Multifunctional DNA Nanomaterials For Tumor Imaging And Therapy

DNA is traditionally considered as the core genetic biomolecule in living systems.From another perspective,due to its inherent biological properties,molecular recognition,sequence programmability and biocompatibility,DNA is a multifunctional molecular building block for the construction of functional materials.In recent years,branched DNA has been widely used in the synthesis of novel biomaterials with promising applications.As excellent synergistic delivery carriers for chemotherapeutic drugs and therapeutic nucleic acids,DNA-based branched functional materials have outstanding advantages such as adjustable size,targeted delivery,good endocytosis and responsive release in the treatment of tumor and other diseases.In this thesis,we designed a series of targeted drug delivery systems based on DNA to successfully achieve integrated research in tumor imaging and therapy.The details are as follows:1.Base excision repair(BER)-based dual-targeted DNA nanodevices are designed to modulate ATP in situ imaging and tumor therapy.BER repaired the mutagenesis of ATP aptamer by uracil(U)and monitored the expression of AP endonuclide 1(APE1)and uracil DNA glycosylase(UDG)in tumor cells.The interaction of APE1 and UDG leads to the production of single nucleotides from the designed UU-ATP aptamer,which is further mediated by polymerase to form a normal ATP aptamer.The UU-ATP aptamer could not bind ATP without the process of BER,but recovered its ability to bind ATP after the completion of BER.Meanwhile,the extended MUC1 aptamer and AS1411 aptamer probes can specifically recognize MUC1 protein and nucleotide in tumor cells,respectively.The designed DNA nanodevices can not only effectively deliver aptamer probes and treat tumors,but also analyze the overexpression of APE1 and UDG in the BER pathway of tumor cells by ATP in situ imaging.Thus,DNA nanodevices of the BER pathway offer potential for cancer therapy.2.A stimulation-responsive mimosa-inspired DNA tetrahedron(MIDT)drug delivery system has been developed for tumor collaborative therapy.MIDT consists of a DNA tetrahedron,a targeting aptamer,and a mimosa structure that responds to dynamic p H changes.Initially in an extracellular neutral environment,MIDT is in an "open" state,immobilizing both small molecule drugs and antisense DNA.After targeting and internalizing tumor cells,stimulation of the acidic environment causes MIDT to "close" like the stimulated mimosa,leading to the transient release of tumor therapeutic drugs.This stimulus-responsive drug delivery system has high biocompatibility and can simultaneously carry a variety of drugs to improve the efficacy of tumor treatment,which is expected to play a greater role in tumor combination therapy.3.To design a self-assembled 3D DNA nanostructure drug delivery system with ATP-triggered drug release for tumor fluorescence imaging analysis and targeted drug delivery.Dox@3D DNA nanostructures are self-assembled by simple one-pot annealing reaction and embedded with drugs.The structure is stable,but it can be induced by high concentration of ATP in tumor cells,which can rapidly cut and release drugs,promote the rapid accumulation of drugs in tumors,and play a therapeutic role,so as to effectively avoid damage to normal tissues.The selfassembled 3DDNA nanostructure drug delivery system is expected to be used for tumor cell recognition,bioimaging,and targeted drug delivery.4.A triple helix probe(THP)molecular switch and MUC1 aptamer functionalized Au NPs were constructed for fluorescence imaging analysis and photothermal therapy(PTT).DNA(two DNA triple-helix probes,MUC1 aptamer)was modified to the surface of Au NPs by stable gold thiol bonds.MUC1 aptamer specifically recognizes tumor cells and can not only serve as a specific tumor marker ATP,but also complete the aggregation of Au NPs in tumor cells.When THP-Au NPs are targeted into tumor cells via MUC1,high intracellular ATP concentration leads to a conformational change in THP,allowing THP to resume burst fluorescence and expose DNA1 and DNA2.Next,the two complementary DNA single strands are hybridized to form a double-stranded structure,which induces aggregation of Au NPs,which are effectively generated under near-infrared radiant heat and cause photothermal ablation of tumor cells.We investigated the dynamic operation of THP-Au NPs in the presence of ATP and demonstrated that they have better imaging and therapeutic effects in MCF-7 tumor models.