Electrochemical DNA Sensor Based On Fe₃O₄ Magnetic Nanocomposites

There are two main problems in the current development of electrochemical DNA?E-DNA?sensors: First,not only is it difficult to hybridize between probe DNA and target DNA molecules in a complex system,but the non-specific adsorption of DNA during hybridization will result in a higher blank signal,resulting in the lower hybridization efficiency of two DNA molecules;Second,relying solely on the hybridization mechanism between the probe DNA and the target DNA molecule could make the detection sensitivity low.Therefore,it is necessary to design a scheme for amplifying the detection signal to further improve the sensitivity.In this paper,Fe₃O₄ NPs are used to construct E-DNA biosensors to detect the target DNA,which can effectively eliminate the above interference and further improve the sensitivity.In summary,on the premise of synthesizing Fe₃O₄@Au NPs and alkynyl Fe₃O₄@Si O₂ NPs composite materials,E-DNA biosensors of Fe₃O₄@Au NPs and alkynyl Fe₃O₄@Si O₂ NPs were constructed,respectively,and successfully used for highly sensitive detection target DNA.The main contents are as follows::1.Fe₃O₄ magnetic nanocomposites were synthesized.Fe₃O₄ nanoparticles?NPs?with good morphology and uniform size were synthesized following the solvothermal method.In detail,by optimizing the preparation conditions,changing the concentration of sodium citrate and sodium acetate to adjust the size and morphology of Fe₃O₄ NPs,this work selected Fe₃O₄ NPs with a particle size of 80 nm,when sodium citrate and sodium acetate were 67.5 mmol/L and 3.6 mol/L,respectively.Then Fe₃O₄@Au NPs were successfully prepared using Na BH4 in situ reduction of HAu Cl4.Besides,the Stober method was used to synthesize Fe₃O₄@Si O₂ NPs which were then modified on the surface with alkynyl groups.After optimizing the preparation process,the results show that the one-step synthesis method of nitrogen protection is beneficial to the alkynylation of Fe₃O₄@Si O₂.2.The E-DNA sensor based on Fe₃O₄@Au NPs magnetic composite nanomaterials was proposed for electrochemical detection of target DNA.There are three DNA strands for capturing DNA?DNA1?,signaling DNA?DNA2?and target DNA?DNA3?.In the presence of DNA3,these DNAs would adopt a duplexed structure through Watson–Crick base pairing,positioning between the modified functional groups in DNA1 and DNA2 in proximity to each other.The methylene blue?MB?current on the electrode surface was used as the electrical signal to detect the target DNA.It is demonstrated that the the sensor obtained the best electrical signal of the sensor whenhybridized at 2 ?M DNA1 and 2 ?M DNA2,250 ?g/m L Fe₃O₄@Au for 2 h.The corresponding calibration curve exhibited a perfectly linear relationship between the increase in the electrochemical intensity and the DNA3 concentration in the range from10 n M to 100 n M.The linear regression equation can be expressed as I?e-7/A?=0.01243C?n M?+0.57511,with a correlation coefficient of 0.998,indicating that the sensor can be used to detect target molecules.3.A novel E-DNA sensor of alkynyl Fe₃O₄@Si O₂ magnetic nanocomposite was developed.DNA1 is modified in alkynylated Fe₃O₄@Si O₂ magnetic composite nanomaterial by light click reaction,and then DNA2 is added.With the addition of DNA3,the electrochemical signal in the presence of target can be detected by alternating current voltammetry?ACV?through Watson–Crick base pairing.