RESUMO
Low-cost piezoelectric devices, such as simple frequency monitoring quartz crystal microbalance (QCM) devices, have good clinical utility as fast diagnostic tools for the detection of several diseases. However, unspecific antigen recognition, poor molecular probe adsorption and the need for sample dilution are still common drawbacks that hinder their use in routine diagnosis. In this work, piezoelectric sensors were previously coated with thin films of bacterial cellulose nanocrystals (CN) to provide a more sensitive and adapted interface for the attachment of monoclonal immunoglobulin G (IgGNS1) and to favor specific detection of non-structural protein 1 (NS1) of dengue fever. The assembly of the immunochip surface was analyzed by atomic force microscopy (AFM) and the NS1 detection was followed by quartz crystal microbalance with (QCM-D) and without energy dissipation monitoring (QCM). The CN surface was able to immobilize 2.30±0.5mgm-2 of IgGNS1, as confirmed by AFM topography and phase images along with QCM-D. The system was able to detect the NS1 protein in serum with only 10-fold dilution in the range of 0.01-10µgmL-1 by both QCM and QCM-D. The limits of detection of the two devices were 0.1µgmL-1 for QCM-D and 0.32µgmL-1 for QCM. As a result, QCM-D and QCM apparatuses can be used to follow NS1 recognition and have good potential for more sensitive, fast and/or less expensive diagnostic assays for dengue.
Assuntos
Vírus da Dengue/isolamento & purificação , Dengue/diagnóstico , Nanopartículas/química , Polissacarídeos Bacterianos/química , Técnicas de Microbalança de Cristal de Quartzo/instrumentação , Proteínas não Estruturais Virais/sangue , Anticorpos Imobilizados/química , Bactérias/química , Técnicas Biossensoriais/instrumentação , Celulose/química , Dengue/sangue , Dengue/virologia , Desenho de Equipamento , Humanos , Imunoensaio/instrumentação , Dispositivos Lab-On-A-Chip , Nanopartículas/ultraestrutura , Proteínas não Estruturais Virais/análiseRESUMO
Films of non-stoichiometric tungsten oxides have been deposited onto glassy carbon surfaces by electrodeposition from acidic W(VI) solutions and the chemical stability of these oxides was investigated by using the electrochemical quartz crystal microbalance. At these modified surfaces, rotating disc electrode voltammetric experiments indicated that iodate is electrocatalytically reduced in a mass-transport controlled process. The influence of the film thickness on the response to iodate was investigated and the results indicated a linear relationship between catalytic current and film thickness for relatively thin oxide layers. The modified electrode was employed successfully as an amperometric sensor for iodate in a flow injection apparatus. The linear response of the developed method is extended from 5 micromol L(-1) to 5 mmol L(-1) iodate with a limit of detection (signal-to-noise=3) of 1.2 micromol L(-1). The repeatability of the method for 41 injections of a 1 mmol L(-1) iodate solution was 0.8% and the throughput was determined as 123 h(-1). Interference from other oxidant anions such as nitrate and nitrite was not noticeable, whereas bromate and chlorate interfere at slight levels. The method was used in the determination of the iodate content in table salt samples.