Philippine Pili (Canarium ovatum, Engl.) varieties as source of essential minerals and trace elements in human nutrition

Publication date: June 2018
Source:Journal of Food Composition and Analysis, Volume 69
Author(s): Cristopher G. Millena, Rosario S. Sagum
Macro and micro mineral profiles as well as potential toxic metals of both pulp and kernel of seven Pili nut (Canarium ovatum) varieties were established. Further, bioavailability was assessed through in vitro method simulating gastric and intestinal condition. Quantification was done using Microwave Plasma-Atomic Emission Spectrometry. Major macro minerals in pulp are K and Ca while K, P, and Mg for the kernel. Pili nut also contains Na, Fe, Al, Zn, Mn, Cu, Ni, and Cr. Potential antioxidant Se is below the limit of quantitation, same with toxic Pb and Cd. Bioavailability of the pulp's and the kernel's minerals in the small intestine is high for Mg (pulp: 75.8–90.3%, kernel: 54.4–61.2%) and Ca (pulp: 15.8–40.9%, kernel: 13.7–22.5%). After colonic fermentation of Pili nut kernel, appreciable amounts of Mg > Ca > Cu > Mn were still available for absorption. Fe and Zn are not detected in the large intestine due perhaps to an elevated phytic acid. Tannic acid is higher in pulp. Significant differences were observed in some established parameters that may be attributed to distinctions per variety. The Pili nut is a source of several essential minerals that are bioavailable for human nutrition.



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Sensitive and selective fluorometric determination and monitoring of Zn2+ ions using supermicroporous Zr-MOFs chemosensors

Publication date: June 2018
Source:Microchemical Journal, Volume 139
Author(s): Islam M. El-Sewify, Mohamed A. Shenashen, Ahmed Shahat, Mahmoud M. Selim, Mostafa M.H. Khalil, Sherif A. El-Safty
We report the fabrication of water-stable, supermicroporous fluorescent chemosensors (MFCs) using Zr-based metal-organic frameworks (MOFs) as scaffolds for selective fluorescent determination of the ultra-traces of heavy metals, such as Zn²⁺ ions from water resources. The MFCs structures was developed by direct decoration of hydrophobic fluorescent probes (2,2′-((1Z,12Z)-5,9-dithia-2,12-diazatrideca-1,12-diene-1,13 diyl) diphenol), (S1) into the Zr-based metal-organic frameworks (MOFs). Significantly, the MFCs design with uniform super-microgroove pores, long-range intergrowing crystal, and dense decoration of fluorescent probes, leading to create active hook surface sheaths as sensitive and selective chemosensors platforms for ultra-trace monitoring of Zn²⁺ ions. The MFCs supermicro-crystal structures have shown synergistic enhancement in selective sensing assay associated with low-detection limit up to part-per-billion (ppb), wide-range determination (0.5ppb to 2000ppb) and fast response monitoring in the order of second during the binding of Zn²⁺ ion target. The selectivity of Zn²⁺ ions fluorometric sensing process in a heterogeneous mixture of inorganic cations and anions was mainly dependent on the structure of the fluorescent probe, pH condition, competitive ion system composition, and Zn-to-fluorescent probe binding procedure. Our developed MFCs showed a wide range of detection of Zn²⁺ ions with a considerably low detection limit of approximately 10⁻⁹mol/L, in optimal working condition. The long-term stability of MFCs with fluorescent surface functionality enabled the practical and multiple reuse/cycles of Zn²⁺ ion determination.

Graphical abstract

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Sub-inhibitory concentrations of heavy metals facilitate the horizontal transfer of plasmid-mediated antibiotic resistance genes in water environment

