Tethered DNA scaffolds on optical sensor platforms for detection of hipO gene from Campylobacter jejuni

DNA biosensors have gained increased attention over traditional diagnostic methods due to their fast and responsive operation and cost-effective design. The specificity of DNA biosensors relies on single-stranded oligonucleotide probes immobilized to a transduction platform. Here, we report the development of biosensors to detect the hippuricase gene (hipO) from Campylobacter jejuni using direct covalent coupling of thiol- and biotin-labeled single-stranded DNA (ssDNA) on both surface plasmon resonance (SPR) and diffraction optics technology (DOT, dotLab) transduction platforms. This is the first known report of the dotLab to detect targeted DNA. Application of 6-mercapto-1-hexanol as a spacer thiol for SPR gold surface created a self-assembled monolayer that removed unbound ssDNA and minimized non-specific detection. The detection limit of SPR sensors was shown to be 2.5 nM DNA while dotLab sensors demonstrated a slightly decreased detection limit of 5.0 nM (0.005 μM). It was possible to reuse the SPR sensor due to the negligible changes in sensor sensitivity (∼9.7 × 10 -7 ΔRU) and minimal damage to immobilized probes following use, whereas dotLab sensors could not be reused. Results indicated feasibility of optical biosensors for rapid and sensitive detection of the hipO gene of Campylobacter jejuni using specific ssDNA as a probe. © 2011 Elsevier B.V.

Electrochemical determination of antimalarial drug amodiaquine in maternal milk using a hemin-based electrode

Voltammetric analysis of amodiaquine using a hemin biosensor revealed a well-defined peak at 0.14 V (vs. Ag/AgCl), corresponding to the oxidation of amodiaquine at pH 7.0. The electrodic behavior indicated that the oxidation process was irreversible, and that it was controlled by diffusion. In addition to advantages such as high selectivity and sensitivity, the method developed could be used for the analysis of breast milk containing amodiaquine without any need for prior sample treatment, an important consideration in routine analysis laboratories. Measurements of the drug contained in breast milk were used to validate the technique. The detection limit for standard solutions was 3.30 mg L-1, and the quantification limit was 11.0 mg L-1. ©The Electrochemical Society.

An optimised electrochemical biosensor for the label-free detection of C-reactive protein in blood

C-reactive protein (CRP) is an acute phase protein whose levels are increased in many disorders. There exists, in particular, a great deal of interest in the correlation between blood serum levels and the severity of risk for cardiovascular disease. A sensitive, label-free, non-amplified and reusable electrochemical impedimetric biosensor for the detection of CRP in blood serum was developed herein based on controlled and coverage optimised antibody immobilization on standard polycrystalline gold electrodes. Charge transfer resistance changes were highly target specific, linear with log. CRP. concentration across a 0.5-50. nM range and associated with a limit of detection of 176. pM. Significantly, the detection limits are better than those of current CRP clinical methods and the assays are potentially cheap, relatively automated, reusable, multiplexed and highly portable. The generated interfaces were capable not only of comfortably quantifying CRP across a clinically relevant range of concentrations but also of doing this in whole blood serum with interfaces that were, subsequently, reusable. The importance of optimising receptor layer resistance in maximising assay sensitivity is also detailed. © 2012.

Evaluation of the interactions of DNA with the textile dyes Disperse Orange 1 and Disperse Red 1 and their electrolysis products using an electrochemical biosensor

A disposable pencil graphite electrode modified with dsDNA was used in combination with square wave voltammetry in order to evaluate the interaction of DNA with the textile dyes Disperse Orange 1 (DO1) and Disperse Red 1 (DR1), and with the products of their electrolysis. Significant changes in the characteristic oxidation peaks of the guanine and adenine moieties of immobilized dsDNA were observed after incubation of the modified electrode for 180 s in solutions of the dyes in their original forms. The same was observed using the electrolysis products obtained by oxidation and reduction conversions. The oxidation peak currents of the guanine and adenine moieties decreased when the concentrations of DO1 and DR1 were increased up to 5.0 × 10 -6 and 1.0 × 10-6 mol L-1, respectively; the signal decreases were more pronounced after interaction with the oxidized dyes, compared to the reduced compounds. The interactions between DNA and DO1, DR1, and the electrolyzed dyes were further investigated by UV-vis spectrophotometry in solution, and different effects such as hypochromism and hyperchromism were observed in the resulting DNA spectra. The investigated interactions showed clear evidence of changes in the DNA structure, and suggested a predominant intercalation mode leading to damage in the biomolecule. © 2013 Elsevier B.V.

