Frequent Contamination Research Articles

A colorimetric aptasensor based on gold nanoparticles for detection of microbial toxins: an alternative approach to conventional methods

Frequent contamination of foods with microbial toxins produced by microorganisms such as bacteria, fungi, and algae represents an increasing public health problem that requires the development of quick and easy tools to detect them at trace levels. Recently, it has been found that colorimetric detection methods may replace traditional methods in the field because of their ease of use, quick response, ease of manufacture, low cost, and naked-eye visibility. Therefore, it is suitable for fieldwork, especially for work in remote areas of the world. However, the development of colorimetric detection methods with low detection limits is a challenge that limits their wide applicability in the detection of food contaminants. To address these challenges, nanomaterial-based transduction systems are used to construct colorimetric biosensors. For example, gold nanoparticles (AuNPs) provide an excellent platform for the development of colorimetric biosensors because they offer the advantages of easy synthesis, biocompatibility, advanced surface functionality, and adjustable physicochemical properties. The selectivity of the colorimetric biosensor can be achieved by the combination of aptamers and gold nanoparticles, which provides an unprecedented opportunity to detect microbial toxins. Compared to antibodies, aptamers have significant advantages in the analysis of microbial toxins due to their smaller size, higher binding affinity, reproducible chemical synthesis and modification, stability, and specificity. Two colorimetric mechanisms for the detection of microbial toxins based on AuNPs have been described. First, sensors that use the localized surface plasmon resonance (LSPR) phenomenon of gold nanoparticles can exhibit very strong colors in the visible range because of changes caused by aggregation or disaggregation. Second, the detection mechanism of AuNPs is based on their enzyme mimetic properties and it is possible to construct a colorimetric biosensor based on the3,3',5,5'-tetramethylbenzidine/Hydrogen peroxide, TMB/H2O2 reaction to detect microbial toxins. Therefore, this review summarizes the recent applications of AuNP-based colorimetric aptasensors for detecting microbial toxins, including bacterial toxins, fungal toxins, and algal toxins focusing on selectivity, sensitivity, and practicality. Finally, the most important current challenges in this field and future research opportunities are discussed.

Morphological and chemical characterization of Alternaria populations from apple fruit

Alternaria is a frequent contaminant of apple fruit, causing severe economic losses. It can produce external lesions and mouldy core, characterised by a rotten area in the apple core.In the present study, morphological and chemical characterization of Alternaria from apples was performed, evaluating differences related to agricultural practices and type of disease.A low morphological diversity was observed; most of the isolates were identified as A. tenuissima sp.-grp. (95 %). A. arborescens sp.-grp. and A. gaisen sp.-grp. were present in a proportion of 1 %, and 3 % of the isolates showed intermediate characteristics between these sp.-grps. and were identified as Alternaria sp. The chemical diversity was greater; 27 secondary metabolites were produced by the apple isolates. The most frequents were altertoxin-I (85 %), altechromone A (76 %), tentoxin (69 %), and tenuazonic acid (68 %). The alternariols were produced in a lower frequency when comparing with isolates from other crops; alternariol, 58 % and alternariol monomethyl ether, 57 %. The predominant secondary metabolite profile included compounds from different chemical families, such as dibenzopyrones, tetramic acids, perylene quinones, and cyclic tetrapeptides.A wider metabolomic capacity was observed in isolates from conventional apples when compared to those from organic fruit, with the predominance of strong producers of altertoxins and alternariols. The isolates from mouldy core showed higher ability to produce metabolites from different chemical families than those from external lesions. The wide chemical diversity of the Alternaria apple population should be considered to assess the health risk associated with apple by-products.

