Μm Size Range Research Articles

Sorting and Weathering Trends of Soil at Gale Crater, Mars: Implications for Regional Pedological Processes

AbstractDetailed soil characterization at Gale crater based on in situ observations has revealed compositional trends within soils, while the physical and chemical processes underlying the compositional trends remain to be evaluated. Here we use the grain‐morphometrical and geochemical trends across the Wentworth‐classes of 48 in situ soil targets at Gale crater to evaluate underlying pedological processes and potential chemical weathering signatures. The concentration of olivine minerals within the ∼250 to ∼500 μm size range indicates the prevalence of heavy mineral sorting in a granulometric sense in Gale soils that surpasses the possible effect of the cratering‐induced mixing processes. The extent of olivine sorting in soils varies spatially and is influenced by the targets' aeolian setting. The finest portion of Gale soils (<125 μm) is likely a mixture of allochthonous sediment, globally sourced from atmospheric suspension, and autochthonous counterparts from the weathering of local rocks, while the coarser soils (>125 μm) are mostly sourced from local rocks, with possible inputs from both the unaltered parent rock of the Stimson formation and the bedrocks that have undergone diagenetic alteration. If applicable globally, this would reinforce prior inferences that even dust‐mantled regions are geochemically heterogeneous owing to a substantial fraction of soils derived from underlying lithology. The low chemical weathering intensity and coupling of mobile elements in soils suggest localized, low pH and low water‐to‐rock ratio aqueous weathering conditions under predominantly cold and arid climates, which may occur either during post‐pedogenetic alteration in soils or during the acidic alteration of source rocks.

Microplastic Aerosol Contamination in Porto (Portugal)

Microplastic pollution, particularly particles smaller than 5 mm, poses significant environmental and health risks due to their potential for inhalation and long-range transport. This study provides the first long-term assessment of airborne microplastics and fibers in Porto, Portugal, over 18 months (September 2022 to March 2024). Bi-weekly samples were collected using a Microplastic Collector NILU, which were size-fractionated into five categories (>125 μm, 125–63 μm, 63–25 μm, 25–12 μm, and 12–1.2 μm) and quantified via optical microscopy. Microplastic concentrations ranged from 26 to 1484 MPs/day/m2, while fiber concentrations varied from 14 to 646 fibers/day/m2. With a focus on the 12–1.2 μm size range due to their classifications as PM10 and PM2.5, the highest microplastic concentrations were 164 MPs/day/m2 (12–1.2 μm) and 534 MPs/day/m2 (25–12 μm). Recovery rates varied among polymers, with PP, PE-HD, and ABS showing high accuracy (75.9%) and PES significantly lower (26.5%). This study highlights the significant temporal variability in airborne microplastic and fiber pollution, correlations with meteorological parameters, and the need for ongoing monitoring and targeted mitigation strategies to address associated health risks.

Assessing new microalgae species as potential feed for bivalve spat in nursery culture

ABSTRACT Microalgae remains a primary food source for hatchery and nursery culture of juvenile bivalves. However, there is a mismatch between the characteristics of the microalgae currently used in nursery culture and the feeding abilities and nutritional requirements of juveniles of some bivalve species, such as the green-lipped mussel, Perna canaliculus. Therefore, there is a need to identify new species of microalgae for this purpose that have favourable cell size, good growth performance under culture conditions and appropriate nutritional content for juvenile bivalves by using these characteristics as primary selection criteria. In this study, the growth performance under standard culture conditions of four microalgae species (Chrysochromulina camella, Gymnodinium simplex, Pyramimonas parkeae and Stephanodiscus niagarae) which are of a sufficiently large cell size to meet the needs of juvenile mussels (i.e. 10–20 µm size range) were tested in comparison to three commonly cultured commercial species (Chaetoceros muelleri, Diacronema lutheri and Tisochrysis lutea). Results show that G. simplex, S. niagarae and the two strains of P. parkeae (P. parkeae (C) and P. parkeae (I)) can achieve similar biomass as the reference species in the intermediate (1 L) culture stages despite the large difference in cell densities. The poor growth of C. camella in F/2 media indicates a necessity of determining its appropriate culture conditions before further assessing its suitability as a nursery feed for juvenile bivalves. The proximate analysis of S. niagarae, G. simplex and P. parkeae (I) reveals nutritional profiles conducive to spat development. However, the P. parkeae (C) strain contained low carbohydrate content, suggesting inferior nutritional value compared to the P. parkeae (I) strain, showing that variants of the same species can have different biochemical composition and suggesting the former might have limited suitability for feeding in nursery culture. The findings indicate that G. simplex, S. niagarae and P. parkeae (C) hold sufficient promise as spat feed in nursery culture to warrant further testing to confirm their efficacy as live microalgal feed for bivalve spat.

