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Dunnschichttransistoren konnen als bioelektronische Bauelemente genutzt werden, um solche Aufgaben auszufuhren wie Erkennung oder Steuerung der Freisetzung biologischer Spezies sowie Umwandlung der elektrischen Aktivitat von Zellen oder sogar Organen wie des Gehirns. Organische Materialien sowie Graphen oder Zinkoxid werden als druckbare Halbleiterschicht eingesetzt, was zu leistungsfahigen kostengunstigen bioelektronischen Sensoreinheiten fuhren kann, die moglicherweise sehr nutzlich fur Vor-Ort-Anwendungen sind. Von Interesse sind unter anderem die elektrolytgesteuerten Transistoren, da sie aufgrund der hohen Kapazitat der Ladungsdoppelschichten als kapazitatsmodulierte Bauelemente betrieben werden konnen. Speziell die Kapazitat der Bioschicht, die in einer Reihe von Kondensatoren geringer ist, beeinflusst den Ausgangsstrom des Bauelementes. Solch ein Phanomen ermoglicht eine auserst hohe Empfindlichkeit gegen sehr schwache Wechselwirkungen. Samtliche Aspekte, die diese Vorgange bestimmen, werden besprochen.

Printable and flexible thin-film transistors (TFTs) have gained significant attention over the last few years thanks to their implementation in many different sectors. Beside applications in large-area electronics such as flat displays, sensors and radio frequency identification tags, these devices have been widely investigated for life sciences applications too, including label-free biosensors, systems for drug delivery and implantable platforms. This review highlights the recent advances in the field of highly performing low-cost TFT devices realized by printing or printing compatible technologies and suitable for bioelectronics applications. Novel printable materials used as semiconductors, dielectrics and electrodes as well as printing technologies useful for the realization of the elicited devices are discussed as well. Particularly attention is given to printing techniques employed for the deposition of biological materials and to methods for realizing 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.

A polyanionic proton conductor, named poly(4-styrenesulfonic acid) (PSSH), was used to gate an Organic Thin-Film Transistor (OFET) based on p-type poly(2,5-bis(3-tetradecylthiophen-2-yl)thienol 3,2-bthiophene) (pBTTT-C14) organic semiconductor (OSC). Different device configurations were evaluated and a bottom gate - top contact (BGTC) device was investigated as transducer for gas sensing measurements. The sensors' performance in terms of stability, repeatability and reproducibility were evaluated when the device was exposed to different concentrations of 1-butanol. Comparison with a conventionally gated OFET (SiO2 dielectric instead of PSSH) was also performed. Display Omitted

In this article, we propose the usage of gate voltage pulses of alternating polarity, to effectively suppress the hysteresis in organic field effect transistors (OFETs). The hysteretic behaviour of poly(3-hexylthiophene-2,5-diyl) (P3HT) based OFETs is systematically investigated by using continuous and pulsed sweep voltage mode. On the basis of the experimental results, both time settings and mode of gate bias voltage influence the carrier transport in the semiconductor channel. Hysteresis-free transfer characteristic curves are obtained by applying diametrically opposed gate pulses of a few milliseconds in duration. Stable on-current transient measurements are also achieved by implementing the pulse mode, thus allowing on-line gas sensing measurements to be successfully performed. Finally, the response of the sensor upon exposure to different concentrations of analyte vapours is found to be in good agreement with the Langmuir adsorption isotherm model.

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.

The detailed action mechanism of volatile general anesthetics is still unknown despite their effect has been clinically exploited for more than a century. Long ago it was also assessed that the potency of an anesthetic molecule well correlates with its lipophilicity and phospholipids were eventually identified as mediators. As yet, the direct effect of volatile anesthetics at physiological relevant concentrations on membranes is still under scrutiny. Organic field-effect transistors (OFETs) integrating a phospholipid (PL) functional bio inter-layer (FBI) are here proposed for the electronic detection of archetypal volatile anesthetic molecules such as diethyl ether and halothane. This technology allows to directly interface a PL layer to an electronic transistor channel, and directly probe subtle changes occurring in the bio-layer. Repeatable responses of PL FBI-OFET to anesthetics are produced in a concentration range that reaches few percent, namely the clinically relevant regime. The PL FBI-OFET is also shown to deliver a comparably weaker response to a non-anesthetic volatile molecule such as acetone. © 2012 Elsevier B.V.