Implementing Catalysts into Electrospun Composite Carbon Nanofiber (CNF) Electrodes for Ammonia Production from Photoelectrocatalytic Nitrate Reduction

While novel carbon nanomaterials can serve as electrodes with exceptional electrical properties, carbon nanofibers (CNFs) merit further investigation for applications as electrodes in environmentally-relevant photoelectrocatalysis. Tunable, durable CNF structures can be easily synthesized as a convenient framework for catalyst implementation. Herein we investigate how catalysts can be integrated into carbon nanofiber mats to enhance the photoelectrocatalysis of nitrate reduction. As a frequent contaminant in agriculturally-intensive regions, the negative value of nitrate containing streams may be used to produce ammonia as a value-added product and to improve water quality in the resulting output stream. Catalysts were implemented using different methods (in situ sol gel, chemical reduction, electrochemical) on two different CNF composites (with and without titanium dioxide). We focus on copper as a catalyst due to its promising performance and economic advantage over traditional platinum group metals. After thorough characterization of the catalyst-CNF frameworks via XPS, XRD, Raman, the catalyst performance was measured by nitrate reduction product selectivity, catalyst lifetime, and Faradaic efficiency. The flexibility of CNF synthesis and catalyst implementation will provide photoelectrodes with properties desirable for the electrochemical reduction of nitrate in environmental conditions to generate valuable products. This work will help identify the types and properties of next-generation carbon composite electrode materials that are most promising for resource recovery and for improving photoelectrochemical catalytic cells purposed for drinking water treatment.

Bioenergetic Status of the Intestinal and Hepatic Cells after Short Term Exposure to Fumonisin B1 and Aflatoxin B1.

Fumonisin B1 (FB1) and aflatoxin B1 (AFB1) are frequent contaminants of staple foods such as maize. Oral exposure to these toxins poses health hazards by disrupting cellular signaling. However, little is known regarding the multifaced mitochondrial dysfunction-linked toxicity of FB1 and AFB1. Here, we show that after exposure to FB1 and AFB1, mitochondrial respiration significantly decreased by measuring the oxygen consumption rate (OCR), mitochondrial membrane potential (MMP) and reactive oxygen species (ROS). The current work shows that the integrity of mitochondria (MMP and ROS), that is the central component of cell apoptosis, is disrupted by FB1 and AFB1 in undifferentiated Caco-2 and HepG2 cells as in vitro models for human intestine and liver, respectively. It hypothesizes that FB1 and AFB1 could disrupt the mitochondrial electron transport chain (ETC) to induce mitochondrial dysfunction and break the balance of transferring H+ between the mitochondrial inner membrane and mitochondrial matrix, however, the proton leak is not increasing and, as a result, ATP synthesis is blocked. At the sub-toxic exposure of 1.0 µg/mL for 24 h, i.e., a viability of 95% in Caco-2 and HepG2 cells, the mitochondrial respiration was, however, stimulated. This suggests that the treated cells could reserve energy for mitochondrial respiration with the exposure of FB1 and AFB1, which could be a survival advantage.

Seed vitality and fungal contamination in Abies nebrodensis

Seeds of Abies nebrodensis were subjected to laboratory tests aimed to detect fungal contaminants and to obtain xenobiotic-free seedlings, by the use of different surface sterilising agents. Moreover, hot water at 60 °C was used to suppress any fungal microorganisms colonizing the inner tissues. Alternaria alternata, Aspergillus flavus and Stemphylium vesicarium were the most frequent fungal contaminants. Non-contaminated seeds showed germination values ranging from 0 to 36.4% depending on the applied sterilization protocol. Further analyses will be carried out to establish the influence of these fungi on the seed germination process and their relationship with seedlings of A. nebrodensis.

Occurrence of Mycotoxins and Toxigenic Fungi in Cereals and Application of Yeast Volatiles for Their Biological Control.

Fungal infections in cereals lead to huge economic losses in the food and agriculture industries. This study was designed to investigate the occurrence of toxigenic fungi and their mycotoxins in marketed cereals and explore the effect of the antagonistic yeast Cyberlindnera jadinii volatiles against key toxigenic fungal strains. Aspergillus spp. were the most frequent contaminating fungi in the cereals, with an isolation frequency (Fr) of 100% in maize, followed by wheat (88.23%), rice (78.57%) and oats (14.28%). Morphological and molecular identification confirmed the presence of key toxigenic fungal strains in cereal samples, including A. carbonarius, A. flavus, A. niger, A. ochraceus and A. parasiticus. Aflatoxins (AFs) were detected in all types of tested cereal samples, with a significantly higher level in maize compared to wheat, rice, oats and breakfast cereals. Ochratoxin A (OTA) was only detected in wheat, rice and maize samples. Levels of mycotoxins in cereals were within EU permissible limits. The volatiles of Cyberlindnera jadinii significantly inhibited the growth of A. parasiticus, A. niger and P. verrucosum. The findings of this study confirm the presence of toxigenic fungi and mycotoxins in cereals within the EU permissible limits and the significant biocontrol ability of Cyberlindnera jadinii against these toxigenic fungi.