Godanti bhasma (anhydrous CaSO4) induces massive cytoplasmic vacuolation in mammalian cells: A model for phagocytosis assay

Phagocytosis is an essential physiological mechanism; its impairment is associated with many diseases. A highly smart particle is required for understanding detailed sequential cellular events in phagocytosis. Recently, we identified an Indian traditional medicine named Godanti Bhasma (GB), a bioactive calcium sulfate particle prepared by thermo-transformation ofgypsum. Thermal processing of the gypsum transforms its native physicochemical properties by removing water molecules into the anhydrous GB, which was confirmed by Raman and FT-IR spectroscopy. GB particle showed a 0.5–5 µm size range and a neutral surface charge. Exposure of mammalian cells to GB particles showed a rapid cellular uptake through phagocytosis and induced massive cytoplasmic vacuolation in cells. Interestingly, no cellular uptake and cytoplasmic vacuolation were observed with the parent gypsum particle. The presence of the GB particles in intra-vacuolar space was confirmed using FESEM coupled with EDX. Flow cytometry analysis and live tracking of GB-treated cells showed particle internalization, vacuole formation, particle dissolution, and later vacuolar turnover. Quantification of GB-induced vacuolation was done using neutral red uptake assay in cells. Treatment of lysosomal inhibitors (BFA1 or CQ) with GB could not induce vacuolation, suggesting the requirement of an acidic environment for the vacuolation. In the mimicking experiment, GB particle dissolution in acidic cell-free solution suggested that degradation of GB occurs by acidic pH inside the cell vacuole. Vacuole formation generally accompanies with cell death, whereas GB-induced massive vacuolation does not cause cell death. Moreover, the cell divides and proliferates with the vacuolar process, intra-vacuolar cargo degradation, and eventually vacuolar turnover. Taken together, the sequential cellular events in this study suggest that GB can be used as a smart particle for phagocytosis assay development in animal cells.

Optimization of high-temperature thermal pretreatment conditions for maximum enrichment of lithium and cobalt from spent lithium-ion polymer batteries

Due to their increasingly high demand, lithium-ion batteries (LIBs) will encounter a scarcity of essential resources if recycling is not prioritized. The current pretreatment methods for spent LIBs used in industrial production are inefficient, costly, and hazardous. The study aimed to maximize the yield of lithium and cobalt from the black mass of spent Lithium-ion batteries through an optimized high-temperature thermal pretreatment process, which combined mechanical (direct crushing) and thermal treatments to facilitate the subsequent recovery of these valuable metals. Sieve analysis showed that direct crushing for 2 min resulted in 40.81 % of the anode material in the 4750 + 2500 μm size range, while 5 min of crushing led to a more even distribution, with 28.57 % in the smallest size range (−75 μm). Heat treatment followed by 2 min of crushing concentrated 52.38 % of the anode material in the 4750 + 2500 μm range. For the cathode material, 2 min of direct crushing distributed 24.49 % in the −2500 + 1250 μm range, while 5 min of crushing accumulated 38.80 % in the −75 μm range. Heat treatment and 2 min of crushing resulted in 56.05 % of the cathode material in the −75 μm range, indicating improved liberation. The combination of heat treatment and mechanical treatment effectively liberates and reduces the size of the active materials, resulting in a higher cumulative mass fraction of finer particles (≤630 μm). Heat treatment at 600 °C for 15 min, followed by 2 min of crushing, dissociated current collectors (Al) from the cathode material, minimized the harmful gas emissions and produced fine particles (630 μm) with minimal Al content (0.8 wt%). The optimal heat treatment condition of 600 °C for 35 min achieved complete decomposition of PVDF and enriched 73.49 wt% cobalt and 5.41 wt% lithium in the black mass, superior to previous studies.

