Dark-field hyperspectral microscopy for label-free microplastics and nanoplastics detection and identification in vivo: A Caenorhabditis elegans study

Microplastic fragmentation by rotifers in aquatic ecosystems contributes to global nanoplastic pollution

The role of aquatic organisms in the biological fragmentation of microplastics and their contribution to global nanoplastic pollution are poorly understood. Here we present a biological fragmentation pathway that generates nanoplastics during the ingestion of microplastics by rotifers, a commonly found and globally distributed surface water zooplankton relevant for nutrient recycling. Both marine and freshwater rotifers could rapidly grind polystyrene, polyethylene and photo-aged microplastics, thus releasing smaller particulates during ingestion. Nanoindentation studies of the trophi of the rotifer chitinous mastax revealed a Young's modulus of 1.46 GPa, which was higher than the 0.79 GPa for polystyrene microparticles, suggesting a fragmentation mechanism through grinding the edges of microplastics. Marine and freshwater rotifers generated over 3.48 × 105 and 3.66 × 105 submicrometre particles per rotifer in a day, respectively, from photo-aged microplastics. Our data suggest the ubiquitous occurrence of microplastic fragmentation by different rotifer species in natural aquatic environments of both primary and secondary microplastics of various polymer compositions and provide previously unidentified insights into the fate of microplastics and the source of nanoplastics in global surface waters.

Underappreciated microplastic galaxy biases the filter-based quantification

Long-term environmental loading of microplastics (MPs) causes alarming exposure risks for a variety of species worldwide, considered a planetary threat to the well-being of ecosystems. Robust quantitative estimates of MP extents and featured diversity are the basis for comprehending their environmental implications precisely, and of these methods, membrane-based characterizations predominate with respect to MP inspections. However, though crucial to filter-based MP quantification, aggregation statuses of retained MPs on these substrates remain poorly understood, leaving us a "blind box" that exaggerates uncertainty in quantitive strategies of preselected areas without knowing overview loading structure. To clarify this uncertainty and estimate their impacts on MP counting, using MP imaging data assembled from peer-reviewed studies through a systematic review, here we analyze the particle-specific profiles of MPs retained on various substrates according to their centre of mass with a fast-random forests algorithm. We visualize the formation of distinct galaxy-like MP aggregation-similar to the solar system and Milky Way System comprised of countless stars-across the pristine and environmental samples by leveraging two spatial parameters developed in this study. This unique pattern greatly challenges the homogeneously or randomly distributed MP presumption adopted extensively for simplified membrane-based quantification purposes and selective ROI (region of interest) estimates for smaller-sized plastics down to the nano-range, as well as the compatibility theory using pristine MPs as the standard to quantify the presence of environmental MPs. Furthermore, our evaluation with exemplified numeration cases confirms these location-specific and area-dependent biases in many imaging analyses of a selective filter area, ascribed to the minimum possibility of reaching an ideal turnover point for the selective quantitive strategies. Consequently, disproportionate MP schemes on loading substrates yield great uncertainty in their quantification processing, highlighting the prompt need to include pattern-resolved calibration prior to quantification. Our findings substantially advance our understanding of the structure, behavior, and formation of these MP aggregating statuses on filtering substrates, addressing a fundamental question puzzling scientists as to why reproducible MP quantification is barely achievable even for subsamples. This study inspires the following studies to reconsider the impacts of aggregating patterns on the effective counting protocols and target-specific removal of retained MP aggregates through membrane separation techniques.

Microplastics released from disposable medical devices and their toxic responses in Caenorhabditis elegans

