Browsing by Author "Biscarini, Fabio"
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- Bioelectrical signal detection using conducting polymer electrodes and the displacement current methodPublication . Inácio, Pedro; Mestre, Ana L G; Medeiros, C.R.; Asgarifar, Sanaz; ELAMINE, Youssef; Canudo, Joana; Santos, João; Bragança, José; Morgado, Jorge; Biscarini, Fabio; Gomes, Henrique L.Conducting polymer electrodes based on poly (3, 4 ethylenedioxythiophene): polystyrene sulfonate were used to record electrophysiological signals from autonomous cardiac contractile cells present in embryoid bodies. Signal detection was carried out by measuring the displacement current across the polymer/electrolyte double-layer capacitance, and compared with voltage detection. While for relatively low capacitance electrodes, the voltage amplification provides higher signal quality, and for high capacitive electrodes, the displacement current method exhibits a higher signal-to-noise ratio. It is proposed that the displacement current method combined with high capacitive polymer-based electrodes is adequate to measure clusters of cells and whole organs. Our approach has a great potential in fundamental studies of drug discovery and safety pharmacology.
- Dual-compartment-gate organic transistors for monitoring biogenic amines from foodPublication . Sergi, Ilenia; Sensi, Matteo; Zanotti, Rian; Tsironi, Theofania; Flemetakis, Emmanouil; Power, Deborah Mary; Bortolotti, Carlo Augusto; Biscarini, FabioAccording to the Food and Agriculture Organization of the United Nations (FAO) more than 14% of the world's food production is lost every year before reaching retail, and another 17% is lost during the retail stage. The use of the expiration date as the main estimator of the life-end of food products creates unjustified food waste. Sensors capable of quantifying the effective food freshness and quality could substantially reduce food waste and enable more effective management of food chain. We propose an electrolyte-gated organic transistor (EGOT) that responds to the release of biogenic amines, like diamines and tyramine, generated by degradation of protein-rich food. The EGOT sensor features a polymeric poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) gate electrode fabricated in the shape of a miniaturized beaker containing an aqueous solution in the inner side (to be exposed to food) and capacitively coupled through a hydrogel to the transistor channel on the outside (not in contact with food). The hydrogen bonds formed by the water-dissolved amines with PEDOT:PSS modulate the EGOT channel across a wide range of amine concentrations. We demonstrate that our sensor can detect different amines by the combinatorial analysis of the response from different channel materials, PEDOT:PSS and the other DPP-DTT, with a limit of detection as low as 100 pM.
- Electrochemical noise and impedance of Au electrode/electrolyte interfaces enabling extracellular detection of glioma cell populationsPublication . Schlett, Paul; Kintzel, Ulrike; Mailaender, Volker; Vandamme, Lode K. J.; Zeck, Gunther; Gomes, Henrique L.; Biscarini, Fabio; de Leeuw, Dago M.Microelectrode arrays (MEA) record extracellular local field potentials of cells adhered to the electrodes. A disadvantage is the limited signal-to-noise ratio. The state-of-the-art background noise level is about 10 mu Vpp. Furthermore, in MEAs low frequency events are filtered out. Here, we quantitatively analyze Au electrode/electrolyte interfaces with impedance spectroscopy and noise measurements. The equivalent circuit is the charge transfer resistance in parallel with a constant phase element that describes the double layer capacitance, in series with a spreading resistance. This equivalent circuit leads to a Maxwell-Wagner relaxation frequency, the value of which is determined as a function of electrode area and molarity of an aqueous KCl electrolyte solution. The electrochemical voltage and current noise is measured as a function of electrode area and frequency and follow unambiguously from the measured impedance. By using large area electrodes the noise floor can be as low as 0.3 mu Vpp. The resulting high sensitivity is demonstrated by the extracellular detection of C6 glioma cell populations. Their minute electrical activity can be clearly detected at a frequency below about 10 Hz, which shows that the methodology can be used to monitor slow cooperative biological signals in cell populations.