Publication date: June 2018
Source:Environmental Pollution, Volume 237
Author(s): Ye Zhang, April Z. Gu, Tianyu Cen, Xiangyang Li, Miao He, Dan Li, Jianmin Chen
Although widespread antibiotic resistance has been mostly attributed to the selective pressure generated by overuse and misuse of antibiotics, recent growing evidence suggests that chemicals other than antibiotics, such as certain metals, can also select and stimulate antibiotic resistance via both co-resistance and cross-resistance mechanisms. For instance, tetL, merE, and oprD genes are resistant to both antibiotics and metals. However, the potential de novo resistance induced by heavy metals at environmentally-relevant low concentrations (much below theminimum inhibitory concentrations [MICs], also referred as sub-inhibitory) has hardly been explored. This study investigated and revealed that heavy metals, namely Cu(II), Ag(I), Cr(VI), and Zn(II), at environmentally-relevant and sub-inhibitory concentrations, promoted conjugative transfer of antibiotic resistance genes (ARGs) between E. coli strains. The mechanisms of this phenomenon were further explored, which involved intracellular reactive oxygen species (ROS) formation, SOS response, increased cell membrane permeability, and altered expression of conjugation-relevant genes. These findings suggest that sub-inhibitory levels of heavy metals that widely present in various environments contribute to the resistance phenomena via facilitating horizontal transfer of ARGs. This study provides evidence from multiple aspects implicating the ecological effect of low levels of heavy metals on antibiotic resistance dissemination and highlights the urgency of strengthening efficacious policy and technology to control metal pollutants in the environments.

Graphical abstract

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Exposure assessment of trace elements in fresh eggs from free-range and home-grown hens analysed by inductively coupled plasma optical emission spectrometry (ICP-OES)

Publication date: June 2018
Source:Journal of Food Composition and Analysis, Volume 69
Author(s): Carmen Rubio, Ibaya Ojeda, Angel J. Gutierrez, Soraya Paz, Dailos González-Weller, Arturo Hardisson
A total of 21 metals (Na, K, Ca, Mg, V, Mn, Fe, Cu, Zn, Cr, Mo, Co, B, Ba, Li, Sr, Ni, Si, Al, Pb, Cd) have been analysed, using inductively coupled plasma atomic emission spectroscopy (ICP-OES), in a total of 288 eggs from free-range and home-grown hens in order to establish differences in metallic content according to the breeding system. Method accuracy was checked by the analysis of certified reference materials (SRM 1515 Apple Leaves, SRM 1548a Typical Diet and SRM 1567a Wheat Flour from NIST) and the recovery percentages were between 97.7–103%. The results obtained were in good agreement with 95% confidence limit with the certified concentrations, relative standard deviation (RSD) values were lower than 25%. Significant differences (p < 0.05) in the metal content between the two breeding systems have been demonstrated. The daily consumption of eggs from free-range hens (24.3 g/person/day for children, 31.2 g/person/day for adults) contributes to the intake of metals, such as Na (2.7% adults, 2.1% children), Fe (7.4% males, 3.7% females, 4.3% children), Zn (4.4% males, 5.9% females, 4.1% children) and Cu (9.6% adults, 8.3% children). Macroelements and trace elements contribution is lower in home-grown eggs and with higher amounts of toxic metals.



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A critical review of melanoma self-screening tools on YouTube – a missed opportunity?

The estimated number of new cases of skin melanoma in the UK is around 15,400 per year and the incidence is rising.1 Commonly, lay individuals are the first to detect their own lesions, either incidentally or during a deliberate self-examination. To reduce patient mortality, early recognition and detection through patient self-examination is key.2 Given this, reliable and accurate information to assist individuals in early detection is essential.

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Pedotransfer functions of potentially toxic elements in tropical soils cultivated with vegetable crops

Abstract

The anthropogenic input of potentially toxic elements (PTEs) from industry, agrochemicals, etc., into the environment are of great concern. Models derived from pedotransfer functions can provide estimates of the levels of PTEs based on soil attributes. Based on the importance of these models in studies in contaminated areas, we assessed the concentrations of the reactive contents of Ba, Cu, Cr, Ni, Pb, and Zn in soils cultivated with vegetable crops in the state of São Paulo, Brazil. We also evaluated the influence of chemical and physical soil attributes on their reactivity and availability. The reactive contents of PTEs represent the fraction of PTEs easily sorbed at the adsorptions sites of organic matter, iron hydroxides, or clay. This fraction can supply information about the PTE content that is more or less readily released into the soil solution. The reactive and available fraction was extracted with 0.43 M HNO₃ and 0.01 M CaCl₂, respectively. The proportion of reactivity of metal pools decreased in the order of Ba>Zn > Cu > Pb > Ni > Cr. The empirical models were able to predict the relationship between the reactive fractions, the pseudototal content, and the soil attributes. The available concentrations of Cr, Cu, Ni, and Pb in the soils were lower than the limit of quantification, while 3% of the Ba content and 1% of the Zn content were available in the soil solution in relation to their pseudototal content, suggesting low mobility of these elements in the soil.