Owing to accelerated urbanization and industrialization, many plastic products have been manufactured and discharged into the environment, causing environmental and public health problems. Plastics in environmental media are further degraded by prolonged exposure to light, heat, mechanical friction, and other factors to form new pollutants called microplastics (MPs). Medical plastics have become a crucial source of plastics in environmental media. However, the release profiles of MPs from medical plastics and their potential ecological and health risks remain unclear. We used optical photothermal infrared spectroscopy to explore the release profiles of eight typical disposable medical devices under high-temperature steam disinfection (HSD). We also evaluated the toxicity of disposable medical devices-derived MPs in Caenorhabditis elegans (C. elegans). Our results showed that the changes in the surface morphology and modification of the disposable medical devices were mainly associated with the material. Polypropylene (PP) and polystyrene (PS) materials exhibited high aging phenomena (e.g., bumps, depressions, bulges and cracks), and HSD broke their oxygen-containing functional groups and carbon chains. By contrast, minor changes in the chemical and physical properties were observed in the polyvinyl chloride (PVC)-prepared disposable medical devices under the same conditions. Further physicochemical characterization indicated that the amount of MPs released from PP-prepared disposable medical devices (P4: 1.27 ± 0.34 × 106) was greater than that from PVC-prepared disposable medical devices (P7: 1.08 ± 0.14 × 105). The particle size of the released MPs was the opposite, PVC-prepared disposable medical devices (P7: 11.45 ± 1.79 μm) > PP-prepared disposable medical devices (P4: 7.18 ± 0.52 μm). Toxicity assessment revealed that disposable medical devices-released MPs significantly increased germ cell apoptosisin C. elegans. Moreover, MPs from PP-prepared disposable medical devices disrupted the intestinal barrier of worms, decreasing their lifespan. Our findings provided novel information regarding the profiles and mechanisms of MP release from disposable medical devices and revealed their potential risks to ecological environment.

Microplastics: challenges of assessment in biological samples and their implication for in vitro and in vivo effects

Microplastics (MPs) have attracted global interest because they have been recognized as emerging pollutants that require urgent attention. MPs are plastic particles with a size between 1 micron and 5 mm (1 µm-5mm); those measuring less than 1 µm are known as nanoplastics (NPs). MP is distributed in the environment in various physical forms that depend on the degradation process, the erosion factors to which it was subjected, or the original form in which it was intentionally manufactured. Humans may be exposed to these pollutants mainly by ingestion or inhalation, which could adversely affect human health with effects that are still unknown due to limitations that are often dependent on their analytical determination and lack of studies over time, as it is a relatively new topic. Therefore, this review focuses on the challenges currently faced by laboratories for determining MPs in different matrices. We highlight the application of methods and techniques to assess the precise levels of exposure to MPs in biological samples. In addition, exposure pathways, sources, and evidence of adverse effects reported in vitro and in vivo studies are described to generate knowledge about their potential threat to human health.

Integrated Passive Sensing Chip for Highly Sensitive and Reusable Detection of Differential-Charged Nanoplastics Concentration

In this work, a new type, highly sensitive, and reusable nanoplastics (NPs) microwave detection method is proposed, which can be used to rapidly analyze NPs with different surface charges and sizes. The effective dielectric constant of NPs varies according to the different concentrations, particle sizes, and surface charges of NPs in aqueous solution. The feasibility of the microwave method for differential-charged NPs detection is verified using a complementary split ring resonator sensor manufactured on a cost-effective printed circuit board, which shows a high sensitivity only for positively charged NPs (PS-NH2) detection. To achieve microwave detection of both positively and negatively charged NPs (PS-SO3H), a microscale spiral-coupled resonator sensing chip is manufactured through integrated passive technology, which demonstrates extremely low detection limits and high sensitivity for both PS-NH2 and PS-SO3H, with different concentrations, particle sizes, and charges. In addition, for NPs solution doped with methyl orange, the device can still perform stable measurements, overcoming the inability of traditional NPs molecular element determination and optical detection methods to detect NPs aqueous solution with organic matter doping and color presence. The proposed microwave detection method could also be extended to sensing detection for detecting other hazardous environmental substances.

Radiolabeling of Micro-/Nanoplastics via In-Diffusion

Micro- and nanoplastics are emerging pollutants with a concerning persistence in the environment. Research into their environmental impact requires addressing challenges related to sensitively and selectively detecting them in complex ecological media. One solution with great potential for alleviating these issues is using radiolabeling strategies. Here, we report the successful introduction of a 64Cu radiotracer into common microplastics, namely polyethylene, polyethylene terephthalate, polystyrene, polyamide, and polyvinylidene dichloride, which allows the sensitive detection of mere nanograms of substance. Utilizing a Hansen Solubility Parameter screening, we developed a swelling and in-diffusion process for tetraphenylporphyrin-complexed 64Cu, which permits one-pot labeling of polymer particles.