A New Spatial–Temporal Depthwise Separable Convolutional Fusion Network for Generating Landsat 8-Day Surface Reflectance Time Series over Forest Regions

Landsat has provided the longest fine resolution data archive of Earth’s environment since 1972; however, one of the challenges in using Landsat data for various applications is its frequent large data gaps and heavy cloud contaminations. One pressing research topic is to generate the regular time series by integrating coarse-resolution satellite data through data fusion techniques. This study presents a novel spatiotemporal fusion (STF) method based on a depthwise separable convolutional neural network (DSC), namely, STFDSC, to generate Landsat-surface reflectance time series at 8-day intervals by fusing Landsat 30 m with high-quality Moderate Resolution Imaging Spectroradiometer (MODIS) 500 m surface reflectance data. The STFDSC method consists of three main stages: feature extraction, feature fusion and prediction. Features were first extracted from Landsat and MODIS surface reflectance changes, and the extracted multilevel features were then stacked and fused. Both low-level and middle-level features that were generally ignored in convolutional neural network (CNN)-based fusion models were included in STFDSC to avoid key information loss and thus ensure high prediction accuracy. The prediction stage generated a Landsat residual image and is combined with original Landsat data to obtain predictions of Landsat imagery at the target date. The performance of STFDSC was evaluated in the Greater Khingan Mountains (GKM) in Northeast China and the Ziwuling (ZWL) forest region in Northwest China. A comparison of STFDSC with four published fusion methods, including two classic fusion methods (FSDAF, ESTARFM) and two machine learning methods (EDCSTFN and STFNET), was also carried out. The results showed that STFDSC made stable and more accurate predictions of Landsat surface reflectance than other methods in both the GKM and ZWL regions. The root-mean-square-errors (RMSEs) of TM bands 2, 3, 4, and 7 were 0.0046, 0.0038, 0.0143, and 0.0055 in GKM, respectively, and 0.0246, 0.0176, 0.0280, and 0.0141 in ZWL, respectively; it can be potentially used for generating the global surface reflectance and other high-level land products.

Lead Nitrate Induces Inflammation and Apoptosis in Rat Lungs Through the Activation of NF-κB and AhR Signaling Pathways

Lead (Pb) is one of the most frequent hazardous air contaminants, where the lungs are particularly vulnerable to its toxicity. However, the Pb distribution and its impact on lung inflammation/apoptosis and particularly the involvement of nuclear factor kappa B (NF-κB) and aryl hydrocarbon receptor (AhR) signaling pathways in Pb-induced lung toxicity have not yet been fully investigated. Adult male Wistar albino rats were exposed to Pb nitrate 25, 50, and 100 mg/kg b.w. orally for 3 days. The histopathological changes of several rat organs were analyzed using hematoxylin and eosin staining. The concentrations of Pb ion in different organ tissues were quantified using inductive coupled plasma mass spectrometry, while gas chromatography-mass spectrometry was used to identify organic compounds. The changes in the mRNA and protein expression levels of inflammatory and apoptotic genes in response to Pb exposure were quantified by using RT-PCR and Western blot analyses, respectively. Treatment of rats with Pb for three consecutive days significantly increased the accumulation of Pb in lung tissues causing severe interstitial inflammation. Pb treatment also increased the percentage of lung apoptotic cells and modulated apoptotic genes (Bc2, p53, and TGF-α), inflammatory markers (IL-4, IL-10, TNF-α), and oxidative stress biomarkers (iNOS, CYP1A1, EphX) in rat lung tissues. These effects were associated with a significant increase in organic compounds, such as 3-nitrotyrosine and myeloperoxidase, and some inorganic elements, such as selenium. Importantly, the Pb-induced lung inflammation and apoptosis were associated with a proportional increase in the expression of NF-κB and AhR mRNAs and proteins. These findings clearly show that Pb induces severe inflammation and apoptosis in rat lungs and suggest that NF-κB and AhR may play a role in Pb-induced lung toxicity.

