Multi-electrode arrays

Cheung KC, Djupsund K, Dan Y (2003) Implantable multi-channel electrode array based on SOI technology. Journal of Microelectromechanical Systems 12 179-184. 

Multiple electrodes have been used to obtain selectivity in electrochemical detection. An early example involved the separation of catecholamines from human plasma using a Vydac (The Separation Group Hesperia, CA) SCX cation exchange column eluted with phosphate-EDTA.61 A sensor array using metal oxide-modified surfaces was used with flow injection to analyze multicomponent mixtures of amino acids and sugars.62 An example of the selectivity provided by a multi-electrode system is shown in Figure 2.63... 

Fig. 3 Schematic illustration of a microfabricated multi-element array A comprising 32 interdigitated microsensor electrodes, and B comprising 64 independently addressable microdisc voltametric electrodes. Each device shows the large area counter electrode (middle) and the reference electrode as a band around the counter electrode...

Pierce introduced an array-of-arrays microplate product called Search-Light in which antibodies are directly printed into the wells of the microplate. Also, we have reviewed MSD s Multi-Spot plate products having antibodies immobilized onto multiple working electrodes. These products (albeit with some novel approaches to create microarrays and means for detection) utilize the classic immunosorbent sandwich assay but have the advantage of parallel processing using microarrays. 

A multi-MIP array has been fabricated photolithographic ally for determination of an albuterol broncholidator (Table 6) [185]. 20-pm diameter acrylic MIP beads have been synthesized by co-polymerization of the benzyl methacrylate functional monomer, MAA functional monomer and HEMA cross-linker in the propylene glycol monomethyl ether acetate porogenic solvent. Thermo-radical polymerization on a Pt electrode was initiated by AIBN. Albuterol was recognized in the... 

Sensors of this type were constructed as multi-electrode arrays bearing chohnesterases of differing sensitivity to organo-phosphates, and the assay extended to milk [35]. Both spiked milk and milk from shops inhibited the activity of the electrodes. In two instances, estimates of the level of organo-phosphates in spiked milk made using sensors were very close to those made using GC-MS. This appears to have been a fortunate co-incidence as the response curves used for calibration were not linear. Nine out of ten milk samples from shops inhibited at least some members of the array. In only one case did the GC-MS assay find insecticides in the samples, but the insecticides were not organo-phosphates. The inhibition shown by the enzyme-based arrays was reversible by pyridine-2-aldoxime... 

Hill, B. A., Kleiner, H. E., Ryan, E. A., Dulik, D. M., Monks, T. J., and Lau, S. S. (1993). Identification of multi-S-substituted conjugates of hydroquinone by HPLC-coulometric electrode array analysis and mass spectroscopy. Chem. Res. Toxicol. 6 459-469. 

The detector disclosed in US-A-S006711 refers to an HgCdTe multi-element detector array formed on a sapphire substrate. The elements have individual electrodes and a common electrode. When the electrodes are formed by a lift-off process, the maximum thickness of the metal layer forming the electrodes is limited due to the operational characteristics of the lift-off process. This results in a non-negligible resistance of the common electrode, which gives the device a low sensitivity. To reduce the resistance of the common electrode, an auxiliaiy electrode is formed on an aperture plate such that when the aperture plate is assembled onto the detector, the auxiliary electrode is pressed onto the common electrode. 

An electrochemical flow detector, based on four working electrodes coated with different permselective film types, for use in flow-injection measurements of multiple nitroaromatic explosives was recently developed [18]. The resulting array response (Fig. 4) offers unique fingerprints of such explosive compounds. Electrochemical devices are extremely attractive for designing such e-nose-type multi-electrode arrays that combine several partially selective electrodes and lead to a distinct response pattern (signature) for mixtures of organic vapors without prior separation [2],... 

Electrochemical detection is very sensitive for the compounds that can be oxidized or reduced at low-voltage potentials. Therefore, it could also be applied in the HPLC analysis of phenolic acids that are present in natural samples at very low concentrations. With the recent advances in electrochemical detection, multi-electrode array detection is becoming a powerful tool for detecting phenolic acids and flavonoids in a wide range of samples. The multi-channel coulometric detection system may serve as a highly sensitive way for the overall characterization of antioxidants the coulometric efficiency of each element of the array allows a complete voltametiic resolution of analytes as a function of their reaction (redox) potential. Some peaks may be resolved by the detector, even if they are unresolved when they leave the HPLC column. ... 

Van Vliet E, Stoppini L, Balestrino M, et al. Electrophysiological recording of reaggregating brain cell cultures on multi-electrode arrays to detect acute neurotoxic effects. Neurotoxicology. 2007 28 1136-1146. 

---