Two stochastic sensors based on modification of nitrogen and boron-doped exfoliated graphene with a complex of protoporphyrin and cobalt, were used for molecular recognition and quantification of MLH1, MSH2, MSH6, PMS2, and KRAS biomarkers in biological samples (whole blood, urine, saliva, tumoral tissue). Limits of determination of fg mL-1 magnitude order and broad linear concentration ranges favorized their determination from very low to higher concentrations in biological samples. The student t-test showed that there is no significant difference between the results obtained by utilizing the two microsensors for screening tests, at 99% confidence level, the results obtained being lowr than the tabulated value.