ECL biosensors

In general, the DNA-based biosensors fabricated by labeling with ECL probe can be divided into three modes (1) dependent on the amount of ruthenium complex integrated into the DNA system without conformation 

3 Detection via the energy transfer between ECL probe and quencher. 

An interesting label-free ECL sensor for DNA detection was developed by using DNA-binding intercalators as co-reactants. Doxorubicin, dauno-rubicin, and 4, 6-diamidino-2-phenylindole (DAPI) (Fig. 7) were recently investigated as good co-reactants for Ru(bpy)3 ECL. Usually, the coreactants selectively intercalate with dsDNA, showing favorable ECL with 

ECL approach, several pathogens were detected and a good specificity of single point mutations for hepatitis disease was accomplished by DAPI intercalated Ru(bpy)3 + ECL. In addition, some ruthenium complex can also be used as ECL-switch molecule with high affinity, such as [Ru(bpy)2dppz] +(dppz = dipyrido[3,2-a 20,30-c]phenazine) ° and Ru(phen)3.  

Z pyndyl ivith nium(li) cDoipm. Daumutioii R, H. R, OH. R.-H) RutbPrt/  

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In this chapter, we summarize advances in the development of ruthenium complex based ECL biosensors mainly focusing on the principle of ECL and their applications in the fabrication of various biosensors. 

Additionally, Ru(bpy)3 /C204 systems were also employed to develop Ru(bpy)3 based enzyme ECL biosensor. In this case, the interaction between H2O2 and C2O4 provides a possible route for H202-generating... 

Quenching effect of ferrocene (Fc) is proved very practical for the development of ECL sensors. A reagentless signal-on ECL biosensor for DNA hybridization detection was developed (see Fig. 6.2). In the development of this biosensor, the quenching effect of Fc on intrinsic cathodic ECL at thin oxide-covered glassy carbon (C/C Oi-x) electrodes was employed. The main advantage of the present sensor lies in the fact that ECL is generated from the electrode itself and no luminophore or luminophore-labeled DNA probe is needed. The detection limit was ca. 5.0 pM (S/N = 3) [18]. 

Cao s group in 2011 designed an ECL biosensor based on the construction of triplex DNA for the detection of adenosine which employs an aptamer as a molecular recognition element and quenches ECL of Ru(bpy)3 by ferrocene monocarboxylic acid (FcA) G ig. 6.5). In the presence of adenosine, the aptamer sequence (Ru-DNA-1) more likely forms the aptamer—adenosine complex with hairpin configuration and the switch of the DNA-1 occurs in conjunction with the... 

Fig. 6.4 The scheme of the ECL biosensor based on the aptamer substitute strategy and ECL quenching effect. Reprinted with permission from Ref. [23]. Copyright 2011 Springer-Verlag...

A new reagentiess ECL biosensor for hydroquinone (HQ) by co-immobilizing the (meso-2,3-dimercaptosuccinic acid) DMSA-CdTe QDs and horseradish peroxidase (HRP) on a glassy carbon electrode, based on its quenching effect to the ECL emission, was demonstrated. The ECL quenching was due to the... 

Several research groups have made contributions to the development of ECL biosensors for applications in pharmaceutics. Many of these examples completely satisfy our requirements, while it seems that still there is need of development in pharmaceutical industry. Currently, various techniques in combination with ECL biosensing formats for the determination of drugs and small molecules have been developed. ECL combined with different systems has also been successfully applied to criminalistic expertize for sensitive determination of narcotics and medicinal preparations [28-33]. 

A performant reagentless ECL system for H2O2 detection based on electrop-olymerized luminol on pre-treated screen-printed electrodes was developed [64]. An ECL biosensor based on carboxylic acid-functionaUzed multi-walled carbon nanotubes (CCX)H-F-MWNT) and Au nanoparticles [65] and immobilization in sol-gel hybrid material was fabricated for sensing the efficiency of ethanol. The intensity of ECL increased linearly with ethanol concentration from 2.5 x 10 5.0 X 10 M and detection limit was 1.0 x 10 M [66]. 

Fig. 7.2 Scheme of the glucose ECL biosensor. Adapted from Ref. [68]. Copyright 2009 Elsevier B.V... 

A FI optical fiber glucose and lactate biosensor [70-72] and a thin-lilm glucose ECL biosensor were also developed based on alcohol-free mesoporous molecular sieve silica modified electrode [73] and immobilization of GOD with MWNT/ Nafion film [74—76]. 

Fig. 7.3 A schematic steps for fabrication of the ECL biosensor (a). Insets are TEM (b) and AFM (c) images of TNTs and ChOx/TNTs/CHIT film. Adapted from Ref. [95]. Copyright 2009 Elsevier B.V...

For a nephrotoxic toxin, ochratoxin A (OTA), an ECL biosensor based on DNA aptamer as the recognition element and N-(4-aminobutyl)-N-ethylisoluminol... 

Lin Z, Chen J, Chen G (2008) An ECL biosensor for glucose based on carbon-nanotube/ Nafion film modified glass carbon electrode. Electrochim Acta 53(5) 2396-2401. doi 10.1016/j. electacta.2007.09.063... 

An electrogenerated chemiluminescence (ECL) biosensor based on polymer-MWNT nanocomposites was prepared by y-irradiation polymerization for ethanol sensing. A higher sensing efficiency for ethanol using the ECL biosensor prepared with PAAc-MWCNT nanocomposites was measured compared with that of an ECL biosensor prepared with PMAc-MWCNT nanocomposites and purified MWCNTs. Experimental parameters affecting ethanol detection were also examined in terms of pH and the content of PAAc-MWCNT nanocomposites in Nafion. Little interference from other compounds was observed for the assay of ethanol. The results suggest that this ECL biosensor could be applied for ethanol detection in real samples. 

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