Electrochemical Reduction of Carbon Dioxide at TiO2/Au Nanocomposites

Herein, we report on the facile synthesis of nanocomposite consisting of TiO₂ and Au nanoparticles (NPs) via a tailored galvanic replacement reaction (GRR). The electrocatalytic activity of the synthesized TiO₂/Au nanocomposites for CO₂ reduction was investigated in an aqueous solution using various electrochemical methods. Our results demonstrated that the TiO₂/Au nanocomposites formed through the GRR process exhibited improved catalytic activities for CO₂ reduction, while generating more hydrocarbon molecules than the typical formation of CO in contrast to polycrystalline Au. GC analysis and NMR spectroscopy revealed that CO and CH₄ were the gas products, whereas HCOO^-, CH₃COO^-, CH₃OH, and CH₃CH₂OH were the liquid products from the CO₂ reduction at different cathodic potentials. This remarkable change was further studied using the density functional theory (DFT) calculations, showing that the TiO₂/Au nanocomposites may increase the binding energy of the formed ^·CO intermediate and reduce the free energy compared to Au, thus favoring the downstream generation of multicarbon products. The TiO₂/Au nanocomposites have high catalytic activity and excellent stability and are easy to fabricate, indicating that the developed catalyst has potential application in the electrochemical reduction of CO₂ to value-added products.

Electrochemical distinction of neuronal and neuroblastoma cells via the phosphorylation of the cellular extracellular membrane

In this contribution we establish a proof of concept method for monitoring, quantifying and differentiating the extracellular phosphorylation of Human SHSY5Y undifferentiated neuronal cells and neuroblastoma cells by three prominent ectokinases PKA, PKC and Src. Herein it is demonstrated that a combination of different experimental techniques, including fluroesence microscopy, quartz crystal microscopy (QCM) and electrochemistry, can be used to detect extracellular phosphorylation levels of neuronal and neuroblastoma cells. Phosphorylation profiles of the three ectokinases, PKA, PKC and Src, were investigated using fluorescence microscopy and the number of phosphorylation sites per kinase was estimated using QCM. Finally, the phosphorylation of the extracellular membrane was determined using electrochemistry. Our results clearly demonstrate that the extracellular phosphorylation of neuronal cells differs significantly in terms of its phosphorylation profile from diseased neuroblastoma cells and the strength of surface electrochemical techniques in the differentiation process. We reveal that using electrochemistry, the percent compositions of neuronal and neuroblastoma cells can also be identified.

Nanoporous Gold for the Miniaturization of In Vivo Electrochemical Aptamer-Based Sensors

Electrochemical aptamer-based sensors enable real-time molecular measurements in the living body. The spatial resolution of these measurements and ability to perform measurements in targeted locations, however, is limited by the length and width of the device's working electrode. Historically, achieving good signal to noise in the complex, noisy in vivo environment has required working electrode lengths of 3-6 mm. To enable sensor miniaturization, here we have enhanced the signaling current obtained for a sensor of given macroscopic dimensions by increasing its surface area. Specifically, we produced nanoporous gold via an electrochemical alloying/dealloying technique to increase the microscopic surface area of our working electrodes by up to 100-fold. Using this approach, we have miniaturized in vivo electrochemical aptamer-based (EAB) sensors (here using sensors against the antibiotic, vancomycin) by a factor of 6 while retaining sensor signal and response times. Conveniently, the fabrication of nanoporous gold is simple, parallelizable, and compatible with both two- and three-dimensional electrode architectures, suggesting that it may be of value to a range of electrochemical biosensor applications.

