Multienzyme sensors

In general, enzymes to be used in multienzyme sensors should fulfill the following requirements ... 

The main hindrance to practical application of those multienzyme sensors is that they respond to all substrates of the sequence. 

Multienzyme Electrodes. Coupling the reactions of two or more immobilized enzymes increases the number of analytes that can be measured. An electro-inactive component can be converted by an enzyme to a substrate that is subsequentiy converted by a second enzyme to form a detectable end product (57). For example, a maltose [69-79-4] sensor uses the enzymes glucoamylase and glucose oxidase, which convert... 

Michel P.E., Gautier S.M., Blum L.J., Effect of compartmentalization of the sensing layer on the sensitivity of a multienzyme-based bioluminescent sensor for L-lactate, Anal. Lett. 1996 29 (7) 1139-1155. 

A similar approach has been used to solve more complicated cases of two enzymes in one layer (Schulmeister and Scheller, 1985, p. Ill) and the multi-layer/multienzyme model (Schulmeister, 1987, p. 223). It is important to note that oxidases are one of the largest group of enzymes and therefore the improved sensors for substrates other than glucose can and have been developed according to this scheme. 

The inactivation of certain enzymes such as cholesterol oxidase (CO) on interaction with Au nanoparticles is overcome by immobilizing CO and cholesterol esterase (CE) in a carragenean hydrogel and coupling with Au particles loaded with HRP. This multienzyme device has been shown to be very useful in the determination of cholesterol in serum and whole blood [172]. The sensor operates at low potentials avoiding major interferences. The presence of the hydrogel enables the analysis of whole blood with no fouling of the electrode surface. 

The lactate oxidation catalyzed by LMO forms the basis of several other multienzyme electrodes (Fig. 86). The LDH-LMO sensor has also been used to assay the activity of alanine aminotransferase (ALAT, EC 2.6.1.2) and pyruvate kinase (PK, EC 2.7.1.40) (Weigelt 1987 Weigelt et al., 1988). The sample was added to the NADH-containing measuring solution and when the steady state signal for endogenous lactate and pyruvate was attained the substrates of the enzyme to be determined... 

Since not all enzyme-catalyzed reactions involve changes in the level of compounds detectable at an electrode, such as oxygen, or hydrogen peroxide, only a limited number of substances can be determined with one-enzyme sensors. One way of overcoming this problem is to couple the catalytic activities of different enzymes either in sequence, in competing pathways, or in cycles. In general, enzymes to be used in multienzyme electrodes should fulfil the following requirements ... 

Kukla A. L., Kanjuk N. I., Starodub N. F., and Shirshov Y. M., Multienzyme electrochemical sensor array for determination of heavy metal ions. Sens. Actuators B, 57, 213-218, 1999. 

Urban, G., Jobst, G., Keplinger, E, Aschauer, E., Tilado, O., Faschlng, R., Kohl, E, 1992. Miniaturized multienzyme biosensors integrated with pH sensors on flexible polymer carriers for in vivo applications. Biosens. Bioelectron. 7, 733-739. 

Other researchers have followed related strategies as described above for detection of IL-6. For example, Wang et. al. [75] reported an amperometric immunosensor to detect interleukin-6 (lL-6) using a AuNP-Poly-dopamine sensor platform and multienzyme-antibody functionalized AuNPs on carbon nanotubes. They obtained a DL of 1 pg mL for lL-6 in buffer. Du et. al. [76] used AuNP-modified screen printed carbon electrode to detect p53 phosphorylated at Ser392 (phospho-p53 ) along with multi-enzyme labeled graphene oxide (GO). 

Solna R, Sapelnikova S, SklMal P, Minther-Nielsen M, Carlsson C, Emneus J, Ruzgas T (2(X)5) Multienzyme electrochemical array sensor for determination of phenols and pesticides. Talanta 65 349-357... 

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