![]() “A field-effect transistor sensor.” European Patent Application no. Here we report a label-free, single-molecule detection platform based on an EGOFET immobilizing ~10 12 anti-human-Immunoglobulin-G (anti-IgG) capturing antibodies on its millimetre-sized gate 26, and demonstrate the selective detection of a single human-IgG in diluted saliva (L. Their sensitivity has so far enabled a detection limit of 40 aM (10 −18 moles l −1, M) or equivalently of 2.4 × 10 3 molecules in 100 μl 25. Electrolyte-gated organic-field-effect-transistors (EGOFETs), 19, 20 in particular, are sensors 21, 22 endowed with selectivity by the integration of bio-recognition elements 21, 23, 24. Printable bioelectronics 14 show promises for healthcare and human well-being 15, 16, 17, 18. Furthermore, the fabrication scalability of nano-transducers can be challenging. Apparently, the current approaches, relying on a nano-transducer hosting few bio-receptors, are unable to sense a cue in a bulk milieu 13 because the interaction cross section is negligibly small. A plasmon-enhanced-field generated in gold nanorods 8 and nanopores 9, 10, as well as nanoscopic force-spectroscopies 11, 12, were also proven capable of single-molecule label-free detection. Paradigmatic is the single DNA strand detection by means of few bio-probes attached to a single-nanotube transistor 7. Label-free single-molecule detection has up until now been achieved with nanometre-sized transducers. To assure a high interaction cross-section, a large number of highly-packed receptors are generally engaged 5, 6. Neurons can track single pheromones 2 while rod cells on the retina respond to single photons 3, 4. Sea urchins’ sperm cells sense environmental cues down to the physical limit to quickly find the oocyte 1. Many systems in nature interact at the single-molecule level. The proposed immunoassay platform is general and can revolutionize the current approach to protein detection. 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 selective and label-free single molecule IgG detection is strikingly demonstrated in diluted saliva while 15 IgGs are assayed in whole serum. ![]() To this end, the gate is bio-functionalized with a self-assembled-monolayer of 10 12 capturing anti-Immunoglobulin-G and is endowed with a hydrogen-bonding network enabling cooperative interactions. 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. Such approaches are inherently unable to sense a cue in a bulk milieu. ![]() 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.
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