Development of a novel label-free impedimetric electrochemical sensor based on hydrogel/chitosan for the detection of ochratoxin A

Ochratoxin A (OTA) is one of the most abundant mycotoxins that contaminate various food products. Herein, we propose a novel label-free impedimetric electrochemical sensor consisting of chitosan/dipeptide nanofibrous hydrogel and immobilized DNA probes with OTA aptamer for the detection of OTA. The thin film of chitosan/dipeptide nanofibrous hydrogel was used as sensing interface and carrier for hybridization chain reaction (HCR) of OTA aptamer and DNA2 strand to form DNA concatemer. The concatemer was dissociated to single-stranded DNA (ssDNA) in the presence of target OTA, and the signal amplification was further implemented by introducing RecJ_f exonuclease, which could digest the single-stranded DNA resulting in OTA recycle. Electrochemical impedance spectroscopy (EIS) has been employed to characterize the properties of the fabricated sensor. A linear detection range of 0.1-100 ng mL^-1 was obtained for OTA with a low detection limit of 0.03 ng mL^-1. Furthermore, the developed sensor was demonstrated in white wine to detect OTA, indicating that the proposed impedimetric sensor has a promising potential application in the food industry.

Consecutive Silver(I) Ion Incorporation into Oligonucleotides containing Cytosine-Cytosine Mispairs

Invited for this month's cover is the group of Prof. Heinz-Bernhard Kraatz from the University of Toronto, Canada. The cover picture shows the consecutive incorporation of Ag^I ions into a DNA duplex containing adjacent C-C mispairs. Read the full text of the article at 10.1002/cplu.202000607.

Copper decorated with nanoporous gold by galvanic displacement acts as an efficient electrocatalyst for the electrochemical reduction of CO2

The reduction of carbon dioxide (CO2) is recognized as a key component in the synthesis of renewable carbon-containing fuels. Herein, we report on nanoporous gold (NPAu) decorated with copper atoms for the efficient electrochemical reduction of CO2. A facile and green galvanic displacement technique was developed to incorporate Cu onto the surface of the nanoporous gold-zinc (NPAuZn) electrode. The effect of zinc on the morphology and electrochemical performance of the formed NPAuCu electrodes for CO2 reduction was systematically investigated. The NPAuCu electrode exhibited 16.9 and 2.86 times higher current density than those of polycrystalline gold and NPAuZn at -0.60 V (vs. RHE) in a 0.1 M CO2-saturated NaHCO3 solution, respectively. A far higher faradaic efficiency was achieved at the NPAuCu electrode for the electrochemical reduction of CO2 to CO, CH4 and HCOOH. The facile synthesis of the NPAuCu electrode demonstrated in the present study can be employed as a promising strategy in the development of high-performance electrocatalysts for energy and environmental applications.

Electrochemical Reduction of CO2 at Coinage Metal Nanodendrites in Aqueous Ethanolamine

Electrocatalytic reduction of CO₂ into usable chemicals is a promising path to address climate change and energy challenges. Herein, we demonstrate the synthesis of unique coinage metal (Cu, Ag, and Au) nanodendrites (NDs) via a facile galvanic replacement reaction (GRR), which can be effective electrocatalysts for the reduction of CO₂ in an ethanolamine (EA) solution. Each metal ND surface was directly grown on glassy-carbon (GC) substrates from a mixture of Zn dust and the respective precursor solution. The electrocatalytic activities of the synthesized ND surfaces were optimized for CO₂ reduction in EA solution by varying their composition. It was determined that a 0.05 mol fraction of EA exhibited the highest catalytic activity for all metal NDs. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) techniques showed that metal-ND electrodes possessed higher current densities, lower onset potentials and lower charge-transfer resistances for CO₂ reduction than their smooth polycrystalline electrode counterparts, indicating improved CO₂ reduction catalytic activity. It was determined, using FTIR and NMR spectroscopy, that formate was produced as a result of the CO₂ reduction.

A novel electrochemical immunosensor for hepatitis B surface antigen based on Fe3O4 nanoflowers and heterogeneous chain reaction signal amplification strategy

Herein, a novel sandwich-type electrochemical immunosensor was fabricated based on Fe₃O₄ nanoflowers (Fe₃O₄ NFs) and heterogeneous chain reaction (HCR) signal amplification strategy for the sensitive detection of hepatitis B surface antigen (HBsAg). The aldehyde-functionalized Fe₃O₄ NFs are used as a supporting matrix to immobilize the hepatitis B surface antibody 1 (HBsAb1). The biotin-modified single-strand DNA (biotin-S0) was connected onto the biotin-HBsAb2 via linkage of streptavidin (SA), followed by addition of methylene blue (MB) modified single strand DNA1 (MB-S1) and DNA2 (MB-S2) for HCR signal amplification. The designed immunosensor exhibited a detection linear range of 0.5 pg mL^-1-0.25 ng mL^-1 and a low detection limit of 0.16 pg mL^-1, with excellent stability, selectivity and reproducibility. Furthermore, HBsAg is detected in the serum samples with a stable and fast response, indicating that the proposed immunosensor has a promising potential application in clinical analysis.

