Preparations Of Polymer Dots And DNA-Dots And Their Biological Applications

Semiconductor polymer quantum dots as a new member of the nanomaterials have been received widely attention. It is obvious that semiconducting polymer nanoparticles had an advantage over traditional organic dyes and inorganic quantum dots. Semiconductor polymer possesses numerous attractive characteristics that make it especially suitable for a variety of sensing applications, such as the large extinction coefficients, high optical stability and thermo-stabilities, excellent luminous efficiency and easily modification in structure. In recent years, semiconductor polymer quantum dots have a wide range of applications, especially in the fields of molecular biology, cell biology, molecular imaging, medical diagnosis and so on. In addition, recent progress in nano techno logy allows for the creation of new materials with high luminous efficiency and exceptional biocompatibility. DNA-dots are derived from DNA via self-assembly under the low temperature, which showed good biocompatibility and low biological toxicity, which could play a great role of the cytoplasmic marker.In this study, poly （9,9-dioctylfluorenyl-2,7-diyl） and poly （styrene-co-maleic anhydride） as precursors prepared PFO-COOH dots and connected with the amino graphene; DNA-dots with high biological compatibility and low biological toxicity were prepared by a raw material of salmon DNA, which had high selectivity of metal ion and applied in biological imaging; herring DNA-dots can be used in the analysis of ferric ion sensing and had good sensitivity and selectivity. The main research work of this paper is summarized as following three parts:（1） Here, we used the modified Hummers’method to synthesis Graphene oxide. Ethylene glycol and ammonia water were used as solvent and nitrogen precursor respectively to prepare amine modified graphene at 180℃ for 10h. In the end, the resultant amine modified graphene was reacted with the carboxyl-functionalized poly（9,9-dioctylfluorenyl-2,7-diyl） dots （PFO-COOH dots） using the standard carboxyl-amine coupling catalyzed by 1-ethyl-3-（3-dimethylaminop ropyl）-carbodiimide （EDC）. An almost entirely quenching in fluorescence intensity was observed in the mixture of PFO-COOH dots and amine modified graphene, which was primarily due to the fluorescence resonance energy transfer （FRET）.（2） A simple method was developed for the synthesis of water-soluble and well-dispersed fluorescent DNA-dots under mild conditions is reported. The resultant DNA-dots were with excellent biocompatibility as well as water solubility. The solution of DNA-dots shows blue fluorescence and luminescence lifetime equals to 2.74ns, with a quantum yield up to 7.5%. It is attractive that DNA-dots can be used as an effective fluorescent probe in biological imaging.（3） We report a new class of fluorescent bio-dots that are derived from DNA via self-assembly at low temperatures down to 85℃, which possesses strong fluorescence with a much longer luminescence lifetime （τ1=1.95ns） than the carbon dots（τ1=0.5ns）. The fluorescence intensity of DNA-dots can be quenched with the addition of Fe³⁺, which is applied for sensing and detecting the content of iron in the Ferrous sulfate retarder.Under optimized conditions, the detection limit as low as 0.045ppm was achieved, and the recoveries of the spiked samples were 94.7～98.5%. Nine determinations of a 4ppm Fe³⁺ standard solution gave a relative standard deviation （RSD） of 4.5%. Accordingly, DNA-dots can meet the requirement for monitoring Fe³⁺ in the Ferrous sulfate retarder.