Reactivity Of DNA On Nano-interface And Its Applications In Biosensing

Bio-nanomaterials technology is a core area of nanoscience and its developmentleads the manufacture of novel materials and the vigorous development of biomedical.Bio-nanomaterials technology combined the physical properties of inorganicnanomaterials and the chemical specificity of polymers to obtain possible un iquefunctionalities, making them attractive in biosensing, drug delivery, material scienceand DNA nanotechnology. A crucial challenge in this area is how to connect thebiomolecules onto inorganic namometerials surface and form an interface formolecular recognition. Understanding the reaction activity of biomolecules onnano-interface is of great significance to develope bio-nanomaterials with highperformance. The research work of this paper mainly includes the systematic researchof DNA activity on nano-interface and the construction of novel DNA functionalizednanostructures. The main findings are as follows:(1) We systemecicallyinvestigated the thermodynamics and kinetics of DNAhybridization on nano-interface. Precise and quantitative control was achieved byapplying diblockDNA-gold nanoparticles (AuNPs) system which we developedrecently. The lateral spacing and surface density of DNA on AuNPs can also besystematically modulated by adjusting the length of the polyA block. We studied howthe self-assembly method, the DNA configuration and loading density influence thestability of DNA on the nano-interface and the activity in the molecular recognitionprocess. This ideal research model providesdeep insight for understanding thebehavior of biomolecules on nano-interface and may provide new materials for theconstruction of high active biological molecular recognition interface.(2) We research the catalytic activity of DNAzymeon AuNPs based on diblockDNA-AuNPs system. A series of loading density and conformation-controllableDNAzyme-AuNPsconjugates was constructed and the loading density of DNAzymecan be tuned by varying the length of polyA. The conformation of DNA with polyA tail turned out to be extended and adopt an upright conformation on AuNPs.Westudied how the self-assembly method, the DNA configuration and loading densityinfluence the catalytic activity of8-17E DNAzyme on the nano-interface, as well asthe response to lead ions. This study offers a deeper insight into the mechanism andcatalysis process of8-17DNAzyme on the surface and may provide a novel catalyticplatform with high activity and improved sensitivity for biosensors.(3) A facile approach to self-assembleunmodified DNA on AgNPsby exploitingintrinsic silver-cytosine coordination was developed. Strong coordination betweensilver and cytosine bases allows the ready formation of DNA-AgNP conjugates,which show favorable stability under conditions of high ionic strength and hightemperature.Thesenanoconjugatespossess even higher efficient molecularrecognitioncapability and faster hybridization kinetics than thiolatedDNA-modifiedAgNPs. More importantly, we could tune the DNA density onAgNPswith the regulation of silver-cytosine coordination numbers, which in turnmodulated theirhybridization for biosensing applications. We further demonstratedthat theseDNA-AgNP conjugates could serve as excellent building blocks forassembling silver and hybrid silver-goldnanostructures with superior plasmonicproperties.(4) A novel method to prepare nanometer-sized gold flower microelectrodes wasproposed. The carbon fiber electrode was etched with flame to nanometer size indiameter. Then, the surface of carbon fiber was encapsulated by electrophoretic paint.After being heated and baked, the prepared carbon fiber electrode was deposited bygold. Size of prepared gold flower microelectrode was about100μm and thedimensions of thorns of the electrode were in nanometers. Thus prepared electrodeexhibited excellent performance and the surface of the electrode can be immobilizedwith specific bioprobes. By combining it with aptamers, we developed anelectrochemical biosensor for the detection of cocaine. This sensor was rapid,label-free, selective and sensitive. This electrode is expected to be useful for thedetection of molecules in single cells and other microenvironment.