Development of nanobiosensors for biotechnological and environmental applications

Abstract

(Nano) Biosensors are hybrid devices that transform chemical information into an analytically useful signal by means of a biochemical mechanism. Biosensors consist of a receptor system, in which a biological component interacts specifically with a given analyte, and a coupled physicochemical transducer that amplifies the signal resulting from such interaction from molecular up to macroscopical level. The purpose of these constructs is the identification, quantification and eventual screening of specific molecules, as present in complex mixtures from moderate to very low concentrations. Therefore, biosensors have utility in analytical research but also in clinical diagnosis, food and pharmaceutical industry, environmental control and process monitoring. The interest in biosensor development has partly arisen from the need of fast and routine analysis of a large number of samples, what requires robustness, sensitivity and reproducibility. Essentially, these instruments can generate either optical or electric signals which are very convenient for instrument development, and the commercial application of many biosensors in research. Work on biosensors has focused mostly on enzyme based sensors, receptor based sensor, nucleic acid based sensors, immunosensors, and microbial sensors. In Chapter 2, we examined the possibility of in situ enzymatic reaction around the SWNTs. As a model reaction system, we selected the enzyme, cyclodextrin glucanotransferase (CGTase), which allows synthesis of cyclodextrins (CDs) from starch. CDs are able to form inclusion complexes with hydrophobic insoluble molecules via host-guest recognition and thereby solubilizing them in aqueous solution. Therefore, we decided to examine whether in situ CD formation around SWNTs from starch by CGTase will result in solubilization of SWNTs. Here, we report successful in situ CGTase reaction on the surface of SWNTs in aqueous solution, and subsequent formation of interesting macrocyclic supramolecu...