Two stochastic sensors based on modification of nitrogen and boron dopped 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.

There is a high request for fast, simultaneous, and early on-site detection of different biomarkers in order to facilitate early diagnostic and personalized treatment of gastric cancer. Therefore, in this paper we proposed a fast screening method based on two needle stochastic sensors modified with chitosan (n = 371–744) for the assay of CA19-9, p53, and CEA in biological samples. The limits of determination obtained for the proposed needle stochastic sensors are lower than for any other method proposed to date; simultaneous assay of the biomarkers was possible from whole blood, saliva and tumoral tissue samples on-site, the results being available within minutes.