Nanomole silver detection in chloride-free phosphate buffer using platinum and gold micro- And nanoelectrodes

The electrochemical determination of ultra-low concentrations of silver requires reliable, reproducible measurements using sensitive analytical techniques. To date, the electrochemical determination of silver in biological buffers and pH neutral media has not been successful in terms of reproducibility. In this work, we report on the determination of ultra-low concentrations of silver in chloride-free phosphate buffer solution (PB, pH 7.4). Detection was conducted at gold and platinum micro and nanoelectrodes using anodic stripping voltammetry (ASV). The micro and nanoelectrodes were fabricated using a Sutter P-2000 laser puller, with physical and electrochemical characterization revealing flat disk-shaped working surfaces of 10–15 μm (microelectrode) and 10–100 nm (nanoelectrodes) in radius. These dimensions were calculated from steady-state limiting currents and confirmed using FE-SEM. The laser pulled electrodes exhibit excellent electrochemical activity when characterized using ferrocene, without the addition of supporting electrolyte, and reproducible stripping voltammetric profiles for the determination of silver, with a LoD of 1.3 pM (1.8%) were obtained in 0.1 M chloride-free phosphate at platinum nanoelectrode. Determination of ultra-low concentrations of silver in chloride-free PB provides the scope to explore the mechanism of action of bioinorganic silver-based anti-bacterial, anti-fungal and anti-cancer drugs in cell media for in vitro and, potentially, in vivo analysis

A Novel Quantitative Electrochemical Method to Monitor DNA Double-Strand Breaks Caused by a DNA Cleavage Agent at a DNA Sensor

Biosensors and Bioelectronics, Vol. 11

Determination of Integrity, Stability and Density of the DNA Layers Immobilised at Glassy Carbon and Gold Electrodes Using Ferrocyanide

The technique chosen to immobilise DNA onto electrodes can determine the density and stability of the resultant immobilised layer. DNA‐modified electrodes were prepared using four common DNA immobilisation methods and characterised using ferrocyanide. The negatively charged DNA strands should repel ferrocyanide anions. The DNA layers created using adsorption at glassy carbon electrodes were unstable, while those created through chemisorption of thiol‐modified DNA onto gold electrodes were repeatable and stable, and returned, on average, 94 % repulsion of the probe. The presented results show how the immobilisation protocol, and DNA type, affects the stability, repeatability, and integrity of resultant DNA layers

Non-trivial solution chemistry between amido-pyridylcalix[4]arenes and some metal salts

Mercury ion complexation reactions were carried out between 3 and various mercury(II) salts. 1H NMR studies showed that the role of solvent, the anion chosen and the initial reaction conditions were critical and that the formation of a “simple” mercury(II) complex was non-trivial. The mercury(II) ion can cause either (i) the formation of an ion-pair system, which have a characteristic doubling of all signals in the 1H NMR spectrum, (ii) a cleavage reaction to occur resulting in the reformation of the calix[4]arene diester compound 2, but only when the reaction is heated and (iii) “simple” mercury binding to the pyridine rings when the binding studies are carried out using NMR titration techniques. The electrochemistry results, on the same systems, show that the initial reaction involves the removal of the phenoxide protons followed by the resulting catalysis of the mercury species. This proton removal is not observed in the NMR spectra of any of the mercury reactions. It was also found that 3 could bind silver and zinc salts and was not selective for mercury(II) as was previously described

Highly Selective Fluorimetric Turn-Off Detection of Copper (II) by Two Different Mechanisms in Calix[4]arene-Based Chemosensors and Chemodosimeters

