Validated method for polystyrene nanoplastic separation in aqueous matrices by asymmetric-flow field flow fraction coupled to MALS and UV-Vis detectors

Plastics with nanosize (nanoplastics, NPLs) must be characterized, since they can be toxic or act as carriers of organic and inorganic pollutants, but there is a lack of reference materials and validated methods in the nanosize range. Therefore, this study has focused on the development and validation of a separation and size characterization methodology of polystyrene latex nanospheres, by using an asymmetric-flow field flow fraction system coupled to multi-angle light scattering and ultraviolet-visible detectors (AF4-MALS-UV). Hence, this work presents a fully validated methodology in the particle size range 30 to 490 nm, with bias between 95 and 109%, precision between 1 and 18%, LOD and LOQ below 0.2 and 0.3 µg respectively, except for 30-nm standard, for both detectors, and showing stable results for 100 analyses.

Discriminating the origin of calcium oxalate monohydrate formation in kidney stones via synchrotron microdiffraction

Nephrolithiasis is a multifactor disease that produces nephrolites in the kidneys. Calcium oxalate hydrate (dihydrated, COD, or monohydrated, COM) stones are the most common ones with more than sixty percent incidence worldwide. They are related to different pathologies, COD with hypercalciuria and COM with hyperoxaluria. COD is an unstable species and transforms into COM (herein named TRA to distinguish the origin of the monohydrated species). TRA and COM are chemically and crystallographically identical leading to misdiagnosis and recurrence increase. In the current study, the composition and crystalline structures of several calcium oxalate stones, classified by morpho-constitutional analysis, were examined by IR and synchrotron through-the-substrate micro-X-ray diffraction (tts-μXRD). Both IR and linear diffractogram studies were able to distinguish between the monohydrated and dihydrated phases but not between COM and TRA, as expected. The analysis of 2D diffraction patterns revealed that TRA showed a lower degree of crystallinity and less texture with respect to COM which can be used as a signature to distinguish between the two. This study confirms that despite the subtle differences between COM and TRA, the origin of the monohydrate oxalates can be unraveled using tts-μXRD. This valuable information should be taken into account in order to improve patients' diagnosis and reduce recurrence by considering and treating the origin of the formed stones.

Comparative evaluation of chemical composition and biological activities of tropical fruits consumed in Manaus, central Amazonia, Brazil

Fruits are widely recognized as sources of biologically active metabolites, such as antioxidant compounds. In this context, fruits commonly consumed in the central Amazonia, especially in its biggest metropolis (Manaus - AM/Brazil), are attractive as potential sources of antioxidant compounds related to biological activities. Most of such fruits are still poorly studied and/or remain unknown outside the Amazon region. Therefore, this study aims to investigate nine fruits (abiu, cubiu, biribá, breadfruit, genipap, peach palm, murici, soursop, and umari) regarding their chemical composition (fixed and volatile), reducing capacity, antioxidant activity, enzyme inhibition, and cytotoxicity. Determination of small organic acids, hydroxycinnamic acids, flavan-3-ols and flavonoid aglycones was done by HPLC-MS/MS, whereas determination of volatile organic compounds (VOCs) was done by HS-SPME/GC-MS. Reducing capacity was determined by the Folin-Ciocalteu method, and antioxidant activities were evaluated by DPPH, ABTS, and H-ORAC_FL assays. In vitro activities regarding inhibition of enzymes were tested for α-glucosidase, lipase, and α-amylase, and anti-glycation activities were evaluated for methylglyoxal and fructose. Cytotoxicity of fruit extracts was evaluated by cell viability of human fibroblast cell line (MRC-5). A total of 16 antioxidant compounds and 139 VOCs were determined, whose profiles were unique for each studied fruit. Total phenolic contents as well as antioxidant activities found herein were similar or even higher than those reported for several traditional fruits. Some of fruit extracts were able to inhibit α-glucosidase and glycation in methylglyoxal and fructose models, whereas none of them was active for lipase and α-amylase. All of the fruit extracts showed to be non-cytotoxic to MRC-5 cell line.

Calcium oxalate kidney stones, where is the organic matter?: A synchrotron based infrared microspectroscopy study

Kidney stones are collections of microcrystals formed inside the kidneys, which affect 6% to 12% of the population worldwide, with an increasing recurrence (50%-72%) after the first episode. The most abundant type is calcium oxalate (66%), described as monohydrated (COM) and dihydrated (COD). An issue in their chemistry is the transformation process of the metastable specie (COD) into the stable one, which is chemically, and in appearance, monohydrated. Since the origin of these species is different, it is important to differentiate between the transformation stage (and what stabilize COD) to understand the physiopathology and prevent the patients' recurrence. This work focuses on the organic matter distribution along these nephroliths by synchrotron radiation-based infrared microspectroscopy. Differences in the asymmetric stretching of the aliphatic hydrocarbons suggest that lipids may participate in the stabilization of COD and as inhibitors of COM formation/development; however, the presence of proteins in the nucleus could indicate a promoting role.

Physico-chemical characterization of playground sand dust, inhalable and bioaccessible fractions

Dust is a mixture of natural and anthropogenic particles originated from multiple sources, which can represent an hazard for human health. Playgrounds are a site of particularly concern, due to sand dust ingestion by toddlers and inhalation. In this study, 37 sands used in public playgrounds in the city of Barcelona were physico-chemically characterized also in relation to routine maintenance activities such as disinfection and sand renewal. The analyzed sands show a felsic mineralogy dominated by Na-feldspar, quartz, and, to a lesser extent, K-feldspar, with minor amounts of clay minerals, carbonates and hematite. Particle fractions below 10, 2.5 and 1 μm represent, on average, 0.65%, 0.17% and 0.07% of bulk volume, respectively, although, due to the human grinding, these initial fractions increased every year by a 18%, 5% and 2% respectively. Disinfection of sands effectively reduced only the NH₄⁺ concentration, among inorganic species. The average metal content was anthropogenically enriched, with respect to the upper continental crust, only for Sb and As. Both elements show high spatial variation indicating local sources such as road traffic for Sb (contributing mostly to the total concentration), and industry for As (also contributing with highly bioaccessible Sb, Cu and Zn). A clear inverse relationship between total concentrations of some elements and their leachable (Sb) and bioaccessible (Sb and Cr) fractions is observed. The most bioaccessible elements were Ca > Ni > Cu > Sr > Cd > Pb, all above the 25% of the total concentration. Bioaccessibility was higher for the carbonate-bearing particles and for the anthropic emitted metals (>50% of Ba, Cu, K, Pb and Zn).