Quantum Dots Labeled DNA Probes For Electrochemical Detection Of Specific Gene Sequences From Genetically Modified Organisms

With the rapid development and application of genetically modified organisms (GMOs), it is necessary to set up a fast, convenient and effective detection method. Electrochemical biosensor can be applied to the detection of inserted gene sequence of GMOs, it would be a simple, reliable and promising method for the analysis of specific sequences from GMO.Quantum dots are nanoparticles with many distinct characteristics and can be used in the filed of biological research. With the increasing and broadening applications of quantum dots, it has been found that quantum dots have many potential usage in many fields such as biochemistry, cell biology, immuno-biology etc. Especially, quantum dots can be used as labels for biological systems.In this paper lead sulfide and cadmium sulfide quantum dot were used as oligonucleotide labels for the electrochemical detection of GMOs. Quantum dots were synthesized in aqueous solution with free carboxyl groups on the surface, which enables it to be easily bound to amino-group modified oligonucleotide. Quantum dots labeled ssDNA probes were furthur characterized by transmission electron microscopy (TEM) and UV-Vis absorption spectra. Target ssDNA were covalently linked on self-assembled gold electrode or immobilized on microplate wells by dry-adsorption method. Electrochemical impedance spectra (EIS) were employed to monitor the changes of surface conditions of gold electrode in different modification processes. After the hybridization reaction was accomplished, the quantum dots anchored on the hybrids were dissolved in the solution by the oxidation with HNO3 and further detected by a sensitive differential pulse anodic stripping voltammetric method. The detection results can be used for monitoring the hybridization reaction and further used for ssDNA detection.According to this principle, quantum dots labeled electrochemical DNA hybridization assay was successfully used for the detection of insert gene sequence of GMOs such as CaMV 35S, NOS, PAT and FMV 35S. The established method extended the quantum dots labeled electrochemical DNA analysis to the specific sequence samples with higher sensitivity and selectivity, which can also have good ability to distinguish the complementary, non-complementary and the three-base mismatched ssDNA sequence. Further, an electrochemical method for the simultaneous detection of two different ssDNA sequences using the different kinds of quantum dots was furthur studied. The proposed method established new way for the detection of different target sequences in one sample.