Accumulation of nanoplastics in human cells as visualized and quantified by hyperspectral imaging with enhanced dark-field microscopy

Nanoplastic (NP) pollution is receiving increasing attention regarding its potential effects on human health. The identification and quantification of intracellular NPs are prerequisites for an accurate risk assessment, but appropriate methods are lacking. Here we present a label-free technique to simultaneously visualize and quantify the bioaccumulation of NPs based on hyperspectral imaging with enhanced dark-field microscopy (HSI-DFM). Using polystyrene NPs (PS NPs) as representative particles, the construction of a hyperspectral library was optimized first with more accurate NP identification achieved when the library was based on intracellular instead of extracellular PS NPs. The PS NPs used herein were labeled with a green fluorescent dye so that the accuracy of HSI-DFM in identifying and quantifying intracellular NPs can be evaluated, by comparing the results with those obtained by fluorescence microscopy and flow cytometry. The validation of HSI-DFM for use in determinations of the NP concentration at the single-cell level allows analyses of the accumulation kinetics of NPs in single living cells. The utility of HSI-DFM in different cell lines and with NPs differing in their chemical composition was also demonstrated. HSI-DFM therefore provides a new approach to studies of the accumulation and distribution of NPs in human cells.

Mechanistic Understanding toward the Maternal Transfer of Nanoplastics in Daphnia magna

Nanoplastics induce transgenerational toxicity to aquatic organisms, but the specific pathways for the maternal transfer of nanoplastics remain unclear. Herein, laser scanning confocal microscopy (LSCM) observations identified the specific pathways on the maternal transfer of polystyrene (PS) nanoplastics (25 nm) in Daphnia magna. In vivo and in vitro experiments showed that PS nanoplastics could enter the brood chamber through its opening and then be internalized to eggs and embryos using LSCM imaging (pathway I). In addition, PS nanoplastics were observed in the oocytes of the ovary, demonstrating gut-ovary-oocyte transfer (pathway II). Furthermore, label-free hyperspectral imaging was used to detect the distribution of nanoplastics in the embryos and ovary of Daphnia, again confirming the maternal transfer of nanoplastics through the two pathways mentioned above. The contribution from pathway I (88%) was much higher than pathway II (12%) based on nanoflow cytometry quantification. In addition, maternal transfer in Daphnia depended on the particle size of PS nanoplastics, as demonstrated by using LSCM and hyperspectral imaging. Unlike 25 nm nanoplastics, 50 nm PS nanoplastics could enter the brood chamber and the eggs/embryos (pathway I), but were not detected in the ovary (pathway II); 100 nm PS nanoplastics were difficult to be internalized by eggs/embryos and could not enter the ovary either. These findings provide insight into the maternal transfer mechanisms of nanoplastics in Daphnia, and are critical for better understanding the transgenerational toxicity of aquatic organisms.

Carboxyl-modified polystyrene microplastics induces neurotoxicity by affecting dopamine, glutamate, serotonin, and GABA neurotransmission in Caenorhabditis elegans

Microplastics (MPs) are ubiquitous in various environmental media and have potential toxicity. However, the neurotoxicity of carboxyl-modified polystyrene microplastics (PS-COOH) and their mechanisms remain unclear. In this study, Caenorhabditis elegans was used as a model to examine the neurotoxicity of polystyrene microplastic (PS) and PS-COOH concentrations ranging from 0.1 to 100 μg/L. Locomotion behavior, neuron development, neurotransmitter level, and neurotransmitter-related gene expression were selected as assessment endpoints. Exposure to low concentrations (1 μg/L) of PS-COOH caused more severe neurotoxicity than exposure to pristine PS. In transgenic nematodes, exposure to PS-COOH at 10-100 μg/L significantly increased the fluorescence intensity of dopaminergic, glutamatergic, serotonergic, and aminobutyric acid (GABA)ergic neurons compared to that of the control. Further studies showed that exposure to 100 μg/L PS-COOH can significantly affect the levels of glutamate, serotonin, dopamine, and GABA in nematodes. Likewise, in the present study, the expression of genes involved in neurotransmission was altered in worms. These results suggest that PS-COOH exerts neurotoxicity by affecting neurotransmission of dopamine, glutamate, serotonin, and GABA. This study provides new insights into the underlying mechanisms and potential risks associated with PS-COOH.

