser diode (LD)-based fluorescence lidar system for in-situ detection of plastic litters in surface waters based on excitation-emission fluorescence spectroscopic data. The experiments were carried out in a controlled environment using a fluorescence lidar system with 405 nm excitation wavelength to determine the fluorescence signals of several plastics at 470 nm emission wavelength. Simultaneous detection of PET plastic and Chlorella vulgaris were also observed to determine the fluorescence influence of chlorophyll in surface waters. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the chemical composition of the plastics used before and after being submerged in the water. Scanning electron microscopy (SEM) and high-resolution camera microscopy were used to analyze the morphology of the submerged PET samples. This study provides a basis for a new in-situ technique using a fluorescence lidar system for submerged or transparent plastics in surface waters.

Micro- and Nanoplastics Produced from Textile Finishes: A Review

The problem of increasing plastic pollution has emerged as a significant societal issue. Plastics can originate from various sources, and there is growing concern among researchers to study and investigate this new category of pollution. The plastic waste is found at the macro, micro, and nanoscale, and its study has had great significance according to the perspective of posing hazardous impacts on living organisms. Given the high demand for functional textiles, the textile industries are supporting the coating of different polymeric based finishes on the surface of textile products. The plastic debris emitted from these coated finishes are in the ranges of nanometric scale, so-called polymeric nanoplastics (PNPs). With the new terminology, polymeric nanoplastics (PNPs) released from textile finishes or coatings are being increasingly mentioned, and the term fibrous microplastics (FMPs) can be seen as outdated. This study is based on an intensive review of a very novel category of debris plastics (PNPs) mostly produced from textile finishes or coatings. In fact, FMPs and PNPs released from synthetic textiles and textiles coated with plastic-based finishes during washing activities are considered to be a major cause that contributes to the current overall load of microplastics (MPs) in the environment. A link between the concentration of NPs from textile fibers and NPs from textile polymeric-based coatings in freshwater and sediments within a particular local setting and the extent of activities of the textile industry has been demonstrated. Invested efforts have been paid to consider and concentrate on plastic pollution (nanoplastics from textile polymeric coatings). We also summarize existing methodologies to elucidate the identification and proactive quantification of nanoplastics shed from the textile polymeric coatings. To this end, more than 40 studies have been done to identify the physical, chemical, and mechanical parameters and to characterize nanoplastics.

Characterization of HDPE microparticles in sludge aerobic digestion and their influence on the process

The occurrence of microplastics (MPs) in wastewater has been studied in the last years. The high efficiency of their removal from wastewater is linked to their transfer to the sludge. In this work, the effect of high-density polyethylene (HDPE) on aerobic digestion was evaluated and these MPs were monitored, characterizing them by three different techniques. Two parallel batch digesters were monitored. AD-Control (meaning Aerobic Digester) operated as a reference, with no external HDPE particles, whereas these polymeric fragments were introduced to the second aerobic digester (AD-HDPE) using ring pulls as microplastic support. FTIR, Raman spectroscopies and fluorescence analysis of these microparticles showed some relevant results that should be highlighted. Higher fluorescence appeared after 7 days in the digester. It coincided with an increase of active volatile suspended solids (AVSS) in the AD-HDPE, which means that an increase of the microbial activity took place. Despite the presence of HDPE particles in the sludge, the digester performance was not compromised. Besides, the HDPE particles did not affect the microbial diversity (Shannon index) of the bacterial community at the end of the experiment compared to the bacterial community of the aerobic digester control tank. Based on the analysis of the relative abundances of microbial taxa, it was concluded that HDPE had selective effects on sludge microbial community, increasing the relative abundance of Bacteroridota phylum.

Identification of different plastic types and natural materials from terrestrial environments using fluorescence lifetime imaging microscopy

Environmental pollution by plastics is a global issue of increasing concern. However, microplastic analysis in complex environmental matrices, such as soil samples, remains an analytical challenge. Destructive mass-based methods for microplastic analysis do not determine plastics' shape and size, which are essential parameters for reliable ecological risk assessment. By contrast, nondestructive particle-based methods produce such data but require elaborate, time-consuming sample preparation. Thus, time-efficient and reliable methods for microplastic analysis are needed. The present study explored the potential of frequency-domain fluorescence lifetime imaging microscopy (FD-FLIM) for rapidly and reliably identifying as well as differentiating plastics and natural materials from terrestrial environments. We investigated the fluorescence spectra of ten natural materials from terrestrial environments, tire wear particles, and eleven different transparent plastic granulates <5 mm to determine the optimal excitation wavelength for identification and differentiation via FD-FLIM under laboratory conditions. Our comparison of different excitation wavelengths showed that 445 nm excitation exhibited the highest fluorescence intensities. 445 nm excitation was also superior for identifying plastic types and distinguishing them from natural materials from terrestrial environments with a high probability using FD-FLIM. We could demonstrate that FD-FLIM analysis has the potential to contribute to a streamlined and time-efficient direct analysis of microplastic contamination. However, further investigations on size-, shape-, color-, and material-type detection limitations are necessary to evaluate if the direct identification of terrestrial environmental samples of relatively low complexity, such as a surface inspection soil, is possible.

