Detection of Helicobacter pylori with a nanobiosensor based on fluorescence resonance energy transfer using CdTe quantum dots

We report on a method for the sensitive determination of Helicobacter that is based on fluorescence resonance energy transfer using two oligonucleotide probes labeled with CdTe quantum dots (QDs) and 5-carboxytetramethylrhodamine (Tamra) respectively. QDs labeled with an amino-modified first oligonucleotide, and a Tamra-labeled second oligonucleotide were added to the DNA targets upon which hybridization occurred. The resulting assembly brings the Tamra fluorophore (the acceptor) and the QDs (the donor) into close proximity and causes fluorescence resonance energy transfer (FRET) to occur upon photoexcitation of the donor. In the absence of target DNA, on the other hand, the probes are not ligated, and no emission by the Tamra fluorophore is produced due to the lack of FRET. The feasibility of the method was demonstrated by the detection of a synthetic 210-mer nucleotide derived from Helicobacter on a nanomolar level. This homogeneous DNA detection scheme is simple, rapid and efficient, does not require excessive washing and separation steps, and is likely to be useful for the construction of a nanobiosensor for Helicobacter species.

Matrices based on meso antibacterial framework

In this paper, the synthesis of three types of porous materials (PMs) (porous Fe₃O₄, MIL-101 metal-organic framework (MOF), and MCM-41 mesoporous silica) by hydrothermal method was performed. The incorporation of Ag nanoparticles (Ag NPs) was carried out after the synthesis reaction of supports in MCM-41 and MIL-101 MOF. Ag core@ porous Fe₃O₄ core–shell system was prepared via a one-pot hydrothermal method. Ag-MIL-101 was obtained using Urtica dioica leaf extract as the green solvent and reducing agent. The antibacterial activity of Ag-PM nanocomposites (NCs) was investigated on both Gram-negative and Gram-positive bacteria. The size of the silver NPs was determined to be 12 and 30 nm in MCM-41 and MIL-101 MOF, respectively. The diameter of Ag core in Ag@Fe₃O₄ shell was ~135 nm. The antibacterial activity of Ag-PMs was in the order Ag-MCM-41 > Ag-MIL-101 > Ag core@Fe₃O₄ shell. The loading percent of Ag NPs in MCM-41 (84%) was more than that in MIL-101 (53%) and Fe₃O₄ (31%). The release of Ag⁺ ions from Ag-MCM-41, Ag-MIL-101, and Ag@Fe₃O₄ NCs was 46, 2, and 1 ppm, respectively. The release of the Ag⁺ ions and, consequently, the antibacterial activity of NCs depend on the uniform distribution, particles size, and the absence of aggregation of Ag NPs in PMs.     

Chemical degradation of crosslinked ethylene-propylene-diene rubber in an acidic environment. Part II. Effect of peroxide crosslinking in the presence of a coagent

An investigation on the time-dependent chemical degradation of ethylene-propylene diene rubber containing 5-ethylidene-2-norbornene as diene cured by peroxide crosslinking in the presence of a coagent in an acidic environment (20% Cr/H₂SO₄) has been made. Two types of rubber, with comparable monomer composition, but having significant differences in molar mass and levels of long chain branching were tested. Dicumyl peroxide and triallylcyanurate under similar conditions were used for curing the rubbers. The molecular mechanisms of chemical degradation at the surface were studied using X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy, which demonstrate that several oxygenated species evolve during exposure. The primary process of degradation is hydrolytic attack on the crosslink sites, which is manifested by a decrease in crosslink density. The surface degradation is found to be strong enough to alter the bulk mechanical properties as observed by the change in retention in tensile strength, elongation at break, modulus at 50% elongation and, the change in micro-hardness. Retention in modulus at 50% elongation is found to follow a negative linear correlation with decrease in crosslink density. With higher molar mass and level of long chain branching more crosslinking occurs and thus comparatively more hydrolytic attack ensues. Scanning electron microscopy shows that the surface topography is significantly altered upon exposure and supports the notion of the dependence of degradation on the crosslinking density of the samples. Importantly, the coagent used in this study is shown to enhance the chemical degradation through formation of weaker sites for hydrolysis. The results also show that upon prolonged exposure the resulting oxygenated species tend to combine with each other.     

Synthesis of functionalized iminolactones via an isocyanide-based three-component reaction

A three-component reaction of the zwitterions generated from isocyanides and dialkyl acetylenedicarboxylate with 1-(4-bromophenyl)-2-thiocyanatoethanone or 1-phenyl-2-thiocyanatoethanone is described. The reaction afforded the corresponding special type of functionalized iminolactone derivatives in good yields at room temperature without using a catalyst.     

Simultaneous Determination of Trace Zinc and Cadmium by Anodic Stripping Voltammetry Using a Polymeric Film Nanoparticle Self‐Assembled Electrode

A promising modified electrode was fabricated by polymerization a conductive polymer film of dipicolinic acid (DPA) onto gold nanoparticle (AuNP)‐cysteine‐gold electrode (Au). The morphology of poly(DPA)‐AuNP‐Au electrode was investigated by scanning electron microscopy (SEM). This chemically modified electrode was used for electrochemical determination of cadmium and zinc in aqueous media using differential pulse anodic stripping voltammetry. The result showed that the modified electrode could clearly resolve the anodic stripping peaks of zinc and cadmium. The linear analytical curves were obtained in the ranges of 0.020–25.0 and 0.045–17.0 µM for zinc and cadmium respectively. The limit of detections (S/N=3) were 0.008 µM for zinc and 0.015 µM for cadmium.     

