Peripheral events in olfaction involve odorant binding proteins (OBPs) whose role in the recognition of different volatile chemicals is yet unclear. Here we report on the sensitive and quantitative measurement of the weak interactions associated with neutral enantiomers differentially binding to OBPs immobilized through a self-assembled monolayer to the gate of an organic bio-electronic transistor. The transduction is remarkably sensitive as the transistor output current is governed by the small capacitance of the protein layer undergoing minute changes as the ligand–protein complex is formed. Accurate determination of the free-energy balances and of the capacitance changes associated with the binding process allows derivation of the free-energy components as well as of the occurrence of conformational events associated with OBP ligand binding. Capacitance-modulated transistors open a new pathway for the study of ultra-weak molecular interactions in surface-bound protein–ligand complexes through an approach that combines bio-chemical and electronic thermodynamic parameters.

Electrolyte-gated organic field-effect transistors are successfully used as biosensors to detect binding events occurring at distances from the transistor electronic channel that are much larger than the Debye length in highly concentrated solutions. The sensing mechanism is mainly capacitive and is due to the formation of Donnan's equilibria within the protein layer, leading to an extra capacitance (CDON) in series to the gating system.

Anchored, biotinylated phospholipids forming the capturing layers in an electrolyte-gated organic field-effect transistor (EGOFET) allow label-free electronic specific detection at a concentration level of 10 nM in a high ionic strength solution. The sensing mechanism is based on a clear capacitive effect across the PL layers involving the charges of the target molecules.

Thin-film transistors can be used as high-performance bioelectronic devices to accomplish tasks such as sensing or controlling the release of biological species as well as transducing the electrical activity of cells or even organs, such as the brain. Organic, graphene, or zinc oxide are used as convenient printable semiconducting layers and can lead to high-performance low-cost bioelectronic sensing devices that are potentially very useful for point-of-care applications. Among others, electrolyte-gated transistors are of interest as they can be operated as capacitance-modulated devices, because of the high capacitance of their charge double layers. Specifically, it is the capacitance of the biolayer, being lowest in a series of capacitors, which controls the output current of the device. Such an occurrence allows for extremely high sensitivity towards very weak interactions. All the aspects governing these processes are reviewed here.

Organic bioelectronic devices comprise advanced tools for monitoring and controlling physiology. [1] Such devices are based upon organic electronic materials that offer efficient signal transduction from electronic input to ionic output and vice versa, while the toolbox of organic chemistry enables design and tailoring of active materials with desired characteristics, such as functionality, processability, and biocompatibility. [2] Organic bioelectronic devices and materials have been applied in a variety of settings with most of the technologic development focused on neuroscience applications such as high resolution recordings of brain activity, [3] inhibition of neuropathic pain, [4] control of epileptic seizures, [5] and understanding of memory consolidation [6] in animal models. While the field of organic bioelectronics has traditionally targeted biomedical applications, its usefulness and applicability in plants has begun to be explored. Glucose export from isolated chloroplasts was monitored in real time using an organic electrochemical transistor, [7] while the growth of a plant was controlled via the organic electronic ion pump (OEIP). [8] The OEIP is an electrophoretic delivery device that converts electronic addressing signals into ionic fluxes offering precise and dynamic delivery of ions and charged biomolecules. [9] In contrast to other drug delivery devices, the OEIP has a simple design, forgoes flow pumps, and delivers only the ion or drug of interest, and not the solvent or dissolved coions. Drug delivery in the absence of fluid flow eliminates convective disturbances of the target fluidic system, such as shear stress, local pressure increases, and excessive perturbation of native ionic concentration gradients. The OEIP technology is based on a polyelectrolyte channel that provides charge selective electrophoretic delivery thanks to its high fixed ionic charge concentration that suppresses the transport of coions. When voltage is applied across the polyelectrolyte channel of an OEIP device, ions of a specific charge are transported selectively through the channel from the source to the target. Conventional OEIP devices have typically utilized planar geometries and have been manufactured using standard microfabrication techniques. [10] The delivery channel Electronic control of biological processes with bioelectronic devices holds promise for sophisticated regulation of physiology, for gaining fundamental understanding of biological systems, providing new therapeutic solutions, and digitally mediating adaptations of organisms to external factors. The organic electronic ion pump (OEIP) provides a unique means for electronically-controlled, flow-free delivery of ions, and biomolecules at cellular scale. Here, a miniaturized OEIP device based on glass capillary fibers (c-OEIP) is implanted in a biological organism. The capillary form factor at the sub-100 µm scale of the device enables it to be implanted in soft tissue, while its hyperbranched polyelectrolyte channel and addressing protocol allows eff...

This review discusses the state-of-the-art strategies for realizing TFTs by printing compatible techniques, focusing the attention on label-free electronic biosensors.

A simple and time-saving wet method to endow the surface of organic semiconductor films with carboxyl functional groups is presented. A thin layer of poly(acrylic acid) (pAA) is spin-coated directly on the electronic channel of an electrolyte-gated organic FET (EGOFET) device and cross-linked by UV exposure without the need for any photo-initiator. The carboxyl functionalities are used to anchor phospholipid bilayers through the reaction with the amino-groups of phosphatidyl-ethanolamine (PE). By loading the membranes with phospholipids carrying specific functionalities, such a platform can be easily implemented with recognition elements. Here the case of biotinylated phospholipids that allow selective streptavidin electronic detection is described. The surface morphology and chemical composition are monitored using SEM and XPS, respectively, during the whole process of bio-functionalization. The electronic and sensing performance level of the EGOFET biosensing platform is also evaluated. Selective analyte (streptavidin) detection in the low pM range is achieved, this being orders of magnitude lower than the performance level obtained by the well assessed surface plasmon resonance assay reaching the nM level, at most

Bottom- and top-contact organic thin film transistors (OTFTs) were fabricated, using poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C16) as p-type channel semiconductors. Four different types of OTFTs were fabricated and investigated as gas sensors against three volatile organic compounds, with different associated dipole moments. The OTFT-based sensor responses were evaluated with static and transient current measurements. A comparison between the different architectures and the relative organic semiconductor was made.