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Assessment of groundwater vulnerability by applying the modified DRASTIC model in Beihai City, China

Abstract

This study assesses vulnerability of groundwater to pollution in Beihai City, China, as a support of groundwater resource protection. The assessment result not only objectively reflects potential possibility of groundwater to contamination but also provides scientific basis for the planning and utilization of groundwater resources. This study optimizes the parameters consisting of natural factors and human factors upon the DRASTIC model and modifies the ratings of these parameters, based on the local environmental conditions for the study area. And a weight of each parameter is assigned by the analytic hierarchy process (AHP) to reduce the subjectivity of humans to vulnerability assessment. The resulting scientific ratings and weights of modified DRASTIC model (AHP-DRASTLE model) contribute to obtain the more realistic assessment of vulnerability of groundwater to contaminant. The comparison analysis validates the accuracy and rationality of the AHP-DRASTLE model and shows it suits the particularity of the study area. The new assessment method (AHP-DRASTLE model) can provide a guide for other scholars to assess the vulnerability of groundwater to contamination. The final vulnerability map for the AHP-DRASTLE model shows four classes: highest (2%), high (29%), low (55%), and lowest (14%). The vulnerability map serves as a guide for decision makers on groundwater resource protection and land use planning at the regional scale and that it is adapted to a specific area.

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Short and Sweet: A Commentary on Short Sleep Duration and Hyperglycemia in Pregnancy

In their meta-analysis of 12 studies, Reutrakul and colleagues unequivocally conclude that short sleep duration is a risk for hyperglycemia in pregnancy, also known as gestational diabetes mellitus (GDM) [1]. This should not be surprising, since short sleep duration is a known risk factor for Type 2 diabetes in the general adult population. In GDM, however, it is twice as serious because two patients, mother and fetus, are impacted by hyperglycemia. The mother may require early induction of labor because the fetus is getting too large for gestational age, a cesarean birth is highly likely, the newborn may require intervention for hypoglycemia, and both mother and infant usually require a longer hospital stay.

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Insights into the structure of plant-insect communities: Specialism and generalism in a regional set of non-pollinating fig wasp communities

Publication date: Available online 21 February 2018
Source:Acta Oecologica
Author(s): F.H.A. Farache, A. Cruaud, J.-Y. Rasplus, M.T. Cerezini, L. Rattis, F. Kjellberg, R.A.S. Pereira
Insects show a multitude of symbiotic interactions that may vary in degree of specialization and structure. Gall-inducing insects and their parasitoids are thought to be relatively specialized organisms, but despite their ecological importance, the organization and structure of the interactions they establish with their hosts has seldom been investigated in tropical communities. Non-pollinating fig wasps (NPFW) are particularly interesting organisms for the study of ecological networks because most species strictly develop their offspring within fig inflorescences, and show a multitude of life history strategies. They can be gall-makers, cleptoparasites or parasitoids of pollinating or of other non-pollinating fig wasps. Here we analysed a set of non-pollinating fig wasp communities associated with six species of Ficus section Americanae over a wide area. This allowed us to investigate patterns of specialization in a diverse community composed of monophagous and polyphagous species. We observed that most NPFW species were cleptoparasites and parasitoids, colonizing figs several days after oviposition by pollinators. Most species that occurred in more than one host were much more abundant in a single preferential host, suggesting specialization. The food web established between wasps and figs shows structural properties that are typical of specific antagonistic relationships, especially of endophagous insect networks. Two species that occurred in all available hosts were highly abundant in the network, suggesting that in some cases generalized species can be more competitive than strict specialists. The Neotropical and, to a lesser extent, Afrotropical NPFW communities seem to be more generalized than other NPFW communities. However, evidence of host sharing in the Old World is quite limited, since most studies have focused on particular taxonomic groups (genera) of wasps instead of sampling the whole NPFW community. Moreover, the lack of quantitative information in previous studies prevents us from detecting patterns of host preferences in polyphagous species.



