Construction And Biochemical Application Of Sensors Based On Functional DNA Quantum Dots And Polymer Quantum Dots

DNA quantum dots(DNA QDs)and semiconductor polymer nanoparticles(Pdots)have good luminous properties and optical stability,excellent biocompatibility and low cytotoxicity,making them suitable for cell imaging,photoelectrochemistry,and pH.It has broad application prospects in the determination of temperature,temperature,ions and related biologically active substances.Low-molecular-weight double-stranded DNA(salmon sperm)was used as the raw material to prepare high-intensity DNA quantum dots(DNA QDs).The fluorescence resonance energy transfer(FRET)effect between DNA QDs and PDA was used to study cysteine in solution.Sensory analysis of amino acids;poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiazole)](PFBT),fluorescein isothiocyanate(FITC)and poly(9,9-dioctylfluorenyl-2,7-diyl)(PFO)as polymer functional monomers to prepare Pdots-PFO-PFBT-FITC(Pdots-PPF)for ratio fluorescence pH sensing and biological imaging;PFBT and tetraphenylporphyrin(TPP)as functional monomers,and poly(styrene-maleic anhydride)(PSMA)as cross A TPP-doped PFBT Pdots(Pdots-TP)was prepared,and Pdots-TP was used as the photosensitive material of the PEC sensor for the tetracycline sensing analysis.The specific research work mainly includes the following three parts:(1)A simple and novel method for detecting cysteine based on the resonance energy transfer between DNA QDs and polydopamine(PDA)was developed.Because the fluorescence emitted by the DNA QDs is absorbed by the PDA molecules,a fluorescence resonance energy transfer(FRET)effect is generated,which causes the fluorescence quenching of the DNA QDs and puts the DNA QDs in a fluorescent"off"state.When cysteine is present,the spontaneous oxidative polymerization reaction from dopamine(DA)to PDA will be blocked,the fluorescence of DNA QDs will be restored,and the fluorescence will be“on”,and the fluorescence recovery of DNA QDs and the cysteine in solution will be restored.The concentration of amino acids is related,and a cysteine fluorescence sensor has been developed.The linear range of the sensor is:10.0?100.0?mol/L,the linear equation is:y=0.0181x-0.0185,and the detection limit is 1.67?mol/L(S/N=3,n=10).The sensor was successfully applied to the determination of cysteine content in human urine samples.The spiked recovery was 98.6%?105.9%.(2)Develop a sensitive pH sensor using the superior fluorescent probe characteristics of polymer quantum dots(Pdots),and successfully apply Pdots-PPF to Hela cell imaging.The sensing performance of Pdots proportional fluorescence pH sensor was evaluated.Three kinds of hydrophilic Pdots were synthesized using PFO,PFBT and FITC as functional monomers:Pdots-PFO-FITC(Pdots-PF),Pdots-PFO-PFBT(Pdots-PP)and Pdots-PFO-PFBT-FITC(Pdots-PPF).In the end,it was found that Pdots-PPF has the best pH sensing performance.When Pdots-PPF is excited with light at 380 nm,pH-insensitive(?ex=439 nm)and pH-sensitive(?ex=517 nm)fluorescence are generated,respectively.This feature makes it possible to build proportional pH sensors using Pdots-PPF.Pdots-PPF's fluorescence emission intensity ratio(I517/I439)varies linearly between pH 3.0 and 8.0,and Pdots-PPF pH sensor shows ideal reversibility and stability in proportional fluorescence pH sensing.More importantly,Pdots-PPF has been successfully used for imaging Hela cells,proving its excellent biocompatibility and low cytotoxicity.(3)A TPP-doped Pdots(Pdots-TP)with photoelectric response was synthesized by the reprecipitation method.Pdots-TP was used as a photosensitive material,and TC aptamers were photoelectrochemical(PEC)aptamer sensors for identification elements.And successfully achieved sensitive detection of tetracycline(TC).After Pdots modified the surface of the ITO glass electrode,the cathode photocurrent signal was generated by the Pdots/ITO electrode due to the photoactive activity of Pdots.After apt was modified on the surface of the Pdots/ITO electrode to make a TC apt/Pdots/ITO electrode,the TC apt The steric hindrance effect photocurrent will decrease;however,when the TC apt/Pdots/ITO electrode reacts specifically with the solution containing TC,it will cause the TC apt to fall off the surface of the TC apt/Pdots/ITO electrode and allow the photocurrent to be restore.Based on this,a method for sensitive detection of TC by a PEC sensor was established,and its linear range was 1.0 nmol/L to 1.0×10~4 nmol/L.The linear equation was:,and the detection limit was 0.26 nmol/L.At the same time,the aptamer sensor was successfully applied to the determination of tetracycline in honey samples with a recovery rate of 96.4%to 104.4%.