Quantitative Estimation of Synergistic Toxicity of Cu and Zn on Growth of Arabidopsis thaliana by Isobolographic Method.

Heavy metal is one of the most frequent soil contaminants and contaminated soils generally include numerous metals. Although exposure to multiple metals may increase the toxicity to humans and ecosystems, only additive effects are considered in the risk assessment. In this study, the synergistic effect of heavy metals (Cu and Zn) on a model plant, Arabidopsis thaliana, was quantified by the isobolographic method. The plant was cultured via the growth assay method on a plant agar containing individual heavy metals or combinations of Cu + Zn in a growth chamber. The concentration of Cu varied by eight levels from 0 to 200 μM and the concentration of Zn also varied by eight levels from 0 to 400 μM. In the combination of metals, each of the three levels of Cu (25–75 μM) and Zn (20–100 μM) were applied. After 8 days, plants were harvested for root/shoot weight and measured for leaf chlorophyll and carotenoid content. The primary and secondary root elongation of A. thaliana was estimated using image analysis to calculate total root length. The EC50 values of Cu and Zn on A. thaliana, based on the total root length, were 40.0 and 76.4 μM, respectively. When two heavy metals were administered in combination, the EC values decreased less than those of the individual metals. The average value of the combination index was 0.6, proving the synergistic toxic effect on the root growth of A. Thaliana. As a result, the isobolograhic method is a useful tool for estimating the quantitative toxic effect of chemicals on plants.

Pathogenomes and variations in Shiga toxin production among geographically distinct clones of Escherichia coli O113:H21.

Infections with globally disseminated Shiga toxin-producing Escherichia coli (STEC) of the O113:H21 serotype can progress to severe clinical complications, such as hemolytic uremic syndrome (HUS). Two phylogeographically distinct clonal complexes have been established by multi locus sequence typing (MLST). Infections with ST-820 isolates circulating exclusively in Australia have caused severe human disease, such as HUS. Conversely, ST-223 isolates prevalent in the US and outside Australia seem to rarely cause severe human disease but are frequent contaminants. Following a genomic epidemiology approach, we wanted to gain insights into the underlying cause for this disparity. We examined the plasticity in the genome make-up and Shiga toxin production in a collection of 20 ST-820 and ST-223 strains isolated from produce, the bovine reservoir, and clinical cases. STEC are notorious for assembly into fragmented draft sequences when using short-read sequencing technologies due to the extensive and partly homologous phage complement. The application of long-read technology (LRT) sequencing yielded closed reference chromosomes and plasmids for two representative ST-820 and ST-223 strains. The established high-resolution framework, based on whole genome alignments, single nucleotide polymorphism (SNP)-typing and MLST, includes the chromosomes and plasmids of other publicly available O113:H21 sequences and allowed us to refine the phylogeographical boundaries of ST-820 and ST-223 complex isolates and to further identify a historic non-shigatoxigenic strain from Mexico as a quasi-intermediate. Plasmid comparison revealed strong correlations between the strains’ featured pO113 plasmid genotypes and chromosomally inferred ST, which suggests coevolution of the chromosome and virulence plasmids. Our pathogenicity assessment revealed statistically significant differences in the Stx2a-production capabilities of ST-820 as compared to ST-223 strains under RecA-induced Stx phage mobilization, a condition that mimics Stx-phage induction. These observations suggest that ST-820 strains may confer an increased pathogenic potential in line with the strain-associated epidemiological metadata. Still, some of the tested ST-223 cultures sourced from contaminated produce or the bovine reservoir also produced Stx at levels comparable to those of ST-820 isolates, which calls for awareness and for continued surveillance of this lineage.