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The immunobiology of mucosal-associated invariant T cell (MAIT) function in primary biliary cholangitis: Regulation by cholic acid-induced Interleukin-7

Publication date: Available online 21 February 2018
Source:Journal of Autoimmunity
Author(s): Xiang Jiang, Min Lian, Yanmei Li, Weici Zhang, Qixia Wang, Yiran Wei, Jun Zhang, Weihua Chen, Xiao Xiao, Qi Miao, Zhaolian Bian, Dekai Qiu, Jingyuan Fang, Aftab A. Ansari, Patrick S.C. Leung, Ross L. Coppel, Ruqi Tang, M. Eric Gershwin, Xiong Ma
Mucosal-associated invariant T (MAIT) cells are novel innate-like T cells constituting a significant proportion of circulating and hepatic T cells. Herein, we extensively examine the phenotypical and functional alterations of MAIT cells and their regulation in a cohort of 56 patients with Primary Biliary Cholangitis (PBC) and 53 healthy controls (HC). Additionally alterations of MAIT cells were assessed before and after UDCA treatment. Finally the localization of MAIT cell in liver was examined using specific tetramer staining and the underlying mechanisms of these alterations in PBC were explored. Our data demonstrated that the frequency and number of circulating MAIT cells were decreased, whereas hepatic MAIT cells were increased in PBC compared to HC. Moreover, circulating MAIT cells were more activated in PBC than HC, reflected by elevated expression levels of granzyme B. Six months of UDCA treatment significantly attenuated the circulating MAIT cells differences in PBC. Of note, the expression levels of IL-7 were significantly increased in both plasma and liver from PBC as compared to HC, which promoted the production of inflammatory cytokines and granzyme B by inducing signal transduction and activation of transcription 5 (STAT5) phosphorylation in MAIT cells. Finally, cholic acid, one of the major bile acids in liver, upregulated IL-7 expression in hepatocyte cell line L02 by inducing Farnesoid X Receptor (FXR) binding to the IL-7 promoter. Hence MAIT cells are activated and enriched in the liver of PBC. Cholic acid-induced IL-7 production in hepatocytes plays a critical role in regulating MAIT cell function, highlighting that hepatocytes may bridge cholangiocyte injury and innate immunity through a bile acid signaling pathway.



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Brain responses associated with different hierarchical effects on cues and targets during rule shifting

Publication date: Available online 21 February 2018
Source:Biological Psychology
Author(s): Jiahui Han, Yingxia Dai, Liufang Xie, Fuhong Li
Numerous studies have explored the neural mechanisms related to task switching or rule shifting, but few have revealed the neural substrates related to rule shifting at different hierarchical levels. The purpose of this study is to explore the different event-related potentials (ERPs) elicited by higher and lower hierarchical levels of rule shifting in a cue-target task. In the task, participants were presented with Arabic digits (1–9, excluding 5), and performed a parity or magnitude judgment according to the preceding cues, a letter R. The rules were constructed in a hierarchical set, and the rule was either repeated or shifted between neighboring trials. Importantly, the rule shifting would be at a higher or lower hierarchical level. The results showed that, for the cues, the higher hierarchical shifting evoked increased P2, P3, late positive component (LPC), and decreased N2 relative to lower hierarchical shifting, reflecting the increased demand in selective attention, rule processing, and proactive control during the rule acquisition stage. For the targets, the hierarchical effects were reversed, and emerged later than the rule shift effect. These findings imply that, in the cue-target rule-shifting task, the brain responds differently to different hierarchical levels of rule shifting.



