Study On Novel Optical Biosensor Method Based On Gold Nanoparticles

A biosensor is an analytical device for the detection of an analyte that combines abiological component (proteins, nucleic acids, enzymes, microorganisms, cells, tissueetc) that interact (binds or recognizes) with the analyte under study with aphysicochemical detector component. The transducer that transforms the signalresulting from the interaction of the analyte with the biological element into anothersignal(optical, piezoelectric, electrochemical, etc) that can be more easily measuredand quantified. The development of new nanomaterials that can improve therecognition and conversion components gave us novel ideal for the design of efficientsensor. Nanomaterials feature unique physicochemical properties that can be of greatutility in creating new recognition and transduction processes for chemical andbiological sensors, as well as improving the S/N ratio by miniaturization of the sensorelements. Gold nanoparticles (AuNPs) possess distinct optical properties, electricalproperties and excellent biocompatibility that make them excellent scaffolds for thefabrication of novel chemical and biological sensors that have been widely used thebiochemical analysis. In this article, we construct several novel biosensor based on thegold nanoparticles to achieve the simple, rapid and accurate detection of the highlyactivity reactive oxygen species that involved in various physiological andpathological regulation, melamine and T4polynucleotide kinase(T4PNK) which caninvolved in cellular DNA damage repair. Details are as follows:1. This chapter was based on redox reaction between the highly reactive oxygenspecies (hROS) and BSA molecules which were employed as a stabilizer and a gentlereducing agent in a one-step synthesis of fluorescent gold nanocluster, the reactionlead to the gold nocluster surface changes, and then the fluorescence quenched. Thedegree of this fluorescence change is dependent on the concentration of highly reactiveoxygen species, within the scope of a certain highly concentration of reactive oxygenspecies. So we could achieve the simple and sensitive detection of highly reactiveoxygen species: hydroxyl radical (OH), Nitrite (ONOO-), hypochlorite (ClO-). The OH had a linear detection range of0.01to5μM and ONOO-linear range is0.5-100μM, while the ClO-linear range is1-150μM. The fluorescent gold nanoclusterssynthesis is simple but with a rapid and sensitive response to the highly reactiveoxygen species. We expected our method can be used as a good platform for the detection of highly reactive oxygen species.2. In this chapter, we utilized the different surface-enhanced Raman scattering(SERS) effect caused by the existence difference of AuNPs for the detection ofmelamine. Melamine can be sensitively detected in aqueous medium through itsselective interaction with polythymine (polyT24) by forming triple H-bonds. PolyT24could adsorbed on the30nm AuNPs and protect AuNPs from salt-induced aggregation,but the protection disappeared in the presence of melamine for the reaction betweenthymine and melamine which results in aggregation of the AuNPs. Gold nanoparticlesin different states have different SERS effect, which is the basis of our method for thedetection of melamine. The experimental results show the dynamic linear range of thepresented sensor is wide through3-decade range from0.01to10μM, and the detectionlimit to18nM.3. We described a novel and simple colorimetric sensors based on theoligonucleotide-modified gold nanoparticles and exonuclease digestion reaction for thedetection of T4polynucleotide kinase (T4PNK) activity. In the absence of T4PNK,phosphorylated does not occur thus no digestion reaction happened. The goldnanoparticles probes protected by the nucleic acid chain can withstand a certain saltconcentration, the solution was red. In the presence of T4PNK, the5′hydroxyl terminiof guanine is phosphorylated, the product was immediately cleaved by λ exonucleaseand RecJ exonuclease. Since the stabilizing effect of the modified DNA strand isdigested, the gold nanoparticles are quickly aggregation under the same saltconcentration with a colour change from red to purple. The result revealed the methodallowed a specific, simple and rapid assay of T4PNK with a linear response rangefrom0to4.0U/mL and a detection limit of0.24U/mL.