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

Rapid detection of microplastics and nanoplastics in seconds by mass spectrometry

Microplastics (MPs) and nanoplastics (NPs) are pervasive pollutants and their analyses by traditional mass spectrometric methods require time-intensive sample preparation (e.g., extraction, digestion, and separation). This study presents a rapid and novel method for detecting MPs and NPs using flame ionization mass spectrometry (FI-MS) in which a dried sample (e.g., powder, soil and tissue) is directly burnt or heated with a flame in front of the MS inlet. FI-MS enables decomposition and ionization of various plastics such as polyethylene terephthalate (PET) and polystyrene (PS), allowing for analysis to be completed as fast as 10 seconds per sample. As a demonstration of application of this technique, PET contaminants in 1 L of bottled water or in 0.65 L of apple juice contained in plastic bottles were quickly detected from a filter paper after sample filtration and brief drying. A 0.89 mg soil sample spiked with 6000 ppm PET microplastics was measured to contain 4.98 µg of PET (5595 ppm, quantitation error: 6.8 %). Strikingly, PS nanoplastics (200 nm size) in mouse placentas were successfully identified and quantified, highlighting the method's ability to analyze biological tissue without tedious sample preparation. Overall, this study demonstrates the high potential of FI-MS for real-world sample analysis of MPs and NPs in environmental, biological, or consumer product samples.

Determination of polystyrene nanospheres and other nanoplastics in water via binding with organic dyes by capillary electrophoresis with laser-induced fluorescence detection

The purpose of this research work was to develop a new method for the quantitative analysis of water samples containing nanoplastics in the presence of microplastics and other colloidal particles. Our approach involved a mixture of fluorescent organic dyes that was added to each water sample for binding with the target nanoplastics. Binding was proven by zeta potential measurements that revealed the point of zero charge shifting from pH 4 for polystyrene nanoparticles, to pH 6.13 after binding with the dye mixture. Centrifugation effectively separated the free dyes from all dye-bound particles in the heterogeneous mixture, thus eliminating any potential interference. Electrokinetic injection of the free dyes in the supernatant allowed efficient separation by capillary electrophoresis (CE), for accurate quantitation individually with laser-induced fluorescence detection. A diode laser was operated at λex of 450 nm to induce fluorescence from the dyes, and an optical interference filter to collect only emission photons with λem of 520 nm. The fluorescence peak intensity decreased for each dye, thereby determining the total binding activity of all plastics and other particles. This new method enables high-throughput screening of water samples for nanoplastics, based on their fast binding with organic dyes in 5 min, rapid analytical separation of dyes by capillary electrophoresis within 10 min, and instantaneous fluorescence intensity measurement of individual dye peaks. Binding percentages as high as 149(±2) %/μg of 9.5-nm polystyrene nanoparticles were attained when using a concentration of 125 μg/mL for each dye. The binding mechanism was mainly attributed to hydrophobic interaction and modified by electrostatic forces. Binding of the four dyes with polystyrene microparticles, casein micelles, and transition metal oxide nanoparticles was verified to demonstrate minimal interference. The method was successfully applied to rapid testing of water samples from various sources, ranging from drinking fountains and household faucets to flowing rivers. The method also applied to a decontamination study wherein a removal of 94 % polystyrene nanospheres (diameter = 80 nm) was achieved by adding only 20 mg of casein powder into 1.6 mL of water containing 36 mg of the nanoplastics initially.

Mechanisms Underlying the Size-Dependent Neurotoxicity of Polystyrene Nanoplastics in Zebrafish

Nanoplastics (NPs) are ubiquitous in the environment, posing significant threats to biological systems, including nervous systems, across various trophic levels. Nevertheless, the molecular mechanisms behind the size-dependent neurotoxicity of NPs remain unclear. Here, we investigated the neurotoxicity of 20 and 100 nm polystyrene NPs (PS-NPs) to zebrafish. Utilizing molecular dynamics simulations and complementary methods, we discovered that PS-NPs initiated neurotoxicity by promoting dimerization of the toll-like receptor 4/myeloid differentiation-2 (TLR4/MD-2) complex. This process involves the binding of PS-NPs to the hydrophobic pocket of MD-2, which induced the flipping of Phe-126 toward the dimer interface and the bending of the C-terminal domain of TLR-4, bringing the two domains into close proximity. Thereafter, the astrocytes and microglia were activated, initiating a cascade of events that include neuroinflammation, central nervous system cell apoptosis, inhibition of motor neuron development, and ultimately alteration of the swimming behavior of zebrafish. Further, 20 nm PS-NPs elicited more severe neurotoxicity than 100 nm PS-NPs, attributed to their higher accumulation in the brain as determined through 14C-labeled PS-NPs and more effective interaction with the TLR4/MD-2 complex. Overall, our study uncovers the mechanisms underlying the size-dependent neurotoxicity of NPs, which merit attention during their risk assessment and regulation.