Discrimination of Microplastics and Phytoplankton Using Impedance Cytometry.

Both microplastics and phytoplankton are found together in the ocean as suspended microparticles. There is a need for deployable technologies that can identify, size, and count these particles at high throughput to monitor plankton community structure and microplastic pollution levels. In situ analysis is particularly desirable as it avoids the problems associated with sample storage, processing, and degradation. Current technologies for phytoplankton and microplastic analysis are limited in their capability by specificity, throughput, or lack of deployability. Little attention has been paid to the smallest size fraction of microplastics and phytoplankton below 10 μm in diameter, which are in high abundance. Impedance cytometry is a technique that uses microfluidic chips with integrated microelectrodes to measure the electrical impedance of individual particles. Here, we present an impedance cytometer that can discriminate and count microplastics sampled directly from a mixture of phytoplankton in a seawater-like medium in the 1.5-10 μm size range. A simple machine learning algorithm was used to classify microplastic particles based on dual-frequency impedance measurements of particle size (at 1 MHz) and cell internal electrical composition (at 500 MHz). The technique shows promise for marine deployment, as the chip is sensitive, rugged, and mass producible.

Revisiting sustainable resources in the combustion products of alumina-rich coal: Critical metal (Li, Ga, Nb, and REY) potential of ash from the Togtoh Power Plant, Inner Mongolia, China

Coal fly ash has gained much attention as a potential alternative source for extracting critical metals such as Li, Ga, Nb, and lanthanides and yttrium (REY). This study investigates their distribution characteristics and modes of occurrence in alumina-rich fly ashes from the Togtoh Power Plant in Inner Mongolia, using various analytical methods. The objective was to provide a reference for the pre-enrichment of critical metals in fly ash. Lithium is primarily present in the glass phase, and its concentration is extremely low in the crystalline phases. Lithium is mainly concentrated in “pure” aluminosilicate glass, and is present but at a low level in Ca-rich aluminosilicate glass. Gallium is primarily present in the glass phase and in corundum, while Nb mainly exists in submicron zircon particles surrounded by Si-Al-Ca glass. Lanthanides and yttrium primarily occur in the glass phase and in crystalline phases, including an intermediate phase composed of the three end-member minerals of the gorceixite-crandallite-florencite series, as well as in monazite, crystalline forms of iron oxides and REY oxides. The Li concentrations in the alumina-rich fly ashes range from 562 to 894 μg/g for Li2O, from 43.9 to 81.9 μg/g for Ga, from 58.7 to 70.6 μg/g for Nb2O5, and from 258 to 450 μg/g for REY oxides, respectively, indicating their substantial potential for resource recovery. Especially, the 2nd row fly ash has the highest contents of these metals, allowing for direct extraction without the necessity for complex pre-processing. Physical separation can further enrich Li, Ga, Nb, and REY in the fly ash. In particular, particle size separation enriches these elements in the < 20 μm size range and magnetic separation enriches Li, Ga, Nb, and REY (except Ce) in the non-magnetic fraction. However, Ce is significantly enriched in the magnetic fraction compared to the original fly ash.