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Dual detection for non-aqueous capillary electrophoresis combining contactless conductivity detection and mass spectrometry

Publication date: 1 June 2018
Source:Talanta, Volume 183
Author(s): Andrea Beutner, Beate Scherer, Frank-Michael Matysik
Coupling of two detectors is a powerful tool to enhance the overall analytical performance generating complementary information and overcoming the limitations of the single detectors. In this work, capacitively coupled contactless conductivity detection (C⁴D) and electrospray ionization mass spectrometry (ESI-MS) were coupled in conjunction with non-aqueous capillary electrophoresis (NACE). Non-aqueous electrolytes are highly compatible with ESI due to their volatility. Moreover, they exhibit low background conductivity, which is essential for the detection with C⁴D. A NACE-C⁴D-MS method was developed using an acetonitrile buffer containing 2 M HAc and 4 mM NH4Ac as background electrolyte. The influence of the inner diameter of the separation capillary on the C⁴D was studied and taken into account. A capillary with 50 µm inner diameter was found to be best suited.The complementarity of the two detectors was shown by determining a sample mixture containing choline, thiamine, nitrate, and chloride as well as bromide and acetylcholine as internal standards. The C⁴D was the detector of choice for the inorganic ions, which were not detectable with the MS whereas the MS had much lower limits of detections for the organic biomolecules. The method was applied on an extract of a food supplement containing the model analytes.

Graphical abstract

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Folic acid-conjugated green luminescent carbon dots as a nanoprobe for identifying folate receptor-positive cancer cells

Publication date: 1 June 2018
Source:Talanta, Volume 183
Author(s): Junli Zhang, Xuewei Zhao, Ming Xian, Chuan Dong, Shaomin Shuang
Early diagnosis is pivotal in subsequent prognosis and treatment of cancer. Herein, folic acid-conjugated carbon dots (FA-CDs) as a fluorescent nanoprobe were fabricated for identifying cancer cells visually. Green luminescent carbon dots (CDs) from active dry yeast (ADY) were readily prepared in scale-up to reach macroscopic production with a high yield of ~50% via a facile and rapid microwave approach. The as-prepared CDs were further combined with folic acid (FA) by covalent bonding to fabricate the FA-CDs for identification of cancer cells over-expressing folate receptor (FR). Experimental outcomes demonstrated that the resultant FA-CDs noninvasively entered into cancer cells via receptor-mediated endocytosis and could differentiate FR-positive HepG2 cells from a cell mixture by fluorescence imaging, which suggests a promising prospect of the FA-CDs as an efficient probe for cancer diagnosis and succeeding personalized therapy.

Graphical abstract

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Fabrication of a novel enzymatic electrochemical biosensor for determination of tyrosine in some food samples

Publication date: 1 June 2018
Source:Talanta, Volume 183
Author(s): Kambiz Varmira, Ghobad Mohammadi, Majid Mahmoudi, Reza Khodarahmi, Khodabakhsh Rashidi, Mehdi Hedayati, Hector C. Goicoechea, Ali R. Jalalvand
In this work, fabrication of a novel and ultrasensitive electrochemical biosensor based on immobilization of tyrosine hydroxylase onto palladium-platinum bimetallic alloy nanoparticles/chitosan-1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide/graphene-multiwalled carbon nanotubes-IL/glassy carbon electrode for determination of L-tyrosine in some high tyrosine foods including cheese, egg and yogurt was reported. Immobilization of tyrosine hydroxylase onto the surface of the biosensor was performed by cross-linking tyrosine hydroxylase and chitosan through the addition of glutaraldehyde. Enzymatic biosensors employ the affinity and selectivity of catalytically active proteins towards their target molecules and here, the tyrosine hydroxylase selectively catalyzes the conversion of tyrosine to levodopa which can be oxidized at lower potentials than tyrosine. The modifications were characterized by electrochemical impedance spectroscopy, cyclic voltammetry, energy dispersive X-ray spectroscopic and scanning electron microscopy. Under optimal conditions, the biosensor detected tyrosine in concentration ranges of 0.01 × 10⁻⁹ to 8.0 × 10⁻⁹ mol L⁻¹ and 8.0 × 10⁻⁹ to 160.0 × 10⁻⁹ mol L⁻¹ with a limit of detection of 0.009 × 10⁻⁹ mol L⁻¹. The biosensor was able to selective determination of tyrosine even in the presence of common interferents therefore, the biosensor was highly selective. The biosensor also showed good operational stability, antifouling properties, sensitivity, repeatability and reproducibility.

