Electrochemical detection microfluidic chips

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The use of ELISA is broad and it finds applications in many biological laboratories over the last 30 years many tests have been developed and vahdated in different domains such as clinical diagnostics, pharmaceutical research, industrial control or food and feed analytics for instance. Our work has been to redesign the standard ELISA test to fit in a microfluidic system with disposable electrochemical chips. Many applications are foreseen since the biochemical reagents are directly amenable from a conventional microtitre plate to our microfluidic system. For instance, in the last 5 years, we have reported previous works with this concept of microchannel ELISA for the detection of thromboembolic event marker (D-Dimer) [4], hormones (TSH) [18], or vitamin (folic acid) [24], It is expected that similar technical developments in the future may broaden the use of electroanalytical chemistry in the field of clinical tests as has been the case for glucose monitoring. This work also contributes to the novel analytical trend to reduce the volume and time consumption in analytical labs using lab-on-a-chip devices. Not only can an electrophoretic-driven system benefit from the miniaturisation but also affinity assays and in particularly immunoassays with electrochemical detection. 

As an example of microchip-based electrochemical immunoassays, we describe here the protocol established for the analysis of interleukin IB by enzyme linked immunosorbent assay (ELISA) with amperometric detection at the sub-pM level in DiagnoSwiss microfluidic chip called Immuchip . 

Electrochemical detection offers also great promise for CZE microchips, and for other chip-based analytical microsystems (e.g., Lab-on-a-Chip) discussed in Section 6.3 (77-83). Particularly attractive for such microfluidic devices are the high sensitivity of electrochemical detection, its inherent miniaturization of both the detector and control instrumentation, low cost, low power demands, and compatibility with micromachining technologies. Various detector configurations, based on different capillary/working-electrode... 

The ability to modulate electrochemical reactivity and effectively switch OFF the reaction was extended further by Wang and coworkers [174] to control, on-demand, the separation and detection processes in microfluidic devices. In this work, the catalytic nickel nanowires were placed, reoriented and removed on-demand at the exit of the separation channel of the microfluidic chip, offering unique possibilities for controlling externally, events inside and outside a microchannel. 

The detection principles for biosensors integrated on microfluidic chips are classified into several types, including optical, electrochemical, and mass-sensitive methods. The trend in the development of detectors has been to constantly pursue two key virtues sensitivity and selectivity. In this regard, the research issues on the detectors for microfluidic systems are not significantly different to those for conventional biosensors. 

Electrochemical detection has been regarded as particularly appropriate strategy for microfluidic chip systems. Electrochemical biosensors in microfluidic chips enable high sensitivity, low detection limits, reusability, and long-term stability. And the detection mechanism and instmmentation for realization are simple and cost-effective. These valuable features have made electrochemical devices receive considerable attention [20,94,95]. The electrochemical detectors are commercially available for a variety of analyses [96]. The review written by Wang summarized the principles of electrochemical biosensors, important issues, and the state-of-the-art [97]. Lad et al. described recent developments in detecting creatinine by using electrochemical techniques [98]. 

Zhu et al. have developed a chip for heavy metal ion electrochemical detection". By controlling the microfluidics, a mercury droplet microelectrode is generated on the chip. Square wave stripping voltammetry is used for analysis. 

Ultrasensitive detection of separated analytes is required for enabling quantitative measurements of intracellular components from single cells on a microfluidic chip. The most widely used detection method is Laser-induced fluorescence (LIF) in a variety of configurations because of its extreme sensitivity and availabiUty of fluorophore conjugation strategies. Absorption measurements are less sensitive than fluorescence detection but they can be applied to unlabeled, general chemical species. Another label-free detecrimi method is electrochemical detection. 

Sensitive and selective detection techniques are of crucial importance for capillary electrophoresis, microfluidic chips, and other microfluidic analysis systems. Electrochemical detector has attracted considerable interest in these fields owing to its high sensitivity, inherent miniaturization of both the detection and control instrumentation, low cost and power demands, and high compatibility with microfabrication technology. The commonly used electrochemical detection approaches can be classified into three general modes COTiductimetry, potentiometry, and amperometry. 

Electrochemical techniques play a key role in CE, microchip CE, and other microfluidic systems. Future directions of electrochemical techniques will focus on the minimization of the electrochemical detection device and the integration of the electronic circuit and the detection electrodes on microfluidic chips. With the rapid development of microfluidic chips, it is highly desirable to develop new theoretical models, experimental methods, and new experimental devices for the electrochemical detection in microfluidic analysis systems. 

Another interesting result is that clamping with 50 xm thin PDMS gaskets did even seal systems where the glass chip had 300 nm thick electrodes on the surface. Planar electrodes microfabricated on glass chips are widely used in microfluidic systems, e. g., for electrochemical detection, ECL (electrochemoluminescence) detection, dielectrophoresis, AC electroosmotic flow and electrohydrody-... 

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