ABSTRACT
Carbon nanotubes (CNTs) have been extensively used to produce electrodes of enhanced performance but have only been very recently exploited in microfluidic devices. In these cases, CNT electrodes had to be produced prior to device assembly, which might damage the CNT layer. Here, we show a fast and simple method for the reversible nanostructuration of microfluidic electrode devices in situ. The procedure is based on the attachment of single-walled CNTs (SWCNTs) onto the surface of magnetic particles (MPs) and magnetic confinement of the MP/SWCNT composite onto the sensor in a two-step process that provided homogeneous coating. As it is shown, subsequent magnet removal allows MP/SWCNT release and electrode reutilization. Compared to most previously described methods, ours is faster, simpler and also reversible.
Subject(s)
Microfluidic Analytical Techniques/methods , Nanotubes, Carbon/chemistry , Electrodes , Ferrocyanides/chemistry , Lab-On-A-Chip Devices , Magnetics , Microfluidic Analytical Techniques/instrumentationABSTRACT
In this work, chronoamperometric myelo-peroxidase (MPO) detection was accomplished using immunofunctionalized magnetic microparticles (MPs), disposable carbon screen-printed electrodes (C-SPEs), and a ready-to-use commercially available tetramethylbenzidine (TMB)-based enzymatic substrate. In order to reach the limit of detection (LOD) needed to study real blood serum samples, assay performance was additionally improved by exploiting CNT wiring, which amplified the signal and decreased the LOD. The optimized assay can be performed in 30 min and yields LODs of 6 and 55 ng mL(-1) in PBS and undiluted human serum, respectively, making it useful for the identification of patients at risk of cardiovascular disease. These results demonstrate that electrode nanostructuring can be accomplished "post-assay," which favors the development of enhanced magneto immunosensors based on the exploitation of cheap and simple SPE devices.
Subject(s)
Immunoassay/instrumentation , Immunoassay/methods , Nanotechnology/methods , Nanotubes, Carbon/chemistry , Peroxidase/chemistry , Benzidines/chemistry , Calibration , Carbon/chemistry , Cardiovascular Diseases/diagnosis , Cardiovascular Diseases/metabolism , Electrochemistry/methods , Electrodes , Humans , Limit of Detection , Magnetics , Spectrophotometry , TemperatureABSTRACT
We show that target binding onto ferrocene-modified magnetic microparticles (MP-Fc) promotes physical sheltering of the labels. This can be measured electrochemically by CNT wiring, which enhances ten-fold the signals registered compared to direct detection of the MPs alone. As a proof of concept, detection of detergents and antibodies is accomplished. In these preliminary experiments, random binding of 0.01% Tween 20 onto MP-Fc was detectable both voltametrically and impedimetrically after a 2 min incubation. Furthermore, affinity capture of 4 µg mL(-1) of biotinylated antibody by streptavidin MP-Fc could be measured in less than 30 min and even in the presence of 1 mg mL(-1) of BSA.
