Significance: Nanoelectronic transistor sensors based on synthesized one- and two-dimensional nanomaterials have achieved real-time label-free detection of a wide range of biological species with high sensitivity, although direct analysis of biological samples has been limited due to Debye charge screening in physiological solutions. This paper describes a general strategy overcoming this challenge involving comodification of the transistor sensor surface with a polymer and receptor, where the polymer forms a permeable layer that increases the effective screening length and receptor enables selective detection of analytes. The capability of this strategy was demonstrated with selective detection of cancer markers in physiological solution, thus opening substantial opportunities for real-time sensing applications in biology and medicine.