This chapter discusses the functioning of graphene-based electronic biosensors and the influence of graphene’s chemical and structural properties on the sensitivity and specificity of these sensors. Graphene exhibits ultrahigh sensitivity for detection owing to its atomic thickness resulting in lateral confinement of carriers, high quantum capacitance, its delocalized p–electrons on crystalline surface, allowing scattering from molecular attachment, and a high carrier mobility, and thus low noise in detection. The mechanism of the graphene/cell detection system is based on carrier-doping via the cell wall’s electronegativity or dipole moment.30 The attributes that enhance the sensitivity of graphene include quantum capacitance: The quantum-coupling of the cell-wall with graphene enhances the effective electric field due to the dipole moment of the interfacing cell wall. In 2008, Vikas Berry et al. fabricated and studied bacteria-interfaced graphenic devices. The bacterial cells were detected on amide-functionalized graphene, synthesized by diaminization of the immobilized graphene oxide sheets to produce chemically modified graphene.