▎ 摘　　要

NOVELTY - Three-dimensional graphene biosensor comprises a substrate upper surface of two sides provided with indium tin oxide and three-dimensional graphene layer provided in the middle of the substrate and covers a portion of indium tin oxide. The uncovered indium tin oxide is located on both sides of the substrate and serves as the source electrode and drain electrode, respectively. USE - The biosensor is useful for detecting the cancer marker MicroRNA (claimed). ADVANTAGE - The method does not require labeling and is simple to operate, convenient to use, and has high selectivity and specificity at a low use voltage and has good safety. DETAILED DESCRIPTION - INDEPENDENT CLAIM are also included for: (1) preparing the biosensor, comprising connecting a three-dimensional graphene biosensor to a detection circuit, preparing three-dimensional graphene skeleton, transferring the three-dimensional graphene skeleton in water to a substrate provided with indium tin oxide on both sides of the upper surface, where the lower surface of the graphene covers the indium tin oxide on both sides of the upper surface of the glass substrate; and (2) detecting MicroRNA based on a three-dimensional graphene biosensor, comprising connecting the three-dimensional graphene biosensor to a detection circuit, connecting the probe DNA to the surface of the three-dimensional graphene skeleton through 1-fluorene butyric acid N-hydroxysuccinimide ester, adding solutions containing different concentrations of MicroRNA to the three-dimensional graphene layer on which the probe DNA immobilized to obtain sensitivity of the biosensor to MicroRNA detection according to the detection gate voltage change.