Remediation plan of nano/microplastic toxicity in food

Microplastic pollution is causing a stir globally due to its persistent and ubiquitous nature. The scientific collaboration is diligently working on improved, effective, sustainable, and cleaner measures to control the nano/microplastic load in the environment especially wrecking the aquatic habitat. This chapter discusses the challenges encountered in nano/microplastic control and improved technologies like density separation, continuous flow centrifugation, oil extraction protocol, electrostatic separation to extract and quantify the same. Although it is still in the early stages of research, biobased control measures, like meal worms and microbes to degrade microplastics in the environment have been proven effective. Besides the control measures, practical alternatives to microplastics can be developed like core-shell powder, mineral powder, and biobased food packaging systems like edible films and coatings developed using various nanotechnological tools. Lastly, the existing and ideal stage of global regulations is compared, and key research areas are pinpointed. This holistic coverage would enable manufacturers and consumers to reconsider their production and purchase decisions for sustainable development goals.

Caenorhabditis elegans as a Prediction Platform for Nanotechnology-Based Strategies: Insights on Analytical Challenges

Nanotechnology-based strategies have played a pivotal role in innovative products in different technological fields, including medicine, agriculture, and engineering. The redesign of the nanometric scale has improved drug targeting and delivery, diagnosis, water treatment, and analytical methods. Although efficiency brings benefits, toxicity in organisms and the environment is a concern, particularly in light of global climate change and plastic disposal in the environment. Therefore, to measure such effects, alternative models enable the assessment of impacts on both functional properties and toxicity. Caenorhabditis elegans is a nematode model that poses valuable advantages such as transparency, sensibility in responding to exogenous compounds, fast response to perturbations besides the possibility to replicate human disease through transgenics. Herein, we discuss the applications of C. elegans to nanomaterial safety and efficacy evaluations from one health perspective. We also highlight the directions for developing appropriate techniques to safely adopt magnetic and organic nanoparticles, and carbon nanosystems. A description was given of the specifics of targeting and treatment, especially for health purposes. Finally, we discuss C. elegans potential for studying the impacts caused by nanopesticides and nanoplastics as emerging contaminants, pointing out gaps in environmental studies related to toxicity, analytical methods, and future directions.

Recent approaches and advanced wastewater treatment technologies for mitigating emerging microplastics contamination - A critical review

Microplastics have been identified as an emerging pollutant due to their irrefutable prevalence in air, soil, and particularly, the aquatic ecosystem. Wastewater treatment plants (WWTPs) are seen as the last line of defense which creates a barrier between microplastics and the environment. These microplastics are discharged in large quantities into aquatic bodies due to their insufficient containment during water treatment. As a result, WWTPs are regarded as point sources of microplastics release into the environment. Assessing the prevalence and behavior of microplastics in WWTPs is therefore critical for their control. The removal efficiency of microplastics was 65 %, 0.2-14 %, and 0.2-2 % after the successful primary, secondary and tertiary treatment phases in WWTPs. In this review, other than conventional treatment methods, advanced treatment methods have also been discussed. For the removal of microplastics in the size range 20-190 μm, advanced treatment methods like membrane bioreactors, rapid sand filtration, electrocoagulation and photocatalytic degradation was found to be effective and these methods helps in increasing the removal efficiency to >99 %. Bioremediation based approaches has found that sea grasses, lugworm and blue mussels has the ability to mitigate microplastics by acting as a natural trap to the microplastics pollutants and could act as candidate species for possible incorporation in WWTPs. Also, there is a need for controlling the use and unchecked release of microplastics into the environment through laws and regulations.

Probing nanoplastics derived from polypropylene face masks with hyperspectral dark-field microscopy

The high worldwide consumption of cheap plastic goods has already resulted in a serious environmental plastic pollution, exacerbated by piling of disposed personal protective equipment because of the recent outbreak of COVID-19. The aim of this study was to assess the feasibility of dark-field hyperspectral microscopy in the 400-1000 wavelength range for detection of nanoplastics derived from weathered polypropylene masks. A surgical mask was separated to layers and exposed to UV radiation (254 nm) for 192 h. Oxidative degradation of the polypropylene was evidenced by ATR FT-IR analysis. UV treatment for 192 h resulted in generation of differently shaped micro- and nano-sized particles, visualized by dark-field microscopy. The presence of nanoparticles was confirmed by AFM studies. The hyperspectral profiles (400-1000 nm) were collected after every 48 h of the UV treatment. The distinct hyperspectral features faded after prolonged UV exposure, but the assignment of some particles to either blue or white layers of mask could still be made based on spectral characteristics.

