Functionalization Strategies for 2D Material FET Biosensors: Recent Advances and Analytical Applications

Objective: Field-Effect Transistor (FET) biosensors based on two-dimensional (2D) materials attract considerable attention because of their rapid electrical response, label-free operation, miniaturization potential, and ultrahigh sensitivity. This review systematically summarizes progress in 2D material-based FET biosensors, focusing on biocompatibility, functionalization, and practical applications while critically assessing translational bottlenecks hindering deployment. Mechanism: 2D materials such as graphene, MoS2, and WSe2 exhibit higher carrier mobility, large surface areas, and tunable surface chemistry, thereby enabling efficient charge transduction upon biomolecular recognition. We examine covalent and noncovalent functionalization approaches, evaluate their effects on interfacial stability, charge transfer efficiency, Debye length limitations, reproducibility, and potential biological risks, and discuss the principles of nucleic acid, protein, peptide, and saccharide sensing enabled by these strategies. Findings in Brief: Despite extraordinary sensitivity in idealized buffer systems—with some devices reaching aM or even zM detection limits—practical applications in complex biological environments are severely constrained by the Debye screening effect. In these environments, excess ions in physiological media effectively shield the electrical charges of target biomolecules, attenuating their electrostatic coupling with the sensing channel and thereby drastically reducing the signal magnitude. Additional barriers include nonspecific adsorption, poor device-to-device reproducibility, insufficient long-term stability, and sample pretreatment. Moreover, most biosafety evaluations remain confined to short-term in vitro assays, while systematic data on chronic toxicity, biodistribution, and long-term in vivo clearance—essential for implantable applications—are still lacking. Conclusions: 2D FET biosensors hold promise for next-generation healthcare and precision medicine; however, clinical translation requires a focus shift from ultralow detection limits to stability, reproducibility, biosafety, and real-sample performance. Future work should integrate scalable fabrication, antifouling, the mitigation of the Debye screening effect, and in vivo safety tests to bridge academic research and clinical applications.