A jellified alginate based capsule serves as biocompatible and biodegradable electrolyte system to gate an organic field-effect transistor fabricated on a flexible substrate. Such a system allows operating thiophene based polymer transistors below 0.5 V through an electrical double layer formed across an ion-permeable polymeric electrolyte. Moreover, biological macro-molecules such as glucose-oxidase and streptavidin can enter into the gating capsules that serve also as delivery system. An enzymatic bio-reaction is shown to take place in the capsule and preliminary results on the measurement of the electronic responses promise for low-cost, low-power, flexible electronic bio-sensing applications using capsule-gated organic field-effect transistors

A model for the electrical characteristics of Functional-Bio-Interlayer Organic Field-Effect Transistors (FBI-OFETs) electronic sensors is here proposed. Specifically, the output current-voltage characteristics of a streptavidin (SA) embedding FBI-OFET are modeled by means of the analytical equations of an enhancement mode p-channel OFET modified according to an ad hoc designed equivalent circuit that is also independently simulated with pspice. An excellent agreement between the model and the experimental current-voltage output characteristics has been found upon exposure to 5 nM of biotin. A good agreement is also found with the SA OFET parameters graphically extracted from the device transfer I-V curves.

A model for the electrical characteristics of Functional-Bio-Interlayer Organic Field-Effect Transistors (FBI-OFETs) electronic sensors is here proposed. Specifically, the output current-voltage characteristics of a streptavidin (SA) embedding FBI-OFET are modeled by means of the analytical equations of an enhancement mode p-channel OFET modified according to an ad hoc designed equivalent circuit that is also independently simulated with PSPICE. An excellent agreement between the model and the experimental current-voltage output characteristics has been found upon exposure to 5 nM of biotin. A good agreement is also found with the SA OFET parameters graphically extracted from the device transfer I-V curves

Polyphenols, as food antioxidants, are of great interest due to their health benefits as they decrease the risks of cancer and coronary cardiopathy (1). Moreover they influence the quality and organoleptic characteristics of foods (2). Lastly, some neurotransmitters are phenolic compounds. Hence the need to work out a sensitive, portable and inexpensive detection methods to monitor these compounds (3). We developed a disposable paper-based bioassay for the detection of phenolic compounds; the assay was successfully applied for the determination of polyphenols in a real matrix such as wine. The colorimetric quantification of the analyte is based on an enzymatic assay. The tyrosinase enzyme has been immobilized on a filter paper by simple over-spotting with 3-methyl-2-benzothiazolinone hydrazone (MBTH), that allows the detection of phenols by forming stable colored adducts with their enzymatic oxidation products. The color intensity of the adduct (developed after 5 min of reaction) was found to increase proportionally with the increase of the phenolic substrate concentrations. Analyte detection can be achieved by eye and quantification can be simply obtained by using a camera phone and an image analysis software. The response, characteristics of the sensor were determined using l-3,4-dihydroxyphenyl-alanine (l-DOPA), an archetype substrate of tyrosinase, as the analyte. This disposable paper-based biosensor relies on a rapid and simple method, without need of sophisticated instrumentation and trained personnel and could be extremely useful in remote locations or developing countries which does not have ready access to laboratory facilities and where simple, sensitive and low cost bioassays are essentials. 1) D. Del Rio, L.G. Costa, M.E. Lean, A. Croizer. Nutr. Metab. Cardiovasc. Dis. 20 (2010) 1-6. 2) I. Ignat, I. Volf, V.I. Popa. Food Chem. 126 (2011) 1821-1835. 3) M. Arciuli, G. Palazzo, A. Gallone, A. Mallardi. Sensors & Actuators: B. Chemical (2013)In press.

In this study the development of a low cost, portable and disposable paper-based bioassay for phenolic compounds is described. The colorimetric detection of the analyte is based on an enzymatic assay. The tyrosinase enzyme has been immobilized on a filter paper by simple over-spotting with 3-methyl-2-benzothiazolinone hydrazone (MBTH), that allows the detection of phenols by forming stable colored adducts with their enzymatic oxidation products. The color intensity of the adduct (developed after 5 min of reaction) was found to increase proportionally with the increase of the phenolic substrate concentrations. Analyte detection can be achieved by eye and quantification can be simply obtained by using a camera phone and an image analysis software. The response characteristics of the sensor were determined using L-3,4-dihydroxyphenyl-alanine (L-DOPA), an archetype substrate of tyrosinase, as the analyte. The sensor gave a LOD of 5 M and a linear response up to 0.5 mM. The polyphenol content in wine was determined by the biosensor and results were compared with that obtained for the phenolic-pool determined by tyrosinase enzymatic assay in solution and for the antioxidant-pool probed by the Folin-Ciocalteau assay. This paper based platform holds potential for the detection of different types of phenolic compounds. The proposed assay has the advantage of rapidity and simplicity over other detection methods, without need of sophisticated instrumentation and trained personnel.

