Electrochemical DNA Hybridization Sensor Using Poly[vinylpyridine Os(bipyridine)2Cl]-co-Ethylamine Redox Polymer

DNA hybridization sensors are important for diseases diagnosis. Until now, many approaches have been proposed for the DNA hybridization examination. These include fluorescence based, electrochemical and colorimetric based. Electrochemical hybridization for detection of DNA sequences requires the development of easy to-use, fast, inexpensive, miniaturized analytical devices. In this work, a simple electrochemical DNA hybridization sensor that uses poly[vinylpyridine Os(bipyridine)2Cl]-co-ethylamine redox polymer as the indicator was assembled. The electrochemical behavior of poly[vinylpyridine Os(bipyridine)2Cl]-co-ethylamine redox polymer polymer with both single stranded DNA (ssDNA-SH) probe and double stranded DNA (dsDNA) was determined. Both cyclic voltammetry and impedance spectroscopy results indicated strong binding of the new redox polymer onto DNA. A hybridization process involving a monolayer of a 24-mer thiol-tethered DNA capture probe on gold electrode and the corresponding complementary strand were clearly demonstrated. DNA double strand after disruption with free radicals could also be detected. The biosensor system has potential for use to recognize of damaged DNA sequences.     Keywords: Cyclic voltammetry; Hybridization; Poly[vinylpyridine Os(bipyridine)2Cl]-co-ethylamine

Artemisinin DNA base interaction studies in presence of Fe (II): LC/TOF MS separation of reaction products

Artemisinin (ART) is a sesquiterpene lactone and a popular malaria drug with potential anticancer properties. In this work, LC/TOF/MS, was used to investigate the reaction of ART with DNA bases. ART-deoxyadenosine and ART-deoxycytidine interactions, were studied in the presence of iron II ions. ART-deoxyadenosine and ART-deoxycytidine reaction mixtures gave chromatographic signatures that remained fairly unchanged at room temperature but grew after incubation at 37 °C. The change in temperature from room temperature to 37 °C was the main driver of adduct formation in these reactions. ART was found to react with Fe(II) ions as observed from several new chromatographic peaks. ART-deoxyadenosine as well as ART-deoxycytidine in the presence of Fe(II) ions resulted in formation of new chromatographic signatures of adducts consisting of DNA bases and ART. It was clear that addition of iron (II) to DNA base-ART mixtures gave rise to new reaction products mediated by a different reaction mechanism. Studies of ART reactions with DNA in vitro is key in elucidating elusive mechanism of this drug

LC-MS/TOF Characterization and Stability Study of Artesunate in Different Solvent Systems

Artemisinin (ART) is a sesquiterpene lactone and a popular malaria drug used in many parts of the world. Artesunate (ARTS) is a semi-synthetic derivative of ART with improved pharmacokinetic properties. However, the half-life of ARTS is less than an hour in vivo. The analysis of this drug in vitro in different solvent systems using LC-MS/TOF showed a solvent-driven breakdown. ARTS breakdown formed several derivatives, including dihydroartemisinin (DHA), artemether (ARTM) and DHA-dimer among others, at different rates in different solvent composition systems. The change in temperature from room temperature to physiological temperature (37 °C) was found to enhance the rate of the ARTS breakdown. In methanol, ARTS mainly formed ARTM with a chromatographic peak decrease of about 3.13%, while methanol and water (90:10) v/v mainly gave rise to DHA and ARTM with about an 80% chromatographic peak decrease. On the other hand, ARTS in methanol and ammonium acetate (85:15) v/v formed DHA, ARTM, DHA-dimer and other reaction peaks with about a 97% peak decrease and the formation of an orange solution pointing to a molecular re-arrangement reaction. These results have an important bearing on research on the analysis of artemisinin drugs conducted on these common solvents

Electrochemical reduction of artemisinin: Chromatographic identification of bulk electrolysis products

Artemisinin is a naturally occurring sesquiterpene lactone with an endo-peroxide bond. This drug is used for treatment of many diseases including malaria. The reduction of this molecule on an electrode surface was carried out by cyclic voltammetry as well as amperometry. Cyclic voltammetry of artemisinin generated one prominent peak wave at -1.0 V and another, smaller one at -0.3 V vs Ag/AgCl reference electrode. The bulk electrolysis of artemisinin on a carbon electrode generated two other irreversible peak waves at around -0.7 and -0.1 V. The concentration of the products was dependent on the time of electrolysis. LC-MS was used to determine the bulk electrolysis products of artemisinin. Initially dihydroartemisinin was generated as the main reduction product. Other reduction products were formed after further reduction of dyhidroartemisinin

Human Rights Violations: An Impetus for Police Reforms in Kenya Between 1978 and 2002

Since independence, police reforms have been influenced by the need to expand democratic space and to ensure protection of human rights. Previous studies have attempted to deconstruct the police reforms. However, the studies have not adequately examined the implications of police reforms on human rights in Kenya. This paper examines police reforms between in Kenya between 1978 and 2002 and their implications on human rights. The study was based on a descriptive survey design and targeted senior serving and retired police officers, government administrators, county government administrators and members of the human rights groups in Nairobi County. Purposive sampling technique was used to select 116 study participants. Data was collected through focus group discussion, interview schedule and document analysis and analyzed based on thematic content analysis. The study findings revealed that Moi’s presidency (between 1978 and 2002) was marked by minimal police reforms but heightened human rights violation including arrests without warrants, detention without trial and torture which resulted in injury and death. This implied that in the absence of substantive reforms, the police disregarded human rights. Hence, the period between 1978 and 2002 was marked by curtailed freedom of association, assembly, speech and expression.Keywords: Human Rights, Police Reforms, human rights discourse, Moi era, Kenya DOI: 10.7176/JLPG/103-06 Publication date: November 30th 202