- Extracellular electrical recording of pH-triggered bursts in C6 glioma cell populationsPublication . Rocha, Paulo R. F.; Medeiros, Maria C. R.; Kintzel, Ulrike; Vogt, Johannes; Araújo, Inês; Mestre, Ana L. G.; Mailaender, Volker; Schlett, Paul; Droege, Melanie; Schneider, Leonid; Biscarini, Fabio; de Leeuw, Dago M.; Gomes, Henrique L.Glioma patients often suffer from epileptic seizures because of the tumor's impact on the brain physiology. Using the rat glioma cell line C6 as a model system, we performed long-term live recordings of the electrical activity of glioma populations in an ultrasensitive detection method. The transducer exploits large-area electrodes that maximize double-layer capacitance, thus increasing the sensitivity. This strategy allowed us to record glioma electrical activity. We show that although glioma cells are nonelectrogenic, they display a remarkable electrical burst activity in time. The low-frequency current noise after cell adhesion is dominated by the flow of Na+ ions through voltage-gated ion channels. However, after an incubation period of many hours, the current noise markedly increased. This electric bursting phenomenon was not associated with apoptosis because the cells were viable and proliferative during the period of increased electric activity. We detected a rapid cell culture medium acidification accompanying this event. By using specific inhibitors, we showed that the electrical bursting activity was prompted by extracellular pH changes, which enhanced Na+ ion flux through the psalmotoxin 1-sensitive acid-sensing ion channels. Our model of pH-triggered bursting was unambiguously supported by deliberate, external acidification of the cell culture medium. This unexpected, acidosis-driven electrical activity is likely to directly perturb, in vivo, the functionality of the healthy neuronal network in the vicinity of the tumor bulk and may contribute to seizures in glioma patients.
- Neuromorphic organic devices that specifically discriminate dopamine from Its metabolites by nonspecific interactionsPublication . Giordani, Martina; Sensi, Matteo; Berto, Marcello; Di Lauro, Michele; Bortolotti, Carlo Augusto; Gomes, Henrique Leonel; Zoli, Michele; Zerbetto, Francesco; Fadiga, Luciano; Biscarini, FabioSpecific detection of dopamine (DA) is achieved with organic neuromorphic devices with no specific recognition function in an electrolyte solution. The response to voltage pulses consists of amplitude-depressed current spiking mimicking the short-term plasticity (STP) of synapses. An equivalent circuit hints that the STP timescale of the device arises from the capacitance and resistance of the poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) in series with the electrolyte resistance. Both the capacitance and resistance of PEDOT:PSS change with solution compositions. Dose curves are constructed from the STP timescale for each DA metabolite from pM to mM range of concentrations. The STP response of DA is distinctive from the other metabolites even when differences are by one functional group. Both STP and sensitivity to DA are larger across the patho-physiological range with respect to those to DA metabolites. Density functional theory calculations hint to a stronger hydrogen bond pattern of DA ammonium compared to cationic metabolites. The exponential correlation between STP and the binding energy of DA metabolites interacting with PEDOT:PSS indicates that the slow dynamics of ionic species in and out PEDOT:PSS is the origin of the neuromorphic STP. The sensing framework discriminates differences of nonspecific interactions of few kcal mol(-1), corresponding to one functional group in the molecule.
- Performance assessment of polymer based electrodes for in vitro electrophysiological sensing: the role of the electrode impedancePublication . Medeiros, Maria C. R.; Mestre, Ana L. G.; INÁCIO, PEDRO; Santos, João M. L.; Araújo, Inês; Bragança, José; Biscarini, Fabio; Gomes, Henrique L.Conducting polymer electrodes based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are used to record extracellular signals from autonomous cardiac contractile cells and glioma cell cultures. The performance of these conducting polymer electrodes is compared with Au electrodes. A small-signal impedance analysis shows that in the presence of an electrolyte, both Au and polymer electrodes establish high capacitive double-layers. However, the polymer/electrolyte interfacial resistance is 3 orders of magnitude lower than the resistance of the metal/electrolyte interface. The polymer low interfacial resistance minimizes the intrinsic thermal noise and increases the system sensitivity. However, when measurements are carried out in current mode a low interfacial resistance partially acts as a short circuit of the interfacial capacitance, this affects the signal shape.