Toward pH-controllable bioelectrocatalysis for hydrogen peroxide based on polymer brushes

In the present work, a biosensor was built with smart material based on polymer brushes. The biosensor demonstrated a pH-sensitive on-off property, and it was further used to control or modulate the electrochemical responses of the biosensor. This property could be used to realize pH-controlled electrochemical reaction of hydrogen peroxide and HRP immobilized on polymer brushes. The composite film also showed excellent amperometric i-t response toward hydrogen peroxide in the concentration range of 0-13 μM. In future, this platform might be used for self-regulating targeted diagnostic, drug delivery and biofuel cell based on controllable bioelectrocatalysis. © 2013 Elsevier B.V.

Luminescence Enhancement of Carboxyl-Coated CdTe Quantum Dots by Silver Nanoparticles

Metallic nanoparticles (NPs) have been used to improve the sensibility of biosensors and bioassays either by enhancing radiative emission or inducing quenching process on fluorescent probes. The aim of this research was to study the interaction of silver and silver-pectin NPs with water-dispersed carboxyl-coated cadmium telluride (CdTe) quantum dots (QDs). Metallic NPs were observed to change the emission of these fluorophores through local field effects. In a solution-base platform, an increase of 82 % was observed for the CdTe emission due to the interaction of QDs and silver-pectin NPs. QDs interaction with silver NPs without pectin was also investigated and a smaller emission enhancement of 20 % was detected. We observed that the NPs' nature and QDs' surface charge and concentration are important parameters for NPs-QDs interaction. Moreover, the presence of the pectin polymer shows to be a key component to the observed fluorescence enhancement. © 2013 Springer Science+Business Media New York.

Switchable biosensor controlled by biocatalytic process

The poly(dimethylamino methacrylate) (PDMAEMA) brush-modified indium tin oxide (ITO) electrode was used to test the switch properties of interfacial activity caused by bioelectrochemical signals. The swelling of the polymer brushes increased when the medium's pH changed from alkaline to acid after glucose was added to the system. A pH change generated in situ by means of biocatalytic reactions enabled bioelectrocatalytic interface's reversible activation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

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 30min. 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. © 2013 Elsevier Inc.

Label free redox capacitive biosensing

A surface confined redox group contributes to an interfacial charging (quantifiable by redox capacitance) that can be sensitively probed by impedance derived capacitance spectroscopy. In generating mixed molecular films comprising such redox groups, together with specific recognition elements (here antibodies), this charging signal is able to sensitively transduce the recognition and binding of specific analytes. This novel transduction method, exemplified here with C-reactive protein, an important biomarker of cardiac status and general trauma, is equally applicable to any suitably prepared interfacial combination of redox reporter and receptor. The assays are label free, ultrasensitive, highly specific and accompanied by a good linear range. © 2013 Elsevier B.V.

Estudo das propriedades dielétricas e de bloqueio das monocamadas automontadas

Pós-graduação em Biotecnologia - IQ

Fabricação e caracterização morfológica de filmes layer-by-layer de DODAB/FTALOCIANINA de níquel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese, caracterização e aplicação de filmes a base de óxido de zinco

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Filmes nanoestruturados para a detecção de glicose e sacarose em bebidas comerciais

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento de um biossensor para a detecção de antibióticos β-lactâmicos no leite crú

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento e aplicação de sensor biomimético descartável para detecção seletiva de hidroquinona

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)