Homogeneous and heterogeneous molecular catalysts for electrochemical reduction of carbon dioxide

Carbon dioxide (CO2) is a greenhouse gas whose presence in the atmosphere significantly contributes to climate change. Developing sustainable, cost-effective pathways to convert CO2 into higher value chemicals is essential to curb its atmospheric presence. Electrochemical CO2 reduction to value-added chemicals using molecular catalysis currently attracts a lot of attention, since it provides an efficient and promising way to increase CO2 utilization. Introducing amino groups as substituents to molecular catalysts is a promising approach towards improving capture and reduction of CO2. This review explores recently developed state-of-the-art molecular catalysts with a focus on heterogeneous and homogeneous amine molecular catalysts for electroreduction of CO2. The relationship between the structural properties of the molecular catalysts and CO2 electroreduction will be highlighted in this review. We will also discuss recent advances in the heterogeneous field by examining different immobilization techniques and their relation with molecular structure and conductive effects.

Electrochemical detection of neuronal extracellular phosphorylation by PKA, PKC and Src

The focus of this work described here is to establish a method for monitoring and quantifying the extracellular phosphorylation of Human SHSY5Y undifferentiated neuronal cells by three ectokinases PKA, PKC and Src; these are kinases that are known to be present in the extracellular matrix. Here is demonstrated that a combination of different experimental techniques, including microscopy and electrochemistry, can be used to detect extracellular phosphorylations. Phosphorylation profiles of the three ectokinases, PKA, PKC and Src, were investigated using fluorescence microscopy and the number of phosphorylation sites per kinase was estimated using QCM. Finally, the phosphorylation of the extracellular membrane was determined using electrochemistry. Our results clearly demonstrate the extracellular phosphorylation of neuronal cells and the strength of surface electrochemical techniques in the investigation of cellular phosphorylation.

Surgical Management of Large Mediastinal Masses–12 Years’ Experience in Apollo Hospitals Dhaka

Objective: The aim of this study was to evaluate the role of surgical treatment for large mediastinal tumors. A retrospective study was done from 6.8.2005 to 11.5.2017. Total 39 patients were included in this study. Age range was from 7 months to 70 years. Male was 24 and female was 15.Background: Most of the tumours were thymoma (12 cases). Others were thymoma with myasthenia gravis in 3 cases, Thymic carcinoma 2 cases, Nodular sclerosing Hodgkin’s lymphoma in 1 case, Schwannoma in 3 cases, Cystic mass in 5 cases, Schwannoma with cystic degeneration in 1 case, Fibromyxoma in 1 case, Dermoid in 4 cases, Teratoma in 3 cases, Fibrosing mediastinitis in thymic mass in 1 case, Lymphoid hyperplasia in 1 case, Malignant Mesenchymal tumour in 1 case, Myxoid Liposarcoma in 1 case.Method: Surgical exposure varies from sternotomy in 22 cases, to clamshell incision in 1 case, posterolateral thoracotomy in 14 cases and anterolateral thoracotomy in 2 cases. Superior Venacava was injured in 1 case, repaired successfully by 6/0 prolene controlled by partial clamp. Some of the mediastinal mass needed careful dissection from lung, pleura, encircling distal aortic arch and proximal part of left subclavian artery, encircling left brachiocephalic vein. 1 case needed reconstruction of sternum with prolene mesh, marsupialization was done in 2 cases, adjacent pleura, fatty tissue, part of pericardium was removed in 5 cases. Lobectomy was needed in 1 case. In 1 case, recurrence of fibrosing mediastinitis needed steroid therapy. Extensive growth of the tumour which involved surrounding vital structures was decided not to proceed for excision in 2 cases.Results: Overall five-years survival rate was 94.87% .2 patients of the series died due to disease process as they were cases of advanced malignant mediastinal mass.Conclusion: Surgical treatment for mediastinal mass specially involving surrounding structures though challenging, gives good outcome.Pulse Vol.10 January-December 2017 p.12-17