The study of proteins confined on a surface has attracted a great deal of attention due to its relevance in the development of bio-systems for laboratory and clinical settings. In this respect, organic bio-electronic platforms can be used as tools to achieve a deeper understanding of the processes involving protein interfaces. In this work, biotin-binding proteins have been integrated in two different organic thin-film transistor (TFT) configurations to separately address the changes occurring in the protein-ligand complex morphology and dipole moment. This has been achieved by decoupling the output current change upon binding, taken as the transducing signal, into its component figures of merit. In particular, the threshold voltage is related to the protein dipole moment, while the field-effect mobility is associated with conformational changes occurring in the proteins of the layer when ligand binding occurs. Molecular Dynamics simulations on the whole avidin tetramer in presence and absence of ligands were carried out, to evaluate how the tight interactions with the ligand affect the protein dipole moment and the conformation of the loops surrounding the binding pocket. These simulations allow assembling a rather complete picture of the studied interaction processes and support the interpretation of the experimental results.

In this contribution, we propose a label-free immunosensor, based on a novel type of electrolyte-gated field-effect transistor (EGOFET), for ultrasensitive detection of the C-reactive protein (CRP). The recognition layer of the biosensor is fabricated by physical adsorption of the anti-CRP monoclonal antibody onto a poly-3-hexyl thiophene (P3HT) organic semiconductor surface. A supplementary nonionic hydrophilic polymer is used as a blocking agent preventing nonspecific interactions and allowing a better orientation of the antibodies immobilized onto the P3HT surface. The whole biomolecule immobilization procedure does not require any pretreatment of the organic semiconductor surface, and the whole functionalization process is completed in less than 30 min. Surface plasmon resonance (SPR) measurements were performed to assess the amount of biomolecules physisorbed onto the P3HT and to evaluate the CRP binding proprieties of the deposited anti-CRP layer. A partial surface coverage of about 23 % of adsorbed antibody molecules was found to most efficiently sense the CRP. The electrical performance of the EGOFET immunosensor was comparable to that of a bare P3HT EGOFET device, and the obtained CRP calibration curve was linear over six orders of magnitude (from 4 pM to 2 μM). The relative standard deviation of the individual calibration points, measured on immunosensors fabricated on different chips, ranged between 1 and 14 %, and a detection limit of 2 pM (220 ng/L) was established. The novel electronic immunosensor is compatible with low-cost fabrication procedures and was successfully employed for the detection of the CRP biomarker in the clinically relevant matrix serum. Graphical abstract Schematic of the EGOFET immunosensor for CRP detection. The anti-CRP monoclonal antibody layer is physisorbed on the P3HT organic semiconductor and the CRP is directly measured by a label-free electronic EGOFET transducer.

The interfacing of biomaterials to electronic devices is one of the most challenging research fields that has relevance to both fundamental studies and the development of highly performing biosensors. Important aspects connected to the field of biosensors based on electrolyte-gated organic transistors are discussed. The main features of biomolecules used as recognition elements along with the strategies reported so far for their deposition on the biosensors transducer surface are presented. An introduction of the involving surface interactions such as covalent binding, physical adsorption, self-assembly and bio-affinity binding strategy is given. Besides, the most relevant surface materials for electronic biosensors development are analysed. In the last part, different electronic biosensors based on electrolyte-gated organic transistors are presented. Particular attention is paid to the biosensors operation mechanism and to the analytical figure of merits. Specific applications such as DNA and proteins detection are also discussed.

Biosystems integration into an organic field-effect transistor (OFET) structure is achieved by spin coating phospholipid or protein layers between the gate dielectric and the organic semiconductor. An architecture directly interfacing supported biological layers to the OFET channel is proposed and, strikingly, both the electronic properties and the biointerlayer functionality are fully retained. The platform bench tests involved OFETs integrating phospholipids and bacteriorhodopsin exposed to 1–5% anesthetic doses that reveal drug-induced changes in the lipid membrane. This result challenges the current anesthetic action model relying on the so far provided evidence that doses much higher than clinically relevant ones (2.4%) do not alter lipid bilayers’ structure significantly. Furthermore, a streptavidin embedding OFET shows label-free biotin electronic detection at 10 parts-per-trillion concentration level, reaching state-of-the-art fluorescent assay performances. These examples show how the proposed bioelectronic platform, besides resulting in extremely performing biosensors, can open insights into biologically relevant phenomena involving membrane weak interfacial modifications.

