Novel Biosensing Technology Based On Nanomaterials

The analysis and detection of biological active substances in the organisms, hasimportant significance for human to obtain life information, such as obtaining thechemical and biological information in the life processes, understanding thestructure-function relationships of biological molecules and explaining the mechanismof life and disease diagnosis. Since the discovery of nano-materials, much attentionhas been attracted due to its superior physical and chemical properties as well as highspecific surface area. Due to the superior propeties of nano-materials, we couldfurther assemble and reform these materials to get the nano-materials with goodbio-compatibility. So the biological activity, stability and spatial orientation could bemaintained in the biological molecular recognition process. On this basis, the furtherconnection of biomolecules with nano particles could be achieved to develop novelnano biosensor based on the nano-materials.In this paper, three novel nanobiosensors, which based on the excellent propertiesof nono-materials and the characteristics and importance of bio-active substances,have been developed to realize the recognition and detection of target molecules.Firstly, based on the principle of Graphene oxide (GO)-hairpin probenanocomposite fluorescence resonant energy transfer, we developed a nanobiosensorfor DNA base excision repair screening. The developed strategy allowed highlysensitive and selective activity screening of Uracil-DNA glycosylase (UDG) becauseof employing the high fluorescence quenching ability of GO and the high fidelity highspecificity of UDG and EnIV. A quite wide dynamic range from0.0017U/mL to0.8U/mL was achieved for UDG assay and the detection limit was estimated to be0.0008U/mL. Furthermore, the homogeneous assay format using simplified instrumentationfor fluorescence signal readouts made the assays robust, easily automated, andscalable for parallel assays of hundreds of samples. The results indicated that thisstrategy offers a simple, robust， cost-effective, highly sensitive and selectivehomogeneous detection platform for UDG activity assay related biochemical studies.Secondly, we have developed a novel concept for enzymatic control of plasmoniccoupling as a SERS nanosensor for DNA demethylation. When the thiol-containingRaman-active dye,5,5′-dithio-bis(2-nitrobenzoic acid)(DTNB) and a thiolated DNAsubstrate probe modified AuNPs were incubated with Bsh1236I and Exo I in the presence of DNA demethylase, demethylase specific demethylation, then DNAsubstrate probe was digested by Endonuclease and exonuclease, destabilizing AuNPsto form aggregates and producing strong plasmonic coupling SERS signal to realizethe detection of demethylase. The developed strategy revealed a dynamic correlationbetween the peak intensities and the demethylase concentrations in the range from0.2to200ng/mL with a detection limit of0.1ng/mL. Hence, this nanobiosensor canprovide a sensitive, robust, rapid and convenient approach for detecting DNAdemethylases and their inhibitors in a homogeneous format.Finally, we proposed a novel analytical method for lipopolysaccharide detection.This strategy relies on surface enhanced Raman scattering based detection offormaldehyde that is produced as the product in the oxidation reactions oflipopolysaccharide and NaIO4. Under room temperature, firstly, thelipopolysaccharide is oxidized by NaIO4, producing formaldehyde. A thiolatedreactive probe, Purpald, is used for the selective reaction with formaldehyde, followedfurther oxidation and the product can self-assemble on gold nanoparticles to deliverthe SERS signal. As a control experiment, it showed a quite weak SERS signal in theabsence of lipopolysaccharide. Therefore the detection of lipopolysaccharide can befinished by the strategy. Under the optimized conditions, the SERS signal increasedwith the increasing concentrations of the lipopolysaccharide and showed a linearcorrelation to lipopolysaccharide concentration in the range from33μg/mL to667μg/mL and the limit of detection of21μg/mL. This method was sensitive, withoutsophisticate experiment procedures and costly labeled reagents, fast and easy torealize. In view of these advantages, this developed strategy was expected to offer asimple, convenient and sensitive homogeneous detection platform forlipopolysaccharide assay.