The mechanisms of arsenic detoxification by the green microalgae chlorella vulgaris

The mechanisms of arsenic interaction with the green microalga Chlorella vulgaris (C. vulgaris) and the potential for its bio-remediation from water were investigated. This was made possible by the development of an improved arsenic extraction from C. vulgaris, leading to successful glutathione and phytochelatins (GSH/PC) complex speciation analysis with 71.1% efficiency. The response of C. vulgaris when challenged by As(III), As(V) and dimethylarsinic acid (DMA) was assessed through experiments on adsorption, efflux and speciation of arsenic (reduction, oxidation, methylation and chelation with GSH/PC). At high phosphate concentration (1.62 mM of PO4-3), poor adsorption of As(V) led to low intracellular uptake; at low phosphate concentration (3.2 μM of PO4-3), an increase in the level of free thiols was observed as well as a moderate decrease in intracellular pH with no evidence for signals of oxidative stress. Chlorella vulgaris cells did not produce any As-GS/PC complex when exposed to As(V). This may indicate that a reduction step is needed for As(V) complexation with GSH/PC. Chlorella vulgaris cells formed DMASV-GS upon exposure to DMA. The formation of this complex in vivo has only been reported once in Brassica oleracea plants. This complex is perhaps a fragment of a bigger molecule and thus part of another detoxification mechanism since its formation was not related to the concentration of DMA in media or the exposure time. It was found that As(III) triggers the formation of arsenic complexes with PC and homophytochelatins (hPC) and their compartmentalisation to vacuoles. It is the first time that, as a result of the newly developed extraction method using sonication, such intact complexes have been identified in C. vulgaris exposed to arsenic and their hPC complexes have been reported in any organism. The potential of C. vulgaris to bio-remediate arsenic from water is highly selective and effective for the more toxic As(III) (for human life) without the potential hazard to reduce As(V) to As(III). This was possible to assess because of the following empirical observations: • At low phosphate (3.2 μM of PO4-3) and in the presence of As(V), C. vulgaris are not likely to grow and be efficient at bio-remediating arsenic. • At high phosphate (1.62 mM of PO4-3) and in the presence of As(V), C. vulgaris are highly likely to grow but are not likely to be efficient at bio-remediating arsenic. However the potential to transform As(V) into more toxic As(III) is very low. • Under any phosphate concentration and in the presence of As(III), C. vulgaris has high potential to bio-remediate arsenic, by storing As(III) into the cell biomass while retaining significantly high growth rates

Exploiting the efficacy of Tyro3 and folate receptors to enhance the delivery of gold nanoparticles into colorectal cancer cells in vitro

Colorectal cancer (CRC) is the fourth most common cancer in the world. Due to its asymptomatic nature, CRC is diagnosed at an advanced stage where the survival rate is <5%. Besides, CRC treatment using chemotherapy, radiotherapy and surgery often causes undesirable side-effects. As such, gold nanoparticles (GNPs) are envisaged in the field for the diagnosis and treatment of CRC. GNPs have unique physical, chemical and electrical properties at the nanoscale which make them suitable for application in biomedicine. However, for GNPs to become clinically effective, their internalisation efficiency in cancer cells must be enhanced. Folate receptor-α (FR) is overexpressed in CRC cells wherein FR helps in the uptake of folic acid within the cells. Tyro3, a novel tyrosine kinase receptor, drives cell proliferation and its overexpression is correlated with poor prognosis in CRC. Their upregulated expression in CRC cells relative to normal cells makes them an ideal target for GNPs using active targeting. Therefore, in this study receptors FR and Tyro3 were simultaneously targeted using specific antibody-coated GNPs in order to enhance the uptake and internalisation of GNPs in CRC cells in vitro. Four different types of coated-GNPs were synthesised GNPs-PEG, GNPs-anti-FR, GNPs-anti-Tyro3 and GNPs-anti-(FR + Tyro3) and incubated (0–50 ng) with three CRC cell lines namely CRL1790, CRL2159 and HCT116. Simultaneous targeting of these receptors by GNPs-anti-(FR + Tyro3) was found to be the most effective in internalisation in CRC cells compared with GNPs targeted singly to FR or Tyro3 (p <0.05). Besides this, results show that Tyro3 mediated similar internalisation efficacy to FR (p <0.05) in CRC cells using ICP-OES

Characterization of industrially pre-treated waste printed circuit boards for the potential recovery of rare earth elements

