Preparation Of Temperature-responsive Fluorescent Polymer Nanoparticle And Carbon Dots And The Study Of Controlled Release Of Drug

In recent years,the fluorescent nanoparticles attracted attentions at home and abroad,especially the polymer dots and carbon quantum dots,due to its outstanding fluorescence brightness,good biocompatibility,and nanoparticles surface modified,nonphotobleaching.Nano-biotechnology provides a new way of thinking and means for biomedical science and related disciplines.This article mainly focus on the preparation and characterization of Pdots and their applications in cell imaging and drug release,and the application of carbon dots in biology detection.The main research works are as follows:（1）We synthesis of different proportion of block copolymer PS-b-PNIPAM by reversible Addition fragmentation chain transfer radical polymerization,the characterization of co-polymer determined by Fourier transform infrared spectroscopy.The molecular weight and distribution index（PDI）of the co-polymers were characterized by gel permeation chromatography（GPC）,the results show that the molecular weight distribution of the co-polymer is narrow,PDI=1.16,the polymerization degree of St and NIPAM is 2,115,respectively;At the same time,according to the results of UV-Vis,the molar ratio of co-polymer is 1:57.The temperature sensitivity of block co-polymers was determined by UV-Vis spectroscopy,and the maximum absorbance ratio was measured at T=20 ^oC and T=40 ^oC,the results show that the amphiphilic block copolymer（1:57）has good temperature sensitivity and is suitable to be a functional ligand for the synthesis of temperature-responsive polymer dots.（2）Nanomaterials have great potential to be applied in the field of intracellular imaging,drug delivery and release.In this chapter,we describe the preparation of nanoparticles with fluorescence and temperature-responsive by co-precipitation,and the characterization the size of nanoparticles by DLS.The variation of the particle size of PFBT polymer dots with temperature was characterized by DLS,and The variation of fluorescence intensity of PFBT polymer dots with temperature was characterized by fluorescence spectroscopy.It is testified that the fluorescence intensity of the original nanoparticles enhanced gradually when the solution was heated from 10 ^oC to 60 ^oC.On the contrary,an obvious reduction in size was observed as the solution temperature increases in the range from 25 ^oC to 60 ^oC.During the heating and cooling processes,subsequently,led to the release of Nile Red from the nanoparticles.What’s more,the drug release behavior of nanoparticles in cells was confirmed by inverted fluorescence microscope In addition,the nanoparticles exhibit a relatively low toxicity according the cytotoxicity experiment,The results of single particle experiment shows that both Pdots and the loaded Nile Red nanoparticles have stable single particle fluorescence intensity.Thus,we expect the design of thermo-responsive drug-loaded nanoparticles represents a novel biosensor and drug release strategy.（3）we demonstrated a convenient and green strategy for the synthesis of bright and water-soluble carbon dots（CDs）by carbonizing sodium citrate in a hydrothermal method.Without post-surface modification,the as-synthesized CDs display fluorescence quantum yield（QY）as high as21.03%and show superior stability not only in concentrated salt solutions but also in neutral and alkaline media.The probe exhibits selective and sensitive recognition capability towards mercury ion(Hg²⁺)in aqueous solution.The fluorescence of CDs can be quenched by Hg²⁺through an effective electron energy transfer process.It displays a linear quenching effect toward mercury ion in the concentration range of 0–15μM with a correlation coefficient（R²）of 0.99.The limit of detection is determined to be 25 nM at the signal to noise ratio of 3.These attractive merits would enable the extensive applications of this probe in environmental science and analytical chemistry in the future.