Studies On The Biological Detection And Technology Of Functional Nucleic Acids And Mesoporous Silica MCM-41Nanomaterial

Biomolecules， including monosomes, polymers and small molecules, is thegeneral term for molecules that are naturally present within an organism.Biomoleculars are basic materials in constituting the body and involve in theactivities of life. With the development of science and technology, the detection ofbiomolecules plays an increasingly important role in medical diagnostics, food safety,terrorism and so forth.Functional nucleic acids are short synthetic DNA and RNA sequences whic hhave been isolated via a combinatorial biology technique known as in vitro selection,or a process also known as systematic evolution of ligands by exponential enrichment（SELEX）. These functional nucleic acids can specifically bind with high affinity to abroad range of analytes such as small biomolecules, proteins, cancer cells and metalions. Typically, functional nucleic acids include two types of nuleic acid molecules.The first being able to perform catalytic reactions （called DNAzymes, ordeoxyribozymes） like protein enzymes, and the other being able to bind to a specifictarget molecule （called aptamers） like antibodies.Nanomaterials possess a series of excellent properties, including surface effect,quantum size effect and volume effect, making them attractive to reseachers. Recently,nanotechnologies have evolved in ceramics, microelectronics, bio-engineering,optoelectronics, chemical industry and the medical domain.The discovery of functional nucleic acids and nanomaterials offers completelynew design ideals and platforms for the biosensor system targeting of all kinds ofcompounds of interest. Two different strategies have been widely employed toimprove the sensitivity of a sensor: lowering the detection background and amplifyingsignal detection.In chapter2, we have developed a new molecular beacon-based junction sensingsystem with high sensitivity for DNA detection with a strong capacity to identifySNPs. The single linear probe typically labels the midsection of the oligonucleotide,but our next-generation junction sensing system uses a hairpin-structured MB withlabels on each end of the oligonucleotide to maintain the cleaving activity of thessDNA-cleaved endonuclease, Nt.BbvCI. These design improvements guarantee a trueand effcient target-triggered enzymatic recycling amplifcation process in our sensing system. They also afford a faster and more sensitive response towards target ing DNAthan the frst-generation junction sensing system.In chapter3, a water-soluble cationic perylene derivative is used as theG-quadruplex fluorescence indicator for simple, rapid and label-free detection of Pb²⁺.Perylene derivatives display weak fluorescence due to the self-aggregation induced byPW17oligonucleotide. Upon addition of Pb²⁺, the folding of PW17into aPb²⁺-stabilized G-quadruplex structure reduced the aggregation of perylene derivativeand an increase in fluorescence intensity was observed. Since Pb²⁺can form morecompact DNA folds, our proposed sensor displayed high sensitivity and se lectivity. Inaddition, the sensing system can be used for the determination of Pb²⁺in urinesamples with satisfactory results.In chapter4, a photon-manipulated mesoporous release system was constructedbased on azobenzene-modifed nucleic acids. In this system, theazobenzene-incorporated DNA double strands were immobilized at the pore ofmesoporous silica nanoparticles. The photoisomerization of azobenzene induced adehybridization/hybridization switch in complementary DNA, causinguncapping/capping at porous gates of mesoporous silica. This nanoplatform permitsholding of guest molecules within the nanopores under visible light but releases themwhen light wavelength turns to the UV range. We envision that this photo controlleddrug release system could catalyze potential applications in cancer therapy.