Rare earth elements (REE) are classified as critical raw materials and the environmental impact of mining them is of growing concern. The recovery of REE from electronic waste (e-waste) could offer a more sustainable practice. Waste printed circuit boards (WPCBs) are an important resource in the e-waste stream due to their content of valuable materials. However, data regarding the concentration and distribution of REE in WPCBs is very limited. The aims of this research were: (a) to analyse the chemical composition of comminuted WPCBs prior to processing (industrially pre-treated) with emphasis on REE, and (b) to determine the distribution of REE and other metals in different size fractions of the pre-treated WPCBs. The samples were supplied by commercial e-waste recycling companies, which makes them representative of the e-waste processing industry in the UK. Correlation between elemental concentrations and particle size was analysed using Spearman’s rank correlation. Most REE concentrations were inversely correlated to the particle size. Concentrations of Y, La and Gd were found up to a thousand times higher in the smaller particle size compared with coarser particles. However, most of base metals including Cu, Sn, Pb and Zn did not show this trend. The present study highlights the occurrence of REE in comminuted WPCBs, and fine fractions as potential sources of these critical elements, currently not recovered during recycling process. A cost-effective sieving step is proposed to enrich the REE content for further recovery, prevent the possible loss of REE and maximize the total material recovered from WPCBs

Characterisation of “flushable” and “non-flushable” commercial wet wipes using microRaman, FTIR spectroscopy and fluorescence microscopy: to flush or not to flush

The introduction to the market of wet wipes, advertised and labelled as “flushable”, has been the subject of controversy due to their perceived potential to block sewer systems as observed with other non-woven cloths such as traditional non-flushable wipes. Non-woven cloths that enter wastewater systems can find their way into the aquatic environment via wastewater effluents and it has been suggested that the breakdown of these fabrics can release materials such as microplastics into the environment. Worldwide research has revealed the alarming number of aquatic organisms affected by the presence of plastic debris in the aquatic environment harbouring a potential risk to humans through the introduction of microplastics into the food chains. However, the actual material composition of flushable wipes, their fate and impacts in the aquatic environment have not yet been scientifically studied. This paper investigates the fibre composition of flushable and non-flushable wipes, specifically with regard to synthetic polymer material, using Fourier transform infrared (FTIR) and microRaman spectroscopy along with fluorescence microscopy. The study demonstrated the presence of polyester (polyethylene terephthalate, (PET)), high-density polyethylene (HDPE) and polyethylene/vinyl acetate (PEVA/EVA) in some flushable wipes and PET in all non-flushable. Other polymers such us polypropylene (PP), low-density polyethylene (LDPE), expanded polystyrene (EPS) and polyurethane (PU) were also identified as potential components in the flushable material. Hence, commercially available wet wipes labelled as flushable could also be considered as a possible source of microplastic fibres in the wastewater streams and, if not retained, in the environment

The mechanisms of arsenic bioremediation from water by the green microalgae Chlorella vulgaris

The presence of arsenic (As) in drinking water is a major global public health issue. Chlorella vulgaris (C.vulgaris) is a common green alga that tolerates high levels of As. Focused sonication was used to extract previously unidentified As-GS/PC complexes from C. vulgaris and their integrity was confirmed by HPLC online with simultaneous HR-ICP-MS and ES-MS/MS detection. The response of C. vulgaris when challenged with As(III), As(V) and dimethylarsinic acid (DMA) was assessed through experiments on toxicity, adsorption, efflux, speciation of arsenic (reduction, oxidation and chelation with GSH/PC) and compartmentalisation (flow cytometry). C. vulgaris cells did not produce any As-GS/PC complexes when exposed to As(V) which may indicate that a reduction step is needed for As(V) complexation with GSH/PC. Cells formed DMASV-GS upon exposure to DMA, but this is not part of a detoxification mechanism. It was found that As(III) triggers the formation of arsenic complexes with PC and homophytochelatins (hPC) and their compartmentalisation in vacuoles. The potential of C. vulgaris to bio-remediate arsenic from water is highly selective for the more toxic As(III) (for human life) without the potential hazard to reduce As(V) to As(III)

Heparan sulfate disaccharide measurement from biological samples using pre-column derivatization, UPLC-MS and single ion monitoring

Glycosaminoglycans are a heterogeneous family of linear polysaccharides comprised of repeating disaccharide subunits that mediate many effects at the cellular level. There is increasing evidence that the nature of these effects is determined by differences in disaccharide composition. However, the determination of GAG disaccharide composition in biological samples remains challenging and time-consuming. We have developed a method that uses derivatization and selected ion recording and RP-UPLCMS resulting in rapid separation and quantification of twelve heparin/heparin sulfate disaccharides from 5 μg GAG. Limits of detection and quantitation were 0.02–0.15 and 0.07–0.31 μg/ml respectively. We have applied this method to the novel analysis of disaccharide levels extracted from heparan sulfate and human cancer cell lines. Heparan sulfate disaccharides extracted from biological samples following actinase and heparinase incubation and derivatized using reductive amination with 2-aminoacridone. Derivatized disaccharides were analyzed used UPLC-MS with single ion monitoring. Eight HS disaccharide subunits were separated and quantified from HS and cell lines in eleven minutes per sample. In all samples the most abundant subunits present were the unsulfated ΔUA-GlcNAc, ΔUA-GlcNAc,6S and ΔUA,2S-GlcNS,6S. There was considerable variation in the proportions and concentrations of disaccharides between different cell lines. Further studies are needed to examine the significance of these differences

