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An electrochemical detection method for chemical sensing has been developed using a DNA aptamer immobilized gold electrode chip. DNA aptamers specifically binding to 17β-estradiol were selected by the SELEX (Systematic Evolution of Ligands by EXponential enrichment) process from a random ssDNA library, composed of approximately 7.2×10¹⁴ DNA molecules. Gold electrode chips were employed to evaluate the electrochemical signals generated from interactions between the aptamers and the target molecules. The DNA aptamer immobilization on the gold electrode was based on the avidin–biotin interaction. The cyclic voltametry (CV) and square wave voltametry (SWV) values were measured to evaluate the chemical binding to aptamer. When 17β-estradiol interacted with the DNA aptamer, the current decreased due to the interference of bound 17β-estradiol with the electron flow produced by a redox …