In this chapter, novel ideas of graphene and CNT based electrical biosensors are provided. A liquid gated graphene field effect transistor (LG-GFET) based biosensor model is analytically developed for electrical detection of Escherichia coli (E. coli) bacteria. E. coli absorption effects on the graphene surface in the form of conductance variation is considered. Moreover, the current-voltage characteristic in terms of conductance model is applied to evaluate the performance of the biosensor model. Furthermore, the CNT-FET platform is employed for modeling biosensor in order to detect Glucose. For diagnosing and monitoring the blood glucose level, glucose oxidase (GOx) based enzyme sensors have been immensely used. According to the proposed CNT-FET structure, charge based analytical modeling approach is used. The charge-based carrier velocity model is implemented to study electrical characteristics of CNT-FET. In the presented model, the gate voltage is considered as a function of glucose concentration. Finally, the both of presented models are compared with published experimental data.