▎ 摘　　要

NOVELTY - Preparing hydrogel, involves (a) using graphite powder as raw material, adding sodium nitrate, sulfuric acid and potassium permanganate to the raw material, mixing materials, adding water to mixture, incubating mixture, again adding water, adding hydrogen peroxide solution to e.g. obtain reaction product, centrifuging reaction product, drying pellet to obtain solid graphene oxide, and ultrasonically dispersing graphene oxide in water to obtain graphene solution, and (b) adding protamine-DNA complex to the graphene solution, and heating mixture to form gel. USE - The method is useful for preparing hydrogel used in detection of mitochondrial DNA mutations in ovarian cancer (claimed), where the hydrogel is used in biosensors. DETAILED DESCRIPTION - Method for preparing hydrogel, involves (a) using graphite powder as raw material, adding sodium nitrate, sulfuric acid and potassium permanganate to the raw material, mixing the materials to obtain viscous mixture, adding water to the viscous mixture, incubating the mixture, again adding water to the mixture, adding hydrogen peroxide solution to the mixture to remove un-reacted potassium permanganate and obtain reaction product, centrifuging the reaction product, drying pellet to obtain solid graphene oxide, and ultrasonically dispersing the graphene oxide in water to obtain graphene solution, and (b) adding protamine-DNA complex to the graphene solution, and heating mixture to form gel comprising graphene oxide and protamine-DNA complex.