Highly Sensitive Detection For Hg²⁺ Using Graphene Oxide-DNA Based Sensors

Mercury ion(Hg²⁺)is one of important factors in the environmental pollution because Hg²⁺ can result in the irreversible effects for animals and plants at low concentration.Furthermore,Hg²⁺ is enriched continuously by the cycle process that does great harm to human.Hg²⁺ can interact with specific DNA sequence,such as multiple T DNA sequences,which leads to the conformation change of DNA.Therefore,many methods have been developed for Hg²⁺ detection based on this principle.However,some methods cannot detect Hg²⁺ in the multiple samples.Some methods have the false signals with high rate for Hg²⁺ detection.Some methods have not highly sensitive in the detection of Hg²⁺.The biosensor is one of research tools in the molecular biology.Here we have developed new the methods and technology based on the biosensors using GO,a novel naomaterial,and DNA sequences for detecting Hg²⁺ in order to overcome these problems.The following projects based on the biosensors have been carried out.1.One sensor detected Hg²⁺ using DNA sequences with multiple T immobilized on the surface of GO.GO was a kind of fluorescence quencher and multiple T sequences DNA was recognition element in this sensor.We removed the redundant DNA sequences modified by FAM,which cannot bind specially to GO in the immobilization process.Furthermore,it can reduce the impact of false signals and improve the detection sensitivity.The detection limit was 9.37 nM that was 20% lower than it was in the physical adsorption process.The second amino group was introduced by using the complementary DNA sequence.The limit of detection in the sensor that was made of with double DNA sequences modified with amino group was 2.52 nM that decreased the detection limit for 75%.2.The second sensor detected Hg²⁺ using DNA sequences with multiple T modified with dual fluorophores.FAM and SYBR Green I were simultaneously used to label DNA sequences.They can promote with each other.The detection limit of the sensor which was made of single DNA sequence modified with amino group and dual fluorophores was 0.43 nM.The detection limit of the sensor which was made of double DNA sequences modified with amino group and dual fluorophores was 0.53 nM that decreased 20%.3 The third sensor detected Hg²⁺ using phosphorothioate DNA sequence immobilized on the surface of GO.Hg²⁺ can specially cleave phosphorothioate DNA site in DNA sequence.Hg²⁺ can be released and recyclely used for the next reaction.The sensor detection limit of Hg²⁺ was 1.37 nM and decreased about 22% comparing with physical adsorption method.4 The detection of Hg²⁺ by the fourth sensor using the phosphorothioate DNA sequences immobilized on the surface of GO combining with microarray.The multiple samples were placed on the slide.It was similar with microarray.The detection of multiple samples can be realized.The detection limit in the biosensor constructed by using PS-DNA physical adsorption on the surface of GO was 3.187 nM.However,the detection limit in the biosensor constructed by using immobilization PS-DNA on the surface of GO was 0.79 nM.The problems in the methods for Hg²⁺ detection can be solved from the above methods.They can push the development for the detection of heavy metal ions in the field of food safety.