Separate evolution of H2 and O2 from H2O on visible light-responsive TiO2 thin film photocatalysts prepared by an RF magnetron sputtering method

Visible light-responsive TiO₂ thin film photocatalysts (Vis-TiO₂) have been prepared on Ti metal foil (Vis-TiO₂/Ti) or ITO glass (Vis-TiO₂/ITO) substrates by a radio-frequency magnetron sputtering (RF-MS) method. The UV–Vis spectra as well as photoelectrochemical performance of Vis-TiO₂ were affected by various calcination treatments such as calcination in air or NH₃. Calcination treatment in NH₃ (1.0 × 10⁴ Pa, 673 K) was particularly effective in increasing the visible light absorption of Vis-TiO₂ as well as in enhancing its photoelectrochemical performance and photocatalytic activity. A novel Vis-TiO₂ thin film photocatalyst (Vis-TiO₂/Ti/Pt) was prepared by an RF-MS method where Vis-TiO₂ was deposited on one side of a Ti metal foil substrate and nanoparticles of Pt were deposited on the other side. The separate evolution of H₂ and O₂ from H₂O could be successfully achieved by using an H-type glass cell consisting of two aqueous phases separated by Vis-TiO₂/Ti/Pt and a proton-exchange membrane. It was found that the rate of the separate evolution of H₂ and O₂ was also dramatically enhanced by calcination treatment of Vis-TiO₂ in NH₃.     

On magnetophoretic separation of blood cells using Halbach array of magnets

Meccanica - Magnetophoretic separation has gained much attention in recent years due to its easy application and low-cost fabrication compared to other active particle separation techniques. Due to...     

Effects of different carbon precursors on synthesis of multiwall carbon nanotubes: Purification and Functionalization

Cyclohexanol and xylene were used as carbon precursors, for synthesis of multiwall carbon nanotubes (MWCNTs) arrays in a CVD system at temperature of 750 °C, using nitrogen as carrier gas and ferrocene as catalyst. Different characterization methods were employed to compare the MWCNTs structure synthesized by these two precursors. All scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and Raman spectroscopy results illustrated that using cyclohexanol could significantly reduce formation of amorphous carbon and catalyst particles in the as-grown CNTs. The less amorphous carbon can be attributed to in situ oxidation in presence of oxygen atom of cyclohexanol. Characterizations showed that MWCNTs with high purity could be obtained using cyclohexanol as carbon precursor. The as-grown MWCNTs were purified by oxidation and acid treatment. Characterization of the purified MWCNTs using HNO₃/H₂SO₄ (1/3 or 1/1), 8 M HCl or 8 M HNO₃ was carried out. The results showed that 8 M HNO₃ could be considered as the best chemical to obtain more pure MWCNTs, less amorphous and metal particles and less damaged MWCNTs. The Raman spectroscopy results demonstrated that HNO₃/H₂SO₄ (1/3) treatment could more disorder the MWCNTs structure and this was attributed to the bigger destroying effect of this acid treatment. Furthermore, the TEM analysis of MWCNTs before and after acid treatment revealed that acid treatment could remove encapsulated catalyst particles. The FTIR analysis illustrated that purification of the MWCNTs with nitric acid could connect the functional groups onto the outer surface of MWCNTs and this resulted in more dispersion of the MWCNTs in water.     

Targeted Therapy of B7 Family Checkpoints as an Innovative Approach to Overcome Cancer Therapy Resistance: A Review from Chemotherapy to Immunotherapy

It is estimated that there were 18.1 million cancer cases worldwide in 2018, with about 9 million deaths. Proper diagnosis of cancer is essential for its effective treatment because each type of cancer requires a specific treatment procedure. Cancer therapy includes one or more approaches such as surgery, radiotherapy, chemotherapy, and immunotherapy. In recent years, immunotherapy has received much attention and immune checkpoint molecules have been used to treat several cancers. These molecules are involved in regulating the activity of T lymphocytes. Accumulated evidence shows that targeting immune checkpoint regulators like PD-1/PD-L1 and CTLA-4 are significantly useful in treating cancers. According to studies, these molecules also have pivotal roles in the chemoresistance of cancer cells. Considering these findings, the combination of immunotherapy and chemotherapy can help to treat cancer with a more efficient approach. Among immune checkpoint molecules, the B7 family checkpoints have been studied in various cancer types such as breast cancer, myeloma, and lymphoma. In these cancers, they cause the cells to become resistant to the chemotherapeutic agents. Discovering the exact signaling pathways and selective targeting of these checkpoint molecules may provide a promising avenue to overcome cancer development and therapy resistance. Highlights: (1) The development of resistance to cancer chemotherapy or immunotherapy is the main obstacle to improving the outcome of these anti-cancer therapies. (2) Recent investigations have described the involvement of immune checkpoint molecules in the development of cancer therapy resistance. (3) In the present study, the molecular participation of the B7 immune checkpoint family in anticancer therapies has been highlighted. (4) Targeting these immune checkpoint molecules may be considered an efficient approach to overcoming this obstacle.