Bio-sensing represents one of the most attractive applications of carbon material based electronic devices; nevertheless, the complete integration of bioactive transducing elements still represents a major challenge, particularly in terms of preserving biological function and specificity while maintaining the sensor's electronic performance. This review highlights recent advances in the realization of field-effect transistor (FET) based sensors that comprise a bio-receptor within the FET channel. A birds-eye view will be provided of the most promising classes of active layers as well as different device architectures and methods of fabrication. Finally, strategies for interfacing bio-components with organic or carbon nano-structured electronic active layers are reported.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a useful technique for the identification of bacteria on the basis of their characteristic protein mass spectrum fingerprint. Highly standardized instrumental analytical performance and bacterial culture conditions are required to achieve useful information. A chemometric approach based on multivariate analysis techniques was developed for the analysis of MALDI data of different bacteria to allow their identification from their fingerprint. Principal component analysis, linear discriminant analysis (LDA) and soft independent modelling of class analogy (SIMCA) were applied to the analysis of the MALDI MS mass spectra of two pathogenic bacteria, Escherichia coli O157:H7 and Yersinia enterocolitica, and the non-pathogenic E. coli MC1061. Spectra variability was assessed by growing bacteria in different media and analysing them at different culture growth times. After selection of the relevant variables, which allows the evaluation of an m/z value pattern with high discriminant power, the identification of bacteria by LDA and SIMCA was performed independently of the experimental conditions used. In order to better evaluate the analytical performance of the approach used, the ability to correctly classify different bacteria, six wild-type strains of E. coli O157:H7, was also studied and a combination of different chemometric techniques with a severe validation was developed. The analysis of spiked bovine meat samples and the agreement with an independent chemiluminescent enzyme immunoassay demonstrated the applicability of the method developed for the detection of bacteria in real samples. The easy automation of the MALDI method and the ability of multivariate techniques to reduce interlaboratory variability associated with bacterial growth time and conditions suggest the usefulness of the proposed MALDI MS approach for rapid routine food safety checks.

A general method to obtain the efficient entrapment of mixtures of glycoenzymes in calcium alginate hydrogel is proposed in this paper. As a proof of principle, three glycoenzymes acting in series (trehalase, glucose oxidase, and horseradish peroxidase) have been coimmobilized in calcium alginate beads. The release of the enzymes from the hydrogel mesh (leakage) is avoided by exploiting the enzyme's aggregation induced by the concanavalin A. The aggregation process has been monitored by dynamic light scattering technique, while both enzyme encapsulation efficiency and leakage have been quantified spectrophotometrically. Obtained data show an encapsulation efficiency above 95% and a negligible leakage from the beads when enzyme aggregates are larger than 300 nm. Operational stability of "as prepared" beads has been largely improved by a coating of alternated shells of polycation poly(diallyldimethylammonium chloride) and of alginate. As a test for the effectiveness of the overall procedure, analytical bioassays exploiting the enzyme-containing beads have been developed for the optical determination of glucose and trehalose, and limit of detection values of 0.2 and of 40 μM, respectively, have been obtained.

In the present study, a back-gate thin-film transistor (TFT) based on a single-walled carbon nanotubes (SWCNTs)/poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) composite semiconductor is proposed as electronic label-free immunosensor for the detection of the C-reactive protein (CRP). The nano-composite semiconducting ultra-thin film is deposited on the channel area of the TFT and is functionalized with a monoclonal anti-CRP antibody coating acting as biorecognition layer. The immunesensor was then used for the selective detection of the CRP both in phosphate buffered saline (PBS) solution and in human serum samples. The proposed immunosensor exhibits high current (10 – 20 µA) and good field-effect carriers mobility. Furthermore, the CRP could be revealed at a detection limit as low as 1 mg/L and in a wide dynamic range (from 0.4 nM to 2.2 µM).