Graphical abstract

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MOF based fluorescent assay of xanthine oxidase for rapid inhibitor screening with real-time kinetics monitoring

Publication date: 1 June 2018
Source:Talanta, Volume 183
Author(s): Lan Chang, Xi-Yuan Yao, Qiao Liu, Di Ning, Qian Wang, Xiao-Meng Du, Wen-Juan Ruan, Yue Li
The activity assay of xanthine oxidase (XO) is of great application value in clinical diagnosis because the abnormal level of this enzyme is related to a series of pathological states. In this work, a Zr based metal-organic framework (BTB-MOF) with stable photoluminescence in pure water and buffer solution was synthesized. The examination about the fluorescent responses of this material to xanthine and its oxidation product, uric acid, showed that, although both of them affected the emission of BTB-MOF in quenching form, the efficiencies presented much difference. Taking advantage of this feature, a fluorescent method was developed for the activity assay of XO, that is, BTB-MOF was added to the enzymatic oxidation system as a sensor to transduce the proceeding of the reaction real-timely to the signal of fluorescent intensity change. Our method can work under the interference of normal biologically related species, and precisely reflect XO activity in the range of 0.2–40 U L⁻¹ (detection limit = 0.004 U L⁻¹). With consecutive fluorescence intensity scan, this assay could be applied as a high speed screening method of XO inhibitors with the testing time of 1 min. This work shows the wide potential application of MOFs in enzyme analysis.

Graphical abstract

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Application of CE-ICP-MS and CE-ESI-MS/MS for identification of Zn-binding ligands in Goji berries extracts

Publication date: 1 June 2018
Source:Talanta, Volume 183
Author(s): Lena Ruzik, Piotr Kwiatkowski
The identification of groups of ligands binding metals is a crucial issue for the better understanding of their bioaccessibility. In the current study, we have intended an approach for identification of Zn-binding ligands based on using capillary electrophoresis combined with inductively coupled plasma mass spectrometry (CE-ICP-MS) and tandem electrospray ionization mass spectrometry (CE-ESI-MS/MS). The approach, which featured the use of the coupling of capillary electrophoresis with inductively coupled plasma mass spectrometry allows to separate and observe zinc ions present in complexes with respect to their size and charge and to identify nine compounds with zinc isotopic profile. CE-ICP-MS provides us with information about presence of zinc species and elemental information about zinc distribution. CE-ESI-MS/MS provide us with information about the most favorable Zn binding ligands: amino acids, flavonols, stilbenoids, fenolic acids and carotenoids.The presented work is the continuation of previous studies based on using LC-ESI-MS/MS, though, now we presented a new solutions with the possibility of changing detectors without changing the separation techniques, what is important without re-optimizing the method. The new presented method allows to identify the zinc-binding ligands in shorter time.

Graphical abstract

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Amplified electrochemiluminescence detection of DNA based on novel quantum dots signal probe by multiple cycling amplification strategy

Publication date: 1 June 2018
Source:Talanta, Volume 183
Author(s): Lu Tan, Junjun Ge, Meng Jiao, Guifen Jie, Shuyan Niu
In the present work, we designed a unique enzyme-aided multiple amplification strategy for sensitive electrochemiluminescence (ECL) detection of DNA by using the amplified gold nanoparticles (GNPS)-polyamidoamine (PAMAM)-CdSe quantum dots (QDs) signal probe. Firstly, the novel GNPS-PAMAM dendrimers nanostructure with good biocompatibility and electroconductibility contains many amino groups, which can load a large number of CdSe QDs to develop amplified ECL signal probe. Then, the presence of target DNA activated the enzyme-assisted polymerization strand-displacement cycling reaction, and a large number of the hairpin template was opened. Subsequently, the opened stem further interacted with the capture hairpin (HP) DNA on the electrode, and the GNPS-PAMAM-CdSe signal probe hybridized with the exposed stem of the HP to trigger the second new polymerization reaction. Meanwhile, the first cycle was generating abundant DNA triggers which could directly open the template. As a result of the cascade amplification technique, a large number of CdSe QDs signal probe could be assembled on the electrode, generating much amplified ECL signal for sensitive detection of target DNA. Thus, this novel QDs-based amplified ECL strategy holds great promise for DNA detection and can be further exploited for sensing applications in clinical diagnostics.

