Research And Application Of Nucleic Acids Functionalized Silver Nanoprobes For MiRNA-21 Detection

Silver nanoparticles,as one of the plasma nanomaterials easy to synthesize and modify,have unique and superior optical properties,such as high molar extinction coefficient,surface enhanced Raman scattering,metal fluorescence enhancement effect,local surface plasmon resonance and so on,and play a good role in the detection of many biomarkers,drugs,pollutants.Mi RNAs,also known as micro RNAs,are endogenous noncoding single strand RNAs with high homology,short sequence and are easy to degrade.Several studies have proved that different kinds of miRNAs can work as oncogene and antioncogene,therefore,accurate and sensitive detection of miRNAs is valuable for early diagnosis and treatment of tumors.On the basis of previous research,this paper further explored the application of silver nanoparticles and the modified nanoprobes in biological and chemical sensing.We chose miRNA-21 as the detection object which was generally recognized as highly expressed in a variety of cancer cells.Based on the methods of fluorescence polarization,fluorescence imaging and detection,a series of silver nanoparticles probes were designed and used for quantitative detection of miRNA-21 and intracellular imaging.(1)A highly sensitive method for miRNA-21 analysis and detection was developed,which relied on the enhanced effect of Ag10 NPs,combined with the principle of strand displacement reaction to achieve asymmetric signal amplification.The detection probe was composed of Ag10 NPs and two self-assembled complementary nucleic acid strands by thiol groups.The nucleic acid strand with a fluorescent group(named 2-FAM)was initially complementary to the chain in contact with Ag10NPs(named 1-SH),then it was replaced by a strand displacement reaction with miRNA-21,which exposed the toehold to react with the nucleic acid strand(named 3-fuel),and miRNA-21 was finally released into the next cycle of amplification,which eventually results in a significant increase in the fluorescence polarization signal change value.The linear range of this method was 100 pM to 16 nM while the detection limit was 93.8 p M,fast and sensitive detection could be achieved in 40 min.This method showed a certain anti-interference ability in the buffer and real biological samples,and achieved fast,accurate and sensitive detection.(2)Based on the decahedral silver nanoparticles,a fluorescent sensor for intracellular imaging and quantitative detection of miRNA-21 was designed.There were several pairs of complementary nucleic acid double chains on a silver nanoparticle,and the chain A labeled with AF488 was connected with the chain B labeled with Cy3 through the principle of complementary base pairing,forming a set of fluorescence resonance energy transfer system.This kind of probes reacted with miRNA-21 to restore the fluorescence of AF488,through the surface fluorescence enhancement effect of silver nanoparticles,it achieved single particle imaging and dynamic analysis and detection of miRNA-21.In general,the sensor could provide a simple and feasible method for the intracellular imaging of miRNA-21,and it was also expected to be applied to the imaging and specific detection of other biomarkers.