Fig. 25. (A) Schematic illustration of the cell detecting system and the molecular interactions between the functionalized graphene (P1, P2, P3) and the different cell types including human peripheral blood mononuclear cells (PBMCs), cancerous cells and circulating tumor cells (CTCs). (B) Illustration of the seven functionalized graphene (P1–P7) derivatives used for the identification of normal, cancerous cells and CTCs. The seven graphene (P1–P7) derivatives include P1: BSA/chemically converted graphene (CCG), P2: CCG, P3: chitosan (Chit)/CCG, P4: polydopamine (DA)/CCG, P5: calf thymus DNA/CCG, P6: gelatin (Gel)/CCG, and P7: polyethylene glycol (PEG)/CCG. (C) Discrimination of different cancerous cell types at a cancer cell density of 100 cells: (a) 2D electrochemistry contour plots of 5 different cancer cell lines including lung (A549), cervical (HeLa), liver (HepG2), leukemia (K562), and breast (MCF-7) to P1–P7 graphene probes; (b) changes in the electron-transfer resistance at the electrolyte/graphene interface measured by the electrochemical impedance spectra for five different cancerous cell lines; A549, HeLa, HepG2, K562 and MCF-7 using P1–P7 graphene derivatives; (c) jackknifed classification recorded using linear discriminant analysis (LDA) for P1–P7 graphene derivatives for A549, HeLa, HepG2, K562 and MCF-7 human cancerous cells; and canonical score plots for the functionalized graphene array-based electrochemical sensor containing P1 + P4 (d), P1 +P5 (e), P2 + P4 (f), and P2 + P5 (g). [Reprinted with permission from ref. 546, L. Wu, H. Ji, Y. Guan, X. Ran, J. Ren and X. Qu, A Graphene-Based Chemical Nose/Tongue Approach for the Identification of Normal, Cancerous and Circulating Tumor Cells, NPG Asia Mater., 2017, 9, e356. Copyright© Nature Publishing Group.].