Pediatric adrenocortical carcinoma (pACC) is a rare and aggressive malignancy of high occurrence in Southern Brazil. pACC is characterized by the usual overproduction of dehydroepiandrosterone ...sulfate (DHEAS), whose detection in serum or plasma can be effective to the early diagnosis of the disease. Therefore, the present paper reports, for the first time, the construction and application of a label-free impedimetric immunosensor to detect DHEAS, which was based on the modification of an oxidized glassy carbon electrode with arginine-functionalized gold nanoparticles (AuNPs-ARG) and anti-DHEA IgM antibodies (ox-GCE/AuNPs-ARG/IgM). AuNPs-ARG was synthesized by a green route, and characterized by UV–VIS spectroscopy, FTIR, TEM, DLS, and XRD. The construction of ox-GCE/AuNPs-ARG/IgM was optimized through factorial design and response surface methodology. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were employed to characterize the optimized immunosensor. The DHEAS detection principle was based on the variation of charge transfer resistance (∆Rct) relative to the Fe(CN)64−/3− electrochemical probe after immunoassays in the presence of the biomarker. A linear relationship between ∆Rct and DHEAS concentration was verified in the range from 10.0 to 110.0 µg dL−1, with a LOD of 7.4 µg dL−1. Besides the good sensitivity, the immunosensor displayed accuracy, stability, and specificity to detect DHEAS. The promising analytical performance of ox-GCE/AuNPs-ARG/IgM was confirmed by quantifying DHEAS in real patient plasma samples, with results that were comparable to the reference chemiluminescence assay. Our results suggest that the presented immunosensor can find clinical applications in the early diagnosis of pACC and to monitor DHEAS levels in other adrenal pathologies.
•A label-free impedimetric immunosensor to detect DHEAS is described.•The use of AuNPs-ARG conferred high stability and sensitivity to the device.•Chemometrics was employed for the optimization of the immunosensor construction.•The immunosensor was able to quantify DHEAS in real patient plasma samples.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The antibacterial activity of a calixarene derivative, p-tert-butylcalix6arene (Calix6), was assessed and was shown not to inhibit the growth of E. coli, S. aureus and B. subtilis bacteria. With the ...aim of gaining more insights into the absence of antibacterial activity of Calix6, the interaction of this derivative with DPPG, a bacterial cell membrane lipid, was studied. Langmuir monolayers were used as the model membrane. Pure DPPG and pure Calix6 monolayers, as well as binary DPPG:Calix6 mixtures were studied using surface pressure measurements, compressional modulus, Brewster angle and fluorescence microscopies, ellipsometry, polarization-modulation infrared reflection absorption spectroscopy and molecular dynamics simulations. Thermodynamic properties of the mixed monolayers were additionally calculated using thermodynamic parameters. The analysis of isotherms showed that Calix6 significantly affects the DPPG monolayers, modifying the isotherm profile and increasing the molecular area, in agreement with the molecular dynamics simulations. The presence of Calix6 in the mixed monolayers decreased the interfacial elasticity, indicating that calixarene disrupts the strong intermolecular interactions of DPPG hindering its organization into a compact arrangement. At low molar ratios of Calix6, the DPPG:Calix6 interactions are preferentially attractive, due to the interactions between the hydrophobic tails of DPPG and the tert-butyl groups of Calix6. Increasing the proportion of calixarene generates repulsive interactions. Calix6 significantly affects the hydrophobic tail organization, which was confirmed by PM-IRRAS measurements. Calix6 appears to be expelled from the mixed films at a biologically relevant surface pressure, π = 30 mN m-1, indicating a low interaction with the cell membrane model related to the absence of antibacterial activity.