ZnO based thin-film transistors are very promising to be used as electronic biosensors due to their very good electronic performances and inherent biocompatibility. Herein, we report on the use of a solution processed ZnO water gated thin-film transistor (WG-TFT) whose channel surface is bio-functionalized with a streptavidin protein layer. This is a very critical process as it endows the device with bio-recognition capabilities. The bio-functionalization process is carried out by attaching an organosilane self-assembled monolayer to the ZnO surface that is coupled to the biomolecule afterwards. A systematic X-Ray Photoelectron Spectroscopy surface characterization allows assessing that the immobilization of the streptavidin proteins on the ZnO surface has been successfully accomplished. Upon deposition of the protein layer, a decrease in the ZnO WG-TFT source-drain current is observed. Such an occurrence is ascribable to the electrostatic effect of the negatively charged protein molecules lying on the ZnO semiconductor layer in contact with the transistor 2D-channel. The deposited streptavidin layer can be prospectively further used for the immobilization and orientation of biotinylated recognition elements in view of the use of ZnO TFTs as electronic biosensors for real-life applications.

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., Organic bioelectronic devices can be used to convert biological recognition events to a signal output. Here, the authors show how a water gated field-effect transistor modified with odorant binding proteins can be used to analyse the enantioselectivity of carvone binding and also estimate free-energy changes.

Ultrasensitive biosensors based on bottom gate organic field-effect transistors can be developed by depositing a functional biological (protein) interlayer directly on the silicon oxide gate dielectric and underneath the organic semiconductor film. However, the deposition methods for assembling the protein biological recognition layer can affect the biosensor analytical performances for the target analyte detection. Here, spin-coating and layer-by-layer techniques were considered as different approaches for streptavidin protein deposition. X-ray photoelectron spectroscopy (XPS) was systematically used in the non-destructive parallel angle resolved mode to characterize the multilayer device at each step of its assembly to gain information on elemental depth profiles. Scanning electron and scanning Helium ion microscopies gave information about stacked layer structure and morphology corroborating XPS results.

Proteins from the Cry 1 family, in particular Cry 1Ab, are commonly expressed in genetically modified Bt maize in order to control chewing insect pests. A sensitive chemiluminescent sandwich enzyme immunoassay for the detection of Cry1Ab protein from genetically modified Bt maize has been developed and validated. A Cry1Ab protein-specific antibody was immobilized on 96- or 384-well microtiter plates in order to capture the Cry1Ab toxin in the sample; the bound toxin was then detected by employing a second anti-Cry1Ab antibody and a horseradish peroxidase-labeled anti-antibody, followed by measurement of the enzyme activity with an enhanced chemiluminescent system. The chemiluminescent assay fulfilled all the requirements of accuracy and precision and exhibited limits of detection of a few pg mL(-1) Cry1Ab (3 or 5 pg mL(-1), depending on the assay format), which are significantly lower than that achievable using conventional colorimetric detection of peroxidase activity and also represent an improvement compared to previously developed Cry1Ab immunoassays. High-throughput analysis can be performed using the 384-well microtiter plate format immunoassay, which also allows one to reduce the consumption of samples and reagents. Validation of the assay, performed by analyzing certified reference materials, proved that the immunoassay is able to detect the presence of the Cry1Ab protein in certified reference samples containing as low as 0.1% of MON 810 genetically modified Bt maize. This value is below the threshold requiring mandatory labeling of foods containing genetically modified material according to the actual EU regulation.

Among the metal oxide semiconductors, ZnO has been widely investigated as a channel material in thin-film transistors (TFTs) due to its excellent electrical properties, optical transparency and simple fabrication via solution-processed techniques. Herein, we report a solution-processable ZnO-based thin-film transistor gated through a liquid electrolyte with an ionic strength comparable to that of a physiological fluid. The surface morphology and chemical composition of the ZnO films upon exposure to water and phosphate-buffered saline (PBS) are discussed in terms of the operation stability and electrical performance of the ZnO TFT devices. The improved device characteristics upon exposure to PBS are associated with the enhancement of the oxygen vacancies in the ZnO lattice due to Na+ doping. Moreover, the dissolution kinetics of the ZnO thin film in a liquid electrolyte opens the possible applicability of these devices as an active element in “transient” implantable systems.

