Stability biosensor applications

With regard to biosensor applications, a wide variety of electrochemically active species (ferrocene, ruthenium complexes, or carbon and metal (Pt, Pd, Au...) [185,186] were also introduced into the sol-gel matrices or adsorbed to improve the electron transfer from the biomolecules to the conductive support [187,188]. For instance, glucose oxidase has been trapped in organically modified sol-gel chitosan composite with adsorbed ferrocene to construct a low-cost biosensor exhibiting high sensitivity and good stability [189]. 

N.A. Chaniotakis, Enzyme stabilization strategies based on electrolytes and polyelectrolytes for biosensor applications. Anal. Bioanal. Chem. 378, 89-95 (2002). 

S. Sotiropoulou, V. Vamvakaki and N.A. Chaniotakis, Stabilization of enzymes in nanoporous materials for biosensor applications, Biosens. Bioelectron, 20 (2005) 1674-1679. 

The third advantage, the chemical stability of DNA aptamers, can solve the main problem of protein-based biosensors. The chemical and physical instability of protein-based biosensors is always claimed in practical use, and this limits the range of biosensor application. However, DNA is chemically stable. It is stable within the pH range 2 to 12 and is thermally renaturable Even if it is denatured at 100°C, it is refolded at room temperature. Even RNA aptamers can gain stability upon 1 modification therefore, aptamers have the potential to enhance the applicability of biosensors in practical contexts. Additionally, aptamers can be immobilized onto substrates using DNA microarray fabrication technology, and aptamer microarrays can be created. 

Chang B, Su Z (2005) Kinetic model for simultaneous cell disruption and aqueous two-phase extraction. J Chem Technol Biotechnol 81(3) 454-460 Chaniotakis NA (2004) Enzyme stabilization strategies based on electrolytes and polyelectrolytes for biosensor applications. J Anal Bioanal Chem 378(l) 89-95 Chaplin MF, Bucke C (1990) Enzyme technology. Cambridge University Press, Cambridge, 264 pp... 

H. Yamato, M. Ohwa, and W. Wernet, Stability of polypyrrole and poly(3,4-ethylenediox-ythiophene) for biosensor application, J. Electroanal. Chem., 397(1-2), 163-170 (1995). 

In addition to nucleic acids, enzymes have also been incorporated into conducting a polymer matrix for biosensor applications. As a transducer, a CP can convert the chemical response into an electric current. To enhance the sensitivity and the response time, fabrication of CPs/enzyme nanocomposites with large surface area is a meaningful objective. Syu and Chang demonstrated the immobilization of urease onto PPy nanotubes over carbon paper substrate by a physical entrapment approach [124]. The composite electrodes exhibited a detection sensitivity for the determination of urea of 53.74 mVdecade and a detection limit on the urea concentration of 1.0 pM. Furthermore, the composite electrode shows rapid response, storage stability and reusability. Lipase can also be covalently immobilized... 

D Souza, S. F. 2001. Immobilization and Stabilization of Biomaterials for Biosensor Applications. Applied Biochemistry and Biotechnology 96 (l-3) 225-238. 

Yamato H, Ohwa M, Wemd W (1995) Stability of polypyrrole and poly(3,4-ethylenedioxythiophene) for biosensor application. J Electroanal Chem 397 163-170 Ludwig KA, Uram JD, Yang JY et al (2006) Chronic neural recordings using silicon microelectrode arrays electrochemicaUy deposited with a poly(3,4-ethylemedioxythiophene) (PEDOT) film. J Neural Eng 3 59-70... 

D Souza SF (2001) Immobilization and stabilization of biomateriais for biosensor applications. Appl Biochem Biotechnol 96 225-238... 

Enzyme electrodes belong to the family of biosensors. These also include systems with tissue sections or immobilized microorganism suspensions playing an analogous role as immobilized enzyme layers in enzyme electrodes. While the stability of enzyme electrode systems is the most difficult problem connected with their practical application, this is still more true with the bacteria and tissue electrodes. 

AET has also demonstrated very high operational thermal stability for immobilized biocatalysts, which is applicable to a multitude of industrial areas including the biocat-alytic and biosensor industries. 

Enzyme-based optical sensor applications will be further described in this book. They are still the most widespread optical biosensors but work is needed to overcome limitations such as shelf life, long term stability, in situ measurements, miniaturization, and the marketing of competitive devices. 

B. Haghighi, S. Varma, F.M. Alizadeh, Y. Yigzaw, and L. Gorton, Prussian blue modified glassy carbon electrodes - study on operational stability and its application as a sucrose biosensor. Talanta 64, 3-12 (2004). 

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