This paper describes the development of a novel glucose biosensor through the layer-by-layer technique (LbL). The self-assembled architectures were composed of a positive-charged silsesquioxane ...polyelectrolyte, 3-n-propylpyridinium silsesquioxane chloride (SiPy+Cl−), nickel (II) tetrassulphophthalocyanine (NiTsPc), and a conductive surface of FTO (fluor tin oxide). The construction of the biosensor was influenced by the isoelectric point (pI) of the glucose oxidase enzyme (GOx), which allowed electrostatic interaction between the outer layer of the silsesquioxane film and the enzyme. The architecture of modified electrode GOx/(SiPy+Cl−/NiTsPc)5.5/FTO was confirmed by UV-Vis, FTIR, and chronoamperometry techniques using different immobilization methods of GOx. Among the studied methods, a higher variation of current was observed for the modified electrode formed by mixed LbL films of SiPy+Cl− and NiTsPc and the enzyme immobilized by drop coating. The stability and reproducibility of the biosensor were verified when the last layer containing the enzyme was coated with 0.2% Nafion® polymer. Under these conditions, a linear response for glucose was obtained in the concentration range of 0.2 to 1.6 mmol L−1 (R2 = 0.991) with a limit of detection of 0.022 mmol L−1. The proposed biosensor was applied to quantify glucose in two different samples of kombucha juices with accuracy, allowing the glucose content of the healthy beverages to be estimated.
Bulky 2,6-disubstituted aryl siloxanes and a disilanamine Marszaukowski, Flavia; Wohnrath, Karen; Boeré, René T
Acta crystallographica. Section E, Crystallographic communications,
03/2020, Volume:
76, Issue:
Pt 3
Journal Article
Peer reviewed
Open access
The crystal structures of 5-bromo-1,3-di-
butyl-2-(tri-methyl-sil-yl)-oxybenzene, C
H
BrOSi, (I), 1,3-di-
butyl-2-(tri-methyl-sil-yl)-oxybenzene, C
H
OSi, (II), and
...-(2,6-diiso-propyl-phen-yl)-1,1,1-trimethyl-
-(tri-methyl-sil-yl)silanamine, C
H
NSi
, (III), are reported. Compound (I) crystallizes in space group
2
/
with
' = 1, (II) in
with
' = 0.5 and (III) in
with
' = 0.25. Consequently, the mol-ecules of (II) are constrained by
and those of (III) by
2
site symmetries. Despite this, both (I) and (II) are distorted towards mild boat conformations, as is typical of 2,6-di-
butyl-substituted phenyl compounds, reflecting the high local steric pressure of the flanking alkyl groups. Compound (III) by contrast is planar and symmetric, and this lack of distortion is compatible with the lower steric pressure of the flanking 2,6-diisopropyl substituents.
Electronic waste contains considerable amounts of gold in its composition, especially some composting pieces like CPUs and memory cards. Recovered gold can have many uses, among those it can be an ...excellent alternative source for low-cost nanoparticles synthesis. Commercial chloroauric acid is the main precursor for nanoparticle synthesis, however its cost makes the process very expensive. Finding a lower cost alternative precursor is very important because it allows to economically enabling several gold nanoparticles applications. Through the hydrometallurgical method, it was possible to recover and to purify the appreciable amount of gold from old CPUs. This gold has been used to synthesize nanoparticles with a size of 198.5 nm and moderate stability. Keywords Electronic Waste Gold Nanoparticles Recovery Turkevich Methode
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abstract Metallic nanoparticles have great potential as a chemotherapeutic agent. The aim of this study was to develop and characterize silver and gold nanoparticles using a simple method, as well as ...evaluating the potential cytotoxic activity in relation to the K-562 cell line. For the synthesis, a solution containing the metallic ions was subjected to magnetic stirring with the aqueous extract of Lavandula dentata L. and a change of colour was observed. With the data obtained from the analyses we concluded that the nanoparticles were successfully obtained by a simple and green method using the aqueous extract of L. dentata. The obtained nanoparticles presented a reduced size, a low level of polydispersion, and a homogenous spherical shape. The nanoparticles presented intense and characteristic diffraction peaks, which could be correlated to the planes of the centred cubic structure of the silver and gold. The two formulations presented predominantly crystalline characteristics. The infrared analysis suggested that the amides and alcohols present in the samples may have been responsible for the reduction and limitation of the size and dispersion of the silver and gold nanoparticles. The cytotoxic assay showed that the nanoparticles demonstrated great potential to reduce the cell viability of the K-562 cell line, especially the gold nanoparticles.