Nanomaterials: An alternative source for biodegradation of toxic dyes

Environment contamination is a colossal worriment across the world, owing to its detrimental and negative impact on health and ecological systems. Dyes are one of the synthetic organic chemicals that are utilised in a variety of fields, including textiles. As a result, throughout one's production and subsequently in fibre colouring, these are becoming frequent industry-contributed contaminants. Increasing globalisation of international market has presented a problem to textile sector in terms of consistency and production. Textile processors' primary concern, as the highly competitive environment and environmental standards grow more severe is about being mindful of the grade of goods and even non-toxicity of their production processes. There seems to be an immediate necessity to look for methods and technologies which are useful in removing dye colours. Even though each has benefits and weaknesses, many physical, chemical, and biological approaches were explored and used with the application being dependent on the effluent properties, technical feasibility, and cost. Several remediation technologies are already developed, but they seem to be ineffective at removing dyes completely. There is a fast growth of nanoparticles applications in the past few years which has opened up newer, innovating, highly efficient, and low-cost dyes remediation systems. Nanomaterials with large surface areas change surface characteristics and distinctive electron conducting capabilities which make them ideal candidate for the treatment of wastewater that contains dyes. In this review, we have highlighted not only the role of nanotechnology in dye remediation processes but also different types of nanomaterials that can be used for the remediation of dyes.

Attenuation of toxicity and occurrence of degradation products of the fungicide tebuconazole after combined vacuum UV and UVC treatment of drinking water

Antifungal azoles are the most frequently used fungicides worldwide and occur as active ingredients in many antifungal pharmaceuticals, biocides, and pesticides. Azole fungicides are frequent environmental contaminants and can affect the quality of surface waters, groundwater, and drinking water. This study examined the potential of combined vacuum UV (185 nm) and UVC (254 nm) irradiation (VUV/UVC) of the azole fungicide tebuconazole and the transformation product 1,2,4-trizole on degradation and changes in ecotoxicity. In vivo ecotoxicity was examined before and after UV treatment using bioassays with test organisms from different trophic levels to integrate changes in biological effect of the parent compound and the degradation products. The test battery included the luminescent bacterium Aliivibrio fischeri, the Gram-positive bacterium Bacillus subtilis, the fungus Fusarium graminearum, the green microalga Raphidocelis subcapitata, and the crustacean Daphnia magna. The combined VUV/UVC treatment of tebuconazole in drinking water efficiently degraded the parent compound at the µg/L-mg/L level and resulted in transformation products with lower toxicity than the parent compound. A direct positive correlation was observed between the applied UV dose (fluence, J/cm2), the disappearance of tebuconazole, and the decrease in ecotoxicity. The combined VUV/UVC process does not require addition of supplementary oxidants or catalysts and our study suggests that VUV/UVC-mediated photolysis of azole fungicides in water can decrease the overall toxicity and represent a potentially environmentally friendly treatment method.

The Ubiquitous Soil Terpene Geosmin Acts as a Warning Chemical.

Known as the smell of earth after rain, geosmin is an odorous terpene detectable by humans at picomolar concentrations. Geosmin production is heavily conserved in actinobacteria, myxobacteria, cyanobacteria, and some fungi, but its biological activity is poorly understood. We theorized that geosmin was an aposematic signal used to indicate the unpalatability of toxin-producing microbes, discouraging predation by eukaryotes. Consistent with this hypothesis, we found that geosmin altered the behavior of the bacteriophagous nematode Caenorhabditis elegans on agar plates in the absence of bacteria. Normal movement was restored in mutant worms lacking differentiated ASE (amphid neurons, single ciliated endings) neurons, suggesting that geosmin is a taste detected by the nematodal gustatory system. In a predation assay, geosmin and the related terpene 2-methylisoborneol reduced grazing on the bacterium Streptomyces coelicolor. Predation was restored by the removal of both terpene biosynthetic pathways or the introduction of C. elegans that lacked differentiated ASE taste neurons, leading to the apparent death of both bacteria and worms. While geosmin and 2-methylisoborneol appeared to be nontoxic, grazing triggered bacterial sporulation and the production of actinorhodin, a pigment coproduced with a number of toxic metabolites. In this system, geosmin thus appears to act as a warning signal indicating the unpalatability of its producers and reducing predation in a manner that benefits predator and prey. This suggests that molecular signaling may affect microbial predator-prey interactions in a manner similar to that of the well-studied visual markers of poisonous animal prey. IMPORTANCE One of the key chemicals that give soil its earthy aroma, geosmin is a frequent water contaminant produced by a range of unrelated microbes. Many animals, including humans, are able to detect geosmin at minute concentrations, but the benefit that this compound provides to its producing organisms is poorly understood. We found that geosmin repelled the bacterial predator Caenorhabditis elegans in the absence of bacteria and reduced contact between the worms and the geosmin-producing bacterium Streptomyces coelicolor in a predation assay. While geosmin itself appears to be nontoxic to C. elegans, these bacteria make a wide range of toxic metabolites, and grazing on them harmed the worms. In this system, geosmin thus appears to indicate unpalatable bacteria, reducing predation and benefiting both predator and prey. Aposematic signals are well known in animals, and this work suggests that metabolites may play a similar role in the microbial world.

