The second order voltammetric technique Differential Alternative Pulses Voltammetry (DAPV) was applied in anodic stripping mode for simultaneous quantification of traces of species having close E1/2. ...The potential‐time waveform and the signal processing allowing the DAPV application in stripping mode are presented. The pulses widths and amplitudes were optimized to obtain maximal sensitivity and resolution at traces of In3+ and Cd2+ (having E1/2 difference of 45 mV) simultaneous quantification in presence of excess of Pb2+. Precise results for both species concentrations were obtained up to In3+ to Cd2+ concentration ratio as high as 1 to 10 without any sample pre‐treatment in purified industrial waste waters using 0.1 mol L−1 HCl as supporting electrolyte.
An activated carbon nanopowder modified glassy carbon electrode (AC‐GCE) was constructed for the sensitive determination of methyl parathion by adsorptive differential pulse anodic stripping ...voltammetry. The simple and rapid modification procedure included only drop‐coating the electrode surface with a laponite stabilized activated carbon nanopowder suspension and drying. The modifier high adsorption ability, combined with its large electroactive surface area allowed a 30‐fold signal increase to be achieved, compared to bare GCE. Under optimized experimental conditions (activated carbon to laponite ratio, pH and accumulation time), the AC‐GCE exhibited a linear response to methyl parathion in two concentration ranges: from 0.01 μmol L−1 to 1 μmol L−1 and from 1 μmol L−1 to 6 μmol L−1. The LOD of 2.5 nmol L−1 (S/N=3) achieved fitted with regulatory norms. It was demonstrated that the as‐prepared AC‐GCE is suitable for routine real samples analysis.
A laponite modified carbon paste electrode was prepared, characterized and applied for the 2,4‐dichlorophenol (2,4‐DCP) voltammetric determination. It takes advantage of the ability of laponite to ...adsorb phenols, as well as of its availability and very low cost. Kinetic and equilibrium data for 2,4‐DCP adsorption by laponite in aqueous dispersions demonstrated that the adsorption process obeyed a pseudo first order kinetic model and was consistent with the formation of adsorbed multilayers on a surface with heterogeneous pore distribution. The composite paste electrode exhibited a heterogeneous surface with 65 % increased surface area and 27 % enhanced catalytic activity compared to the unmodified one. The adsorptive stripping voltammetric determination of 2,4‐DCP at an electrode with an optimized graphite:laponite ratio of 55 : 15 w% using a 3 min accumulation time at pH 5.5 was found to be suitable for its quantification in the linear concentration range extended up to 50 μmol L−1 with a sensitivity of 0.56 μA L μmol−1 and a LOD of 0.2 μmol L−1 (S/N=3).The 2,4‐DCP electrochemical response was not affected by the presence of some structurally similar phenols, like catechol and p‐nitrophenol, while resorcinol, 2‐chlorophenol, and 4‐chlorophenol presented interferences. The results were validated by 2,4‐DCP determination in spiked tap water.
The high resolution second order voltammetric technique, Differential Alternative Pulse Voltammetry (DAPV), was applied for the simultaneous quantification of the mononitrophenol (NP) isomers. ...Complete resolution of the three isomers was achieved at concentration ratios as high as 1 : 5, employing the corresponding anodic and cathodic peaks appeared on the DAPV curve. The working glassy carbon electrode was modified by a nanocomposite of graphite nanopowder and Au nanoparticles to increase the sensitivity. The linear concentration range was found to be extended up to 125 μmol L−1 for both the m‐NP and p‐NP isomers, while the o‐NP isomer presented calibration plot of two linear sections: up to 100 μmol L−1 and up to 225 μmol L−1. The LOD was found to be as low as 1.5 μmol L−1, 2.5 μmol L−1, and 0.5 μmol L−1 for o‐NP, m‐NP, and p‐NP, respectively. The accuracy of the proposed method was evaluated by quantification of spiked tap waters samples. No interference was observed from a range of phenolic compounds such as phenol, 4‐aminophenol, 4‐chlorophenol, 2,4‐dinitrophenol, and resorcinol.
A simple technique for the construction of a versatile diazirine‐functionalized nanostructured platform for enzymes photografting and electrochemical biosensing was proposed in this work. The ...feasibility of the approach was proved by photo crosslinking of an enzyme, tyrosinase, to diazirine‐activated aminated carbon nanotubes coated glassy carbon electrode. The analytical performances of the realized biosensor were evaluated employing catechol as analyte. Then the sensor based on the diazirine‐functionalized nanostructured platform with photografted tyrosinase was applied together with the high resolution technique Differential Alternative Pulses Voltammetry for dopamine determination in the linear concentration range of 5–25 μmol L−1 in the presence of interfering agents as uric acid up to its 100‐fold excess.
Hydrogels are versatile biomaterials characterized by three-dimensional, cross-linked, highly hydrated polymeric networks. These polymers exhibit a great variety of biochemical and biophysical ...properties, which allow for the diffusion of diverse molecules, such as drugs, active ingredients, growth factors, and nanoparticles. Meanwhile, these polymers can control chemical and molecular interactions at the cellular level. The polymeric network can be molded into different structures, imitating the structural characteristics of surrounding tissues and bone defects. Interestingly, the application of hydrogels in bone tissue engineering (BTE) has been gathering significant attention due to the beneficial bone improvement results that have been achieved. Moreover, essential clinical and osteoblastic fate-controlling advances have been achieved with the use of synthetic polymers in the production of hydrogels. However, current trends look towards fabricating hydrogels from biological precursors, such as biopolymers, due to the high biocompatibility, degradability, and mechanical control that can be regulated. Therefore, this review analyzes the concept of hydrogels and the characteristics of chitosan, collagen, and gelatin as excellent candidates for fabricating BTE scaffolds. The changes and opportunities brought on by these biopolymers in bone regeneration are discussed, considering the integration, synergy, and biocompatibility features.
