Silicon microchip

Yakovleva, J., Davidsson, R., Lobanova, A., Bengtsson, M., Eremin, S., Laurell, T., Emneus, J., Microfluidic enzyme immunoassay using silicon microchip with immobilized antibodies and chemiluminescence detection. Anal. Chem. 2002, 74(13), 2994-3004. 

Takao, H., Noda, T., Ashiki, M., Miyamura, K., Sawada, K., Ishida, M., A silicon microchip for blood hemoglobin measurement using multireflection structure. Micro Total Analysis Systems, Proceedings 5th i7AS Symposium, Monterey, CA, Oct. 21-25, 2001, 363-364. 

The basic unit of information in computer science is the binary digit or bit, whose physical realization is a component capable of two stable states, say, 0) and 1). In a conventional computer, these usually correspond to charged and uncharged states of tiny capacitors within a silicon microchip. On an atomic level, bits might in concept be represented by the two orientations of an electron spin or the two polarization states of a photon. Apart from economy of scale, an atomic two-level system has a capability beyond that of a classical component, namely, the possibility of being in a coherent superposition such as... 

An early discovery during the development of microchip PCR was the importance of surface chemistry in microchip operation and design. This work demonstrated that PCR in silicon microchips was severely inhibited if the surface chemistry was unsuitable. These workers noted that the increase in surface area in microchips, relative to volume,... 

Figure 4. (A) Current-time trace recorded upon introduction of [Fe(CN)6] , menadione and glucose to S. cerevisiae cells on an electrode microchip. (B) A silicon microchip for mediated amperometry (upper panel) and a microscope image of S. cerevisiae cells on a microband electrode (widtMength 25/1,000 pm). (Reprinted with permission from Ref. [8], 2009 Elsevier BV.) (Lower panel).

Xu Q, Zhu JJ, Hu XY (2007) Ordered mesoporous polyanifine film as a new matrix for enzyme immobilization and biosensor construction. Anal Chun Acta 597(1) 151—156 Yakovleva J, Davidsson R, Lobanova A et ak (2002) Enzyme immunoassay using silicon microchip with immobilized antibodies and chemiluminescence detection. Antd Chem 74(13) 2994—3004 Yamada H, Kobayashi M (1996) Nitrile hydiatase and its application to industrial production of acrylamide. Biosci Biotechnol Biochem 60 1391—1400 Yamamoto K, Ohgam T, Torimura M et al. (2000) Highly-sensitive flow injection determination of hydrogen peroxide with a peroxidase-immobilized electrode and its application to clinical chemistry. Anal Chim Acta 40(2) 201—207... 

In contrast, very small activity can be observed in the field of HPLC on chip. The simplest approach to microfluidic HPLC devices that mimic typical chromatographic columns include channels packed with chromatographic beads." " " However, an early attempt by Ocvirk et al." " to pack channel on a silicon microchip with beads was not very successful due to technical difficulties, and the 20-mm long microfluidic HPLC column generated only 200 theoretical plates (4000 plates/m). 

MALDI-MS was also implemented as a detection system for monitoring the reaction products of chemical or biochemical reactions in microfluidic reactors. In one approach, a continuous flow glass or silicon microchip that comprised a microdigestion reactor was incorporated into the standard MALDI plate of the MS instrument (Figure 53.13). The vacuum of the MS chamber was used as a driving force for inducing flows in the reaction microchannels. The device was used for organic synthesis and biochemical reactions carried out entirely inside the MALDI-MS vacuum chamber. 

To our knowledge, Denlinger et al. (1994) were the first who successfully built a microchip based calorimeter using a silicon chip they made themselves. Such small systems were increasingly used during the past decade (Schick and Hohne, 2003, 2005) they were normally fabricated with silicon microchips available at that time. The purpose of these devices was originally a different one, but they proved to be suitable for calorimetric purposes. As a result, the chips were more and more optimized for thermal sensing or calorimetric applications (Herwaarden, 2005). 

The Emneus group in Denmark has reported the sensing of atrazine in surface water using microfluidic enzyme immunoassay and chemiluminescence as the transduction technique [19]. Silicon microchips were functionalized with proteins A and G via a hydrophilic polymer layer. An affinity capture competitive immunoassay was performed using a mixture of enzyme tracer [horseradish peroxidase (HRP)], atrazine sample, and antiatra-zine antibody which was subsequently injected on the microchannel, followed by addition of the substrate mixture [luminol/p-iodophenol (PIP)/H202]. Chemiluminescent oxidation of luminol/PIP/H202 in the presence of HRP enzyme was monitored via PMT. 

Microfluidic systems based on the previous recycling reaction are proposed by Emneus et al. for specific analysis of MSG with fluorescence detection [24]. GIDH and D-PhgAT are covalently immobilized on the surface of silicon microchips containing 32 porous flow channels for one of the systems, and on polystyrene Poros beads for the other. The first microfluidic chip is fabricated according to the literature [25,26]. The... 

With silicon microchips, the MSG calibration curve following this protocol is linear between 3.1-50 Xmol L Vith a minimum detection limit of 3 p,mol L calculated using threefold signal-to-noise ratio. 

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