Less impact than suspected: Dietary exposure of three-spined sticklebacks to microplastic fibers does not affect their body condition and immune parameters

Microplastic fibers are frequent anthropogenic contaminants in most aquatic environments and have consequently been detected in the digestive tract of many fish species. Upon ingestion, microplastic fibers pose risks of interference with nutrient uptake, impaired intestinal health, and as a consequence may alter growth performance and fitness. In addition, foreign particles such as fibers might cause tissue irritations and stress, and thus interfere with immune parameters. In nature, fish regularly encounter microplastic fibers as well as fiber debris from natural sources and materials. Thus, we wanted to test the potential impact of microplastic fibers on growth, organosomatic indices, and immune parameters of subadult fish and compare these to possible effects caused by natural fibers. We administered sticklebacks diets, which were supplemented with either polyester or cotton fibers (each at concentrations of 0.2 mg/g and 2 mg/g feed) or a control diet without fiber supplementation for nine weeks. Mortalities did not occur and sticklebacks grew equally well across treatments. Neither organosomatic indices nor immune parameters revealed significant differences between treatments. While natural differences between males and females were observed for some parameters, no treatment-related gender-specific effects were detected. Our results suggest that the dietary uptake of polyester fibers does not affect growth, body condition, gonad development, and immunity of sticklebacks – even at fiber concentrations higher than what can be encountered in the wild. Furthermore, virgin microplastic fibers do not seem to affect fish differently than fibers from natural origin. The present study implies that at least some species are resilient towards pollution with (virgin) microplastic fibers even at high concentrations.

Estimating Effective Porosity in Bedrock Aquifers.

Flow in many bedrock aquifers is through fracture networks. Point to point tracer tests using applied tracers provide a direct measure of time of travel and are most useful for determining effective porosity. Calculated values from these tests are typically between 10-4 and 10-2 (0.01% to 1%), with these low values indicating preferential flow through fracture and channel networks. Tracer tests are not commonly used in site investigations, and specific yield is often used as a proxy for effective porosity. The most popular methods have used centrifuge measurements, water table fluctuations, pumping tests, and packer tests. Specific yield varies substantially with the testing method. No method is as reliable as tracer testing for providing estimates of effective porosity, but all methods provide complementary insights on aquifer structure. Temporal and spatial scaling effects suggest that bedrock aquifers have hierarchical structures, with a network of more permeable fractures and channels, which are connected to less permeable fractures and to the matrix. Consequences of the low effective porosities include groundwater velocities that often exceed 100 m/d and more frequent microbial contamination than in aquifers in unconsolidated sediments. The large uncertainty over the magnitude of effective porosity in bedrock aquifers makes it an important parameter to determine in studies where time of travel is of interest.

Household Water Treatment Practice and Associated Factors in Rural Households of Sodo Zuria District, Southern Ethiopia: Community-Based Cross-Sectional Study.