Reversing the immunosuppressive microenvironment with reduced redox level by microwave-chemo-immunostimulant Ce-Mn MOF for improved immunotherapy

BACKGROUNDS

Reversing the immunosuppressive tumor microenvironment (TME) in the tumor is widely deemed to be an effective strategy to improve immune therapy. In particular, the redox balance in TME needs to be well controlled due to its critical role in mediating the functions of various cells, including cancer cells and immune-suppressive cells.

RESULTS

Here, we propose an efficient strategy to reshape the redox homeostasis to reverse immunosuppressive TME. Specifically, we developed a microwave-chemo-immunostimulant CMMCP to promote the infiltration of the tumor-T cells by simultaneously reducing the reactive oxygen species (ROS) and glutathione (GSH) and improving the oxygen (O₂) levels in TME. The CMMCP was designed by loading chemotherapy drugs cisplatin into the bimetallic Ce-Mn MOF nanoparticles coated with polydopamine. The Ce-Mn MOF nanoparticles can effectively improve the catalytic decomposition of ROS into O₂ under microwave irradiation, resulting in overcoming hypoxia and limited ROS generation. Besides, the activity of intracellular GSH in TME was reduced by the redox reaction with Ce-Mn MOF nanoparticles. The reprogrammed TME not only boosts the immunogenic cell death (ICD) induced by cisplatin and microwave hyperthermia but also gives rise to the polarization of pro-tumor M2-type macrophages to the anti-tumor M1-type ones.

CONCLUSION

Our in vivo experimental results demonstrate that the microwave-chemo-immunostimulant CMMCP significantly enhances the T cell infiltration and thus improves the antitumor effect. This study presents an easy, safe, and effective strategy for a whole-body antitumor effect after local treatment.

Coronas of micro/nano plastics: a key determinant in their risk assessments

As an emerging pollutant in the life cycle of plastic products, micro/nanoplastics (M/NPs) are increasingly being released into the natural environment. Substantial concerns have been raised regarding the environmental and health impacts of M/NPs. Although diverse M/NPs have been detected in natural environment, most of them display two similar features, i.e.,high surface area and strong binding affinity, which enable extensive interactions between M/NPs and surrounding substances. This results in the formation of coronas, including eco-coronas and bio-coronas, on the plastic surface in different media. In real exposure scenarios, corona formation on M/NPs is inevitable and often displays variable and complex structures. The surface coronas have been found to impact the transportation, uptake, distribution, biotransformation and toxicity of particulates. Different from conventional toxins, packages on M/NPs rather than bare particles are more dangerous. We, therefore, recommend seriously consideration of the role of surface coronas in safety assessments. This review summarizes recent progress on the eco-coronas and bio-coronas of M/NPs, and further discusses the analytical methods to interpret corona structures, highlights the impacts of the corona on toxicity and provides future perspectives.

Advanced microplastic monitoring using Raman spectroscopy with a combination of nanostructure-based substrates

Micro(nano)plastic (MNP) pollutants have not only impacted human health directly, but are also associated with numerous chemical contaminants that increase toxicity in the natural environment. Most recent research about increasing plastic pollutants in natural environments have focused on the toxic effects of MNPs in water, the atmosphere, and soil. The methodologies of MNP identification have been extensively developed for actual applications, but they still require further study, including on-site detection. This review article provides a comprehensive update on the facile detection of MNPs by Raman spectroscopy, which aims at early diagnosis of potential risks and human health impacts. In particular, Raman imaging and nanostructure-enhanced Raman scattering have emerged as effective analytical technologies for identifying MNPs in an environment. Here, the authors give an update on the latest advances in plasmonic nanostructured materials-assisted SERS substrates utilized for the detection of MNP particles present in environmental samples. Moreover, this work describes different plasmonic materials-including pure noble metal nanostructured materials and hybrid nanomaterials-that have been used to fabricate and develop SERS platforms to obtain the identifying MNP particles at low concentrations. Plasmonic nanostructure-enhanced materials consisting of pure noble metals and hybrid nanomaterials can significantly enhance the surface-enhanced Raman scattering (SERS) spectra signals of pollutant analytes due to their localized hot spots. This concise topical review also provides updates on recent developments and trends in MNP detection by means of SERS using a variety of unique materials, along with three-dimensional (3D) SERS substrates, nanopipettes, and microfluidic chips. A novel material-assisted spectral Raman technique and its effective application are also introduced for selective monitoring and trace detection of MNPs in indoor and outdoor environments.