A virtual instrument, calorimetric etching solution analyzer based on LabVIEW 2010 platform was developed, characterized and validated for the on-line automated H
2
O
2
concentration monitoring in ...SC-1 etching solution applied in the semiconductor industry. The virtual instrument completely controls all analyzer functions including sampling, analytical response measurement, digital data processing and H
2
O
2
concentration calculation as well as the instrument calibration and real time concentration correction by fresh solution addition to the etching machine. The hardware, the software, the user interface and the instrument functioning are presented and discussed with the analytical characterization and validation by industrial sample analysis in comparison with a standard permanganate method.
Cancer is a serious health problem due to the complexity of establishing an effective treatment. The purpose of this work was to evaluate the activity of a triazaspirane as a migration and invasion ...inhibitor in PC3 prostatic tumor cells through a possible negative regulation of the FAK/Src signal transduction pathway and decreased secretion of metalloproteinases 2 and 9. Molecular docking analysis was performed using Moe 2008.10 software. Migration (wound-healing assay) and invasion (Boyden chamber assay) assays were performed. In addition, the Western blot technique was used to quantify protein expression, and the zymography technique was used to observe the secretion of metalloproteinases. Molecular docking showed interactions in regions of interest of the FAK and Src proteins. Moreover, the biological activity assays demonstrated an inhibitory effect on cell migration and invasion, an important suppression of metalloproteinase secretion, and a decrease in the expression of p-FAK and p-Src proteins in treated PC3 cells. Triazaspirane-type molecules have important inhibitory effects on the mechanisms associated with metastasis in PC3 tumor cells.
New medical devices with anti-inflammatory properties are critical to prevent inflammatory processes and infections in medical/surgical procedures. In this work, we present a novel functionalization ...of silicone for medical use with a polymeric prodrug and a thermosensitive polymer, by graft polymerization (gamma rays), for the localized release of salicylic acid, an analgesic, and anti-inflammatory drug. Silicone rubber (SR) films were functionalized in two stages using graft polymerization from ionizing radiation (
Co). The first stage was grafting poly(
-vinylcaprolactam) (PNVCL), a thermo-sensitive polymer, onto SR to obtain SR-
-PNVCL. In the second stage, poly(2-methacryloyloxy-benzoic acid) (P2MBA), a polymeric prodrug, was grafted to obtain (SR-
-PNVCL)-
-P2MBA. The degree of functionalization depended on the concentrations of monomers and the irradiation dose. The films were characterized by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM-EDX), thermogravimetric analysis (TGA), and contact angle. An upper critical solution temperature (UCST) of the films was demonstrated by the swelling degree as a temperature function. (SR-
-PNVCL)-
-P2MBA films demonstrated hydrolysis-mediated drug release from the polymeric prodrug, pH, and temperature sensitivity. GC-MS confirmed the presence of the drug (salicylic acid), after polymer hydrolysis. The concentration of the drug in the release media was quantified by HPLC. Cytocompatibility and thermo-/pH sensitivity of functionalized medical silicone were demonstrated in cancer and non-cancer cells.
Banana (
spp.) is an important crop worldwide, but black Sigatoka disease caused by the fungus
threatens fruit production. In this work, we examined the potential of the endophytes of banana plants
...and
, as antagonists of
and support plant growth in nutrient limited soils by N-transfer. The two bacterial isolates were identified by MALDI-TOF mass spectrometry and corroborated by 16S rRNA sequence analysis. Both bacteria were positive for beneficial traits such as N-fixation, indole acetic acid production, phosphate solubilization, negative for 1-aminocyclopropane 1-carboxylic acid deaminase and were antagonistic to
. To measure the effects on plant growth, the two plant bacteria and an
strain (as non-endophyte), were inoculated weekly for 60 days as active cells (AC) and heat-killed cells (HKC) into plant microcosms without nutrients and compared to a water only treatment, and a mineral nutrients solution (MMN) treatment. Bacterial treatments increased growth parameters and prevented accelerated senescence, which was observed for water and mineral nutrients solution (MMN) treatments used as controls. Plants died after the first 20 days of being irrigated with water; irrigation with MMN enabled plants to develop some new leaves, but plants lost weight (-30%) during the same period. Plants treated with bacteria showed good growth, but
AC treated plants had significantly greater biomass than the
HKC. After 60 days, plants inoculated with
AC showed intracellular bacteria within root cells, suggesting that a stable symbiosis was established. To evaluate the transference of organic N from bacteria into the plants, the 3 bacteria were grown with
NH
Cl or Na
NO
as the nitrogen source. The
N transferred from bacteria to plant tissues was measured by pheophytin isotopomer abundance. The relative abundance of the isotopomers
872.57, 873.57, 874.57, 875.57, 876.57 unequivocally demonstrated that plants acquired
N atoms directly from bacterial cells, using them as a source of N, to support plant growth in restricted nutrient soils.
might be a new alternative to promote growth and health of banana crops.
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