Detection And Imaging Of Tumor Markers And Tumor Suppression Based On DNA Probes

As a carrier of genetic information of organisms and cells,DNA molecules have the characteristics of simple structure,good biocompatibility,stable structure and easy chemical modification.Therefore,DNA molecules are often used to make biological probes.For example,DNA molecules are assembled into DNA nanostructure structures for detecting biomarkers,or fluorescent molecules are modified at the ends of DNA chains for imaging biomarkers.There are also modified sulfhydryl groups on DNA,which are connected by Au-S bonds to achieve targeted therapy on gold nanomaterials.The probes of the two systems in this paper are designed based on DNA molecules,which are used to detect tumor imaging and tumor suppression research.The first system in this paper is based on the"post-synthesis"of silver nanoclusters?AgNCs?and guanine?G base?to achieve highly sensitive detection of uracil-DNA glycosylase.First,a hairpin DNA?H?containing uracil?U base?was designed,which can be recognized by UDG to form an apurinic/apyrimidinic?AP?site.The AP site on the hairpin DNA can be cleaved by Endo IV enzyme to form a large amount of short strand DNA containing 3'-hydroxyl group?3'-OH?.Subsequently,in the presence of terminal deoxynucleotidyl transferase?TdT?and deoxycytidine triphosphate?dCTP?,a cytosine?C base?-rich DNA strand is formed at the 3'end.It can hybridize with the guanine-rich?G?DNA strand?S?containing AP sites and further react to form DNA hyperbranched structures.The addition of AgNO₃ and NaBH₄ can form silver nanoclusters with fluorescent signals in the DNA hyperbranched structure.At the same time,the rich G bases in the DNA hyperbranched structure can greatly enhance the fluorescent signal of AgNCs.By detecting the fluorescent signal of AgNCs,a highly sensitive detection of UDG can be achieved,with a detection limit of 3.4×10^-5 U mL^-1.Compared with other methods for detecting glycosylase,this method has the advantages of simple operation,fast reaction speed and high sensitivity.The second system in this paper is based on the assembly of DNA triple helix structures on gold nanorods?AuNR?to achieve multiple functions of miRNA detection,nucleolin imaging and tumor treatment.We first design the DNA triple helix structure,with an aptamer strand in the middle.Through the action of the Au-S bond between the modified thiol at the end of the DNA triple helix structure and AuNR,the DNA triple helix structure is attached to AuNR to make a probe.Subsequently,the entire probe can enter the tumor cell through endocytosis,and the miRNA in the cytoplasm will hybridize with the DNA triple helix structure to form a double-stranded DNA rigid structure.The Rox,which was originally close to AuNR,is far from AuNR because it is located at the end of the DNA chain,and the quenching effect disappears,Rox fluorescence signal recovery,Rox fluorescence indicates the presence of miRNA.At the same time,the aptamer chain was released,and the aptamer chain specifically binds to nucleolin in the cytoplasm,which takes the aptamer chain into the cytoplasm.The Cy3 fluorescent molecule on the aptamer chain is far away from AuNR,and its fluorescent signal is recovered.By detecting the fluorescence signal of Cy3,the imaging of nuclear nucleolin can be achieved.In addition,AuNR has a high photothermal conversion efficiency.Under laser irradiation,it can rapidly heat up,generate enough heat to damage tumor cells,and realize tumor treatment.This solution combines miRNA detection,nucleolin imaging and tumor treatment on a single platform,which provides a reference and ideas for the integration of tumor diagnosis and treatment.