Vicky Vamvakaki

Novel carbon materials in biosensor systems.

In this work, novel carbon materials are evaluated as transducers, stabilizers and mediators for the construction of amperometric biosensors. It is shown that materials such as fullerenes and carbon nanotubes are promising materials as electrochemical mediators and enzyme stabilizers. Additionally porous carbon and porous glassy carbon are excellent transducers for amperometric measurements, while they provide cavities adequate for enzyme immobilization. At the same time, the sensitivity to peroxide is shown to depend on the activation procedures. Treatment that introduces oxygen groups increases the sensitivity of the carbon-based sensor to hydrogen peroxide considerably. These materials are used for the construction, mediation and stabilization of glucose biosensor.

Biomimetically synthesized silica-carbon nanofiber architectures for the development of highly stable electrochemical biosensor systems.

Biomimetically synthesized silica and conductive activated carbon nanofibers (CNFs) are used in a synergistic manner for the development of a novel electrochemical biosensor system. Poly(L-lysine) templated silica grows and encapsulates the CNF-immobilized enzyme generating a highly stabilizing nanostructured environment for the underlying protein. Concurrently, CNFs provide both the required surface area for the high-capacity enzyme immobilization required in biosensors as well as direct electron transfer to the inner platinum transducer. As a result, this silica/nanofiber superstructure is an ideal architecture for the development of electrochemical biosensor systems that can withstand exposure to extreme operational conditions, such as high temperatures or the presence of proteases. Acetylcholine esterase is used as the model catalyst and with the aid of spectroscopic data it is shown that the observed high operational stability of the biosensor is due to the direct interaction of the protein with the silica backbone, as well as due to the nanostructured enzyme confinement.

Electrochemical Biosensing Systems Based on Carbon Nanotubes and Carbon Nanofibers

Abstract Carbon nanomaterials are in the forefront of research in a variety of chemical and physical disciplines. Of these, certain nanostructures seem to be suitable for the development of electrochemical biosensors. In particular carbon nanotubes, and carbon nanofibers have specific chemical and physical characteristics that lent them ideal for the development of biosensors with unique analytical characteristics. In particular, their conductivity, surface area, inherent and induced chemical functionalities, and biocompatibility provide the grounds for the development of a new era of electrochemical biosensors. In this review, we will examine the recent developments of biosensor design based on these new nanostructures.

Comparison of protein immobilisation methods onto oxidised and native carbon nanofibres for optimum biosensor development

AbstractThe properties of native and oxidised graphene layered carbon nanofibres are compared, and their utilisation in enzyme biosensor systems using different immobilisation methods are evaluated. The efficient oxidation of carbon nanofibres with concentrated H2SO4/HNO3 is confirmed by Raman spectroscopy while the introduction of carboxylic acid groups on the surface of the fibres by titration studies. The oxidised fibres show enhanced oxidation efficiency to hydrogen peroxide, while at the same time they exhibit a more efficient and selective interaction with enzymes. The analytical characteristics of biosensor systems based on the adsorption or covalent immobilisation of the enzyme glucose oxidase on carbon nanofibres are compared. The study reveals that carbon nanofibres are excellent substrates for enzyme immobilisation allowing the development of highly stable biosensor systems. FigureImmobilization of proteins on carbon nanofibres

Spectro-electrochemical studies of acetylcholinesterase in carbon nanofiber-bioinspired silica nanocomposites for biosensor development

Poly(L-lysine) templated silica and silica/carbon nanofiber nanocomposites are prepared in the presence of acetylcholinesterase from Drosophila melanogaster (Dm. AChE), leading to the formation of a biocompatible electrochemically active nanocomposite structure with high enzyme loading level. Detailed conformational analysis of poly(L-lysine), Dm. AChE and their interactions with the silica and carbon nanofibers is conducted using micro-Raman spectroscopy, while electrochemical impedance spectroscopy is used to probe the rotational mobility of the protein within the poly(L-lysine) templated silica nanocomposites. It is concluded that the enzyme is highly mobile in its active form, while the carbon nanofibers are very efficient electron transfer nanochannels. Based on these results, biosensors with poly(L-lysine) templated silica/nanofiber nanocomposites were developed, utilizing Dm. AChE as the biocatalyst, poly(L-lysine) templated silica nanostructure as the enzyme stabilizing environment and carbon nanofibers as the direct electron transfer channel to the transducer.

The applications of carbon nanostructures and semiconductor materials in the development of biosensors

In recent years, nanomaterials and nanostructures with unique chemical, physical, and mechanical properties have been developed and applied as both sensing matrices and transducers, offering new opportunities for the development of highly sensitive bio-chemical sensors. The chemical and physical characteristics of the electrochemically active carbon nanotubes, nanofibers and fullerenes, as well as their potential applications in biosensors will be first analyzed. In addition, the advances that have been made in the area of biosensors based on semiconductor materials and quantum dots will be presented. The advantages of the use of these two families of nanomaterials in the design of new devices are thus very promising towards future envisioned biosensor applications.