Characteristics of microplastics pollution in important commercial coastal seafood of Central Java, Indonesia

The contamination levels and characteristics of microplastics (MPs) were assessed in commercial seafood from the coastal region of Semarang, Central Java, Indonesia. This study covers milkfish (Chanos chanos), blood cockles (Anadara granosa) and green mussels (Perna viridis). Green mussels had the highest abundance (70.7 ± 48.0 particles/individual), followed by blood cockles (18.3 ± 7.3 particles/individual) and milkfish (5.9 ± 4.3 particles/individual). Fragments dominated in seafood samples (37–87.6 %), except for milkfish, which was mainly dominated by fibres (65,5 %). MPs in the 50-100 µm size range were primarily found in bivalve samples (34–40 %), while larger particles (100-1000 µm) were abundant in milkfish (53.1 %). Most MPs detected were grey in blood cockles (51 %), brown in green mussels (50 %), and black and brown in milkfish (33 %). Regarding polymer types, rubber (12–14 %), styrene copolymers (9–13 %), and cellulose (4–25 %) dominated MPs in milkfish and green mussels. The three most important polymers in blood cockles were cellulose (40 %), polyamide (20 %), and polyethylene (11 %). These findings confirm that MPs contaminate our daily diet, implying that further research is needed into the potential health risks of ingested MPs.

First release of the Pelagic Size Structure database: global datasets of marine size spectra obtained from plankton imaging devices

Abstract. In marine ecosystems, most physiological, ecological, or physical processes are size dependent. These include metabolic rates, the uptake of carbon and other nutrients, swimming and sinking velocities, and trophic interactions, which eventually determine the stocks of commercial species, as well as biogeochemical cycles and carbon sequestration. As such, broad-scale observations of plankton size distribution are important indicators of the general functioning and state of pelagic ecosystems under anthropogenic pressures. Here, we present the first global datasets of the Pelagic Size Structure database (PSSdb), generated from plankton imaging devices. This release includes the bulk particle normalized biovolume size spectrum (NBSS) and the bulk particle size distribution (PSD), along with their related parameters (slope, intercept, and R2) measured within the epipelagic layer (0–200 m) by three imaging sensors: the Imaging FlowCytobot (IFCB), the Underwater Vision Profiler (UVP), and benchtop scanners. Collectively, these instruments effectively image organisms and detrital material in the 7–10 000 µm size range. A total of 92 472 IFCB samples, 3068 UVP profiles, and 2411 scans passed our quality control and were standardized to produce consistent instrument-specific size spectra averaged to 1° × 1° latitude and longitude and by year and month. Our instrument-specific datasets span most major ocean basins, except for the IFCB datasets we have ingested, which were exclusively collected in northern latitudes, and cover decadal time periods (2013–2022 for IFCB, 2008–2021 for UVP, and 1996–2022 for scanners), allowing for a further assessment of the pelagic size spectrum in space and time. The datasets that constitute PSSdb's first release are available at https://doi.org/10.5281/zenodo.11050013 (Dugenne et al., 2024b). In addition, future updates to these data products can be accessed at https://doi.org/10.5281/zenodo.7998799.

Characterization of aerosol and its oxidative potential in a coastal semi-rural site of Southern Italy

Considering the scarce number of studies investigating the oxidative potential of PM2.5 in Italy, a measurement campaign was conducted from February 2020 to October 2020 in a coastal semi-rural site of Basilicata (Southern Italy) with the goal to characterize the fine fraction of ambient particulate matter (PM) and investigate its chemical and toxicological properties, by means of oxidative potential. Different instruments such as an automatic low-volume sampler, an aethalometer and an optical particle counter, were employed for the measurement of PM2.5 mass concentration, equivalent black carbon (eBC) concentration and absorption Ångström exponent (AAE), and particle number size distribution in 0.25–31 μm size range, respectively. 108 daily PM samples, collected on quartz fibre filters, were chemically analysed. Organic (OC) and elemental (EC) carbon content was estimated by thermo-optical transmittance technique (TOT), the concentrations of the main water-soluble ions and total elements were determined by ion chromatography and ED-XRF technique, while the oxidative potential of the water-soluble fraction was estimated through the dithiothreitol (DTT) assay. The mean value of PM2.5 mass concentration was 9.2 ± 2.5 μg/m3 and the average contribution of measured species on PM2.5 mass was 3.3% EC; 19.3% OC; 27.0% secondary inorganic aerosol (sum of SO42−, NH4+ and NO3−), and 10.2% of the other ions and elements. The OC and EC contributions to PM2.5 mass and their mean ratio (OC/EC = 6.6 ± 3.1) suggest that the site is affected by the combined contribution of traffic emissions and biomass combustion (domestic heating and agricultural activities), with the latter prevailing over the traffic, as supported by the mean AAE value of 1.3. The mean OP normalized by sampled volume, OPDTTV, was as high as 0.34 ± 0.22 nmol/min·m3, a value comparable to those recorded for PM2.5 in suburban areas of Italy. The correlation between OPDTTV and the chemical species observed in the PM2.5 samples showed a good agreement with the carbonaceous component OC (r = 0.62) and with some ions, K+ and SO42− (r = 0.60). These results identify combustion sources as the most responsible for the relatively high OPDTTV activity of PM2.5 recorded in this area.