A fast and ultrasensitive chemiluminescent enzyme immunoassay for aflatoxin M(1) in milk samples has been developed and validated. The method is an indirect competitive type format involving the immobilization of an aflatoxin M(1)-bovine serum albumin conjugate on 384 well black polystyrene microtiter plates and the use of a secondary antibody labeled with horseradish peroxidase detected with a luminol-based substrate. Aflatoxin M(1) standard solutions were prepared in milk-based buffer, and milk samples were analyzed without any cleanup procedure. The limit of quantification was 1 ppt, the coefficient of variation was below 9% for both intra- and interassay precision, and the recovery ranged from 96 to 122%. The method is specific, and other aflatoxins do not significantly cross-react with the antibody. Twenty-four milk samples were analyzed, and a good correlation was observed (y = 0.98x + 1.71, r(2) = 0.98, n = 24) when the data were compared with a reference high-performance liquid chromatography method with a fluorescent detector. The developed method is suitable for an accurate, sensitive, and high-throughput screening of aflatoxin M(1) in milk samples with a reduction of costs and increased detectability, as compared with previously developed immunoassays.

Functional bio-interlayer organic field - effect transistors (FBI-OFET), embedding streptavidin, avidin and neutravidin as bio-recognition element, have been studied to probe the electronic properties of protein complexes. The threshold voltage control has been achieved modifying the SiO 2 gate diaelectric surface by means of the deposition of an interlayer of bio-recognition elements. A threshold voltage shift with respect to the unmodified dielectric surface toward more negative potential values has been found for the three different proteins, in agreement with their isoelectric points. The relative responses in terms of source – drain current, mobility and threshold voltage upon exposure to biotin of the FBI-OFET devices have been compared for the three bio-recognition elements.

An organic field-effect transistor (OFET) integrating bacteriorhodopsin (bR) nanoassembled lamellae is proposed for an in-depth study of the proton translocation processes occurring as the bioelectronic device is exposed either to light or to low concentrations of general anesthetic vapors. The study involves the morphological, structural, electrical, and spectroscopic characterizations necessary to assess the functional properties of the device as well as the bR biological activity once integrated into the functional biointerlayer (FBI)-OFET structure. The electronic transduction of the protons phototranslocation is shown as a current increase in the p-type channel only when the device is irradiated with photons known to trigger the bR photocycle, while Raman spectroscopy reveals an associated C=C isomer switch. Notably, higher energy photons bring the cis isomer back to its trans form, switching the proton pumping process off. The investigation is extended also to the study of a PM FBI-OFET exposed to volatile general anesthetics such as halothane. In this case an electronic current increase is seen upon exposure to low, clinically relevant, concentrations of anesthetics, while no evidence of isomer-switching is observed. The study of the direct electronic detection of the two different externally triggered proton translocation effects allows gathering insights into the underpinning of different bR molecular switching processes. © 2014 American Chemical Society.

Organic field-effect transistors including a functional biorecognition interlayer, sandwiched between the dielectric and the organic semiconductor layers, have been recently proposed as ultrasensitive label-free biosensors capable to detect a target molecule in the low pM concentration range. The morphology and the structure of the stacked bilayer formed by the protein biointerlayer and the overlying organic semiconductor is here investigated for different protein deposition methods. X-ray scattering techniques and scanning electron microscopy allow us to gather key relevant information on the interface structure and to assess target analyte molecules capability to percolate through the semiconducting layer reaching the protein deposit lying underneath. Correlations between the structural and morphological data and the device analytical performances are established allowing us to gather relevant details on the sensing mechanism and further improving sensor performances, in particular in terms of sensitivity and selectivity. © 2014 American Chemical Society.

We report on the use of a polyanionic proton conductor, poly(acrylic acid), to gate a poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene]-based organic field-effect transistor (OFET). A planar configuration of the OFET is evaluated, and the electrical performance and implementation on a flexible substrate are discussed.

A polyanionic proton conductor, named poly(4-styrenesulfonic acid) (PSSH), was used to gate an Organic Thin-Film Transistor (OFET) based on p-type poly(2,5-bis(3-tetradecylthiophen-2-yl)thienol [3,2-b]thiophene) (pBTTT-C14) organic semiconductor. Upon applying a negative gate bias, a large electric double layer capacitors (EDLCs) are formed at the gate-PSSH and at the pBTTT-PSSH interfaces due to the proton migration in the polyelectrolyte. Different device configurations are evaluated and their electrical performance along with their implementation on flexible Kapton substrates is discussed.

