The Construction Of Biosensor Based On Gold Nanoparticles-quantum Dots And Its Application In Nucleic Acid And MUC1 Detection

The construction of biosensors is the research priority in the biosensing field.Gold nanoparticles(Au NPs),a type of metal nanomaterial,play an essential role in numerous biosensors due to their advantages of remarkable optical properties,good biocompatibility,easy synthesis and easy surface modification.As an outstanding fluorescent nanomaterial,quantum dots(QDs)have been widely applied in biosensing by virtue of advantages such as wide excitation,narrow emission spectra,tunable emission lines,high quantum yield and easy surface modification.It is worth mentioning that the fluorescence of quantum dots could be effectively quenched by gold nanoparticles in a certain distance(1～40 nm)through the nanosurface energy transfer(NSET).Moreover,both of them could be easily modified by nucleic acids,which provide favorable conditions for the construction of aptasensors.Therefore,Au NPs-QDs is a competitive donor-acceptor pair that has been commonly used in quench-recovery("Off-On")fluorescence biosensors.However,it has been reported that due to the strong quenching effect,the fluorescence of quantum dots couldn’t be fully recovered in the fluorescence recovery("On")state,which aroused an adverse impact on the analytical performance of the biosensor.Thus,this issue needs to be solved urgently.In view of this,our work focused on the improvement and construction of the Au NPs-QDs biosensor.Firstly,we made improvement for the Au NPs-QDs biosensor toward the above issue,and then we constructed a novel Au NPs-QDs ratiometic fluorescence biosensor.The main research contents are as follows:(1)Due to the electrostatic adsorption,the DNA conjugated with Au NPs are easily adsorbed on the surface of Au NPs,which limits the recognition ability of the DNA.It is noteworthy that the introduction of 6-mercaptohexanol(MCH)could eliminate the nonspecific adsorption,and the DNA configuration would change from "curl" to "upright" state.Inspired by this work,we introduced MCH to the surface of DNA-Au NPs.Significantly,an additional role of MCH was found in keeping the free DNA-QDs further away from the surface of DNA-Au NPs,thereby significantly enhancing the fluorescence recovery ratio.More importantly,the employment of MCH endowed the Au NPs-QDs biosensor with improved analytical performance,which contributed to higher sensitivity and wider linear range.The limit of detection was 1.19 n M.Moreover,by simply converting recognition sequence to aptamer,the biosensor was applied to the detection of biomarker MUC1 to demonstrate its universality for other target assay,and the limit of detection was 1.78 n M.(2)The anti-interference ability of the Au NPs-QDs biosensor in the above work was still deficient.Therefore,in this work,with the aid of DNA strand displacement reaction,a novel Au NPs-QDs ratiometic fluorescence biosensor was constructed by bringing in two kinds of DNA-QDs with different emission wavelengths.Then the Au NPs-QDs ratiometic fluorescence biosensor was applied in the detection of specific DNA sequence.Significantly,the anti-interference ability and sensitivity of the Au NPs-QDs ratiometic fluorescence biosensor were improved in comparison to the above work.And the detection limit was 0.49 n M.In addition,compared with other ratiometic fluorescence biosensors based on QDs,this biosensor showed outstanding advantages of simple operation,no damage to QDs and short analysis time.