Can water mites’ parasitism influence the number of microplastics ingested by aquatic insects?

Microplastic pollution endangers both aquatic and terrestrial ecosystems. Their spread across the food chain also endangers human health. Wastewater treatment plants (WWTPs) can be viewed as the final barrier between microplastics and the environment. In addition, it is well-known that water mites are abundant parasites in aquatic ecosystems, and nearly all insect orders with aquatic stages are considered potential hosts for at least one water mite species. However, no studies have been conducted to test the direct and indirect effects of parasites on population dynamics in freshwater ecosystems or the role of predators in shaping the behavior and life histories of aquatic organisms. Thus, this work aimed to study the seasonal abundance, distribution, composition, and risk assessment of MPs in surface water, aquatic insects (Coroxide and Notonectidae), and for the first time, water mites (Hydrachnidiae), as well as the effect of water mites’ parasitism on the number of MPs ingested by aquatic insects in two of the most polluted wastewater sites (S1 and S2) in Sohag Governorate, Egypt. The two wastewater sites receive different wastewater inputs (domestic and industrial). The results showed that the MPs abundance in surface water was higher in S2 than in S1 during the four seasons of the year, where the microplastic abundance in surface water was 2.05 ± 0.79 and 3.01 ± 0.9 particles/L in S1 and S2, respectively. Also, MPs were significantly higher in S2 in two insect taxa (Corixidae and Notonectidae) that are known to be infected by water mites. In contrast, the number of MPs was lower in S1, where water mites were absent. In addition, our results showed that adult water mites accumulated MPs. Overall, the 500–2000 µm size range was the most prevalent for both wastewater sites. Fibers were the most common MP morphotype discovered, followed by fragments. The dominant colors of MP were blue, red, and black. Furthermore, FTIR spectroscopy revealed the existence of three distinct polymers, namely polyester (PES), polypropylene (PP), and polyethylene (PE). To the best of our knowledge, this is the first study to examine the effect of water mites’ parasitism on the number of MPs ingested by aquatic organisms. However, Further research is needed to confirm our suggestion.

Erosion rate of lunar soil under a landing rocket, part 1: Identifying the rate-limiting physics

Multiple nations are planning activity on the Moon's surface, and to deconflict lunar operations we must understand the sandblasting damage from rocket exhaust blowing soil. Prior research disagreed over the scaling of the erosion rate, which determines the magnitude of the damage. Reduced gravity experiments and two other lines of evidence now indicate that the erosion rate scales with the kinetic energy flux at the bottom of the laminar sublayer of the gas. Because the rocket exhaust is so fast, eroded particles lifted higher in the boundary layer do not impact the surface for kilometers (if at all; some leave the Moon entirely), so there is no saltation in the vicinity of the gas. As a result, there is little transport of gas kinetic energy from higher in the boundary layer down to the surface, so the emission of soil into the gas is a surprisingly low energy process. In low lunar gravity, a dominant source of resistance to this small energy flux turns out to be the cohesive energy density of the lunar soil, which arises primarily from particles in the 0.3 to 3 μm size range. These particles constitute only a tiny fraction of the mass of lunar soil and have been largely ignored in most studies, so they are poorly characterized.