Isoxazolo‐pyrene tethered calix[4]arenes selectively detect copper(II) ions without interference from related perchlorate ions. The fluorescence emission of the probes, synthesised by nitrile oxide alkyne cycloaddition, and characterised by spectroscopic and crystallographic data, is rapidly reduced by Cu(II) ions. Detection limits are in the micromolar or sub‐micromolar range (0.3–3.6 μM) based on a 1 : 1 sensor:analyte interaction. Voltammetric behaviour and 1H NMR data provide new insights into the sensing mechanism which is dependent on the calixarene substitution pattern. When the calixarene lower rim is fully substituted, Cu(II) detection occurs through a traditional chelation mechanism. In contrast, for calixarenes 1,3‐disubstituted on the lower rim, detection takes place through a chemodosimetric redox reaction. The isolation of a calix[4]diquinone from the reaction with excess Cu(ClO4)2 provides confirmation that the sensor–analyte interaction culminates in irreversible sensor oxidation

Mapping the DNA Damaging Effects of Polypyridyl Copper Complexes with DNA Electrochemical Biosensors

Several classes of copper complexes are known to induce oxidative DNA damage that mediates cell death. These compounds are potentially useful anticancer agents and detailed investigation can reveal the mode of DNA interaction, binding strength, and type of oxidative lesion formed. We recently reported the development of a DNA electrochemical biosensor employed to quantify the DNA cleavage activity of the well-studied [Cu(phen)2]2+ chemical nuclease. However, to validate the broader compatibility of this sensor for use with more diverse—and biologically compatible—copper complexes, and to probe its use from a drug discovery perspective, analysis involving new compound libraries is required. Here, we report on the DNA binding and quantitative cleavage activity of the [Cu(TPMA)(N,N)]2+ class (where TPMA = tris-2-pyridylmethylamine) using a DNA electrochemical biosensor. TPMA is a tripodal copper caging ligand, while N,N represents a bidentate planar phenanthrene ligand capable of enhancing DNA interactions through intercalation. All complexes exhibited electroactivity and interact with DNA through partial (or semi-) intercalation but predominantly through electrostatic attraction. Although TPMA provides excellent solution stability, the bulky ligand enforces a non-planar geometry on the complex, which sterically impedes full interaction. [Cu(TPMA)(phen)]2+ and [Cu(TPMA)(DPQ)]2+ cleaved 39% and 48% of the DNA strands from the biosensor surface, respectively, while complexes [Cu(TPMA)(bipy)]2+ and [Cu(TPMA)(PD)]2+ exhibit comparatively moderate nuclease efficacy (ca. 26%). Comparing the nuclease activities of [Cu(TPMA)(phen)] 2+ and [Cu(phen)2]2+ (ca. 23%) confirms the presence of TPMA significantly enhances chemical nuclease activity. Therefore, the use of this DNA electrochemical biosensor is compatible with copper(II) polypyridyl complexes and reveals TPMA complexes as a promising class of DNA damaging agent with tuneable activity due to coordinated ancillary phenanthrene ligands

Gamification to Improve First Year Engagement

The purpose of this project was to examine the role of Gamification in increasing first year student engagement within the third level educational setting. A literature review was carried out in order to explore the teaching philosophy behind gamification in education and review the quantitative and qualitative evidence regarding its use. Gamification can be broadly described as the application of gaming methods and elements in non-gaming contexts in order to improve user engagement and user experience (Deterding et al., 2011). Qualitative analysis suggests these factors result in beneficial emotional and social impacts on students, particularly in the area of increasing student engagement. This advantage of the use of gamification in enhancing student engagement can be linked to better student retention, particularly in the first year of third level education (Mooney et al., 2010; Nelson & Clarke, 2011). Furthermore, there is a positive correlation between lecture attendance and outcomes of examinations (O\u27Dwyer, 2011; O\u27Dwyer, 2011). However, quantitative analysis within the literature on the cognitive impact of gamification is lacking (Dominguez et al., 2013). In order to enhance a deeper learning experience careful planning of gamification activities must be implemented. When used correctly, gamification provides a unique tool within third level education to promote creative, independent enquiring students who effectively participate in these \u27serious games\u27. The findings of this literature review are outlined within this report and are aimed to supplement the infographic artefact, video and website created as part of the group project