Graphical abstract

Quantitative assessment of in vivo distribution of nanoplastics in bivalve Ruditapes philippinarum using reliable SERS tag-labeled nanoplastic models

Nanoplastics (NPs) as emerging marine pollutants can be taken up by seafood organisms. It is crucial to quantitatively assess NP's distribution behavior in organisms to elucidate concentration dependent biological effects. Such a knowledge gap has remained due to the lack of reliable NP models and analytical methods. Herein, surface enhanced Raman scattering (SERS)-labeled NP models were developed and their bioavailability, distribution and accumulation in Ruditapes philippinarum, a typical marine bivalve, were quantitatively studied. Taking advantage of the sensitive and characteristic SERS signals of the NP models, distribution could be quickly and accurately obtained by the Raman imaging technique. Moreover, quantitative analysis of NPs could be performed by the detection of gold element contents via inductively coupled plasma mass spectroscopy (ICP-MS) detection. ICP-MS results revealed that after 3 days exposure of monodispersed NPs (100 nm, 0.2 mg L^-1), the digestive gland accumulated 86.7% of whole-body NPs followed by gill (5.2%), mantle (5.1%), foot (1.3%), exhalant siphon (1.1%), and adductor (0.6%). Upon 11 days depuration, 98.7% of NPs in the digestive gland were excreted, whereas the clearance ratios in other organs were much lower. NP aggregates (around 1.5 μm) demonstrated similar distribution and clearance trends to the monodispersed ones. However, the accumulation amount in each organ was 15.2% to 77.6% lower. Surface adherence and passive ingestion routes resulted in NP accumulation, which contributed to the comparable NP abundance in these organs. Additionally, boiling treatment (mimicking a cooking process) did not decrease the NP amount in these organs. This work provided a dual-mode and quantitative analysis protocol for NPs for the first time, and suggested the risk of NP uptake by humans via bivalve seafood diets.

Optical Microscopy Systems for the Detection of Unlabeled Nanoparticles

Label-free detection of nanoparticles is essential for a thorough evaluation of their cellular effects. In particular, nanoparticles intended for medical applications must be carefully analyzed in terms of their interactions with cells, tissues, and organs. Since the labeling causes a strong change in the physicochemical properties and thus also alters the interactions of the particles with the surrounding tissue, the use of fluorescently labeled particles is inadequate to characterize the effects of unlabeled particles. Further, labeling may affect cellular uptake and biocompatibility of nanoparticles. Thus, label-free techniques have been recently developed and implemented to ensure a reliable characterization of nanoparticles.

This review provides an overview of frequently used label-free visualization techniques and highlights recent studies on the development and usage of microscopy systems based on reflectance, darkfield, differential interference contrast, optical coherence, photothermal, holographic, photoacoustic, total internal reflection, surface plasmon resonance, Rayleigh light scattering, hyperspectral and reflectance structured illumination imaging. Using these imaging modalities, there is a strong enhancement in the reliability of experiments concerning cellular uptake and biocompatibility of nanoparticles, which is crucial for preclinical evaluations and future medical applications.

Label-Free Live-Cell Imaging of Internalized Microplastics and Cytoplasmic Organelles with Multicolor CARS Microscopy

As the bioaccumulation of microplastics (MPs) is considered as a potential health risk, many efforts have been made to understand the cellular dynamics and cytotoxicity of MPs. Here, we demonstrate that label-free multicolor coherent anti-Stokes Raman scattering (CARS) microscopy enables separate vibrational imaging of internalized MPs and lipid droplets (LDs) with indistinguishable shapes and sizes in live cells. By simultaneously obtaining polystyrene (PS)- and lipid-specific CARS images at two very different frequencies, 1000 and 2850 cm^-1, respectively, we successfully identify the local distribution of ingested PS beads and native LDs in Caenorhabditis elegans. We further show that the movements of PS beads and LDs in live cells can be separately tracked in real time, which allows us to characterize their individual intracellular dynamics. We thus anticipate that our multicolor CARS imaging method could be of great use to investigate the cellular transport and cytotoxicity of MPs without additional efforts for pre-labeling to MPs.