Spray-drying of PEI-/PPI-based nanoparticles for DNA or siRNA delivery

Spray-drying of nucleic acid-based drugs designed for gene therapy or gene knockdown is associated with many advantages including storage stability and handling as well as the possibility of pulmonary application. The encapsulation of nucleic acids in nanoparticles prior to spray-drying is one strategy for obtaining efficient formulations. This, however, strongly relies on the definition of optimal nanoparticles, excipients and spray-drying conditions. Among polymeric nanoparticles, polyethylenimine (PEI)-based complexes with or without chemical modifications have been described previously as very efficient for gene or oligonucleotide delivery. The tyrosine-modification of linear or branched low molecular weight PEIs, or of polypropylenimine (PPI) dendrimers, has led to high complex stability, improved cell uptake and transfection efficacy as well as high biocompatibility.In this study, we identify optimal spray-drying conditions for PEI-based nanoparticles containing large plasmid DNA or small siRNAs, and further explore the spray-drying of nanoparticles containing chemically modified polymers. Poly(vinyl alcohol) (PVA), but not trehalose or lactose, is particularly well-suited as excipient, retaining or even enhancing transfection efficacies compared to fresh complexes. A big mesh size is critically important as well, while the variation of the spray-drying temperature plays a minor role. Upon spray-drying, microparticles in a ∼ 3.3 – 8.5 µm size range (laser granulometry) are obtained, dependent on the polymers. Upon their release from the spray-dried material, the nanoparticles show increased sizes and markedly altered zeta potentials as compared to their fresh counterparts. This may contribute to their high efficacy that is seen also after prolonged storage of the spray-dried material.We conclude that these spray-dried systems offer a great potential for the preparation of nucleic acid drug storage forms with facile reconstitution, as well as for their direct pulmonary application as dry powder.

Modelling the effect of shape on atmospheric microplastic transport

Microplastics are particles less than 5 mm in size and are a growing scientific concern, given the potential harm caused across ecosystems as a result of the global use of plastics. Most microplastics are non-spherical in shape, however, most atmospheric modelling studies to date treat microplastics as simple spheres when assessing transport. To further understand the effects of shape and size on atmospheric microplastic transport, the HYSPLIT model was utilized to identify potential differences. It was shown that the extent of microplastic transport and deposition varied significantly by shape for particles larger than 6 μm, but for particles smaller than 6 μm, the differences were not significant. Long fibres deposited over a 32% greater area than spherical particles at the largest equivalent size of 23.5 μm. The maximum deposition area occurred for particles with an equivalent size of 4.5 μm, varying in deposition area by less than 0.25% by the shapes considered. As particles smaller than 10 μm have a large potential to cause adverse health effects and shape affects transport in the 6 μm–10 μm size range, accurately modelling the shape of atmospheric microplastic transport is crucial to determining the range and amount of deposition globally.

Pulsed laser ablation of polymer-based magnetic nanocomposites for oil spill remediation

Oil spills represent a critical environmental threat, particularly to marine ecosystems, necessitating the development of efficient and eco-friendly remediation technologies. This study explores the application of pulsed laser ablation (PLA) in fabricating polymer-based magnetic nanocomposites, with a focus on polyvinylpyrrolidone, chitosan, and methyl cellulose. These polymers, renowned for their proficiency in adsorbing pollutants from various oils, were combined with magnetite nanoparticles (NPs) in a compressed tablet form. The PLA process facilitated the generation of nanocomposites, which were subsequently collected using an external magnetic field. The chemical composition of these composites was analyzed through Fourier-transform infrared (FTIR) and Raman spectroscopy, while particle sizes were determined using the Leica Image Processing and Analysis System. The study revealed that PLA is a green, single-step, and effective technique for preparing magnetic nanocomposites, producing particles predominantly in the 400 nm–4 µm size range. Furthermore, the application of these composites in oil/water separation demonstrated with separation commencing approximately 1 s after the application of a magnetic field. These findings underscore the potential of PLA in crafting magnetic nanocomposites for the rapid and environmentally sustainable remediation of oil spills.