Implications of Police Reforms on Human Rights Practice During the Democratic Transition in Kenya, 2003-2009

Globally reforms in the security sector have been influenced by the need to safeguard human rights. This paper examines the nexus between police reforms and human rights practice in Kenya during the democratic transition in Kenya (2003-2009). The paper argues that while there have been numerous police reforms, the police institution has continued to engage in acts of human rights violation in complete disregard of international human rights provisions. The findings revealed that during the democratic transition between 2003 and 2009 reforms in the police institution were enacted to protect human rights. However, impunity, resource scarcity and lack of political goodwill continuous to slow down security sector reform progress. Keywords: Police reforms, democratic and constitutional transition, human rights practice DOI: 10.7176/JLPG/128-04 Publication date: January 31st 202

Carbon nanofiber modified with osmium based redox polymer for glucose sensing

Electrochemical detection of glucose was performed on carbon nanofibers containing an osmium based redox polymer and using glucose oxidase enzyme. Redox polymer assembled on the nanofibers provided a more stable support that preserved enzyme activity and promoted the electrical communication to the glassy carbon electrode. The morphologies, structures, and electrochemical behavior of the redox polymer modified nanofibers were characterized by scanning electron microscope, energy dispersive spectrometer and voltammetry. The glucose oxidase showed excellent communication with redox polymer as observed with the increased activity toward glucose. Both cyclic voltammetry and amperometry showed a linear response with glucose concentration. The linear range for glucose determination was from 1 to 12 mM with a relatively high sensitivity of 0.20±0.01 μA mM−1 for glucose oxidase in carbon nanofibers and 0.10±0.01 μA mM−1 without carbon nanofibers. The apparent Michaelis–Menten constant (Km) for glucose oxidase with carbon nanofibers was 0.99 mM. On the other hand, the Km value for the glucose oxidase without the nanofibers was 4.90 mM

Developing Eco-Friendly and Cost-Effective Porous Adsorbent for Carbon Dioxide Capture.

To address the issue of global warming and climate change issues, recent research efforts have highlighted opportunities for capturing and electrochemically converting carbon dioxide (CO2). Despite metal doped polymers receiving widespread attention in this respect, the structures hitherto reported lack in ease of synthesis with scale up feasibility. In this study, a series of mesoporous metal-doped polymers (MRFs) with tunable metal functionality and hierarchical porosity were successfully synthesized using a one-step copolymerization of resorcinol and formaldehyde with Polyethyleneimine (PEI) under solvothermal conditions. The effect of PEI and metal doping concentrations were observed on physical properties and adsorption results. The results confirmed the role of PEI on the mesoporosity of the polymer networks and high surface area in addition to enhanced CO2 capture capacity. The resulting Cobalt doped material shows excellent thermal stability and promising CO2 capture performance, with equilibrium adsorption of 2.3 mmol CO2/g at 0C and 1 bar for at a surface area 675.62 m2/g. This mesoporous polymer, with its ease of synthesis is a promising candidate for promising for CO2 capture and possible subsequent electrochemical conversion

Electrochemical reduction of artemisinin: Chromatographic identification of bulk electrolysis products

Artemisinin is a naturally occurring sesquiterpene lactone with an endo-peroxide bond. This drug is used for treatment of many diseases including malaria. The reduction of this molecule on an electrode surface was carried out by cyclic voltammetry as well as amperometry. Cyclic voltammetry of artemisinin generated one prominent peak wave at -1.0 V and another, smaller one at -0.3 V vs Ag/AgCl reference electrode. The bulk electrolysis of artemisinin on a carbon electrode generated two other irreversible peak waves at around -0.7 and -0.1 V. The concentration of the products was dependent on the time of electrolysis. LC-MS was used to determine the bulk electrolysis products of artemisinin. Initially dihydroartemisinin was generated as the main reduction product. Other reduction products were formed after further reduction of dyhidroartemisinin

Carbon nanofiber modified with osmium based redox polymer for glucose sensing

Electrochemical detection of glucose was performed on carbon nanofibers containing an osmium based redox polymer and using glucose oxidase enzyme. Redox polymer assembled on the nanofibers provided a more stable support that preserved enzyme activity and promoted the electrical communication to the glassy carbon electrode. The morphologies, structures, and electrochemical behavior of the redox polymer modified nanofibers were characterized by scanning electron microscope, energy dispersive spectrometer and voltammetry. The glucose oxidase showed excellent communication with redox polymer as observed with the increased activity toward glucose. Both cyclic voltammetry and amperometry showed a linear response with glucose concentration.  The linear range for glucose determination was from 1 to 12 mM with a relatively high sensitivity of 0.20±0.01 μA mM−1 for glucose oxidase in carbon nanofibers and 0.10±0.01 μA mM−1 without carbon nanofibers. The apparent Michaelis–Menten constant (Km) for glucose oxidase with carbon nanofibers was 0.99 mM. On the other hand, the Km value for the glucose oxidase without the nanofibers was 4.90 mM