Introduction:In Ethiopia, access to safe drinking water is very low, and even safe water at the point of distribution is subjected to frequent and substantial contamination during collection, transport, and storage. The purpose of this study was to assess the level of household water treatment practices and associated factors in rural households of the Sodo Zuria district, southern Ethiopia.Methods:A community-based cross-sectional study was conducted in 836 households using a multistage sampling technique. A structured and pre-tested questionnaire was used. Binary and multivariate logistic regression analysis was used.Results:The household water treatment practice was 44.1%. Households having a higher estimated monthly income, AOR = 1.5 (1.23, 3.47), older age greater than 45 years, AOR = 1.69 (1.08, 2.64), fetching water twice a day, AOR = 2.8 (1.21, 9.17), weekly washing of the water storage container, AOR = 0.3 (0.11, 0.83), and using the dipping technique to draw water from the collection jar, AOR = 1.67 (1.14, 2.42) were significant factors in the practice of household water treatment in the study.Conclusions:The household water treatment practice was low. Higher estimated monthly income, older household heads, fetching water twice per day, washing the water storage container weekly, and dipping techniques to draw water from water storage containers were significant factors of household water treatment practices. Thus, proper hygiene of water storage, and engaging the community in income-generating activities were recommended.

Isolation of High Purity Mouse Mesenchymal Stem Cells through Depleting Macrophages Using Liposomal Clodronate

BACKGROUND:The use of mouse bone marrow mesenchymal stem cells (mBMSCs) represents a promising strategy for performing preclinical studies in the field of cell-based regenerative medicine; however, mBMSCs obtained via conventional isolation methods have two drawbacks, i.e., (i) they are heterogeneous due to frequent macrophage contamination, and (ii) they require long-term culturing for expansion.METHODS:In the present study, we report a novel strategy to generate highly pure mBMSCs using liposomal clodronate. This approach is based on the properties of the two cell populations, i.e., BMSCs (to adhere to the plasticware in culture dishes) and macrophages (to phagocytose liposomes).RESULTS:Liposomal clodronate added during the first passage of whole bone marrow culture was selectively engulfed by macrophages in the heterogeneous cell population, resulting in their effective elimination without affecting the MSCs. This method allowed the generation of numerous high-purity Sca-1+CD44+F4/80− mBMSCs (> 95%) with just one passaging. Comparative studies with mBMSCs obtained using conventional methods revealed that the mBMSCs obtained in the present study had remarkably improved experimental utilities, as demonstrated by in vitro multilineage differentiation and in vivo ectopic bone formation assays.CONCLUSION:Our newly developed method, which enables the isolation of mBMSCs using simple and convenient protocol, will aid preclinical studies based on the use of MSCs.

Multitask Deep Learning Framework for Spatiotemporal Fusion of NDVI

High spatial and temporal resolution normalized difference vegetation index (NDVI) time series are indispensable for monitoring land surfaces dynamics in spatiotemporally heterogeneous areas. Spatiotemporal fusion (STF) is one of the most common methods used for producing such data. These methods require the use of one or two pairs of fine images (with fine spatial but rough temporal resolution, such as Landsat images) and coarse images [with fine temporal but rough spatial resolution, such as Moderate Resolution Imaging Spectroradiometer (MODIS)]. A coarse image at the prediction date is also required to predict the corresponding missing fine image in the time series. Recently, the proposed deep learning (DL)-based STF methods have achieved promising fusion performance but are challenged in areas with frequent cloud contamination and landcover change prediction, while they also suffer from unstable fusion performance. Moreover, current STF methods lack a quality assessment process for the fusion results. To address these limitations, in this article, we propose a multitask DL framework for STF of NDVI time series, which integrates two types of DL-based STF methods. Four experiments in two study sites were conducted to test the effectiveness of the proposed method, and the results indicate that it achieves accurate and stable fusion capable of predicting landcover changes even when image pairs obtained at long intervals are used. In addition, a fusion uncertainty estimation method is proposed, which has the potential to be used as a quality assessment metric.