Among the metal oxide semiconductors, ZnO has been widely investigated as a channel in thin film transistors (TFTs) due to its excellent electrical properties, optical transparency and simple fabrication via solution processed techniques. Herein, we are reporting a solution processable ZnO based thin-film transistor, gated through a liquid electrolyte having 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 buffer solution (PBS), are discussed in terms of operation stability and electrical performance of the ZnO TFT devices. Improved device characteristics upon exposure to PBS are associated with the enhancement of the oxygen vacancies in ZnO lattice, possibly due to Na+ doping. Moreover, dissolution kinetics of ZnO thin film in liquid electrolyte opens to possible applicability of these devices as active element in “transient” implantable systems.

Methods to immobilize proteins are of particular relevance for biosensing. In biosensors, proteins have to be assembled according to suitable architectures on solid surfaces such as electrodes, optical windows, or the organic semiconductor layer of electronic devices and their integrity and activity have to be preserved. This chapter deals with the use of immobilized proteins in several types of biosensors. The importance of molecular architecture control, particularly with synergistic combination of proteins and “other” materials, is evidenced. Different methodologies for protein assembly are described, highlighting the environmental applications of the protein based biosensors. Results from the literature, grouped into large areas covering optical and electrochemical biosensors and also sensing exploiting field-effect transistors, are reported. Layer by layer (LbL) immobilization of proteins on the transparent substrate of optical biosensors is proposed for its advantageous control of molecular architecture and versatility to accommodate layers having different functionalities. Covalent immobilization is evaluated as an alternative process for the controlled incorporation of the recognition element on/into the electrode surface, in the case of electrochemical transducers. Finally, the integration of immobilized proteins in electronic devices is presented, especially in the context of using field-effect transistors (FETs) for biosensing. It is hoped that this survey may assist researchers in choosing materials, molecular architectures, and detection principles, which may be tailored for specific 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.

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 nanostructured electronic active layers are reported.

Here, the phase behavior of the commercial non-ionic surfactant Solutol HS15 in water was investigated. The focus was on the evolution of the system nanostructure at low water content. Particularly, it was demonstrated that spherical micelles found in dilute surfactant solutions coalesce at a surfactant volume fraction close to 0.5. As consequence, a heterogeneous pseudo-binary mixture occurs. No liquid crystalline phases were detected even at the highest HS15 concentrations in water. Alteration of the micellar morphology induced by the addition of D9-tetrahydrocannabinol to the surfactant/water binary system was also investigated. It was found that the cannabinoid molecules become entrapped within the surfactant hydrophobic tails, thus increasing the surfactant effective packing parameter and inducing a radical change of the micelle shape. At sufficiently low water content (18–35 wt.%), such alteration of the interfacial packing results in a lamellar organization of the surfactant molecules.

Here, the phase behavior of the commercial nonionic surfactant Solutol® HS15 in water was investigated. The focus was on the evolution of the system nanostructure at low water content. Particularly, it was demonstrated that at low water content spherical micelles are present. Micelles coalesce at a surfactant volume fraction close to 0.5. As consequence, a heterogeneous pseudo-binary mixture occurs. No liquid crystalline phases were detected even at the highest HS15 concentrations in water. A morphological change of the micelles occurred on addition of the cannabinoid 9-tetrahydrocannabinol (THC). THC is entrapped within the surfactant tails modifying the micelle shape. At sufficiently low water content (18-35 wt%) such alteration of the interfacial packing results in a lamellar organization of the surfactant molecule

In this paper gold nanoparticles (Au-NPs) have been used as colorimetric reporters for the detection of sugars. The synthesis of Au-NPs has been obtained in presence of glucose as reducing agent in different conditions, allowing the formation of pink or blue coloured NPs, and has been employed in the design of two colorimetric assays. Both assays rely on the analyte induced intensity increase (without any shift) of the NPs plasmon band absorption. The “pink assay” is based on the sugar assisted chemical synthesis of NPs and it represents a simple one-step colorimetric approach to the quantification of all potentially reducing sugars (sucrose included) with a LOD of 10 M. The “blue assay” is based on the Au-NP synthesis catalyzed by the enzyme glucose oxidase and it is specific for glucose, with a LOD of 5 M. Compared to the classical bi-enzymatic (glucose oxidase/peroxidase) optical assay, it uses only one enzyme and doesn’t suffer of the bleaching of the final colour because the reporter Au-NPs are very stable.

