The Novel Aptasensors Based On 2D Nanocomposites:for Cadmium And Cancer Marker Detection

Aptamers are single-stranded DNA or RNA nucleotides that are synthesized using the Systematic Evolution of Ligands by Exponential Enrichment.Based on the special three-dimensional structure of the aptamer,which has strong specificity and high affinity for the target recognition,it utilizes the intermolecular hydrogen bonding,electrostatic interaction and Van der Waals Forces to interact with targets.Electrochemical biosensing technology has advantages of high sensitivity,less sample usage,high speed and simplicity,and has a wide range of applications in the field of environmental monitoring and biomedicine.In this work,we constructed two electrochemical biosensors based on nanomaterials and aptamers.(1)The use of electrochemical detection of toxic substances in the environment is an important mean of environmental monitoring.We reported in detail the Carbon Nitride Graphene/Heavy Iron/Aptasensor(GCN/Cd2+/Aptasensor)to detect cadmium in drinking water.The aptamers taken from the literature are single-stranded DNA nucleotides specifically bound to cadmium ions.Carbon nitride graphene composites were characterized by FTIR,X-ray diffraction,scanning electron microscope and transmission electron microscopy.The composite materials had not only the unique cavities but also the good conductivity because of the added graphene.Therefore,based on previous work,an electrochemical sensor with wide detection range,high sensitivity and specificity was constructed.A wider detection range of 1nM-1mM and a higher sensitivity of 0.337 nM was obtained.(2)Detection of cancer markers is an important aspect in the biomedical field.We constructed Graphene-Gold Nanoparticles/Alpha-fetoprotein/Aptasensor(Gr-AuNPs/AFP/Aptasensor)for the early diagnosis of liver cancer patients.Firstly,the graphene gold nanoparticle composites were synthesized and characterized by UV and transmission electron microscopy.The results show that the graphene gold nanoparticles were uniformly deposited on the graphene substrate.Then the alpha-fetoprotein aptamer with thioglycolic was linked to the composites through the strong adsorption between the gold and sulfur bonds.Thus Gr-AuNPs/AFP/Aptasensor was constructed by Electrochemical Impedance for the detection of alpha-fetoprotein.This electrochemical sensor could be used for the detection of alpha-fetoprotein in a wide linear range,with high sensitivity and high specificity(1.5 fg/ml-15 ?g/ml,LOD=0.849 fg/ml).To sum up,in this paper,we have successfully constructed GCN/Cd2+/Aptasensor and Gr-AuNPs/AFP/Aptasensor.They provided new experimental methods and ideas for the detection of pollutants in the environment and the early diagnosis of cancer.