RESUMEN
We report on direct label-free protein detection in high ionic strength solution and human plasma by a dual-gate nanoribbon-based ion-sensitive field-effect transistor (NR-ISFET) biosensor system with excellent sensitivity and specificity in both solution-gate (SG) and dual-gate (DG) modes. Compared with previously reported results, the NR-ISFET biosensor enables selective prostate specific antigen (PSA) detection based on antibody-antigen binding in broader detection range with lower LOD. For the first time, real-time specific detection of PSA of 10â¯pM to 1⯵M in 100â¯mM phosphate buffer (PB) was demonstrated by conductance measurements using the polyethylene glycol (PEG)-modified NR-ISFET biosensors in DG mode with the back-gate bias (VBG) of 20â¯V. Due to larger maximum transconductance value resulting from the modulation of NR-ISFET channel by the back gate in DG mode, the detection range can be broadened with larger linear detection region (100â¯pM to 100â¯nM) and lower limit of detection (LOD, 10â¯pM) as compared to those in SG mode. Moreover, the influence of different back-gate bias from VBG =â¯5â¯V to VBG =â¯25â¯V on the biosensor performance has been investigated. Furthermore, direct PSA detection of 100â¯pM to 1⯵M in human plasma was demonstrated by using the PEG-modified NR-ISFET in DG mode, enabling direct detection of protein in human blood for clinical applications since the LOD of 100â¯pM PSA can meet the clinical requirements.