Alkyl-methylimidazolium based ionic liquids are proposed as gating electrolytes in field-effect transistors and the ionic properties are seen to influence the devices electrical performance. Specifically, over a selection of different cations and anions correlations have been established between the ion-pairing occurring in the pure ionic-liquid and the intensity of the current circulating in the transistor channel in the on state. Ion-pairing was determined by means of pulse-gradient-spin-echo (PGSE) NMR experiments. Moreover, the effect of the ions chemical structure and hydrophobicity on the off-current and on the field-effect mobility as well as on the threshold voltage, are discussed. The occurrence of hysteresis in the current–voltage transfer curves is evaluated and associated to the electrolyte molar conductivity and the ions self-diffusion coefficients. The gained understanding allows to optimize the system reaching better device performance level. Moreover, thanks to the well-known bio-compatibility of this class of ionic liquids, application in electrolyte gated biosensors can be foreseen.

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.

We report on the response of reaction center (RC) from Rhodobacter sphaeroides (an archetype of membrane proteins) to the exposure at high temperature. The RCs have been solubilized in aqueous solution of the detergent N,N,-dimethyldodecylamine-N-oxide (LDAO). Changes in the protein conformation have been probed by monitoring the variation in the absorbance of the bacteriochlorine cofactors and modification in the efficiency of energy transfer from tryptophans to cofactors and among the cofactors (through fluorescence measurements). The RC aggregation taking place at high temperature has been investigated by means of dynamic light scattering. Two experimental protocols have been used: i) isothermal kinetics, in which the time evolution of RC after a sudden increase of the temperature is probed; ii) T-scans, in which the RCs are heated at constant rate. The analysis of the results coming from both the experiments indicate that the minimal kinetic scheme requires an equilibrium step and an irreversible process. The irreversible step is characterized by a activation energy of 20514 kJ/mol and is independent from the detergent concentration. Since the temperature dependence of the aggregation rate was found to obeys to the same law, the aggregation process is unfolding-limited. On the other hand, the equilibrium process between the native and a partially unfolded conformations was found to be strongly dependent on the detergent concentration. Increasing the LDAO content from 0.025 wt% to 0.5 wt% decreases the melting temperature from 49°C to 42°C. This corresponds to a sizeable ( 22 kJ/mol at 25°C) destabilization of the native conformation induced by the detergent. The nature of the aggregates formed by the denatured RCs depends on the temperature. For temperature below 60°C compact aggregates are formed while at 60°C the clusters are less dense with a scaling relation between mass and size close to that expected for diffusion-limited aggregation. The aggregates final size of formed at different temperatures indicate the presence of an even number of proteins suggesting that these clusters are formed by aggregation of dimers.

The bacterial reaction center (RC) has become a reference model in the study of the diverse interactions of quinones with electron transfer complexes. In these studies, the RC functionality was probed through flash-induced absorption changes where the state of the primary donor is probed by means of a continuous measuring beam and the electron transfer is triggered by a short intense light pulse. The single-beam set-up implies the use as reference of the transmittance measured before the light pulse. Implicit in the analysis of these data is the assumption that the measuring beam does not elicit the protein photochemistry. At variance, measuring beam is actinic in nature at almost all the suitable wavelengths. In this contribution, the analytical modelling of the time evolution of neutral and chargeseparated RCs has been performed. The ability of measuring light to elicit RC photochemistry induces a first order growth of the charge-separated state up to a steady state that depends on the light intensity and on the occupation of the secondary quinone (QB) site. Then the laser

There is an increasing interest in low cost, timesaving, yet reliable, point-of-care assays. Direct electronic, label-free transduction of bio-recognition events represents a compelling alternative offering miniaturization, easy data handling and processing. Low costs and versatility can be provided if organic electronic devices such as organic fi eld-effect transistors (OFETs) are used as transducers. [ 1 , 2 ] At the beginning, OFET sensors were mostly involved the detection of volatile chemical analytes, [ 3 , 4 ] while organic electronics allowed fabrication of sensing circuits on fl exible substrates. [ 5 , 6 ] However, bare OFET-sensor responses are based on weak interactions that are non-specifi c in nature. Specifi city can be achieved by endowing the OFET with receptor molecules capable of selectively interacting with given analytes.

A general method to obtain the efficient entrapment of mixtures of glyco-enzymes in calcium alginate hydrogel is proposed in this paper. As a proof of principle, three glyco-enzymes acting in series (trehalase, glucose oxidase and horseradish peroxidase) have been co-immobilized in calcium alginate beads. The release of the enzymes from the hydrogel mesh (leakage) is avoided by exploiting the enzymes 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 spectrophotometrically been quantified. 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 bio-assays exploiting the enzyme containing beads have been developed for the optical determination of glucose and trehalose and Limit of Detection values of 0.2 uM and of 40 uM respectively have been obtained.

