Over the past several decades, there has been a growing need for the detection and quantification of chemical and biological species in different areas, including biomedical research, health care, agriculture, and environmental monitoring. Among available sensor technologies, potentiometric biosensors based on electrolyte-gated field-effect transistors are very promising due to their high sensitivity, rapid electronic readout, and label-free analyte detection [1,2]. However, two major challenges have limited their use in complex physiological samples such as blood or serum: 1) screening of the analyte charge by the background ions and 2) non-specific adsorption [3-5]. In this work, we overcome these challenges by tailoring the graphene sensing surface with short specific biorecognition molecules and a polymer polyethylene glycol, and demonstrate direct detection of proteins with femtomolar detection limit in whole serum [6]. Multi-parametric analysis of the device’s electronic response shows that the mechanism behind this very sensitive detection cannot be explained by a commonly reported electrostatic gating effect. Rather, the observed combination of charge neutrality point (CNP) shifts and asymmetric mobility changes are attributed to the modulation of scattering by charged impurities, which seem to dominate the device’s transfer characteristics. The presented approach is universal, does not require any sample pretreatment, labelling or washing steps, and can enable the next generation of point-of-care devices for diagnostics of human and animal diseases, if the large-scale manufacturing of graphene can be standardized.  

[1]A. Tarasov et al., Biosens. Bioelectron. 79, 669 (2016)

[2]A. Tarasov et al., 2D Materials 2, 044008 (2015) 

[3]A. Zhang and C.M. Lieber, Chem. Rev. 116, 215 (2016)

[4]O. Gutierrez-Sanz et al. ACS Sensors 2, 1278 (2017)

[5]M. Filipiak et al., Sens. Actuators B: Chem. 255, 1507 (2018)

[6]N. Andoy et al., Adv. Mater. Technol., in revision

Over the past several decades, there has been a growing need for the detection and quantification of chemical and biological species in different areas, including biomedical research, health care, agriculture, and environmental monitoring. Among available sensor technologies, potentiometric biosensors based on electrolyte-gated field-effect transistors are very promising due to their high sensitivity, rapid electronic readout, and label-free analyte detection [1,2]. However, two major challenges have limited their use in complex physiological samples such as blood or serum: 1) screening of the analyte charge by the background ions and 2) non-specific adsorption [3-5]. In this work, we overcome these challenges by tailoring the graphene sensing surface with short specific biorecognition molecules and a polymer polyethylene glycol, and demonstrate direct detection of proteins with femtomolar detection limit in whole serum [6]. Multi-parametric analysis of the device’s electronic response shows that the mechanism behind this very sensitive detection cannot be explained by a commonly reported electrostatic gating effect. Rather, the observed combination of charge neutrality point (CNP) shifts and asymmetric mobility changes are attributed to the modulation of scattering by charged impurities, which seem to dominate the device’s transfer characteristics. The presented approach is universal, does not require any sample pretreatment, labelling or washing steps, and can enable the next generation of point-of-care devices for diagnostics of human and animal diseases, if the large-scale manufacturing of graphene can be standardized.  

[1]A. Tarasov et al., Biosens. Bioelectron. 79, 669 (2016)

[2]A. Tarasov et al., 2D Materials 2, 044008 (2015) 

[3]A. Zhang and C.M. Lieber, Chem. Rev. 116, 215 (2016)

[4]O. Gutierrez-Sanz et al. ACS Sensors 2, 1278 (2017)

[5]M. Filipiak et al., Sens. Actuators B: Chem. 255, 1507 (2018)

[6]N. Andoy et al., Adv. Mater. Technol., in revision