Study On Construction And Application Of Quantum-Dots/Cerasome Fluorescent Sensor

Quantum dots(QDs)as a new class of fluorescent nanomaterial,featuring unique optical and electronic properties such as high-brightness,broad-band absorption,narrow-band emission,and high resistance to photobleaching,as well as energy transfer and charge transfer,have been widely used in the field of biomedical engineering.Encapsulation of QDs with cerasome can significantly improvethe fluorescence stability,anti-interference capability and biocompatibility of the QDs,which are highly desirable for advancing new biosensing systems..In this thesis,a novel QD/cerasome fluorescent sensor was designed,constructed and used for the detection of micro RNA-21,wherein fluorescence resonance energy transfer(FRET),signal amplification and ratiometric fluorescence were utilized.The main contents are as follows:1.Cerasome-forming lipid was synthesized in the laboratory.By controlling the ratios of cerasome-forming lipid and phospholipids,cerasomes in average diameter of 100 nm were prepared by thin-film ultrasound method.Furthermore,dual-emissive QDs were successfully encapsulated into the cerasomes by using the film evaporationand-ultrasonic method: the red-emissive and green-emissive QDs were located in the inner cavity and the lipid bilayer,respectively.By simply changing the amount of green-emissive QDs,encoded QD/cerasomes with green–to-red ratios of 2:1,1:1 and 1:2 were prepared.The newly developed QD/cerasomes have exhibited high fluorescence stability and excellent biocompatibility.2.By typical EDC/NHS reaction,hairpin probes with 3'-quencher was conjugated to the surface of cerasome to construct a QD/cerasome fluorescence sensor.For the sensor,the fluorescence of green-emissive QDs in the lipid bilayer was quenched by the 3'-quencher through FRET,whereas the fluorescence of red-emissive in the inner cavity remained unchanged,which could be used for biosensing in fluorescence ratiometry.3.The QD/cerasome sensor was successfully used for visual detection of mi RNA-21 with high sensitivity and specificity.The sensitive detection was realized via FRETbased signal transduction combined with catalytic hairpin assembly(CHA)and hybridization chain reaction(HCR)-based signal amplification.The visualization was realized via the fluorescence ratiometry: the red fluorescence was used as the internal reference,the green fluorescence was enhanced as a function of mi RNA-21 abundance.The QD/cerasome sensor has achieved the limit of detection as low as 3.7 f M,and the linear dynamic range of 4 orders of magnitude,showing “red-yellowgreen” traffic light-type visualization effect.4.PEG-modified poly-dopamine(PEG-PDA)which adsorbed hairpin structure nucleic acids constructed nanocarriers(PEG-PDA/HPs)to improve the monodisperse of PDA and increase the signal-to-noise ratio of cell fluorescence imaging.The combination of a QDs/cerasome fluorescence sensor and a nucleic acid nanocarrier("Biosensor + Nanocarrier")realizes fluorescence imaging of mi RNA-21 in situ imaging of cell and intracellular quantitative/semi-quantitative fluorescent analysis.Fluorescent imaging detection of different cell cycles and different cancer cells is come ture.