We present an investigation on the effect of inter-micellar connection (branches) on the rheology of wormlike micelles. The system chosen is made of lecithin, minute amounts of water and organic solvents. Lecithin and water self-assemble into wormlike reverse micelles that can be branched or unbranched depending on the oil composition (and on the water content). In this respect, cyclohexane favours disconnected reverse micelles while isooctane promotes the formation of branches. By using mixtures of cyclohexane and isooctane as oil phase and different water/lecithin ratios, the branch density of the system can be finely tuned. PGSE-NMR experiments allow to distinguish between branches free (unbranched) and branched systems and the response of the very same samples to mechanical stress has been measured by rheology. This allows, for the first time, an experimental correlation between rheological properties and the presence of branches. It turned out that the presence of few inter-micellar connections sensibly decreases the zero-shear viscosity measured in steady state flow curves. Comparison with oscillatory rheology experiments indicates that the main effect of branches is to shorten the terminal relaxation time by speeding-up the reptation.

For the first time the ability of the first generation dendrimer belonging to the family of polyesterbenzylether, (3,5)12G1-PE-BMPA-(OH)4, to form dendrimersomes is presented together with their capability to reconstitute the integral membrane protein complex called Reaction Centre (RC) purified from the photosynthetic bacterium Rhodobacter sphaeroides. Size, polydispersity and time stability of the empty and protein containing dendrimersomes are presented together with the photochemical activity of the guest protein. The RC presence appears to strongly enhance the self-assembly properties of the Janus dendrimer, leading to the formation of proteo-dendrimersomes showing a photochemical activity similar to that found for RC in solution. The interaction of the embedded RC with reduced cyt-c has also been investigated, indicating that the incorporation of the protein is vectorial (almost 90% of the guest protein faces the dendrimerosomes exterior with its cyt-c docking site) at variance with lecithin liposomes where the reconstitution is essentially statistical.

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.

In Alzheimer's disease (AD), native Aβ protein monomers aggregate through the formation of a variety of water-soluble, toxic oligomers, ultimately leading to insoluble fibrillar deposits. The inhibition of oligomers formation and/or their dissociation into non-toxic monomers, are considered an attractive strategy for the prevention and treatment of AD. A number of studies have demonstrated that small molecules, containing single or multiple (hetero)aromatic rings, can inhibit protein aggregation, being potentially effective in AD treatment. Starting from previously reported data on the antiamyloidogenic activity of a series of 3-hydrazonoindolinones, compound PT2 was selected to deeply investigate the inhibitory mechanism in the Aβ aggregation cascade. We compared data from DLS, 1H, 13C, 15N HSQC NMR, CD, TEM and ThT fluorescence measures to ascertain the interactions with amyloidogenic species formed in vitro during the aggregation process, and confirmed this feature with cell viability tests on HeLa cultured cells. PT2 was effective in disrupting toxic oligomers and mature amyloid fibrils, stabilizing Aβ as non-toxic, β-sheet arranged, ThT-insensitive protofilaments. It also strongly reduced cellular toxicity caused by Aβ and showed good antioxidant properties in two radical scavenging tests. Taken together, these data confirmed that PT2 is a small molecule inhibitor of Aβ oligomerization and toxicity, displaying also additional activity as antioxidant.

Addition of small amounts of lauric acid (LA) to a micellar solution of sodium dodecyl sulfate (SDS, 11.5 wt%) and cocamidopropyl betaine (CAPB, 3 wt%) has a dramatic effect on the rheological properties and phase behaviour of the system. The viscosity increases by more than one order of magnitude up to a weight ratio LA/SDS = 0.17 and decreases for further LA loading. The decrease in viscosity is associated to the formation of a birefringent liquid crystalline phase. The evolution of the system from isotropic micelles in absence of LA to lyotropic liquid crystals up to a weight ratio LA/SDS = 0.30 was probed by a combination of 23Na NMR quadrupolar splitting, measurements of water and surfactant self-diffusion coefficients via 1H-PGSE-NMR and rheology. The evolution of the water self-diffusion coefficients indicates that LA induced a dramatic increase in the anisotropy of disk shaped micelles. Birefringent samples always showed a well developed 23Na quadrupolar splitting with a line shape typical of monodomain samples. This suggests that the whole sample is easily oriented within the spectrometer electromagnet as usually observed for nematic liquid crystals. Sample spinning first destroys the alignment (only a single peak is discernible in the 23Na NMR spectrum). Then, upon prolonged spinning, the alignment develops again. This indicates that the system is composed by disk-like micelles aligning themselves with their normal perpendicular to the magnetic field. On the other hand, the linear viscoelastic response close to the nematic transition shows features usually observed in wormlike micellar systems (e.g. nearly Maxwellian behaviour). To reconciliate the rheological data and the NMR evidences of discoid micelles, the formation of columnar stacks of discoid micelles is proposed. The rheology of the isotropic phase can therefore be interpreted in terms of entanglements of “living columnar stacks” of discoid micelles, and the nematic phase observed at high LA content could be attributed to a nematic columnar phase NCol formed by the alignment of such stacks.

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 (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.