Microplastics (Polystyrene) Exposure Induces Metabolic Changes in the Liver of Rare Minnow (Gobiocypris rarus)

Microplastics are environmental contaminants and an emergent concern. Microplastics are abundant in freshwater and can cause biochemical stress in freshwater organisms. In the current study, rare minnows (Gobiocypris rarus) were exposed to 1μm polystyrene microplastics at 200 μg/L concentration. We observed various sublethal effects after four weeks of exposure but no mortality. Numerous cellular and tissue alterations were observed in the liver. Differential metabolites and differentially expressed genes between control and exposure groups were identified and mapped to pathways in the Kyoto Encyclopedia of Genes and Genomes. The combination of transcriptomic and metabolomic analyses revealed significantly varied metabolic pathways between the two groups. These pathways were involved in glucolipid, amino acid, and nucleotide metabolism. Results demonstrated that MP exposure induced immune reaction, oxidative stress, and disturbed glycolipid and energy metabolism. The current study provided novel insights into the molecular and metabolic mechanisms of microplastic ecotoxicology in rare minnow.

Nanomechanical Atomic Force Microscopy to Probe Cellular Microplastics Uptake and Distribution

The concerns regarding microplastics and nanoplastics pollution stimulate studies on the uptake and biodistribution of these emerging pollutants in vitro. Atomic force microscopy in nanomechanical PeakForce Tapping mode was used here to visualise the uptake and distribution of polystyrene spherical microplastics in human skin fibroblast. Particles down to 500 nm were imaged in whole fixed cells, the nanomechanical characterization allowed for differentiation between internalized and surface attached plastics. This study opens new avenues in microplastics toxicity research.

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.

Bloch Surface Waves Mediated Micro-Spectroscopy

Micro-spectroscopy is a critical instrument for spectrum analysis in various applications such as chemical and biological analysis, environment detection, and hyperspectral imaging. However, current micro-spectral technique requires bulky and costly spectrometer. In this report, a new type of Bloch surface wave (BSW) based micro-spectrometer is proposed. A single silicon nanoparticle sitting on a dielectric multilayer substrate is used to excite the BSW which acts as a nanoscale unknown source. Taking advantage of the dispersion relations of BSWs, an abundant spectrally related database is formed that is useful for spectrum retrieval applications. Back-focal plane images are used to monitor the change of angular spectrum corresponding to the dispersion relationship of Bloch surface waves. Combined with an iterative algorithm, experimental retrieval of visible-range monochromatic and broadband light spectrums can be obtained. The resolution of the spectrometers can reach 2 nm across a wavelength range of 130 nm. The method in this work is CMOS compatible, enabling spectra retrieval for nanoscale radiators and can also be used to measure and retrieve the microscopic spectrum signal rapidly and timely without conventional scanning monochromator spectrometer.

Label-free identification of microplastics in human cells: dark-field microscopy and deep learning study

The development of an automatic method of identifying microplastic particles within live cells and organisms is crucial for high-throughput analysis of their biodistribution in toxicity studies. State-of-the-art technique in the data analysis tasks is the application of deep learning algorithms. Here, we propose the approach of polystyrene microparticle classification differing only in pigmentation using enhanced dark-field microscopy and a residual neural network (ResNet). The dataset consisting of 11,528 particle images has been collected to train and evaluate the neural network model. Human skin fibroblasts treated with microplastics were used as a model to study the ability of ResNet for classifying particles in a realistic biological experiment. As a result, the accuracy of the obtained classification algorithm achieved up to 93% in cell samples, indicating that the technique proposed will be a potent alternative to time-consuming spectral-based methods in microplastic toxicity research.

What have we known so far about microplastics in drinking water treatment? A timely review

Microplastics (MPs) have been widely detected in drinking water sources and tap water, raising the concern of the effectiveness of drinking water treatment plants (DWTPs) in protecting the public from exposure to MPs through drinking water. We collected and analyzed the available research articles up to August 2021 on MPs in drinking water treatment (DWT), including laboratory- and full-scale studies. This article summarizes the major MP compositions (materials, sizes, shapes, and concentrations) in drinking water sources, and critically reviews the removal efficiency and impacts of MPs in various drinking water treatment processes. The discussed drinking water treatment processes include coagulation-flocculation (CF), membrane filtration, sand filtration, and granular activated carbon (GAC) filtration. Current DWT processes that are purposed for particle removal are generally effective in reducing MPs in water. Various influential factors to MP removal are discussed, such as coagulant type and dose, MP material, shape and size, and water quality. It is anticipated that better MP removal can be achieved by optimizing the treatment conditions. Moreover, the article framed the major challenges and future research directions on MPs and nanoplastics (NPs) in DWT.

