Detection And Treatment Of Tumor Based On DNA-templated Silver Nanoclusters

Tumor markers are widely present in tumor tissues,body fluids or serums of patients with abnormal expression levels.Accurate diagnosis and treatment evaluation of cancers mainly rely on sensitive monitoring of tumor markers.DNA-templated silver nanoclusters(DNA-AgNCs)have the advantages of high quantum yield,high stability,tunable fluorescence emission,and good biocompatibility,which can be applied as a novel kind of label-free fluorescent probes for biosensing and biomedical detection.In this paper,novel fluorescent probes are designed based on DNA-AgNCs,and a series of biosensors are constructed for highly sensitive detection of tumor markers and intracellular imaging.In addition,we have further explored the application of DNA-AgNCs in cancer therapy combined with other functional nanomaterials.The specific research contents are as follows:1.A novel fluorescence method is proposed for simultaneous detection of alpha-fetoprotein(AFP)and carcinoembryonic antigen(CEA).The polydopamine nanosphere@silver nanocluster(PD AN@AgNC)system is introduced for fluorescence quenching and recovery.AgNCs with different emissions are synthesized using different DNA templates,which also contain aptamer sequences towards AFP and CEA,respectively.These single-stranded DNA sequences could be adsorbed on the surface of the PDAN through π-π stacking,which result in the quenching of AgNCs.However,in the presence of corresponding tumor markers,aptamer/target complexes can be formed which release AgNCs from the surface of the PDAN.The recovered fluorescence emissions could be used to indicate the concentrations of the tumor markers.This PDAN@AgNC system has been validated preliminarily to screen human serum samples with excellent results.It has advantages of simplicity,enzyme/antibody-free feather,low cost and convenient operation.2.For the detection of specific miRNA marker,a novel strategy is developed coupling chameleon AgNCs with hybridization chain reaction.Generally,the signal DNA probe is designed to contain two pieces of DNA templates for the synthesis of AgNCs,which are in close proximity due to the hairpin structure.A series of hybridization reactions can be triggered by target miRNA,which open the hairpin of signal probe and separate the two pieces of segmental AgNCs.Controllable color switching from red to yellow is thus achieved.Note that signal generation and amplification are integrated into one step,which is a great advance compared with previous amplified systems.The proposed strategy provides a sensitive fluorescent detection of miRNA down to 2.8 pM with high selectivity.On the other hand,we have developed a series of novel logic gates for multiplex miRNA analysis based on chameleon AgNCs.DNA dumbbell and four-way junction structures are ingeniously designed to construct OR gate and AND gate,respectively.By introducing different miRNA inputs,separations of two AgNCs are controlled and the fluorescence property of AgNCs changes.By studying the ratiometric fluorescence responses,sensitive and selective analysis of multiple miRNAs can be achieved.3.Telomerase is overexpressed in most cancer cells and telomerase activity can be used as an important marker for early diagnosis.We have developed novel fluorescence logic gates for simultaneous analysis of telomerase activity and miRNA.A DNA duplex is assembled which can be destroyed by telomerase catalyzed extension or miRNA mediated strand displacement.The released single-stranded DNA further initiates the subsequent hybridization chain reaction.The output response of the OR gate originates from fuel strand-templated silver nanoclusters(AgNCs).On the other hand,a three-way junction is constructed for the AND gate,which can be destroyed in the presence of miRNA and telomerase.The finally released DNA is also applied to trigger the hybridization chain reaction for the generation of a fluorescence response.The constructed logic gates are sensitive and reliable in the analysis of telomerase and miRNA.4.In terms of cancer treatment,we have developed a novel and effective combination nanoplatform for cancer theranostics.Folic acid(FA)is first modified on the photothermal agent of polydopamine nanosphere,which possesses excellent near-infrared(NIR)absorbance and thermal conversion features.Temperaturesensitive AgNCs are then synthesized on the DNA template that also loads the anticancer drug doxorubicin(Dox).After accumulation in cancer cells,polydopamine nanosphere generates cytotoxic heat upon excitation of NIR light for photothermal therapy.On the other hand,the temperature increment is able to destroy the template of AgNCs,leading to the fluorescence variation and controlled release of Dox for chemotherapy.The combined nanosystem exhibits outstanding fluorescence tracing,NIR photothermal transduction,as well as chemo drug delivery capabilities.Both in vitro and in vivo results demonstrate excellent tumor growth suppression phenomena and no apparent adverse effects.This work provides a powerful targeted nanoplatform for cancer theranostics.