Preparation Of DNA Functionalized Quantum Dot Biosensor And Study On Detection Of Alpha-fetoprotein

Objective: Alpha fetoprotein(AFP)is the one of important tumor marker for hepatocellular carcinoma(HCC).To date,various methods for the detection of AFP,but they are time-consuming and vulnerable to radioactive contamination.In this paper,based on nucleic acid aptamers capable of specific target recognition and their own fluorescence characteristics of nanomaterial quantum dots,we produce a new fluorescent "turn on-off" sensor system for detection AFP with the properties of facile procedure and rapid.We provide a new direction for rapid detection of tumor markers.Methods: First,according to the AFP specific aptamer sequence(DNA1),we design a single-stranded DNA(DNA2)that is partially complementary pairing to the DNA1.The rest sequence of DNA2 can be self-complementary pairing,forming a double-chain structure.We design a single-stranded DNA(DNA3)that is DNA2 Complementary sequence.Secondly,we assemble DNA functionalized water-soluble quantum dots(DNA3-Qds)by "one-step" method.The DNA functionalized quantum dots with the best fluorescence intensity were selected by changing the experimental conditions.We synthesized Graphene oxide(GO)by Hummers method,and assemble it with DNA3-Qds.Owing to the quenching effect of GO on the fluorescence yield,GO optimal concentration can be determined by a change in the fluorescence intensity of the system.Finally,the formation of the double-chain structure was verified by gel electrophoresis.We incubate AFP and double-chain structure.Following pre-incubation,they were assembled with GO-DNA3-Qds.The fluorescence spectra were recorded to observe the relationship between fluorescence intensity change and AFP concentration.Results: We successfully prepared water-soluble DNA3-Qds with the best performance which met the fluorescence requirements for subsequent preparation of sensor system.At this point,the system fluorescence "turn on".We screened the optimal concentration of GO as 75?g/ml.T he system fluorescence is quenched and "turn off" when assembled with the DNA3-QDs.we have tested that DNA1 and DNA2 can form stable double-chain structures in the presence of no AFP.After joining the AFP,the double-chain structures was opened due to the specific DNA1 binding with AFP.The free DNA2 is complete complementary pairing to DNA3 in the system.At the same time,DNA3-QDs and GO separat e,the system fluorescence recovery "turn on".Experimental results show a good linear relationship between AFP concentration and system fluo rescence intensity.The biosensor possesses a low limit of detection of 0.8ng/m L,linear dynamic range of 5-300ng/m L.Conclusions: We applied the assembly of aptamers and quantum dots and the quenching effect of GO on the fluorescence yield successfully developed a biosensor capable of rapid detecting AFP.Provide a new method for clinical detection of AFP.