Butyl-methylimidazolium based ionic liquids with two different anions are suggested as gating electrolytes in field-effect transistors. Thanks to the selection of two anions with different polarity it was possible to evaluate the effect of the ions properties such as the chemical structure and the grade of hydrophobicity on the off-current and on the field-effect mobility. Moreover the occurrence of any electrochemical doping in the organic semiconductor was evaluated in three different drain-source voltage ranges. The bio-compatibility of this class of ionic liquids is well-known and a better understanding of their behaviour could lead towards new application for electrolyte-gated biosensors.

Differentiation of enantiomers remains one of the most attractive and important research areas in analytical chemistry due to its impact on pharmaceutical, chemical, biotechnology, and food industries. For a long time chiral separation techniques, such as high performance liquid chromatography (HPLC), gas chromatography (GC), and capillary electrophoresis (CE), have represented the gold standard for the separation and determination of enantiomers. These techniques, besides being time consuming and expensive, are also not suitable for real time analysis. Therefore, the development of fast and reliable chiral sensors remains a challenge to achieve on-line analysis of enantiomers in both gas and liquid samples. The scope of this chapter is to provide an overview on the basic functioning principles, as well as on the performance level, of solid-state sensing devices for enantiomers differentiation. Particular attention is paid to work providing a set of analytical figures of merit (sensitivity, repeatability, reproducibility, limit-of-detection, etc.) as well as to studies involving miniaturized (or miniaturizable) analytical devices that can deliver real-time, on-line, and label-free information on chiral compounds.

The manuscript deals with the synthesis and properties of four new all-donor alternating poly(arylene-ethynylene)s DBSA, DBSTA, DTSA, and DTSTA. The polymers have been obtained by a Sonogashira cross-coupling of 9,10-diethynyl-anthracene with the dibromo-derivatives of 9,9-dioctyl-dibenzosilole (DBSA), 2,7-dithienyl-9,9-dioctyl-dibenzosilole (DBSTA), 4,4-dioctyl-dithienosilole (DTSA), or 2,6-dithienyl-9,9-dioctyl-dithienosilole (DTSTA). The polymers exhibited absorption profiles and frontier orbital energies strongly dependent on their primary structure. Density functional theory calculations confirmed experimental observations and provided an insight into the electronic structure of the macromolecules. In particular, the effects exerted by the thiophene units in DBSTA and DTSTA on the optical properties of the corresponding polymers could be rationalized with respect to DBSA and DTSA. Preliminary photovoltaic measurements have established that the performance of DTSA is among the highest reported for an all-donor polymer. Moreover, UV irradiation of DTSA films under air evidenced a remarkable photostability of this material, providing further evidence that ethynylene-containing electron-rich systems are promising donors for organic solar cells applications. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4860-4872

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.

Differentiation of enantiomers remains one of the most attractive and important research areas in analytical chemistry due to its impact on pharmaceutical, chemical, biotechnology, and food industries. For a long time chiral separation techniques, such as high performance liquid chromatography (HPLC), gas chromatography (GC), and capillary electrophoresis (CE), have represented the gold standard for the separation and determination of enantiomers. These techniques, besides being time consuming and expensive, are also not suitable for real time analysis. Therefore, the development of fast and reliable chiral sensors remains a challenge to achieve on-line analysis of enantiomers in both gas and liquid samples. The scope of this chapter is to provide an overview on the basic functioning principles, as well as on the performance level, of solid-state sensing devices for enantiomers differentiation. Particular attention is paid to work providing a set of analytical figures of merit (sensitivity, repeatability, reproducibility, limit-of-detection, etc.) as well as to studies involving miniaturized (or miniaturizable) analytical devices that can deliver real-time, on-line, and label-free information on chiral compounds.

A Functional Bio-Interlayer Organic Field-Effect Transistor (FBI-OFET) sensor, embedding a streptavidin protein capturing layer, capable of performing label-free selective electronic detection of biotin at 3 part per trillion (mass fraction) or 15 pM, is proposed here. The response shows a logarithmic dependence spanning over 5 orders of magnitude of analyte concentration. The optimization of the FBI analytical performances is achieved by depositing the capturing layer through a controllable Layer-by-Layer (LbL) assembly, while an easy processable spin-coating deposition is proposed for potential low-cost production of equally highly performing sensors. Furthermore, a Langmuirian adsorption based model allows rationalizing the analyte binding process to the capturing layer. The FBI-OFET device is shown to operate also with an antibody interlayer as well as with an ad hoc designed microfluidic system. These occurrences, along with the proven extremely high sensitivity and selectivity, open to FBI-OFETs consideration as disposable electronic strip-tests for assays in biological fluids requiring very low detection limits.