This work is devoted to highlighting some peculiar aspects of ionic liquid selfaggregation in water, which is still a matter of wide debate. Here, the whole water /1-butyl-3-methyl imidazolium (bmim+) tetrafluoborate (BF4-) phase diagram was thoroughly re-investigated, at a molecular level, by means of 1H and 19F PGSTE and 11B relaxation NMR experiments performed at room temperature. The analysis of H2O, bmim? and BF4 ions self-diffusion coefficients and the 11B relaxation times revealed that ion-pair dissociation is a progressive process starting at a H2O molar fraction equal to 0.2 and ending at high water content. More importantly, the collected results indicate that H2O and ions diffuse within different domains, strongly suggesting that the system under investigation is actually nanostructured. This fact agrees with some other recent works focusing on the possible mesoscopic order that ionic liquids possess when dissolved in water because of their hydrophobic tail segregation.

Bright Field Microscopy and Atomic Force Microscopy techniques are used to investigate morphological properties of synthetic eumelanin, obtained by oxidation of L-DOPA solution, deposited on glass and mica substrates. Deposits of eumelanin are characterized by aggregates with different shape and size. On a micrometric scale, filamentous as well as granular structures are present on glass and mica substrates, with a larger density on the former than on the latter. On a nanometric scale, filamentous aggregates, several microns long and about 100 nm wide and high, and granular aggregates, ~50 nm high and 100 nm wide, are found on both substrates, whereas point-like deposits less than 10 nm high and less than 50 nm wide are found on mica substrate. Dynamic Light Scattering measurements and Atomic Force Microscopy images support the evidence that eumelanin presents only nanometric point-like aggregates in aqueous solution, whereas such nanoaggregates organize themselves according to granular and filamentous structures when deposition occurs, as a consequence of interactions with the substrate surface.

Determination of phenolic derivatives is very important in medical, food and environmental samples because of their relevant significance in health care and pollution monitoring. Tyrosinase-based biosensors are promising tools for this purpose because of several advantages with respect to currently used detection methods. A key aspect in the development of a biosensor is the effective immobilization of the enzyme. In this work, ordered tyrosinase films on an optical transparent support were immobilized by a “layer-by-layer” (LbL) assembly, alternating the enzyme with the polycation polymer poly(dimethyldiallylammonium chloride). As confirmed by UV–vis spectroscopy, the LbL deposition allowed a high loading of enzyme. The immobilized tyrosinase functionality was proven and its kinetic parameters were spectrophotometrically determined. The prepared biosensor was used to optically detect the o-diphenolic compound l-3,4-dihydroxyphenyl-alanine (l-DOPA) and exhibited good repeatability and time stability. The sensing properties of the system were studied by means of both absorption and fluorescence spectroscopy. The bioassay based on the absorbance measurements gave a LOD of 23M and a linear response up to 350M. The bioassay based on the fluorescence measurements gave a LOD of 3Mand a linear response in the range of tens of micromolar (the exact value depends on the number of mushroom tyrosinase layers). Biosensor sensitivity could be modulated varying the number of the immobilized enzyme layers.

The functioning principles of electronic sensors based on organic semiconductor field-effect transistors (OFETs) are presented. The focus is on biological sensors but also chemical ones are reviewed to address general features. The field-induced electronic transport and the chemical and biological interactions for the sensing, each occurring at the relevant functional interface, are separately introduced. Once these key learning points have been acquired, the combined picture for the FET electronic sensing is proposed. The perspective use of such devices in point-of-care is introduced, after some basics on analytical biosensing systems are provided as well. This tutorial review includes also a necessary overview of the OFET sensing structures, but the focus will be on electronic rather than electrochemical detection. The differences among structures are highlighted along with the implications on the performance level in terms of key analytical figure of merits such as: repeatability, sensitivity and selectivity

Dioxiranes are used as reagents in a myriad of synthetically useful oxidations performed in aqueous medium. To extend such an approach also to substrates that are highly hydrophobic, we propose here the use of microemulsions based on the surfactant hexadecyltrimethylammonium hydrogen sulphate (CTAHS) because of its high stability against peroxide species. In this paper, we examine the dioxirane (isolated or generated in situ) reactivity in different CTAHS microemulsions. Yield and selectivity of the oxidation of -methylstyrene (2) by dimethyldioxirane (DDO, 1a) generate “in situ” and of laurolactam (3) by isolated methyl(trifluorometyl)dioxirane (TFDO, 1b) were studied. For each microemulsion, the aggregate size and the localization of the components were determined by a combination of NMR and light scattering techniques. The hydrodynamic radius of the micelles is close to the length of the surfactant and this suggests they are spherical in shape. When acetone (the precursor of 1a) is present in the formulation, it partitions itself between the aqueous bulk and the micellar palisade so that the dioxirane eventually formed is readily available to oxidize substrates secluded in the micelle. Apolar substrates, confined within the micelles, are protected from uncontrolled oxidations, leading to an astonishing high selectivity of oxidation of laurolactam (3) to 12-nitro-lauric acid (3a) by TFDO (1b). This opens the way to an easy and green procedure (performed in water under mild conditions) to synthetize omega-nitroacids.

