Single-molecule detection with a millimetre-sized transistor

Abstract

Label-free single-molecule detection has been achieved so far by funnelling a large number of ligands into a sequence of single-binding events with few recognition elements host on nanometric transducers. Such approaches are inherently unable to sense a cue in a bulk milieu. Conceptualizing cells’ ability to sense at the physical limit by means of highly-packed recognition elements, a millimetric sized field-effect-transistor is used to detect a single molecule. To this end, the gate is bio-functionalized with a self-assembled-monolayer of 1012 capturing anti-Immunoglobulin-G and is endowed with a hydrogen-bonding network enabling cooperative interactions. The selective and label-free single molecule IgG detection is strikingly demonstrated in diluted saliva while 15 IgGs are assayed in whole serum. The suggested sensing mechanism, triggered by the affinity binding event, involves a work-function change that is assumed to propagate in the gating-field through the electrostatic hydrogen-bonding network. The proposed immunoassay platform is general and can revolutionize the current approach to protein detection.

Ultimately Sensitive Organic Bioelectronic Transistor Sensors by Materials and Device Structure Design

“…In Figure the essential structures of an OFET comprising a resistor (S and D contacts covered by an organic semiconductor), whose conductivity is controlled by the gate electrode (G) through an electrolyte (e.g., water), are shown. For a stable and reproducible operation, care must be taken to make sure that the layer of biological recognition elements is covalently anchored to one of the FET electronic interfaces.…”

“…A biolayer attached to the gate is shown here along with its capacitance C BIO in series with the previous ones; similarly, a structure where the channel material is biofunctionalized can be used. EGOFETs based on electronic channel materials, such as P3HT and graphene, have been proposed, and EGOFETs are operated almost invariably as potentiometric sensors.…”

“…As in 100 μL of a 10 × 10 −18 m solution, there are around 10 3 particles; it means they are able to detect at the physical limit. An example of such ultrasensitive devices is the SiMoT EGOFET, where the gate is biofunctionalized with 2 × 10 12 recognition elements covalently attached to a 0.5 cm 2 gold gate, which is equivalent to ≈10 × 10 −9 m recognition elements that would be available for the binding in 100 μL. The binding is very fast as it occurs even at very low concentration in the minute timescale.…”

“…This device is addressed as Single Molecule with a large Transistor (SiMoT). Reproduced under the terms of the Creative Commons CC BY License . Copyright 2018, The Authors.…”

“…Relevantly, EGOFET sensors have been proven to reach limit of detections (LODs) in the 10 −18 m (attomolar) range . Very recently, they have been proven capable of detecting biomarkers at the physical limit reaching LODs of 10 −21 m (zeptomolar) with a technology called “Single Molecule with a large Transistor” (SiMoT) . Relevant is also the approach of the organic electrochemical transistors (OECTs) and the OFET‐based biosensors …”