Recent advances in microplastic removal from drinking water by coagulation: Removal mechanisms and influencing factors

Microplastics (MPs) are emerging contaminants that are widely detected in drinking water and pose a potential risk to humans. Therefore, the MP removal from drinking water is a critical challenge. Recent studies have shown that MPs can be removed by coagulation. However, the coagulation removal of MPs from drinking water remains inadequately understood. Herein, the efficiency, mechanisms, and influencing factors of coagulation for removing MPs from drinking water are critically reviewed. First, the efficiency of MP removal by coagulation in drinking water treatment plants (DWTPs) and laboratories was comprehensively summarized, which indicated that coagulation plays an important role in MP removal from drinking water. The difference in removal effectiveness between the DWTPs and laboratory was mainly due to variations in treatment conditions and limitations of the detection techniques. Several dominant coagulation mechanisms for removing MPs and their research methods are thoroughly discussed. Charge neutralization is more relevant for small-sized MPs, whereas large-sized MPs are more dependent on adsorption bridging and sweeping. Furthermore, the factors influencing the efficiency of MP removal were jointly analyzed using meta-analysis and a random forest model. The meta-analysis was used to quantify the individual effects of each factor on coagulation removal efficiency by performing subgroup analysis. The random forest model quantified the relative importance of the influencing factors on removal efficiency, the results of which were ordered as follows: MPs shape > Coagulant type > Coagulant dosage > MPs concentration > MPs size > MPs type > pH. Finally, knowledge gaps and potential future directions are proposed. This review assists in the understanding of the coagulation removal of MPs, and provides novel insight into the challenges posed by MPs in drinking water.

Microplastics in water: Occurrence, fate and removal

A global study on tap water samples has found that up to 83% of these contained microplastic fibres. These findings raise concerns about their potential health risks. Ingested microplastic particles have already been associated with harmful effects in animals, which raise concerns about similar outcomes in humans. Microplastics are ubiquitous in the environment, commonly found disposed in landfills and waste sites. Within indoor environments, the common sources are synthetic textiles, plastic bottles, and packaging. From the various point sources, they are globally distributed through air and water and can enter humans through various pathways. The finding of microplastics in fresh snow in the Antarctic highlights just how widely they are dispersed. The behaviour and health risks from microplastic particles are strongly influenced by their physicochemical properties, which is why their surfaces are important. Surface interactions are also important in pollutant transport via adsorption onto the microplastic particles. Our review covers the latest findings in microplastics research including the latest statistics in their abundance, their occurrence and fate in the environment, the methods of reducing microplastics exposure and their removal. We conclude by proposing future research directions into more effective remediation methods including new technologies and sustainable green remediation methods that need to be explored to achieve success in microplastics removal from waters at large scale.

Awareness for artifacts in fluorescence microscopy of β-TCP

Fluorescence analysis of β-TCP ceramics is often used to describe cells found on said ceramics. However, we found, to our knowledge, so far undescribed artifacts which might sometimes be hard to differentiate from cells due to shape and fluorescence behavior. We tried prolonged ultrasound washing as well as Technovit 9100 fixation to reduce these artifacts. While untreated dowels showed no reduction in artifacts no matter the further treatment, Technovit fixation reduced the artifacts with even further reduction achieved by mechanical cleaning. As a consequence, scientists working with these dowels and likely even other types should try to avoid creating false positive results by considering the existence of these artifacts, checking additional filters for unusual fluorescence and by reducing them by using Technovit fixation when possible.

Identification of marine microplastics based on laser-induced fluorescence and principal component analysis

Although the laser-induced fluorescence method shows great potential for microplastic particle detection, overlapping fluorescence signals make accurate type and proportion identification difficult. This paper presents the identification of marine microplastics based on laser-induced fluorescence and principal component analysis. This method works by measuring the fluorescence spectra of water-containing microplastic samples irradiated with a 405-nm laser, which are then analyzed using the principal component analysis (PCA) method. The nine types of microplastics were differentiated based on their positions in the PCA score plot. The mixed sample was positioned between the pure microplastic samples. The component ratio determines its position relative to that of the pure microplastic samples. The first two principal components of the mixed microplastics were linearly dependent. Natural seawater had less influence on the detection, and a mass concentration as low as 0.03% was detected.