A Functional Bio-Interlayer Organic Field-Effect Transistor (FBI-OFET) sensor, embedding a streptavidin protein capturing layer, capable to perform label-free specific electronic detection of biotin at 3 part-per-trillion (mass fraction) or 15 pM, is here proposed. The response shows a logarithmic dependence on the analyte concentration along with a dynamic range spanning over five orders of magnitude. 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. A Langmuirian adsorption based model allows to rationalize the analyte binding to the capturing layer whose analytical performances are discussed accordingly. The FBI-OFET device is shown to operate also with an antibody interlayer as well as with an ad hoc designed micro-fluidic system. These occurrences, along with the proven extremely high sensitivity and selectivity, open to FBI-OFETs appraisal as a suitable platform for disposable electronic strip-tests for assays in biological fluids requiring very low detection limits.

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 cm^2 V^-1 s^-1 range and an on/off current ratio of 10^3. This achievement opens perspectives to the development of FET biosensors potentially capable to operate in direct contact with physiological fluids.

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.

The design and characterisation of an optical biosensor based on a photosynthetic protein deposited on a quartz surface is here presented. The protein Reaction Center (RC), purified from Rhodobacter sphaeroides, has been immobilized in alternate layers with the cationic polymer poly(dimethyl diallyl) ammonium chloride (PDDA). In this assembly the protein retains its integrity and functionality maintaining its ability to bind herbicides. Upon exposure to continuous light some RC absorbance bands dramatically reduce their intensity (bleaching) and the extent of such a bleaching reflects the amount of bound herbicides. These properties have been exploited for the design of a simple optical biosensor for herbicide. The characterization of the biosensor in detecting the broad family of triazine herbicides is presented. Performance characteristics, such as limits of detection (LOD) and quantification (LOQ), upper determination limit (UDL) and linear range for each herbicide were determined. Among the most striking features of the biosensor are the long lifetime (several months), the high reproducibility and the relatively high sensitivity of detection that can be further enhanced by preconcentrating the samples to be analysed. As a whole, these characteristics coupled to the low demanding instrumental setup, let the RC/PDDA assembly particularly appealing even for the realization of a stand alone analytical apparatus.

With the aim of quantitatively investigate the anion binding to a fully non-ionic surface, the self-diffusion coefficients of four different anions were probed in a Triton X-100 micellar solution by means of multinuclear PGSTE-NMR measurements. The salt concentration used was sufficiently low to avoid any observable alteration of the surface of interaction (the micellar ensemble). A specific anion binding was detected. Through a careful data modeling, anions affinity to the micellar surface could quantitatively be placed in the order (CH3)2AsO2− >> CH3COO− > H2PO4− > F−, that represents a Hofmeister series. Since the micellar aggregates here used as model surface do not bear any electric charge and only the surfactant hydrophilic moiety is exposed to the bulk, electrostatics or hydrophobic interactions cannot be considered relevant to justify the different anion binding. Therefore, the observed ion specificity can be rationalized only calling into play the non-electrostatic interactions occurring between the anions and the micellar surface.

We present a first investigation about the non-linear flow properties and transient orientational-order fluctuations observed in the shear-thinning lecithin–water–cyclohexane wormlike micellar system at a concentration near to the zero-shear isotropic–nematic phase transition. From rheological measurements the stress plateau was found shifted to very low values of the applied shear rate gamma_dot, compared to most of the concentrated living polymer systems reported in the literature. Rheo-small angle neutron scattering (Rheo-SANS) experiments performed in the flow-vorticity plane revealed periodical fluctuations of both the order parameter P2 and the angular deviation phi from the vorticity axis as determined from the scattering peaks. The periods of the oscillations were not found to depend on imposed gamma_dot. A theoretical model was also developed to explain the oscillatory dynamics of the shear-induced nematic order parameter in terms of the presence of standing waves of the director orientation profile along the circumference of the Couette cell. The experimental results of the periodic order parameter fluctuations together with their theoretical modelling shed significant new insights on the shear banding phenomenon, particularly its microscopic mechanism.

