Enzymeless biosensors: a novel area for the development of amperometric sensors

The aim of this work is to describe the recent area that it has been developed for the construction of amperometric sensors, with the purpose to make possible a more effective electron transfer between enzyme and electrode. The advances reported in the literature will be described, such as enzymatic configurations that can be mimic using the chemistry of the artificial enzymes.123128Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Fast assembly of non-thiolated DNA on gold surface at lower pH

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jcis.2013.08.043 © 2013. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In a typical protocol for attaching DNA to a gold electrode, thiolated DNA is incubated with the electrode at neutral pH overnight. Here we report fast adsorption of non-thiolated DNA oligomers on gold electrodes at acidic pH (i.e., pH ∼3.0). The peak-to-peak potential difference and the redox peak currents in typical cyclic voltammetry of [Fe(CN)6]3− are investigated to monitor the attachment. Compared with incubation at neutral pH, the lower pH can significantly promote the adsorption processes, enabling efficient adsorption even in 30 min. The adsorption rate is DNA concentration-dependent, while the ionic strength shows no influence. Moreover, the adsorption is base-discriminative, with a preferred order of A > C ≫ G, T, which is attributed to the protonation of A and C at low pH and their higher binding affinity to gold surface. The immobilized DNA is functional and can hybridize with its complementary DNA but not a random DNA. This work is promising to provide a useful time-saving strategy for DNA assembly on gold electrodes, allowing fast fabrication of DNA-based biosensors and devices.National Natural Science Foundation of China || 20905012 University of Waterloo || Canadian Foundation for Innovation || Ontario Ministry of Research & Innovation || Natural Sciences and Engineering Research Council Americas Program |

Biomimetic polymers in analytical chemistry. Part 2: applications of MIP (Molecularly Imprinted Polymers) in the development of chemical sensors

The aim of this paper is the description of the strategies and advances in the use of MIP in the development of chemical sensors. MIP has been considered an emerging technology, which allows the synthesis of materials that can mimic some highly specific natural receptors such as antibodies and enzymes. In recent years a great number of publications have demonstrated a growth in their use as sensing phases in the construction of sensors . Thus, the MIP technology became very attractive as a promising analytical tool for the development of sensors.10871101Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Glutathione-s-transferase modified electrodes for detecting anticancer drugs

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.bios.2014.02.070. © 2014. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/With the fast growth of cancer research, new analytical methods are needed to measure anticancer drugs. This is usually accomplished by using sophisticated analytical instruments. Biosensors are attractive candidates for measuring anticancer drugs, but currently few biosensors can achieve this goal. In particular, it is challenging to have a general method to monitor various types of anticancer drugs with different structures. In this work, a biosensor was developed to detect anticancer drugs by modifying carbon paste electrodes with glutathione-s-transferase (GST) enzymes. GST is widely studied in the metabolism of xenobiotics and is a major contributing factor in resistance to anticancer drugs. The measurement of anticancer drugs is based on competition between 1-chloro-2,4-dinitrobenzene (CDNB) and the drugs for the GST enzyme in the electrochemical potential at 0.1 V vs. Ag/AgCl by square wave voltammetry (SWV) or using a colorimetric method. The sensor shows a detection limit of 8.8 μM cisplatin and exhibits relatively long life time in daily measurements.University of Waterloo || Natural Sciences and Engineering Research Council || Emerging Leaders in the Americas Program |

Polímeros impressos com íons: fundamentos, estratégias de preparo e aplicações em química analítica

Chemical imprinting technology has been widely used as a valuable tool in selective recognition of a given target analyte (molecule or metal ion), yielding a notable advance in the development of new analytical protocols. Since their discovery, molecularly imprinted polymers (MIPs) have been extensively studied with excellent reviews published. However, studies involving ion imprinted polymers (IIPs), in which metal ions are recognized in the presence of closely related inorganic ions, remain scarce. Thus, this review involved a survey of different synthetic approaches for preparing ion imprinted adsorbents and their application for the development of solid phase extraction methods, metal ion sensors (electrodes and optodes) and selective membranes

Construção e aplicação de optodos em sistemas analiticos baseados em variações de pH

