Functional DNA In Combination With Nanomaterial Used For Biological Imaging And Sensing

Functional DNA including DNAzymes and aptamers,which are DNA molecules with enzymatic function and biorecognition function respectively.They are used for biological sensing,cell imaging while treated with different modifications.In recent years,the development of functional DNA in biomedicine has experienced some challenges,such as poor cellular uptake,rapid nuclease degradation and high false positives.In order to overcome these defects,other nanomaterials such as metal,carbon and upconversion nanoparticles or nanocapsules were used to transport and assist functional DNA.Nanomaterials can be designed and synthesized according to the needs of different sizes and shapes,and these materials have a unique chemical and physical properties,not only can be a carrier of DNA,but also excellent signal body,sensors and amplifiers.This paper describes functional DNA-nanomaterials complexes which is used for cell imaging and biosensing,and it will expand the use of both in biomedical applications.In chapter two,it developments a facile and universal strategy for phase-transfer and surface biofunctionalization of upconversion nanoparticles(UCNPs)using aptamer-pendant DNA tetrahedron nanostructures(Apt-tet).The Janus DNA tetrahedron nanostructures are constructed by three carboxyl group-modified DNA strands and one aptamer sequence.The pendant linear sequence is an aptamer,in this case AS 1411,known to specifically bind nucleolin,typically overexpressed on the plasma membranes of tumor cells.After the phase-transfer,UCNP has hydrophilic properties and is selective for cancer cells,therefore can be used for biological imaging.Given these unique features,we believe that our strategy of surface modification and functionalization may become a new paradigm in phase-transfer agent design and further expand biomedical applications of hydrophobic nanomaterials.In chapter three,it designs a selectively permeable poly(methacrylic acid)(PMA)nanocapsules to encapsulate functional DNA for Adenosine Triphosphate(ATP)sensing in living cells.Since functional DNA are concentrated in the nanocapsules,an increasing reaction rate is obtained in vitro.During endocytosis,polymeric capsules simultaneously improve cellular uptake of functional DNAs and preserve their structural integrity inside the confined capsule space.More importantly,selective shell permeability allows for the free diffusion of small molecular targets through capsule shells,but limits the diffusion of large biomolecules,such as nuclease and nonspecific protein.PMA nanocapsules could reduce false positives and enhance detection accuracy.Furthermore,they are biocompatible and biodegradable.In view of these advantages,PMA nanoparticles are expected to be widely used in biochemistry and biosensing.