Synthesis and molecular and supramolecular structures of a series of triarylphosphines P(Ph)3–n {4-RO-3,5-( t Bu)2-C6H2} n (n = 1, 3; R = SiMe3, H) are reported. Chemical oxidation products ...E=P(Ph)3–n {4-RO-3,5-( t Bu)2-C6H2} n (E = O, S, and Se; n = 1, 3; R = SiMe3, H) are also reported. Crystal structures of the reported compounds were determined by single-crystal X-ray diffraction, using a Hirshfeld atom refinement with NoSpherA2 through OLEX2, which provides an average improvement in C–C bond distance precision of 35%. Phosphine basicity for the phosphines with n = 1, R = H and n = 3, R = SiMe3, H was determined using the 1 J P,Se values of the respective selenides; 1 J P,Se = 699 Hz for E = Se, n = 3, and X = H identifies the most basic triarylphosphine ever reported. Intermolecular interactions allow classification of the 17 structures into 4 categories: those with only dispersion-induced short contacts, those with frustration of H-bonding, those with only classic H-bonding, and those with combinations of classic and frustration of H-bonding. A “double phenol embrace” classified by an R 2 2(4) graph set is a weak intermolecular synthon organizing lattices with 2,6-ditertbutylphenol functional groups. Classic H-bonding occurs only when E = O.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
A sensor array made up of nanostructured Langmuir−Blodgett (LB) films is used as an electronic tongue capable of identifying sucrose, quinine, NaCl, and HCl at the parts-per-billion (ppb) level, ...being in some cases 3 orders of magnitude below the human threshold. The sensing units comprise LB films from conducting polymers and a ruthenium complex transferred onto gold interdigitated electrodes. Impedance spectroscopy is used as the principle of detection, and the importance of using nanostructured films is confirmed by comparing results from LB films with those obtained from cast films.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
The mechanism of chemotherapeutic action of Ru-based drugs involves plasma membrane disruption and valuable insights into this process may be gained using cell membrane models. The interactions of a ...series of cytotoxic η6-p-cymene ruthenium(II) complexes, Ru(η6-p-cymene)P(3,5-C(CH3)3-C6H3)3Cl2 (1), Ru(η6-p-cymene)P(3,5-CH3-C6H3)3Cl2 (2), Ru(η6-p-cymene)P(4-CH3O-3,5-CH3-C6H2)3Cl2 (3), and Ru(η6-p-cymene)P(4-CH3O-C6H4)3Cl2 (4), were examined using Langmuir monolayers as simplified healthy and cancerous outer leaflet plasma membrane models. The cancerous membrane (CM1 and CM2) models contained either 40 % 1,2- dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 30 % cholesterol (Chol), 20 % 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and 10 % 1,2-dipalmitoyl-sn-glycero-3-phospho-l-serine (DPPS). Meanwhile, the healthy membrane (HM1 and HM2) models were composed of 60 % DPPC or DOPC, 30 % Chol and 10 % DPPE. The complexes affected surface pressure isotherms and decreased compressional moduli of cancerous and healthy membrane models, interacting with the monolayers headgroup and tails according to data from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). However, the effects did not correlate with the toxicity of the complexes to cancerous and healthy cells. Multidimensional projection technique showed that the complex (1) induced significant changes in the CM1 and HM1 monolayers, though it had the lowest cytotoxicity against cancer cells and is not toxic to healthy cells. Moreover, the most toxic complexes (2) and (4) were those that least affected CM2 and HM2 monolayers. The findings here support that the ruthenium complexes interact with lipids and cholesterol in cell membrane models, and their cytotoxic activities involve a multifaceted mode of action beyond membrane disruption.
Display omitted
•Ru complexes interact with both healthy and cancer plasma membrane models.•The cytotoxicity of Ru complexes in unrelated to their effect on membrane models.•Ru complexes either cross or penetrate the cell membrane.•The mechanism of action of Ru complexes goes beyond simple cell membrane disruption.
Full text
Available for:
IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