Investigating dental structure response to air abrasion: a finite element analysis

Air abrasion particles, propelled by a compressed air stream, remove material from the tooth’s surface. The air abrasion parameter plays an important role in removing the strains or plaque from the teeth. The research outcomes shed light on the stress distribution within dental structures using the finite element approach. Enamel, as the hardest and outermost layer of the tooth, consistently bears the highest stress levels during air abrasion procedures, regardless of whether the impact pressure is set at 80 or 100 psi. While enamel takes the initial force, it gradually transfers these forces to the dentin layer beneath, a denser but slightly less hard tissue. For abrasive particles falling within the 40 μm to 100 μm size range, an impact pressure of 80 psi is found to strike an optimal balance between effective material removal and minimizing damage to dental structures. However, when working with larger particles exceeding 100 μm, increasing the impact pressure to 100 psi becomes preferable to maintain efficiency and precision. The results of this research provide valuable guidance for enhancing dental procedures with a strong focus on patient safety and the maintenance of dental health. It underscores the importance of thoughtfully adjusting parameters like particle size and impact pressure to attain favourable treatment results while prioritizing the health and comfort of patients.

Fluorescent Graphitic Carbon Nitride (g-C3N4)-Embedded Hyaluronic Acid Microgel Composites for Bioimaging and Cancer-Cell Targetability as Viable Theragnostic.

Fluorescent graphitic carbon nitride (g-C3N4) doped with various heteroatoms, such as B, P, and S, named Bg-C3N4, Pg-C3N4, and Sg-C3N4, were synthesized with variable band-gap values as diagnostic materials. Furthermore, they were embedded within hyaluronic acid (HA) microgels as g-C3N4@HA microgel composites. The g-C3N4@HA microgels had a 0.5-20 μm size range that is suitable for intravenous administration. Bare g-C3N4 showed excellent fluorescence ability with 360 nm excitation wavelength and 410-460 emission wavelengths for possible cell imaging application of g-C3N4@HA microgel composites as diagnostic agents. The g-C3N4@HA-based microgels were non-hemolytic, and no clotting effects on blood cells or cell toxicity on fibroblasts were observed at 1000 μg/mL concentration. In addition, approximately 70% cell viability for SKMEL-30 melanoma cells was seen with Sg-C3N4 and its HA microgel composites. The prepared g-C3N4@HA and Sg-C3N4@HA microgels were used in cell imaging because of their excellent penetration capability for healthy fibroblasts. Furthermore, g-C3N4-based materials did not interact with malignant cells, but their HA microgel composites had significant penetration capability linked to the binding function of HA with the cancerous cells. Flow cytometry analysis revealed that g-C3N4 and g-C3N4@HA microgel composites did not interfere with the viability of healthy fibroblast cells and provided fluorescence imaging without any staining while significantly decreasing the viability of cancerous cells. Overall, heteroatom-doped g-C3N4@HA microgel composites, especially Sg-C3N4@HA microgels, can be safely used as multifunctional theragnostic agents for both diagnostic as well as target and treatment purposes in cancer therapy because of their fluorescent nature.

The odd couple: Caffeine and microplastics. Morphological and physiological changes in Mytilus galloprovincialis.