Fast and portable fluorescence lifetime analysis for early warning detection of micro- and nanoplastics in water

The presence of plastic fragments in aquatic environments, particularly at the micro- and nano-scale, has become a significant global concern. However, current detection methods are limited in their ability to reveal the presence of such particles in liquid samples. In this study, we propose the use of a fluorescence lifetime analysis system for the detection of micro- and nanoplastics in water. This approach relies on the inherent endogenous fluorescence of plastic materials and involves the collection of single photons emitted by plastic fragments upon exposure to a pulsed laser beam. Briefly, a pulsed laser beam (repetition frequency = 40 MHz) shines onto a sample solution, and the emitted light is filtered, collected, and used to trace the time distributions of the photons with high temporal resolution. Finally, the fluorescence lifetime was measured using fitting procedures and a phasor analysis. Phasor analysis is a fit-free method that allows the measurement of the fluorescence lifetime of a sample without any assumptions or prior knowledge of the sample decay pattern. The developed instrument was tested using fluorescence references and validated using unlabelled micro- and nano-scale particles. Our system successfully detected polystyrene particles in water, achieving a remarkable sensitivity with a detection limit of 0.01 mg/mL, without the need for sample pre-treatment or visual inspection. Although further studies are necessary to enhance the detection limit of the technique and distinguish between different plastic materials, this proof-of-concept study suggests the potential of the fluorescence lifetime-based approach as a rapid, robust, and cost-effective method for early warning detection and identification of plastic contaminants in aquatic environments.

Toxicological Profile of Polyethylene Terephthalate (PET) Microplastic in Ingested Drosophila melanogaster (Oregon R+) and Its Adverse Effect on Behavior and Development

Microplastics are readily available in the natural environment. Due to the pervasiveness of microplastic pollution, its effects on living organisms necessitate further investigation. The size, time of exposure, and amount of microplastic particles appear to be the most essential factor in determining their toxicological effects, either organismal or sub-organismal. For our research work, we preferred to work on a terrestrial model organism Drosophila melanogaster (Oregon R+). Therefore, in the present study, we characterized 2-100 µm size PET microplastic and confirmed its accumulation in Drosophila, which allowed us to proceed further in our research work. At larger dosages, research on locomotory activities such as climbing, jumping, and crawling indicated a decline in physiological and neuromuscular functions. Our studies also determined retarded development in flies and decreased survival rate in female flies after exposure to the highest concentration of microplastics. These experimental findings provide insight into the possible potential neurotoxic effects of microplastics and their detrimental effects on the development and growth of flies.

Microplastics in water: types, detection, and removal strategies

Microplastics are one of the most concerning groups of contaminants that pollute most of the surroundings of the Earth. The abundance of plastic materials available in the environment moved the scientific community in defining a new historical era known as Plasticene. Regardless of their minuscule size, microplastics have posed severe threats to the life forms like animals, plants, and other species present in the ecosystem. Ingestion of microplastics could lead to harmful health effects like teratogenic and mutagenic abnormalities. The source of microplastics could be either primary or secondary in which the components of microplastics are directly released into the atmosphere and the breakdown of larger units to generate the smaller molecules. Though numerous physical and chemical techniques are reported for the removal of microplastics, their increased cost prevents the large-scale applicability of the process. Coagulation, flocculation, sedimentation, and ultrafiltration are some of the methods used for the removal of microplastics. Certain species of microalgae are known to remove microplastics by their inherent nature. One of the biological treatment strategies for microplastic removal is the activated sludge strategy that is used for the separation of microplastic. The overall microplastic removal efficiency is significantly high compared to conventional techniques. Thus, the reported biological avenues like the bio-flocculant for microplastic removal are discussed in this review article.

Microplastics in food - a critical approach to definition, sample preparation, and characterisation

The ubiquity of microplastics (MPs) is a more and more frequently brought up topic. The fact that such particles are present in food raises particular concern. Information regarding the described contamination is incoherent and difficult to interpret. Problems appear already at the level of the definition of MPs. This paper will discuss ways of explaining the concept of MPs and methods used for its analysis. Isolation of characterised particles is usually performed using filtration, etching and/or density separation. Spectroscopic techniques are commonly applied for analysis, whereas visual evaluation of the particles is possible thanks to microscopic analysis. Basic information about the sample can be obtained by the combination of Fourier Transform Infrared spectroscopy or Raman spectroscopy and microscopy or using the thermal method combined with spectroscopy or chromatography. The unification of the research methodology will allow a credible assessment of the influence of this pollution coming from food on health.

Development of an Inexpensive and Comparable Microplastic Detection Method Using Fluorescent Staining with Novel Nile Red Derivatives

Fluorescent staining of microplastics as a detection method is consistently gaining importance in microplastics research, as it is fast, easy to use, and requires low technical effort. In this study, a complete procedure was developed, from sample collection to sample processing and detection, to measure microplastics with low cost and time requirements. The developed procedure was tested by measuring the microplastics in the effluent of a German wastewater treatment plant over a period of one year. The results show that the process is especially well suited to investigate temporal variations of microplastic contamination, which requires a large number of samples to be processed. Further, the precision and selectivity of the detection process could be improved by applying newly developed Nile red derivatives for fluorescent staining. A low budget modification of a microscope for fluorescent imaging is compared to a modification with precise optical bandpass filters. A script enabling automated microplastic detection and counting was developed, improving the accuracy and comparability of the process.

Identification of micro- and nanoplastics released from medical masks using hyperspectral imaging and deep learning

In this study, dark-field microscopy-based hyperspectral imaging augmented with deep learning data analysis was applied for effective visualisation, detection and identification of microplastics released from polypropylene medical masks.