Enhanced determination of As-phytochelatin complexes in Chlorella vulgaris using focused sonication for extraction of water-soluble species

The most challenging areas in the analysis of As–GS/PC complexes are their extraction from small amounts of biological material and the maintenance of their stability during HPLC separation. Focused sonication was used to extract these complexes from Chlorella vulgaris and the integrity of such complexes was determined by HPLC online with simultaneous HR-ICP-MS and ES-MS/MS detection. Water soluble arsenic species were extracted with an improved 71.1% (SE 0.78) efficiency and much reduced extraction times (30 s) allowing the determination of unstable arsenic phytochelatin (PC) and glutathione (GS) species in small biomass making the method particularly well-suited for cell cultures. Here, it was found that C. vulgaris produces the following intact phytochelatins and homo-phytochelatins (with Ala and desGly instead of Gly) complexes when cells are exposed to As(III): As(III)–PC2, GS–As(III)–PC2, As(III)–(PC2)2, MMA(III)–PC2, As(III)–PC3, As(III)–PC4, As(III)–γ-(Glu–Cys)3–Ala, GS–As(III)–γ-(Glu–Cys)2–Ala, As(III)–γ-((Glu–Cys)2)2–Ala, MMA(III)–γ-(Glu–Cys)2–Ala, As(III)–γ-(Glu–Cys)2, GS–As(III)–γ-(Glu–Cys)2. When the alga was exposed to DMA, only DMASV–GS was found. In contrast, cells did not produce any complex when exposed to As(V). It is the first time that, as a result of the newly developed extraction method using sonication, such complexes have been identified in Chlorella vulgaris exposed to arsenic and their intact arsenic homo-phytochelatins have been reported in any organism

Release of microplastic fibres and fragmentation to billions of nanoplastics from period products: preliminary assessment of potential health implications

Health effects related to the plastic content of disposable period products have not been recognized or scientifically addressed. To begin to understand their potential impact on the environment and human health, this study employed standardised in vitro tests (Syngina), infrared spectroscopy (FTIR), confocal Raman microscopy, scanning electron microscopy (FEG-SEM) and nanoparticle tracking analysis (NTA) to characterize the bulk chemical composition of different components in period products, and quantified the amount of fibres released using in vitro experiments, and measured their fragmentation into smaller particles (nanoplastics) under conditions that mimic vaginal fluids. It was found that 12 out of 24 of the tested products contain synthetic polymers (plastics) that would be in direct contact with the vaginal wall when in use. Many of the products released fibres during in vitro tests and also fragmented to release up to 17 billion nanoplastics per tampon. These micro fibres and nanoplastics could be released into the environment upon disposal. The health implications within the body are unknown, but due to the large quantity of nano size plastics being released, public health concern could manifest in three ways: from the nanoplastics themeselves, from release of contaminants adsorbed to the nanoplastics and finally, from leaching of additives associated with the production of the plastics

Effect of anthropogenic pollution on the fitness of tetracycline sensitive Shigella flexneri in Thames river water

Urban rivers may be source of antibiotics contamination that could support spread of antibiotic resistant bacteria (ARB) to the population. It is important to understand to what extent the presence of pollutants in urban rivers influences fitness of ARB. In an exercise to estimate this contribution, microcosms were generated from Thames river (London, UK) from different locations: upstream and downstream the city center. The concentration of the polycyclic aromatic hydrocarbons (PAHs) benzo(a)pyrene, pyrene and phenantrene was found to be 128, 171 and 128 times higher in downstream sector when compared to upstream sector, respectively. Filtered microcosms for each sector were enriched with tetracycline at lethal (10 μg/mL) and sub-lethal (10 ng/mL) concentrations and the fitness of an isogenic pair of Shigella flexneri 2a YSH6000 (tetR) and S. flexneri 2a 1363 (tetS) was then measured. In the presence of selective pressure in upstream microcosms, the resistant strain outcompeted the sensitive one, as expected. In contrast, sensitive S. flexneri tetS was found to significantly compete with resistant S. flexneri tetR at lethal concentrations of tetracycline in downstream microcosms, where levels of PAHs were the highest. Further experiments showed that PAHs rendered the resistant S. flexneri tetR ∼20% more sensitive to tetracycline. Sensitive S. flexneri tetS strain was able to persist at lethal concentration of tetracycline in downstream microcosms, at higher concentrations of PAHs. Our findings suggest that in a polluted river sensitive S. flexneri cells may still thrive in presence of selective pressure. Fitness tests provide an additional tool to measure bioavailability