Research On The Detection Of Nucleic Acid Based On Silver Nanoclusters Fluorescent Probe

DNA detection related to disease diagnose, gene profiling, environmental analysis and forensic analysis. Hence, it is of great significance to develop methods for sensitive and selective DNA detection. Nowadays, there are many DNA detection methods, such as chemiluminescence, electrochemistry, colorimetry, fluorescence etc. Fluorescent probes are becoming increasingly popular due to their convenience operation, rapid binding kinetics, and ease of automation. Therefore, there has been ever-increasing demands to develop simple, sensitive, selective and cost effective label-free fluorescent methods for DNA detection.For DNA detection, the development of new fluorescent sensors is an interesting research area. The key point is to develop the fluorescent sensor with proper size, low toxicity, strong fluoresence intensity, good photostability and high sensitivity. The used fluorescent sensors such as organic fluorescent dyes and quantum dots, have been widely applied in DNA detection. However, the organic fluorescent dyes show low photostability, and the quantum dots have big size and high toxicity. Taken these into account, there are many limits in applying the the organic fluorescent dyes and the quantum dots. With the nanomaterials advancement, new nanomaterials have promoted the development of analytical chemistry. Especially, silver nanoclusters using the DNA as templates, DNA-Ag NCs, have drawn a lot of attention. DNA-Ag NCs have many advantages: strong fluorescent emission, high photostability and small size. What’s more, the fluorescent emission bands can be tuned throughout visible and near infrared range, by simply varying the DNA sequence and length. DNA-Ag NCs have become new kinds of fluorescent sensors and have made a great progress in the past 10 years. DNA-Ag NCs have successfully applied in detecting nucleic acids, proteins, peptides, small molecules, metal ions etc. DNA-Ag NCs have even been used in the biological imaging.There is a specific phenomenon that two DNA-Ag NCs with little intrinsic fluorescent emission can be lighted up through single stranded DNA hybridization. Moreover, there is a stronger fluorescnece enhancement upon placing two darkish DNA-Ag NCs together to form a probe pair through their complementary linkers than that observed by placing darkish DNA-Ag NCs close to the G-rich DNA activator. In addition, if a single stranded DNA(ssDNA) is partially complementary to the other two kinds of ssDNAs respectively, DNA sequence competing reaction for hybridization happens, where three kinds of DNAs coexist in a solution. Two of the three ssDNAs, which have greater combining capacity, will bind together through hybridization and produce double stranded DNAs.Herein, we build a new simple and selective fluorescent sensor for DNA detection, based on the above principles. In the resent work, we design two kinds of ssDNA probes for DNA-Ag NCs synthesis, and both of them have two regions: a segment used as templates for synthesis of DNA-Ag NCs and a complementary segment for hybridization. After silver nanoclusters nucleation reaction, both synthesized DNA-Ag NCs barely have fluorescent emission. Whereas, they form DNA-Ag NCs pair and show enhanced fluorescence through hybridization. We design the probe DNA complementary to a portion of the target DNA. When adding the target DNA into the solution containing these two DNA-Ag NCs, the bulk solution exhibits a weak fluorescence signal, because the formation of DNA-Ag NCs pair is blocked by the DNA competing reaction. We succeed in detecting the H1N1 target DNA and the DNA-Ag NCs pair offers a platform for potential application in label-free analysis of the target DNA detection.