A Ratiometric Fluorescent Biosensor Based on Exonuclease ⅢAmplification Strategy for Pathogenic Bacterial Gene Detection / 分析化学

Food-borne pathogenic bacteria seriously threaten public health. Based on the mechanism of fluorescence resonance energy transfer (FRET), a ratiometric fluorescence biosensor was constructed by integration of Exo III-based signal amplification strategy. The Cy3 labeled R1-DNA firstly hybridized with Cy5 labeled R2-DNA to form duplex of R1/R2. Cy3 showed a low fluorescence response while Cy5 showed a high fluorescence response. The addition of target pathogenic bacterial gene (Lac Z gene) could de-hybridize the R1/R2,resulting in the fluorescence decreasing of Cy5 and the fluorescence recovering of Cy3. Under the assistance of Exo III, the signal change was further amplified. The detection of limit reached as low as 5.29 pmol/L. The linear detection range was from 10 pmol/L to 2000 pmol/L. The developed ratiomtric detection strategy significantly reduced the possibility of false-positive and false-negative detection results.

A Fluorescence Biosensor for Detection of Mercury Ion Based on Oligonucleotide / 分析化学

A simple,fast and highly sensitive fluorescence analysis method for detection of mercury ion was developed based on N-methyl-mesoporphyrin IX (NMM)/G-quadruplex DNA system and specific T-Hg-T mismatches.In this strategy,a large number of thymine was introduced into guanine-rich oigonucleotides which could form G-quadruplex.In the presence of Hg2+,guanine-rich oigonucleotides and complementary strand could form double-stranded DNA molecule by specific T-Hg-T mismatch pair,leading to destruction of G-quadruplex DNA structure.In the absence of Hg2+,guanine-rich oigonucleotides spontaneously formed G-quadruplex DNA structure that could bound NMM to generate intense fluorescence.Based on the above facts,a sensitive fluorescence biosensor for determination of Hg2+ was fabricated.And the optimal conditions for Hg2+ determination were as follows:buffer solution pH of 6.7,20 mmol/L KCl and 2.5 μmol/L NMM in buffer and incubation for 2 h.Under the optimal conditions,the fluorescence intensity signal change (F0-F) and the Hg2+ concentration exhibited a linear correlation within 50 nmol/L to 1000 nmol/L range with a low detection limit of 22.8 nmol/L (3σ).The biosensor exhibited good selectivity toward common metal ions.The developed method was successfully employed to detect Hg2+ in tap water with recovery of 106.1％-107.8％.