Unique copper and reduced graphene oxide nanocomposite toward the efficient electrochemical reduction of carbon dioxide

The electrochemical reduction of CO₂ to useful chemicals and fuels has garnered a keen and broad interest. Herein, we report a unique nanocomposite consisting of Cu nanoparticles (NPs) and reduced graphene oxide (rGO) supported on a Cu substrate with a high catalytic activity for CO₂ reduction. The nanocomposite was optimized in terms of the composition of Cu NPs and rGO as well as the overall amount. A gas chromatograph was employed to analyze the gaseous products, whereas a chemical oxygen demand (COD) method was proposed and utilized to quantify the overall liquid products. The optimized nanocomposite could effectively reduce CO₂ to CO, HCOOH and CH₄ with a Faradaic efficiency (FE) of 76.6% at −0.4 V (vs. RHE) in a CO₂ saturated NaHCO₃ solution. The remarkable catalytic activity, high FE, and excellent stability make this Cu-rGO nanocomposite promising for the electrochemical reduction of CO₂ to value-added products to address the pressing environmental and energy challenges.

Antibiotic and Herbal Sensitivity of Some Aeromonas sp. Isolates Collected from Diseased Carp Fishes

Studies were conducted to identify Aeromonas sp. isolates collected from disease affected carp fishes (Cyprinus carpio and Labeo rohita), their antibiotic sensitivity pattern and sensitivity to 121 herb extracts. A total of 19 Aeromonas sp. isolates were identified from a total of 84 different isolates through a series of physiological, morphological and biochemical tests. Seven antibiotics viz., streptomycin, chloramphenicol, erythromycin, sulphamethoxazole, cephradine, oxytetracycline and gentamycin were tested by disc diffusion method where all of the Aeromonas sp. isolates were found sensitive to streptomycin, erythromycin and gentamycin. But, 78.95% of the isolates were found resistant to oxytetracycline. In addition, 5%, 11%, and 16% isolates exhibited resistance to chloramphenicol, cephradine and sulphamethoxazole, respectively. Twenty one percent of the isolates showed multiple resistance to the antibiotics. A total of 121 herb extracts were evaluated for their sensitivity to the fish pathogenic Aeromonas sp. isolates. Among these, 23 herbs were found to possess antimicrobial activity. Leaf extracts of Eugenia caryophyllus, Spondias pinnata and Terminalia chebula were found to inhibit the growth of all the Aeromonas sp. isolates. In this study, multiple antibiotic resistant isolates were also found to be sensitive to several herb extracts. Thus, herbal treatment would promise a greater viable solution for effective treatment of fish disease.DOI:http://dx.doi.org/10.3329/pa.v21i1-2.16758 Progress. Agric. 21(1 & 2): 117 - 129, 2010

Antitumor activity of epifriedelanol from Vitis trifolia

The isolation and NMR spectral data of epifriedelanol from Vitis trifolia are reported. It demonstrated antitumor activity in a potato disc bioassay.

Suicidal Death Autopsy Analysis at Dhaka Medical College

A cross sectional study was carried out at the department of Forensic Medicine in Dhaka Medical College during the period of January 2008 to December 2009. Data were collected from 3rd copy of the post mortem reports which were preserved in the department of Forensic Medicine with the verbal consent of the doctors who performed autopsy report. During this period total 5114 autopsies were conducted. Out of this 970 cases (19%) were suicidal in nature. It was noticed that all suicidal deaths occurred from 10 years to all age group respectively, but top amongst age group of suicidal deaths occurred in between 21 to 30 years of people. Suicidal deaths are more common in female than male. Suicidal deaths due to hanging is highest, next common causes of death due to organophosphorus compund poisoning. Suicidal deaths by hanging is more in female than male but in poisoning cases male are more lvictimised than female. Objectives of our study are to see the occurrence and methods of suicidal death. DOI: http://dx.doi.org/10.3329/bmj.v40i1.9957 BMJ 2011; 40(1): 18-21