Quantum Dots Based Fluorescent Probes For Spectrum Research On Interactions Between Anti-cancer Drug And DNA

Quantum dots（QDs） is a kind of unique optical and electrochemical properties of new type of functional nanomaterials. Thioglycollic acid（TGA） modified CdTe/CdS QDs and Glutathione（GSH） capped CdTe QDs are synthesized via the hydrothermal procedure. The interactions of QDs, antibiotic drugs and biological macromolecules build a solid base for the controlling of the fluorescent reversible regulation of the system. This study was developed by means of ultraviolet–visible（UV–vis） absorption, fluorescence（FL）, resonance Rayleigh scattering（RRS） spectroscopy, transmission electron microscopy（TEM） and so on. And the main investigations are as follows: 1. Detection of DNA utilizing a fluorescent reversible change of a biosensor based on the electron transfer from quantum dots to polymyxin B sulfateA fluorescent ??turn off–on‘‘ pattern for the detection of herring sperm DNA（hsDNA） had been designed through utilizing the interaction between polymyxin B sulfate（PMBS） and hsDNA as an inherent performance and the fluorescent transformation of glutathione（GSH）-CdTe quantum dots（QDs） as anexternal manifestation. Due to the occurrence of the photoinduced electron transfer from the QDs to PMBS, the fluorescence of GSH-CdTe QDs could be effectively quenched by PMBS, causing the system into ??off‘‘ state. With the addition of hsDNA, the quenched fluorescence of GSH-CdTe QDs could be restored for the reason that PMBS embedded into hsDNA double helix structure to form new complex and peeled off from the surface of GSH-CdTe QDs, leading the system into ??on‘‘ condition. Corresponding experimental results illustrated that the relative recovered fluorescence intensityof GSH-CdTe QDs–PMBS system was near proportional to the concentration of hsDNA with in the range of 0.059–15.0 μg·m L^-1. This proposed method demonstrated a good linear correlation coefficient of 0.9937 and a detection limit（3 σ/K） of 0.018 μg·mL^-1 for hsDNA. This dual-directional fluorescent biosensor overcame the selectivity problem commonly existed in the traditional mono-directional fluorescence detection mode and owned perfect analysis applications in biochemical DNA monitoring. 2. Fluorescent reversible regulation based on the interactions of topotecan hydrochloride, neutral red and quantum dotsThe interactions of topotecan hydrochloride（THC）, neutral red（NR） and thioglycolic acid（TGA） capped CdTe/CdS quantum dots（QDs） built a solid base for the controlling of the fluorescent reversible regulation of the system. This study was developed by means of ultraviolet–visible（UV–vis） absorption, fluorescence（FL）, resonance Rayleigh scattering（RRS） spectroscopy and transmission electron microscopy（TEM）. Corresponding experimental results revealed that the fluorescence of TGA-CdTe/CdS QDs could be effectively quenched by NR, while the RRS of the QDs enhanced gradually with the each increment of NR concentration. After the addition of THC, the strong covalent conjugation between NR and THC which was in carboxylate state enabled NR to be dissociated from the surface of TGA-CdTe/CdS QDs to form more stable complex with THC, thereby enhancing the fluorescence of the TGA-CdTe/CdS QDs-NR system. What is more, through analyzing the optical properties and experimental data of the reaction between TGA-CdTe/CdS QDs and NR, the possible reaction mechanism of the whole system was discussed. This combination of multiple spectroscopic techniques could contribute to the investigation for the fluorescent reversible regulation of QDs and a method could also be established to research the interactions between camptothecin drugs and dyes.3. A dual-fluorescence biosensor assembled by quantum dots and phenazinium dyes: A comparative study for DNA detectionA dual-fluorescence ―turn off–on‖ biosensor, which consists of quantum dots（GSH-CdTe QDs） whose fluorescence was quenched by safranine T（ST） via an electron transfer process, had been developed for herring sperm DNA（hsDNA） detection. Initially, in the ―turn off‖ stage, the strong fluorescence of GSH-CdTe QDs could be effectively quenched by ST owing to the occurrence of the electron transfer from the photoexcited GSH-CdTe QDs to ST. And then, the high affinity of DNA to ST enabled the ST attached to the surface of GSH-CdTe QDs, to become embedded into hsDNA double helix structure to form stable complex and moved away from the QDs. Therefore, the recognition of hsDNA could be realized via the fluorescence restoration of the QDs–ST based biosensor, namely of the fluorescence ―turn on‖ procedure. This designed biosensor exhibited good sensitivity and selectivity, for the reason that the detection limit for DNA reached 10.8 ng·m L^-1, meanwhile, neither biologically relevant metal ions, common organic compounds, nor the amino acid had any significant interference in the detection mode. Hence, this simple, fast, sensitive, and selective biosensor owned perfect analysis applications in biochemical DNA monitoring.