Narrative medicine and narrative practice: partners in the creation of meaning

Background Narrative medicine has emerged as an approach to whole person care and to support the clinician-patient therapeutic relationship. Although training in narrative medicine is usually based on the study of literary or artistic works, the same attitude of close reading can also be applied in conversations with patients or learners.MethodWe held a two-day narrative medicine workshop, incorporating two approaches: 'Conversations Inviting Change' (CIC) and humanities-based narrative medicine as taught by Columbia University. The workshop was primarily experiential, with theoretical components of both approaches. Participants brought active concerns for confidential breakout sessions and engaged in text-based and reflective writing exercises. Participants generated metaphors to describe these approaches to narrative medicine.Results Participants included a mix of community and hospital-based practitioners, pre-dominantly doctors. Participants considered the two approaches to be compatible and enhance each other. One metaphor generated was that Columbia style narrative medicine is ’like an individual lens which allows you to see things clearer’, it allows practitioners a different perspective on their patients and that CIC teaching ‘is a frame of glasses in which the lenses could be placed to enhance the ease of use’. Another metaphor was that the former ‘is like learning from a cadaver in the anatomy lab’, while the latter ‘is like running a clinical simulation’.Conclusion We believe this was the first workshop integrating these approaches to narrative medicine. They appear to be highly complementary. Both approaches lead to enhanced attention to narratives which has clear applicability to clinical practice

Highly Selective Fluorimetric Turn-Off Detection of Copper(II) by Two Different Mechanisms in Calix[4]arene-Based Chemosensors and Chemodosimeters

Isoxazolo-pyrene tethered calix[4]arenes selectively detect copper(II) ions without interference from related perchlorate ions. The fluorescence emission of the probes, synthesised by nitrile oxide alkyne cycloaddition, and characterised by spectroscopic and crystallographic data, is rapidly reduced by Cu(II) ions. Detection limits are in the micromolar or sub-micromolar range (0.3–3.6 μM) based on a 1:1 sensor:analyte interaction. Voltammetric behaviour and 1 H NMR data provide new insights into the sensing mechanism which is dependent on the calixarene substitution pattern. When the calixarene lower rim is fully substituted, Cu(II) detection occurs through a traditional chelation mechanism. In contrast, for calixarenes 1,3-disubstituted on the lower rim, detection takes place through a chemodosimetric redox reaction. The isolation of a calix[4] diquinone from the reaction with excess Cu(ClO4)2 provides confirmation that the sensor–analyte interaction culminates in\ud irreversible sensor oxidation

CÉLULAS SOLARES SENSIBILIZADAS COM CORANTE UTILIZANDO HIBISCO E SUCO DE FRAMBOESA COMO TINTURAS

Células solares sensibilizadas com corantes têm se apresentado como uma promissora alternativa de energia frente ao uso de combustíveis fósseis, tornando os países menos dependentes de fontes não renováveis de energia. Este aumento do interesse por este tipo de célula solar deve-se principalmente a uma preocupação ambiental recorrente na comunidade científica: o aquecimento global e seus efeitos. Aliado a isso, esses dispositivos apresentam alta eficiência, baixo custo e procedimento de preparação simplificado, além de utilizar pigmentos naturais como sensibilizadores orgânicos. Neste sentido, 12 células solares sensibilizadas com corantes foram fabricadas utilizando três tipos de dióxido de titânio, TiO2, como semicondutor (pigmento, Degussa P-25 e Kit Man Solar). Três tipos de solventes (metanol, ácido nítrico e etileno-glicol) foram empregados para preparar as soluções e um kit comercial (Man Solar, dióxido de titânio dissolvido em ácido acético diluído) foi utilizado para fins de comparação. Os corantes foram obtidos de extratos de flores de hibisco e suco de framboesa. A partir da caracterização eletroquímica foi possível determinar a potência, eficiência e a energia produzida por cada célula. Verificou-se que as células fabricadas com ácido nítrico e TiO2 pigmento, apresentaram produção de energia de 430 mV, superiores àquelas feitas com o kit Man Solar. Porém, as células do kit foram as que apresentaram melhor eficiência, obtendo-se até 63% de funcionamento similar ao de uma célula ideal