The Effects of Nanoplastics on the Dopamine System of Cerebrocortical Neurons

Nanoplastics (NPx) can enter living organisms, including humans, through ecosystems, inhalation, and dermal contact and can be found from the intestine to the brain. However, it is unclear whether NPx accumulates and affects the dopamine system. In this study, we investigated the effects of NPx on the dopamine system in cultured murine cerebral cortex neurons. Cultured cerebrocortical neurons were treated with 100 nm NPx at the following concentrations for 24 h: 1.896 × 105, 3.791 × 106, 7.583 × 107, 1.571 × 109, 3.033 × 1010, and 3.033 × 1011 particles/mL. Dopamine-associated proteins were analyzed using immunofluorescence staining. NPx treatment induced its accumulation in neurons in a dose-dependent manner and increased the levels of dopamine receptors D1 and D2 and their co-expression. However, NPx treatment did not affect the levels of other dopamine receptors, dopamine transporters, tyrosine hydroxylase, and microtubule-associated protein 2, or synaptophysin in neuronal structures. This study demonstrated that NPx is a potential modulator of the dopamine system via its receptors rather than its synthesis and reuptake in neurons and may be associated with dopamine-based psychiatric disorders.

Genotoxic and neurotoxic potential of intracellular nanoplastics: A review

Plastic waste comprises polymers of different chemicals that disintegrate into nanoplastic particles (NPLs) of 1-100-nm size, thereby littering the environment and posing a threat to wildlife and human health. Research on NPL contamination has up to now focused on the ecotoxicology effects of the pollution rather than the health risks. This review aimed to speculate about the possible properties of carcinogenic and neurotoxic NPL as pollutants. Given their low-dimensional size and high surface size ratio, NPLs can easily penetrate biological membranes to cause functional and structural damage in cells. Once inside the cell, NPLs can interrupt the autophagy flux of cellular debris, alter proteostasis, provoke mitochondrial dysfunctions, and induce endoplasmic reticulum stress. Harmful metabolic and biological processes induced by NPLs include oxidative stress (OS), ROS generation, and pro-inflammatory reactions. Depending on the cell cycle status, NPLs may direct DNA damage, tumorigenesis, and lately carcinogenesis in tissues with high self-renewal capabilities like epithelia. In cells able to live the longest like neurons, NPLs could trigger neurodegeneration by promoting toxic proteinaceous aggregates, OS, and chronic inflammation. NPL genotoxicity and neurotoxicity are discussed based on the gathered evidence, when available, within the context of the intracellular uptake of these newcomer nanoparticles. In summary, this review explains how the risk evaluation of NPL pollution for human health may benefit from accurately monitoring NPL toxicokinetics and toxicodynamics at the intracellular resolution level.

Fluorescent labeling of micro/nanoplastics for biological applications with a focus on "true-to-life" tracking

The increased environmental presence of micro-/nanoplastics (MNPLs) and the potential health risks associated with their exposure classify them as environmental pollutants with special environmental and health concerns. Consequently, there is an urgent need to investigate the potential risks associated with secondary MNPLs. In this context, using "true-to-life" MNPLs, resulting from the laboratory degradation of plastic goods, may be a sound approach. These non-commercial secondary MNPLs must be labeled to track their presence/journeys inside cells or organisms. Because the cell internalization of MNPLs is commonly analyzed using fluorescence techniques, the use of fluorescent dyes may be a sound method to label them. Five different compounds comprising two chemical dyes (Nile Red and Rhodamine-B), one optical brightener (Opticol), and two industrial dyes (Amarillo Luminoso and iDye PolyPink) were tested to determine their potential for such applications. Using commercial standards of polystyrene nanoplastics (PSNPLs) with an average size of 170 nm, different characteristics of the selected dyes such as the absence of impact on cell viability, specificity for plastic staining, no leaching, and lack of interference with other fluorochromes were analyzed. Based on the overall data obtained in the wide battery of assays performed, iDye PolyPink exhibited the most advantages, with respect to the other compounds, and was selected to effectively label "true-to-life" MNPLs. These advantages were confirmed using a proposed protocol, and labeling titanium-doped PETNPLs (obtained from the degradation of milk PET plastic bottles), as an example of "true-to-life" secondary NPLs. These results confirmed the usefulness of iDye PolyPink for labeling MNPLs and detecting cell internalization.

