Sulfur doping in graphene (S-rGO) with a thiophenic bond (CSC) was achieved by using a novel biomass precursor derived from mushroom. Electrical conductivity was increased with sulfur doping that shows n-type contribution. S-rGO show robust sensitivity and excellent recoveries for the detection of 8-hydroxy-2′-deoxyguanosine (8-OHdG), a cancer risk biomarker.