We present an extensive rheology study of the wormlike micelle system lecithin-water-cyclohexane. In this system the micelles are really wormlike, meaning that there are no signs of micellar branching, as it has previously been demonstrated by NMR self-diffusion experiments (Angelico et al. Phys. Rev. Lett. 1998, 81, 2823). Wormlike micelles break and recombine, processes that are important for the stress relaxation. When branching is highly unfavorable, micelle recombination reactions only involve micelle ends, the concentration of which are very low when the micelles are very long. Hence, the break and recombination kinetics is very slow for true wormlike micelles. In the present system, the stress relaxation times are of the order of an hour. This is about three to four orders of magnitude longer than what commonly is observed in systems claimed to contain wormlike micelles. We conclude that systems with true wormlike micelles are very rare. An exponential stress relaxation is observed except at lower concentrations, where the micellar breaking time appears to exceed the reptation time. Because of the slow dynamics, the linear elastic modulus can be obtained from small rapid shear deformations, for which the system obeys Hooke’s law. Larger deformations result in a fracture of the micellar network at a critical strain gamma*~FI-1, where FI is the micelle volume fraction. For gamma<gamma* we may still obtain fracture, although with a lag time, tau*, that decreases with increasing gamma, and vanishes when gamma=gamma*. Extrapolating gamma* to zero deformation we obtain the estimate ≈250 s at the highest concentration FI=0.29. This time we interpret as equilibrium micellar breaking time for the system at rest. A quantity not previously measured.

Organic field-effect transistors including a functional bio-recognition interlayer, sandwiched between the dielectric and the organic semiconductor layers, have been recently proposed as ultrasensitive label-free biosensors capable to detect target molecule in the low pM concentration range. The morphology and the structure of the stacked bilayer formed by the protein bio-interlayer and the overlying organic semiconductor is here investigated for different protein deposition methods. X-ray scattering techniques and scanning electron microscopy allow 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 to gather relevant details on the sensing mechanism and further improving sensor performances, in particular in terms of sensitivity and selectivity.

A series of isatin-3-arylhydrazones were synthesized and evaluated in vitro as inhibitors of Ab1e40 aggregation using a thioflavin T fluorescence method. An exploration of the effects on Ab1e40 aggregation of a number of diverse substituents at phenylhydrazone group and 5,6- positions of the indolinone nucleus led us to single out some new anti-aggregating compounds with IC50 values in the low micromolar range. The most active compounds carry methoxy- or hydroxy- substituents in the indolinone 5,6-positions and lipophilic groups such as iPr and Cl at 40- and 30-position, respectively, of the phenylhydrazone moiety. Two derivatives are noteworthy, namely 18 (IC50 ¼ 0.4 mM) and 42 (IC50 ¼ 1.1 mM). The in vitro effects of the highly active, water soluble, compound 42 on the temporal evolution of Ab1e40 fibrils formation were further investigated by circular dichroism spectroscopy, transmission electron microscopy and dynamic light scattering studies, which clearly showed that this compound delayed and lowered the amyloid fibril formation.

Here we investigate the structural evolution of TX100 micelles upon loading with several linear and cyclic alkanes by DLS, PGSE-NMR, 2D NOESY NMR, viscosity measurements, and molecular dynamic simulations. Our results confirm that TX100 alone forms spherical, onion-like micelles made of several partially interpenetrating surfactant layers where the polyethylene glycol chains are in contact with the tetramethyl-butyl-phenyl moieties. Loading with non-penetrating oils larger than decane induces a decrease in micellar size and hydration because the alkane molecules compete with both water and tetramethyl-butyl-phenyl groups for the polyethylene glycol chains. This results in the partial peeling of the “onion” and in the dehydration of polyethylene glycol chains so that the micelles increase in number and decrease in size upon alkane loading. In contrast, small and penetrable oils (mainly cyclo-alkanes) first swell the onion-like micelles (inducing an increase in size) and only above a critical oil/surfactant ratio does the oil induce the weakening of the multilayer structure and the dehydration of polyethylene glycol chains found in long linear alkanes.

The kinetics of the p-nitrophenyl butyrate hydrolysis reaction, catalyzed by Candida rugosa lipase in the water-in-oil microemulsion cetyltrimethylammonium bromide/water/pentanol/hexane, was investigated. The results described in the present manuscript reveal two peculiar characteristics of the reaction: (i) the initial rate of hydrolysis is very fast and (ii) by decreasing the water content of the microemulsion, the reaction rate approaches the typical behavior of reactions performed in aqueous solution. In particular, for microemulsion systems with a high water content, the end points of the reactions are dictated by the shape stability of the microemulsion. For these systems, our methodological approach shows that the process follows a second-order kinetics equation, indicative of the dual role played by water, which is involved both as a component of the microemulsion, i.e., relevant for the microemulsion stability and as a reagent of the hydrolysis reaction. In contrast, for microemulsions containing a small amount of water, after the hydrolysis reaction the system seems to fall in the no existence range of the microemulsion. Accordingly, the kinetics results are more complex: in the initial stage, the reaction follows a zero-order kinetics equation, while for longer reaction times a first-order kinetics equation fits the experimental data, as would be expected for an enzymatic reaction in a homogeneous system. (c) 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:360-366, 2014

A new optical biosensor for trehalose determination has been realized immobilizing three glycoenzymeson a transparent support. Trehalase, glucose oxidase and horseradish peroxidase have been alternatedwith layers of Concanavalin A by a “layer-by-layer” (LbL) deposition. The driving force of this assembly isthe biospecific complexation between Concanavalin A and sugar residues in the glycoenzymes. As con-firmed by UV–vis spectroscopy, the LbL deposition allowed a high ordinate architecture with high loadingof enzymes. After the assembly, the functionality of immobilized enzymes was spectrophotometricallyproven, demonstrating also that they can act in series catalyzing cascade reactions.The prepared biosensor was used to optically detect trehalose, giving a LOD of 10 M and a linearresponse up to 4 mM, and it showed also good time stability. The trehalose content in a real sample(eyewash) was successfully determined by the biosensor.