Nanoplastic at environmentally relevant concentrations induces toxicity across multiple generations associated with inhibition in germline G protein-coupled receptor CED-1 in Caenorhabditis elegans

Nanoplastics at environmentally relevant concentrations (ERCs) could cause transgenerational toxicity on organisms. Caenorhabditis elegans is an important model for the study of transgenerational toxicology of pollutants. Nevertheless, the underlying mechanisms for the control of transgenerational nanoplastic toxicity by germline signals remain largely unclear. In C. elegans, exposure to 1-100 μg/L polystyrene nanoparticle (PS-NP) decreased expression of germline ced-1 encoding a G protein-coupled receptor at parental generation (P0-G). After PS-NP exposure at P0-G, transgenerational decrease in germline ced-1 expression could be detected. Meanwhile, the susceptibility to transgenerational PS-NP toxicity was observed in ced-1(RNAi) animals. After PS-NP exposure at P0-G, germline RNAi of ced-1 increased expressions of met-2 and set-6 encoding histone methylation transferases. The susceptibility of ced-1(RNAi) to transgenerational PS-NP toxicity could be inhibited by RNAi of met-2 and set-6. Moreover, in PS-NP exposed met-2(RNAi) and set-6(RNAi) nematodes, expressions of ins-39, wrt-3, and/or efn-3 encoding secreted ligands were decreased. Therefore, our results demonstrated that inhibition in germline CED-1 mediated the toxicity induction of nanoplastics at ERCs across multiple generations in nematodes.

Specific spectral sub-images for machine learning evaluation of optical differences between carbon ion and X ray radiation effects

Advances in radiotherapy, particularly the exploration of alternative radiation types such as carbon ions have updated our understanding of its effects and applicability on chondrosarcoma cells. Here we compare the optical effects produced by carbon ions (CI) and X-rays (XR) radiations on chondrosarcoma cells nuclei and set an automated method for evaluating the radiation-induced alterations without the need of chemical marking. Hyperspectral images (HSI) of SW1353 chondrosarcoma line carry detectable optical changes of the cells irradiated either with CI or XR compared to non-irradiated ones (REF). The differences between the spectral profiles of CI, XR and REF nuclei classes led to partitioning the HSIs into spectral sub-images. The changes are detected by support vector machine (SVM) classifiers whose performances are evaluated by the most used point metrics: sensitivity (SEN), accuracy (ACC), and precision (PREC), applied on spatial feature values. Specific interaction mechanisms by radiation type reveal distinct subintervals where HSIs changes are more prominent, and the classifiers perform at best. For CI the best classifiers are obtained for sub-images in the interval (424-436 nm), while for XR the best classifiers are obtained for sub-images in the interval (436-445 nm). The classifiers work better with texture features than roughness features in both cases. The classifier with the best SEN point metric in the testing phase is the most suitable to measure the irradiation efficiency irrespective of the radiation type. The altered nuclei are easier to discriminate when irradiated with CI than with XR. The study proves that SVM with optical data offers a rapid, automated, and label-free method for evaluating radiation-induced alterations in chondrosarcoma nuclei, thereby enabling effective analysis of extensive data.

Column coded scanning aperture hyperspectral imaging system

The line scanning hyperspectral imaging system (LS-HIS), which relies on a mechanical slit or spatial light modulation device for single channel spatial scanning, is widely used in various fields such as biomedical imaging and remote sensing. However, in scenes that require low light illumination, a decrease in luminous flux will increase exposure time, leading to a significant decrease in scanning efficiency and signal-to-noise ratio (SNR). To address this issue, we present a flexible column coded scanning aperture hyperspectral imaging system (CCSA-HIS) using a spatial light modulator digital micromirror device (DMD). By introducing the concept of multiplex and constructing a multiplexing encoding matrix, we form a one-dimensional multi-column coded scanning aperture, which greatly improves scanning efficiency. Experimental comparisons demonstrate that this approach achieves higher SNR and equivalent spatial and spectral resolution in significantly less sampling time compared to LS-HIS. In short, our scheme provides a new imaging technology for the field of hyperspectral imaging with good theoretical value and engineering significance.