Construction Of Amphiphilic Functional Nucleic Acids And Their Applications In Disease Theranostics

Functional nucleic acids are oligonucleotides with specific functions including molecular recognition and catalytic activity.With advantages of programmability,simple synthesis,high chemical stability and convenient modification,functional nucleic acids have broad application prospects in bioanalysis,biosensing and disease theranostics.DNA nanotechnology mainly refers to the design and manufacture of artificial nucleic acid structures.DNA nanotechnology not only provides new technologies and methods for the construction of the complex nanostructures and precise controls of its properties,but also plays an important role in bioscience,material research and environmental science.Among various materials used to construct DNA nanostructures,amphiphilic functional nucleic acids,composed of a hydrophilic nucleic acid and a hydrophobic compound,have attracted broad interest,because of their high efficient and uniform self-assembly,providing potentially powerful tools for basic research and clinical applications.In this paper,intermolecular G-quadruplexes and photocleavage reactions are employed to regulate the self-assembly of amphiphilic functional nucleic acids.Based on the efficient self-assembly of amphiphilic functional nucleic acids on the biomembrane,we designed aptamer-based exosomes for targeted cancer chemotherapy,which induced selective and potent therapeutic efficacy on target cancer cells.We also constructed efficient and stable DNA tetrahedron nanoprobes on the cell membrane to monitor the extracellular microenvironment in real time.The main contents are summarized as follows:(1)In Chapter 2,we have engineered self-assemble stability-tunable DNA micelles using photocontrollable dissociation of intermolecular G-quadruplexes.Before exposure to UV light,G-quadruplexes are introduced into DNA micelles to lock the whole structure,resulting in enhanced stability against the destruction of serum albumin.However,once reaching the target position and exposed to light,the G-quadruplex formation is blocked by the hybridization with the complementary sequence realeased by the light-cleavable reaction,resulting in the loss of stability of the DNA micelles.This strategy enables DNA micelles to be stability-tunable,and are expected to provide a new tool for intelligent disease theranostics.(2)In Chapter 3,we modified exosomes with diacyllipid-aptamer conjugates by efficient hydrophobic interaction.By combining the cancer-targeted capability of aptamers and the superiority of exosomes as natural vehicles,we successfully constructed a biocompatible cancer-targeted drug delivery platform for improving the efficacy of chemotherapy.(3)In Chapter 4,we further decorated DNA tetrahedron nanostructure on the cell membrane.By increasing the number of the hydrophobic cholesterol tag of the DNA tetrahedron,the efficiency and stability of the membrane-anchored DNA tetrahedron nanoprobes were significantly improved.Meanwhile,the three-dimensional structure of the tetrahedron can support the probe and reduce non-specific adsorption on the surface of the cell membrane.We used ATP as a model target molecule.This membrane-anchored nanoprobe is able to monitor ATP secretion by neuron cells.Meanwhile,this cell membrane-anchored nanoprobe can be used to detect different target molecules by simply changing the sequence design of the nucleic acid probe,providing potentially powerful tools for versatile applications in cell biology,biomedical research,drug discovery,and tissue engineering.