A plasma deposition (PE-CVD) process is proposed to functionalize the surface of P3HT organic semiconductor with an hydrophilic coating characterized by carboxyl groups. The functionalized P3HT is employed as electronic active layer in an electrolyte gated organic field-effect transistor (EGOFET). Nanometric coatings were plasma deposited at the surface of P3HT from glow discharges fed with ethylene and acrylic acid vapors. The surface chemical composition of coated P3HT along with its wettability, have been assessed by means of X-ray photoelectron spectroscopy and water contact angle. Results show that PE-CVD is a valid approach to functionalize P3HT surfaces with carboxyl groups, leaving negligible adverse effect on the EGOFET performances. Possibly, chemical or biological species could be immobilized on PE-CVD-functionalized EGOFETs, opening to further developments in their use as sensors. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A non-invasive test for oro-ileal transit time (OITT) evaluation was developed, based on the measurement of tauroursodeoxycholic acid (TUDCA) oral fluid concentration profile after its oral administration. Exploiting the fact that TUDCA is actively absorbed only in the ileum, OITT is measured as the time corresponding to TUDCA maximum oral fluid concentration ( t max ). To measure oral fluid TUDCA concentration in a point-of-care setting, an ultrasensitive portable immunosensor was developed, based on a competitive chemiluminescent enzyme immunoassay (CL-EIA), using immobilized anti-TUDCA antibody and an ursodeoxycholic acid (UDCA)-peroxidase conjugate as tracer, detected by enhanced chemiluminescence employing a portable charge-coupled device (CCD)-based device. The test was validated in 24 healthy subjects before and after treatment with Loperamide, a drug that increases OITT. The developed CL-EIA was accurate and precise, with a LLOQ of 50 pmol L −1 . The measured OITT for healthy subjects (291 ± 50 min) was fairly well correlated with OITT values obtained by measuring TUDCA in serum ( r = 0.89). An increased OITT was observed in all the studied subjects after Loperamide treatment. The CL immunosensor can be employed directly in gastroenterology and paediatric units and it can thus represent a new non-invasive simple test for OITT evaluation in a point-of-care setting, with improved diagnostic utility.

ZnO thin films, prepared using a printing-compatible sol–gel method involving a thermal treatment below 400 °C, are proposed as active layers in water-gated thin-film transistors (WG-TFTs). The thin-film structure and surface morphology reveal the presence of contiguous ZnO crystalline (hexagonal wurtzite) with isotropic nano-grains as large as 10 nm characterized by a preferential orientation along the a-axis. The TFT devices are gated through a droplet of deionized water by means of electrodes characterized by different work functions. The high capacitance of the electrolyte allowed operation below 0.5 V. While the Ni, Pd, Au and Pt gate electrodes are electrochemically stable in the inspected potential range, electrochemical activity is revealed for the W one. Such an occurrence leads to an increase of capacitance (and current), which is ascribed to a high output current from the dissolution of a lower capacitance W-oxide layer. The environmental stability of the ZnO WG-TFTs is quite good over a period of five months.

Correction for ‘Printable and flexible electronics: from TFTs to bioelectronic devices’ by M. Magliulo et al., J. Mater. Chem. C, 2015, 3, 12347–12363.

A totally innovative electrolyte-gated field effect transistor, embedding a phospholipid film at the interface between the organic semiconductor and the gating solution, is described. The electronic properties of OFETs including a phospholipid film are studied in both pure water and in an electrolyte solution and compared to those of an OFET with the organic semiconductor directly in contact with the gating solution. In addition, to investigate the role of the lipid layers in the charge polarization process and quantify the field-effect mobility, impedance spectroscopy was employed. The results indicate that the integration of the biological film minimizes the penetration of ions into the organic semiconductor thus leading to a capacitive operational mode as opposed to an electrochemical one. The OFETs operate at low voltages with a field-effect mobility in the 10−3 cm2 V−1 s−1 range and an on/off current ratio of 103. This achievement opens perspectives to the development of FET biosensors potentially capable to operate in direct contact with physiological fluids. funding agencies|European Union|248728