- Reviewing the correlation of fish quality alteration and in‐package headspace composition: evidence from a pH freshness indicator case studyPublication . Basdeki, Evgenia; Vasilaki, Stamatia Eleni; Sensi, Matteo; Flemetakis, Emmanouil; Biscarini, Fabio; Power, Deborah Mary; Tsironi, Theofania; Swarup RoySmart packaging is a continuously evolving sector that may provide solutions to several cold chain management challenges and shows great potential toward food waste reduction. Fish is a highly nutritious yet perishable commodity with increasing statistics of annual loss and waste. This study investigates the application of pH-sensitive indicators on fish products, aiming to analyze and highlight the importance of comprehensive monitoring of the physicochemical alterations and their interactions with the headspace composition during refrigerated storage of fresh fish. Insights into this process can contribute to developing more practical spoilage indicators and dynamic shelf life prediction methods. A brief case study is presented on the development and application of a smart indicator prototype. The freshness pH indicator was prepared by incorporating methyl red into a starch and cellulose matrix using the dip coating method and was tested for its sensitivity to pH, ammonia vapor, and the detection of gilthead sea bream spoilage. The deterioration in the quality of sea bream fillets, as indicated by the observed color change of the indicator, was confirmed through microbiological and chemical analyses of the fish flesh. The color response of the pH indicator (red-pink turned pale yellow) was found to correlate with fish alteration patterns and reflected the headspace gas composition thus enabling "real-time" monitoring of fish spoilage.
- Ultra-low noise PEDOT:PSS electrodes on bacterial cellulose: A sensor to access bioelectrical signals in non-electrogenic cellsPublication . Inacio, Pedro M. C.; Medeiros, Maria C. R.; Carvalho, Tiago; Félix, Rute; Mestre, Ana; Hubbard, Peter; Ferreira, Quirina; Morgado, Jorge; Charas, Ana; Freire, Carmen S. R.; Biscarini, Fabio; Power, Deborah; Gomes, Henrique L.This study is focused on the particular advantages of organic-based devices to measure cells that do not generate action potentials, also known as non-electrogenic cells. While there is a vast literature about the application of organic conductors to measure neurons, cardiomyocytes and brain tissues, electrical measurements of non-electrogenic cells are rare. This is because non-electrogenic cells generate weak signals with frequencies below 1 Hz. Designing low noise devices in a millihertz frequency range is extremely challenging due to the intrinsic thermal and 1/f type noise generated by the sensing electrode. Here, we demonstrate that the coating of cellulose nanofibers with conducting PEDOT:PSS ink allows the fabrication of a nanostructured surface that establishes a low electrical double-layer resistance with liquid solutions. The low interfacial resistance combined with the large effective sensing area of PEDOT:PSS electrodes minimizes the thermal noise and lowers the amplitude detection limit of the sensor. The electrode noise decreases with frequency from 548 nV r.m.s at 0.1 Hz to a minimum of 6 nV r.m.s for frequencies higher than 100 Hz. This low noise makes it possible to measure low frequency bioelectrical communication signals, typical of non-electrogenic cells, that have until now been difficult to explore using metallic-based microelectrode arrays. The performance of the PEDOT:PSS-based electrodes is demonstrated by recording signals generated by populations of glioma cells with a signal-to-noise ratio as high as 140.
- Whole organic electronic synapses for dopamine detectionPublication . Giordani, Martina; Di Lauro, Michele; Berto, Marcello; Bortolotti, Carlo A.; Vuillaume, Dominique; Gomes, Henrique L.; Zoli, Michele; Biscarini, FabioA whole organic artificial synapse has been fabricated by patterning PEDOT:PSS electrodes on PDMS that are biased in frequency to yield a STP response. The timescale of the STP response is shown to be sensitive to the concentration of dopamine, DA, a neurotransmitter relevant for monitoring the development of Parkinson's disease and potential locoregional therapies. The sensitivity of the sensor towards DA has been validated comparing signal variation in the presence of DA and its principal interfering agent, ascorbic acid, AA. The whole organic synapse is biocompatible, soft and flexible, and is attractive for implantable devices aimed to real-time monitoring of DA concentration in bodily fluids. This may open applications in chronic neurodegenerative diseases such as Parkinson's disease.