Graphical abstract

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A novel amperometric biosensor based on covalently attached multilayer assemblies of gold nanoparticles, diazo-resins and acetylcholinesterase for the detection of organophosphorus pesticides

Publication date: 1 June 2018
Source:Talanta, Volume 183
Author(s): Bin Jiang, Pei Dong, Jianbin Zheng
Using an ionic layer-by-layer self-assembly technique, colloidal gold nanoparticles (AuNPs) and diazo-resins (DAR) were immobilised on the surface of a p-aminobenzenesulfonic acid-modified glassy carbon electrode to form a matrix composite membrane for acetylcholinesterase (AChE) immobilisation. Photo-sensitive DAR was used as the assembly interlayer to convert the ionic bond into a covalent bond to improve the biosensor stability. These fabrication processes were followed by electrochemical impedance spectroscopy and cyclic voltammetry to verify the membrane formation. Because of the introduction of AuNPs/DAR/AChE biofilms, the modified electrode exhibited excellent electron transfer mediation and electrical conductivity. In addition, it exhibited high sensitivity in the range of linear concentration from 1.0 × 10⁻⁸ to 1.0 × 10⁻¹² g L⁻¹ with the detection limit of 5.12 × 10⁻¹³ and 5.85 × 10⁻¹³ g L⁻¹ for malathion and methyl parathion, respectively. More importantly, the presented biosensor considerably improved stability because the electrostatic interaction was converted into covalent bonds by UV irradiation. It is a simple, cheap and stable method for quantitative detection of organophosphorus pesticides, and this method may pave a way for the sensitive, simple detection of different analytes without the need of expensive instrumentation.

Graphical abstract

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Facile preparation and characterization of new green emitting carbon dots for sensitive and selective off/on detection of Fe3+ ion and ascorbic acid in water and urine samples and intracellular imaging in living cells

Publication date: 1 June 2018
Source:Talanta, Volume 183
Author(s): Mojtaba Shamsipur, Karam Molaei, Fatemeh Molaabasi, Mohsen Alipour, Naader Alizadeh, Saman Hosseinkhani, Morteza Hosseini
Carbon dots (CDs) have gained great attention as multifunctional materials because of their interesting properties and general applicability. However, there are some reports for the preparation of highly luminescent green-emitting CDs (G-CDs), although these reports seem not to be extensible. Herein, new G-CDs (quantum yield: 27.2%) were synthesized from a facile hydrothermal treatment of p-aminosalicylic acid and ethylene glycol dimethacrylate as both carbon and nitrogen source and cross-linking agent, respectively. The chemical composition and optical properties of the as-prepared G-CDs were successfully investigated using transmission electron microscopy, atomic force microscopy, dynamic light scattering, X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and fluorescence and UV–vis spectroscopies. Interestingly, the fluorescence intensity of G-CDs was selectivity quenched by Fe³⁺ in the range of 0.05–10.0 µmol Lˉ¹, with a detection limit of 13.7 nmol Lˉ¹. Meanwhile, ascorbic acid found to reduce Fe³⁺ to Fe²⁺, thereby causing restoration of the fluorescence of G-CDs. The detection limit for ascorbic acid detection was estimated as 82.0 nmol Lˉ¹ over a linear range from 0.2 to 11.0 µmol Lˉ¹. Furthermore, the designed sensing platform was successfully utilized to the detection of Fe³⁺ and ascorbic acid in water and urine samples and to intracellular imaging without surface modification.

Graphical abstract

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Case Reports: Liver Abscess After Hepatic Stereotactic Body Radiation Therapy

Publication date: Available online 21 February 2018
Source:Practical Radiation Oncology
Author(s): Meghan W. Macomber, Stephanie K. Schaub, Smith Apisarnthanarax




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