Microplastics in mangroves and coral reef ecosystems: a review

Microplastic pollution has recently been identified as a major issue for the health of ecosystems. Microplastics have typically sizes of less than 5 mm and occur in various forms, such as pellets, fibres, fragments, films, and granules. Mangroves and coral reefs are sensitive and restricted ecosystems that provide free ecological services such as coastal protection, maintaining natural cycles, hotspots of biodiversity and economically valuable goods. However, urbanization and industrial activities have started contaminating even these preserved ecosystems. Here we review sources, occurrence, and toxicity of microplastics in the trophic levels of mangrove and coral reef ecosystems. We present detection methods, such as microscopic identification and spectroscopy. We discuss mitigating measures that prevent the entry of microplastics into the marine environment.

Dark-field/hyperspectral microscopy for detecting nanoscale particles in environmental nanotoxicology research

Nanoscale contaminants (including engineered nanoparticles and nanoplastics) pose a significant threat to organisms and environment. Rapid and non-destructive detection and identification of nanosized materials in cells, tissues and organisms is still challenging, although a number of conventional methods exist. These approaches for nanoparticles imaging and characterisation both inside the cytoplasm and on the cell or tissue outer surfaces, such as electron or scanning probe microscopies, are unquestionably potent tools, having excellent resolution and supplemented with chemical analysis capabilities. However, imaging and detection of nanomaterials in situ, in wet unfixed and even live samples, such as living isolated cells, microorganisms, protozoans and miniature invertebrates using electron microscopy is practically impossible, because of the elaborate sample preparation requiring chemical fixation, contrast staining, matrix embedding and exposure into vacuum. Atomic force microscopy, in several cases, can be used for imaging and mechanical analysis of live cells and organisms under ambient conditions, however this technique allows for investigation of surfaces. Therefore, a different approach allowing for imaging and differentiation of nanoscale particles in wet samples is required. Dark-field microscopy as an optical microscopy technique has been popular among researchers, mostly for imaging relatively large specimens. In recent years, the so-called "enhanced dark field" microscopy based on using higher numerical aperture light condensers and variable numerical aperture objectives has emegred, which allows for imaging of nanoscale particles (starting from 5 nm nanospheres) using almost conventional optical microscopy methodology. Hyperspectral imaging can turn a dark-field optical microscope into a powerful chemical characterisation tool. As a result, this technique is becoming popular in environmental nanotoxicology studies. In this Review Article we introduce the reader into the methodology of enhanced dark-field and dark-field-based hyperspectral microscopy, covering the most important advances in this rapidly-expanding area of environmental nanotoxicology.

Restoration of a XVII Century’s predella reliquary: From Physico-Chemical Characterization to the Conservation Process

We report on the restoration of a XVII century’s predella reliquary, which is a part of a larger setup that includes a wall reliquary and a wooden crucified Christ, both belonging to the church of “Madre Maria SS. Assunta”, in Polizzi Generosa, Sicily, Italy. The historical/artistic and paleographic research was flanked successfully by the scientific objective characterization of the materials. The scientific approach was relevant in the definition of the steps for the restoration of the artefact. The optical microscopy was used for the identification of the wood species. Electron microscopy and elemental mapping by energy-dispersive X-ray (EDX) was successful in the identification of the layered structure for the gilded surface. The hyperspectral imaging method was successfully employed for an objective chemical mapping of the surface composition. We proved that the scientific approach is necessary for a critical and objective evaluation of the conservation state and it is a necessary step toward awareness of the historical, liturgical, spiritual and artistic value. In the second part of this work, we briefly describe the conservation protocol and the use of a weak nanocomposite glue. In particular, a sustainable approach was considered and therefore mixtures of a biopolymer from natural resources, such as funori from algae, and naturally occurring halloysite nanotubes were considered. Tensile tests provided the best composition for this green nanocomposite glue.