Electrochemical determination of PIK3CA gene associated with breast cancer based on molybdenum disulfide nanosheet-supported poly(indole-6-carboxylic acid)

Abstract

In our study, we report the development of molybdenum disulfide (MoS₂) nanosheet-supported poly(indole-6-carboxylic acid) (PIn6COOH) and its usage for the electrochemical determination of circulating tumor DNA (ctDNA) such as PIK3CA gene associated with breast cancer. The MoS₂ nanosheets prepared by the solvent exfoliation method from commercial bulk MoS₂ were first immobilized on the surface of a carbon paste electrode; then, PIn6COOH, a novel electroactive material, was electropolymerized on the MoS₂ substrate by the potentiostatic method to form a unique nanocomposite structure. The physical adsorption between aromatic In6COOH monomers and MoS₂ efficiently improved the electropolymerization efficiency, resulting in increased electrochemical response of PIn6COOH. Owing to the presence of abundant carboxyl groups, probe ssDNA was covalently immobilized on the carboxyl-terminated PIn6COOH/MoS₂ nanocomposite through free amines of DNA sequences based on 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydrosulfosuccinimide crosslinking reaction. The covalently immobilized probe ssDNA could selectively hybridize with its target DNA to form dsDNA on the surface of the PIn6COOH/MoS₂ nanocomposite. The self-signal changes of PIn6COOH induced by DNA immobilization and hybridization could be sensitively recognized via cyclic voltammetry and electrochemical impedance spectroscopy. This developed biosensor showed high performance of DNA hybridization with a detection limit of 1.5 × 10⁻¹⁷ mol L⁻¹ for the detection of PIK3CA gene. The easy construction of this biosensor besides its fine sensitivity and very low time consumption can make this PIn6COOH/MoS₂ nanocomposite very highly competitive for further applications in carcinoma diagnostic and therapeutic fields.