Polysilsesquioxane with potent resistance to intraoral stress: Functional coating material for the advanced dental materials

Since the oral cavity is a harsh environment where various germs and chemical and mechanical stress exist simultaneously, well-organized hybrid technology should be considered in the design of cutting-edge dental materials. Although the Clear Overlay Appliance (COA) is widely used as a transparent orthodontic device, it still requires specific modifications to overcome the poor durability and frequent contamination that cause the patient's therapeutic burden. Herein, robust polysilsesquioxane (PSQ) containing quaternary ammonium cations (QACs) and long alkyl chains (LACs) in a durable siloxane matrix are reported as coating materials for the advanced COAs. The PSQ coatings are engineered to have a ladder-like structure that exhibits excellent stability under various pH and enzymatic conditions. Experiments simulating the dynamic intraoral are established to investigate the effects of PSQ coatings for the functional improvement of COA. The QACs and LACs firmly fixed to the siloxane matrix cause bacterial contact killing to prevent the contamination of COAs in the environment exposed to bacteria. The ladder-like siloxane matrix of the coating protects the COAs from intraoral abrasion forces and shearing movements with its flexible adaptability to external stresses. This study clarifies the clinical application potential of the coated COAs via in-vivo experiments using the beagle model.

Biomass-Derived Carbon Supported on Nickel Oxide for Efficient Urea Oxidation Reaction

In recent years, there has been a fast-growing trend in developing urea (CO(NH2)2) as a substitute H2 carrier in energy conversion due to its high energy density, nontoxicity, stability and non-flammability.[1] Urea, a byproduct in the metabolism of proteins and a frequent contaminant in wastewater, is an abundant compound that has demonstrated favorable characteristics as a hydrogen-rich fuel source with 6.7 wt.% in gravimetric hydrogen content.Also, there is 2-2.5 wt.% urea from mammal urine, therefore, 0.5 million tons of additional fuels will be produced per year just from human urine (240 million tons each year). Electrochemical oxidation has been recognized as an efficient strategy for urea conversion and wastewater remediation. Thus, the chemical energy harvested from urea/urine can be converted to electricity via urea oxidation reaction (UOR). Moreover, the removal of urea from water is a priority for improving drinking water quality and presents an opportunity for UOR. However, the transition of UOR from theory and laboratory experiments to real-world applications is largely limited by the conversion efficiency, catalyst cost and the feasibility of wide-spread usage.Recent studies implementing common transition metals and their oxides, particularly nickel, have found similar success while having much lower material costs. For instance, Luo et al. prepared ultrathin and porous nickel hydroxide nanosheets for efficient UOR, and found that 1.82 V (vs. RHE, Reversible Hydrogen Electrode) was needed to achieve a large current density of 298 mA cm-2.[2] However, there is still a sluggish kinetics of UOR at the anodic area owing to the multi-electron transfer and multiple gas-adsorption/desorption procedures. To address this key issue, the coordination of high surface area and, conductive materials are considered beneficial. Biomass-derived carbon materials have been increasingly implemented in electrochemical energy conversion and detection owing to their low-price, porous structure and high conductivity. Hierarchical porous activated carbons are favored in particular due to their variety in pore size and volume, the potential for modification, and synthesis from waste biomaterials. One promising material that has demonstrated notable electrochemical properties is the eggshell membrane (ESM). ESM is a thin, protein-based membrane functioning as a gas-exchange interface for the embryo within the egg to the outside world via its abundant micro- and nano-sized pores. Aside from the traditional methods of waste management, ESM has been used in the production of clean energy where it replaces coal, oil or natural gases to generate electricity through fuel cell devices. ESM collected from waste eggshells has demonstrated excellent electrochemical behavior on its own in energy storage and conversion as well an ability to be infused with different transition metal oxides for sensing purposes.In this abstract, we reported a low-cost UOR electrocatalyst (C@NiO), composed of nickel oxide nanoparticles anchored on the porous carbon derived from the biowaste eggshell membrane via hydrothermal synthesis and pyrolysis strategy[3]. Benefiting from the strong synergistic effect between nickel oxide and the porous carbon, the as-prepared electrode only needs 1.36 V versus RHE to realize 10 mA cm-2 in 1.0 M alkali solution containing 0.33 M urea, and delivers 25 mA cm-2 at 1.46 V. In addition, in the viewpoint of the theoretical calculations, its intermediate (C@NiOOH), which formed from C@NiO in alkaline solution, made this electrocatalyst possessing the ability to effectively hinder “CO2 poisoning”, as well as ensuring its superior performance for UOR.