In order to improve the dispersion of multi-walled carbon nanotubes (MWCNTs) in aqueous media, their surface functionalization was carried out in O2-fed low-pressure plasmas. Differently from what can be found in the literature of this field, homogeneous functionalization was achieved by generating the plasma inside vials containing the nanotube powders properly stirred. Experimental parameters, such as input power, treatment time and pressure, were varied to investigate their influence on the process efficiency. A detailed characterization of the plasma treated nanotubes, dry and in aqueous suspension, was carried out with a multi-diagnostic analytical approach, to evaluate their surface chemical properties, morphology, structural integrity and stability in the colloidal state. The plasma grafting of polar ionizable (e.g. acid) groups has been proved to successfully limit the agglomeration of MWCNTs and to produce nanotubes suspensions that are stable for one month and more in water.

Organic thin film transistor (OTFT) technology can be implemented to develop cost-effective and label-free bio-affinity sensor chips, having a field-effect transport directly coupled to a bio-sensing process, useful to high-throughput testing and point-of-care applications. Biological recognition elements such as antibodies or other proteins can be integrated in OTFT devices to confer specificity. In this study the use of lipid bilayers as support for biomolecules immobilization is investigated. Preliminary results in terms of electrical resistance and capacitance of the lipid bilayers are presented.

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 biointer-layer(FBI)are here proposed for the electronic detection of archetypal volatile anesthetic molecules such as diethylether 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 PLFBI-OFET to anesthetics are produced in a concentration range that reaches few percent,namely the clinically relevant regime. The PLFBI-OFET is also shown to deliver a comparably weaker response to a non-anesthetic volatile molecule such as acetone

In this Highlight, the studies on wormlike reverse micelles are critically reviewed in light of recent results that demonstrated the impact that micellar branching has on dynamics, rheology and phase behavior. Due to the large number of papers and to their historical importance, a large emphasis is on the reverse micelles formed by water addition to lecithin in oil solution. It is discussed how subtle changes in the system composition can drastically change the micellar connectivity, phase behavior and rheology

L'invenzione consiste in un transistore “electrolyte gated” che integra uno strato di elementi biologici di riconoscimento in grado di rivelare selettivamente il loro ligando di affinità presente ad una concentrazione nel range dello zepto-molare (10-12 M).

La struttura del dispositivo proposta nella domanda di brevetto no. EP 16207596.4 è stata migliorata per rendere il dispostivo piu’ stabile.

Si tratta di un sensore a transistore, cos’ come del suo array, capace di rivelare, in modo affidabile, selettivo e label-free fino ad una singola molecola di DNA così come di anticorpi e peptidi. noltre il semiconduttore usato è un composito nanostrutturato a base di un polimero semiconduttore, facile da preparare, scalabile ed economico, è anche particolarmente stabile quando impiegato in diretto contatto con l’acqua.

Transistor comprising at least one conductive layer (4), at least one gate dielectric layer (3) and at least one semiconducting film (1) deposited on top of a receptor molecule layer (2) previously deposited or covalently linked to the surface of the gate dielectric (3). Said layer of biological material is constituted by single or double layers of phospholipids, layers made of proteins such as receptors, antibodies, ionic channels and enzymes, single or double layers of phospholipids with inclusion or anchoring of proteins such as: receptors, antibodies, ionic channels and enzymes, layers made of oligonucleotide (DNA, RNA, PNA) probes, layers made of cells or viruses, layers made of synthetic receptors for example molecules or macromolecules similar to biological receptors for properties, reactivity or steric aspects.

Transistor comprising at least one conductive layer, at least one dielectric layer and at least one thin organic semiconductor film and characterized by at least one layer of biological material deposited directly on the surface of the dielectric. Said layer of biological material is constituted by single or double layers of phospholipids, layers made of proteins such as receptors, antibodies, ionic channels and enzymes, single or double layers of phospholipids with inclusion or anchoring of proteins such as: receptors, antibodies, ionic channels and enzymes, layers made of oligonucleotide (DNA, RNA, PNA) probes, layers made of cells or viruses, layers made of synthetic receptors for example molecules or macromolecules similar to biological receptors for properties, reactivity or steric aspects.