Study On Construction And Application Of Quantum-dots-liposome Fluorescent Sensor

Fluorescent sensor has inherent advantages such as good selectivity,high sensitivity,simple and low cost,promoting their applications in biomedical research.The construction of quantum dots(QDs)based fluorescent sensor have become a focus in recent years,because of their unique photophysical properties,such as broad-band absorption,size-dependent narrow-band emission and resistance to photobleaching.By coating QDs with liposome,fluorescence stability,anti-interference capability and biocompatibility ofthe sensorsare proposed to be improved.In addition,the surface of liposome can be easy modified,exihibiting high flexibility toward various sensing application..In this paper,a ratiometric fluorescent sensor,based on QDs/liposome,has been designedfor detection of microRNA-21,with resonance energy transfer mechanism.The main contents are as follows:1.Liposomes are synthesized based on the thin film evaporation-and-ultrasonic method and theirdiameters can be well controlled.By doping carboxyl phospholipids,thesurface of liposomes is functionized with carboxyl groups,facilitating with further bioconjugation.2.Dual-emissive QDs/liposomes are constructed by doping green emissive QDs in the thin flim evaporation process and doping red emissive QDs in the ultrasonic process.The size of the dual-emissive QDs/liposomes is controlled to be about 80 nm.Besides,the surface of the liposomes is modified with carboxyl groups for further bioconjugation.3.Based on the dual-emissive QDs/liposomes,the fluorescent sensors are constructed by first conjugating with capture probes ofinicroRNA-21,and then hybridizing with AuNC modified short-length DNA(AuNC-DNA).The AuNCs quench the fluorescence of green-emissive QDs by resonance energy transfer,while the fluorescence of red emissive QDs stays constant.In the presence of microRNA-21,capture probes competitively hybridize with the target against AuNC-DNA,resulting in detachment of AuNC-DNA from the dual-emissive QDs/liposomes.Accordingly,the resonance energy transfer is interrupted,acausing the recovery of the fluorescence of green emissive QDs.With the ratiometric fluorescence,the sensor has achieved sensitive microRNA-21 detection,with improved visualization capability.