Method for preparing nanocomposite and label-free aptamer electrochemical sensor of gamma-interferon based on the nanocomposite

A method for preparing a nanocomposite and a label-free aptamer electrochemical sensor of γ-interferon based on the nanocomposite, comprising the following steps:

• (1) adding molybdenum disulfide (MoS2) powder to a mixed solvent of ethanol and distilled water to obtain a first mixed solution, performing a first ultrasonic treatment on the first mixed solution in a water bath, then centrifuging the first mixed solution to separate and remove a precipitate to obtain a MoS2 homogeneous dispersion for subsequent use;
• (2) preparing an aqueous solution of chloroauric acid and adding the aqueous solution of chloroauric acid to an aqueous solution of poly(amidoamine) dendrimer (PAMAM) to obtain a second mixed solution, stirring and mixing the second mixed solution evenly with magnetic stirring, dropwise adding an aqueous solution of sodium borohydride to the second mixed solution to obtain a gold nanoparticles (AuNPs)-supported dendrimers (PAMAM/AuNPs) dispersion, and removing residual reactants from the PAMAM/AuNPs dispersion by a dialysis treatment;
• (3) dropwise adding the PAMAM/AuNPs dispersion to the MoS2 homogeneous dispersion to obtain a third mixed solution;
• performing a second ultrasonic treatment on the third mixed solution in a water bath and then performing a magnetic stirring treatment to the third mixed solution to carry out a reaction to obtain a PAMAM/AuNPs/MoS2 nanocomposite dispersion;
• (4) adding a cross-linking agent to a surface of a bare glass carbon electrode subjected to a polishing treatment, and then drip-coating the PAMAM/AuNPs/MoS2 nanocomposite dispersion to obtain a PAMAM/AuNPs/MoS2 modified electrode;
• diluting a γ-interferon nucleic acid aptamer with a buffer solution to obtain a fourth mixed solution, heating the fourth mixed solution to a predetermined temperature, and then cooling the fourth mixed solution to room temperature, allowing the fourth mixed solution to form an aptamer chain with a secondary hairpin structure, and thus allowing a sulfhydryl group at a terminal of the aptamer chain to be connected to a surface of the AuNPs via an Au—S bond to obtain a PAMAM/AuNPs/MoS2-aptamer modified electrode;
• and
• (5) adding a redox probe methylene blue (MB) into an electrolyte immersed with the PAMAM/AuNPs/MoS2-aptamer modified electrode;
• wherein, with an increasing of γ-interferon, an electrochemical signal peak of the MB enhances gradually;
• then, fitting a linear relationship between a current intensity of the electrochemical signal peak of the MB and a concentration of the γ-interferon to construct the label-free aptamer electrochemical sensor for detecting the γ-interferon.