In recent years, the presence of pharmaceuticals and microplastics (MPs) in aquatic ecosystems has raised concerns about their environmental impact. This study explores the combined effects of caffeine, a common pharmaceutical pollutant, and MPs on the marine mussel Mytilus galloprovincialis. Caffeine, at concentrations of 20.0 μg L-1, and MPs (1 mg L-1, 35-50 μm size range), was used to mimic real-world exposure scenarios. Two hundred M. galloprovincialis specimens were divided into four groups: caffeine, MPs, Mix (caffeine + MPs), and Control. After a two-week acclimation period, the mollusks were subjected to these pollutants in oxygen-aerated aquariums under controlled conditions for 14 days. Histopathological assessments were performed to evaluate gill morphology. Cellular volume regulation and digestive gland cell viability were also analyzed. Exposure to caffeine and MPs induced significant morphological changes in M. galloprovincialis gills, including cilia loss, ciliary disk damage, and cellular alterations. The chitinous rod supporting filaments also suffered damage, potentially due to MP interactions, leading to hemocyte infiltration and filament integrity compromise. Hemocytic aggregation suggested an inflammatory response to caffeine. In addition, viability assessments of digestive gland cells revealed potential damage to cell membranes and function, with impaired cell volume regulation, particularly in the Mix group, raising concerns about nutrient metabolism disruption and organ function compromise. These findings underscore the vulnerability of M. galloprovincialis to environmental pollutants and emphasize the need for monitoring and mitigation efforts. RESEARCH HIGHLIGHTS: The synergy of caffeine and microplastics (MPs) in aquatic ecosystems warrants investigation. MPs and caffeine could affect gill morphology of Mytilus galloprovincialis. Caffeine-exposed cells had lower viability than the control group in the NR retention test. MPs and mix-exposed cells struggled to recover their volume.

A reliable method to determine airborne microplastics using quantum cascade laser infrared spectrometry

The number of studies dealing with airborne microplastics (MPs) is increasing but sampling and sample treatment are not standardized, yet. Here, a fast and reliable method to characterize MPs is presented. It involves the study of two passive sampling devices to collect atmospheric bulk deposition (wet and dry deposition) and three digestion methods (two alkaline-oxidative and an oxidative) to treat the samples. The alkaline-oxidative method based on KOH and NaClO was selected for a mild organic matrix digestion. In addition, some operational parameters of a high-throughput quantum cascade laser-based infrared device (LDIR) were optimized: an effective automatic tiered approach to differentiate fibres from particles (>90 % success in validation) and a criterion to establish positive matches when comparing an unknown spectrum against the spectral database (proposed match index > 0.85). The procedural analytical recoveries were very good for particles (82–90 %) and slightly lower for fibres (62–73 %). Finally, the amount and type of MPs deposited at a sub-urban area NW Spain were evaluated. Most common polymers were Polyethylene (PE), Polypropylene (PP) and Polyethylene terephthalate (PET). The deposition rates ranged 98–1220 MP/m2/day, ca. 1.7 % of the total collected particles. More than 50 % of the total MPs deposited were in the 20–50 μm size range, whereas fibres were mostly in the 50–500 μm size range.

Laser Ablation for Nondestructive Sampling of Microplastics in Single-Particle ICP-Mass Spectrometry.

In this work, laser ablation (LA) was characterized as a method for sampling and introducing microplastic particles (MPs) into an inductively coupled plasma (ICP) for subsequent 13C+ monitoring using an ICP-mass spectrometer operated in single-event mode. MPs of different types (PS, PMMA, and PVC) and sizes (2-20 μm) were introduced intactly. The laser energy density did not affect the particle sampling across a wide range (0.25-6.00 J cm-2). Single-shot analysis separated clustered MPs (2-7 MPs per cluster) during the LA and particle transport processes, allowing the temporally resolved analysis of the individual constituting MPs. Line scanning showed superior performance when using a small laser beam diameter combined with a high repetition rate. The 13C+ signal intensity correlated linearly (R2 >0.9945) with the absolute C mass in a 2-10 μm size range, while the use of He in the collision-reaction cell (CRC) allowed extension of the linear range to 20 μm. The LA approach generated narrower 13C+ signal distributions than the traditional solution-based approach (dry versus wet plasma conditions) and proved successful for the analysis of a mixed suspension (containing four sizes of PS MPs in a 2-5 μm size range) and for sampling MPs from PVDF and glass microfiber filters, with the latter offering a lower background.