Applications Of Metal-Organic Framework MIL-101in Fluorescence Analysis

Due to the excellent chemical and physical properties, such as the diversity of structure and composition, the opened metal sites, adjustable morphology, excellent water and thermal stability, metal-organic frameworks (MOFs) have been widely used in the field of analytical chemistry, gas storage, drug delivery, imaging, chromatographic separation and catalysis. As an excellent family of MOFs. MIL-101has become the researchers’focus because of its high stability, large surface area and pore size. However, the reports about the interactions between biological molecules and MOFs are still relatively rarely. In this thesis, we have studied the interaction between MIL-101and DNA. Here, MIL-101was first employed as a low the background signal platform and a fluorescence anisotropy amplification platform, to achieve the determination of HIV-1DNA. mercurv and iodide ions. The main contents are as follows:(1) The detection of HIV-1DNA with high sensitivity When using DNA-intercalating dye SYBR Green I (SG) as a fluorescent indicator to detect DNA, it shows a high background fluorescence because of the non-specific adsorption between SG and DNA. thus the signal-to-background ratio is relatively low. In order to decrease the high background fluorescence, we have introduced MIL-101as a low background platform to improve the signal-to-background ratio. In the absence of target DNA, SG/DNA probe complexes are adsorbed on the surface of MIL-101due to the electrostatic and π-π stacking interactions, thereby quenching fluorescence of SG. While in the presence of target DNA. for the formation of double-stranded DNA structure. SG can bind the dsDNA structure in the mode of intercalation and minor groove binding. Meanwhile, the rigid dsDNA structure can be far away from the surface of MIL-101to avoid the fluorescence quenching, leading to the great enhancement of SG fluorescence signal. Therefore, we have established of a highly sensitive method for detection of HIV-1DNA. The results showed that by the introduction of MIL-101, the signal-to-background ratio can be improved as high as8-fold, and the detection limit was73pM. The selectivity of single-base mismatches was also improved.(2) A dual mode logic gate for the detection of mercury and iodide ions Based on MIL-101, we employed SG as a signal indicator, two13T-mismatched base sequences as the probe DNAs, fluorescence anisotropy (FA) and fluorescence intensity as the output signals to detection of the mercury ions and iodide ions. In the absence of MIL-101, the signal-to-background ratio is relatively low because of the high background fluorescence of SG/P; the deviation for both the mass and the size of SG between the single-stranded and thedouble-strandedwasrestricted, so the change of FA value was too small to measure. When MIL-101was employed, the flexible SG/ssDNA complex can be absorbed on the surface of MIL-101by means of π-π stacking and electrostatic interactions between nucleotide bases and MIL-101. thus the fluorescence of SG/P can be quenched. As a consequence, the background signal is lowered. Meanwhile, as SG/P is absorbed on MIL-101, the mass and size of SG is enlarged, the rotation of SG is restricted, then resulting in the enhancement of the FA signal. When Hg2+is present, for Hg2+can bind between the N3nitrogen atoms of the thymine. the T-T mismatched base can form T-Hg2+-T base pairs. Thus, the fluorescence of SG is enhanced as it binds the dsDNA in the mode of intercalation and minor groove binding. For the dsDNA can be far away from the surface of MIL-101, the mass and size of SG is almost unchanged, and the rotation of SG is relatively free, leading to a decrease of the FA signal. So, Hg2+can be detected by the large value change of FA. When in the presence of I-, as is well-known, I-ion is a strong Hg2+-binder, and can be used to unfold the T-Hg2+-T double-strandedstructure, resulting in the melting of dsDNA. Therefore, the SG/P can be absorbed on MIL-101again. Consequently, the fluorescence of SG is decreased, and the FA of SG is enhanced. As expected, a new detection method of Hg2+and I-has been successfully constructed, and successfully used in the detection of both the content of water.Through those studies, we have successfully developed the methods with high sensitivity for the detection of DNA, mercury and iodide ions based on MIL-101, and expanded the application of non-fluorescent metal-organic frameworks.