Orientador: Graciliano de Oliveira Neto, Ivo Milton Raimundo JuniorTese (doutorado) - Universidade Estadual de Campinas, Instituto de QuimicaResumo: Foram construídos optodos para pH usando indicadores ácido-base imobilizados covalentemente a feixes bifurcados de fibras ópticas de vidro, através de silanização em meio orgânico. Os optodos mostraram bom desempenho, com faixa de resposta de 5 unidades de pH e vida útil maior que 170h. Estes optodos foram empregados como detectores em sistemas FIA para determinação de CO2, nas faixas de concentração de 2,0x10-1,0x10 mol L e 2,0x10-0,1 mol L), mostrando resposta rápida, boa reversibilidade e reprodutibilidade (RSD < 4 %). Estes optodos foram também acoplados a sistemas enzimáticos para determinação de oxalato (usando as enzimas oxalato oxidase e catalase) e salicilato (empregando a enzima salicilato hidroxilase), mostrando faixas lineares de 8,0x10-9,5x10 mol L e 5,0x10-1,0x10 mol L, respectivamente. Foram construídos também optodos para pH, obtidos através da polimerização química da anilina nos poros de lâminas de vidro poroso do tipo Vycor. Estes sensores apresentaram tempo de resposta de 4 minutos, boa reversibilidade e reprodutibilidade, vida útil de 5 meses, faixa de resposta de 4,5 unidades de pH e não sendo afetados por variações de temperatura e força iônica das soluções.Abstract: Optodes for pH measurements were constructed employing the chemical immobilization of acid - base indicators, on the surface of bifurcated optical fiber bundle, previously silanized in organic medium. The optodes showed good performance, with an analytical working range of ca 5 pH units and lifetime longer than 170 hours. These optodes were employed as detectors in FIA systems for determination of CO2 in the concentration ranges of 2,0x10-1,0x10 mol L and 2,0x10-1.0x10 mol L), showing fast response, good reversibility and reproducibility (RSD < 4 %). They were also used in enzymatic systems for determination of oxalate (employing oxalate oxidase together with catalase) and salicylate (employing salicylate hydroxilase), in the ranges of 8,0x10-9,5x10 mol L and 5,0x10-1,0x10 mol L, respectively. Optodes based on Pani/PVG were also constructed, by polymerizing chemically aniline into the porous of the Vycor glass. The sensor showed response time of 4 min, good reversibility and reproducibility, lifetime of 5 months, response range of 4.5 pH units and non - significant sensitivity to temperature and ionic strength variations.Doutorad

Biomimetic sensor based on 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H- porphyrin iron (III) chloride and MWCNT for selective detection of 2,4-D

Exploitation of the electronic properties of carbon nanotubes for the development of voltammetric and amperometric sensors to monitor analytes of environmental relevance has increased in recent years. This work reports the development of a biomimetic sensor based on a carbon paste modified with 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin iron (III) chloride (a biomimetic catalyst of the P450 enzyme) and multi-wall carbon nanotubes (MWCNT), for the sensitive and selective detection of the herbicide 2,4- dichlorophenoxyacetic acid (2,4-D). The sensor was evaluated using cyclic voltammetry and amperometry, for electrochemical characterization and quantification purposes, respectively. Amperometric analyses were carried out at -100 mV vs. Ag/AgCl(KClsat), using a 0.1 mol L-1 phosphate buffer solution at pH 6.0 as the support electrolyte. Under these optimized analytical conditions, the sensor showed a linear response between 9.9 × 10-6 and 1.4 × 10-4 mol L-1, a sensitivity of 1.8 × 104 (±429) μA L mol -1, and limits of detection and quantification of 2.1 × 10 -6 and 6.8 × 10-6 mol L-1, respectively. The incorporation of functionalized MWCNT in the carbon paste resulted in a 10-fold increase in the response, compared to that of the biomimetic sensor without MWCNT. In addition, the low applied potential (-100 mV) used to obtain high sensitivity also contributed to the excellent selectivity of the proposed sensor. The viability of the application of this sensor for analysis of soil samples was confirmed by satisfactory recovery values, with a mean of 96% and RSD of 2.1% (n = 3). © 2013 Elsevier B.V