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This work was partially supported by the Italian Institute of Technology (IIT)., We would like to express our gratitude to R. Cingolani and his group at IIT, as well as to the other Sensing Technology Group Members at the Free University of Bolzano. This work was partially supported by the BBVA foundation through the 2019 Leonardo Grant for Researchers and Cultural Creators., Tetracycline (TC) is a widely known antibiotic used worldwide to treat animals. Its residues in animal-origin foods cause adverse health effects to consumers. Low-cost and real-time measuring systems of TC in food samples are, therefore, extremely needed. In this work, a three-electrode sensitive and label-free sensor was developed to detect TC residues from milk and meat extract samples, using CO2 laser-induced graphene (LIG) electrodes modified with gold nanoparticles (AuNPs) and a molecularly imprinted polymer (MIP) used as a synthetic biorecognition element. LIG was patterned on a polyimide (PI) substrate, reaching a minimum sheet resistance (R-sh) of 17.27 +/- 1.04 omega/sq. The o-phenylenediamine (oPD) monomer and TC template were electropolymerized on the surface of the LIG working electrode to form the MIP. Surface morphology and electrochemical techniques were used to characterize the formation of LIG and to confirm each modification step. The sensitivity of the sensor was evaluated by differential pulse voltammetry (DPV), leading to a limit of detection (LOD) of 0.32 nM, 0.85 nM, and 0.80 nM in buffer, milk, and meat extract samples, respectively, with a working range of 5 nM to 500 nM and a linear response range between 10 nM to 300 nM. The sensor showed good LOD (0.32 nM), reproducibility, and stability, and it can be used as an alternative system to detect TC from animal-origin food products., Italian Institute of Technology (IIT)

Chemical biosensors with the capacity to continuously monitor various neurotransmitter dynamics can be powerful tools to understand complex signaling pathways in the brain. However, in vivo detection of neurochemicals is challenging for many reasons such as the rapid release and clearance of neurotransmitters in the extracellular space, or the low target analyte concentrations in a sea of interfering biomolecules. Biosensing platforms with adequate spatiotemporal resolution coupled to specific and selective receptors termed aptamers, demonstrate high potential to tackle such challenges. Herein, we review existing literature in this field. We first discuss nanoparticle-based systems, which have a simple in vitro implementation and easily interpretable results. We then examine methods employing near-infrared detection for deeper tissue imaging, hence easier translation to in vivo implementation. We conclude by reviewing live cell imaging of neurotransmitter release via aptamermodified platforms. For each of these sensors, we discuss the associated challenges for translation to real-time in vivo neurochemical imaging. Realization of in vivo biosensors for neurotransmitters will drive future development of early prevention strategies, treatments, and therapeutics for psychiatric and neurodegenerative diseases., Journal of Neuroscience Methods, 365, ISSN:0165-0270, ISSN:1872-678X

Nowadays, there is a high demand for sensitive and selective real-time analytical methods suitable for a wide range of applications, from personalized telemedicine, drug discovery, food safety, and quality control, to defense, security, as well as environmental monitoring. Biosensors are analytical devices able to detect bio-chemical analytes (e.g., neurotransmitters, cancer biomarkers, bio-molecules, and ions), through the combination of a bio-recognition element and a bio-transduction device. The use of customized bio-recognition elements such as enzymes, antibodies, aptamers, and ion-selective membranes facilitates achieving high selectivity. Among the different bio-transduction devices currently available, electrolyte-gated field-effect transistors, in which the dielectric is represented by an ionic liquid buffer solution containing the targeted analyte, are gaining increasing attention. Indeed, these bio-transduction devices are characterized by superior electronic properties and intrinsic signal amplification that allow the detection of a wide range of bio-molecules with high sensitivity (down to pM concentration). A promising semiconducting material for bio-transduction devices is represented by carbon nanotubes, due to their unique electrical properties, nanosize, bio-compatibility, and their simple low-cost processability. This work provides a comprehensive and critical review of electrolyte-gated carbon nanotube field-effect transistor-based biosensors. First, an introduction to these bio-sensing devices is given. Next, the device configurations and operating principles are presented, and the most used materials and processes are reviewed with a particular focus on carbon nanotubes as the active material. Subsequently, different functionalization strategies reported in the literature, based on enzymes, antibodies, aptamers, and ion-selective membranes, are analyzed critically. Finally, present issues and challenges faced in the area are investigated, the conclusions are drawn, and a perspective outlook over the field of bio-sensing technologies, in general, is provided., Applied Physics Reviews, 8 (4), ISSN:1931-9401

In this work, we realized a flexible electrolyte-gated field-effect transistor (EG-FET) based on a spray-coated semi-conducting single-walled carbon nanotube (SWCNTs) network. The device was functionalized with anti-spermidine antibodies for a specific detection of polyamine spermidine - a well-known chemical indicator of food quality. The spray-coated SWCNTs films were modified with a bifunctional molecule, which binds to the nanotubes via non-covalent π−π interactions and leaves a free NHS-ester group for amide coupling of the antibodies, ensuring controlled immobilization. Transfer and output curves were recorded for device characterization, showing a typical p-type behavior with an on–off ratio of 190 A/A and a threshold voltage around 0 V. The calibration curve of the fabricated EG-FET immunosensor shows a linear detection range for spermidine from 0.001 to 100 nM, with 99.83% coefficient of determination.

In this work, we present a novel flexible amperometric sensor for nitrate detection, based on a silver (Ag) working electrode modified with single-walled carbon nanotubes (SWCNTs) and copper (Cu). A simple and low-cost fabrication technique combining printing and electrochemical deposition was used: after spray deposition of SWCNTs on the screen-printed Ag working electrode, Cu was electrodeposited. The electrochemical performance of our sensors was analyzed and compared to reference sensors fabricated without SWCNTs (Cu/Ag), proving the capability of SWCNTs to improve the sensitivity and the performance of the sensors thanks to the increased electroactive surface area. In fact, the Cu/SWCNTs/Ag sensors showed higher catalytic activity towards the electro-reduction of nitrate (sensitivity: 18.19 µA/mM), as well as a lower limit of detection (LOD: 0.281 nM) in comparison to the Cu/Ag sensors (sensitivity: 12.19 µA/mM and LOD: 0.381 nM). Full sensor functionality after repetitive mechanical bending to 5 mm radius was also proven.

Ochratoxin A (OTA) is one of the most widely known and highly toxic types of mycotoxins, able to contaminate different food products and result in serious health problems for consumers. It is therefore important to detect OTA using fast, simple and reliable techniques. In this work, bendable and stretchable selective OTA biosensors were screen-printed on Polyethylene terephthalate (PET) and Poly(dimethylsiloxane) (PDMS), respectively. The working electrodes (WE) were coated with single-walled carbon nanotubes (SWCNTs) and then immobilized with anti-OTA antibodies. The biosensor showed selectivity to OTA compared to another interfering mycotoxin. Furthermore, they were mechanically stable to 5000 cycles of bending down to 7.5 mm diameter, as well as to 300 iterations of stretching up to 33.5%. The presented biosensors have a linear detection range of 0.01 – 1 ng/mL with a limit of detection (LOD) of 0.08 and 0.13 ng/mL in grape juice for the bendable and stretchable biosensor, respectively. These values are one order of magnitude lower than the maximum allowable limits set by the European Union for both grape juice and wine.

The quest for short channel length transistors is an important challenge in semiconductor industry. A similar trend is observed in the field of flexible electronics where sensor conditioning circuits and transceivers have to be realized on plastic foils. Here the use of a focused Ga+ ion beam (FIB) to structure the channel of a flexible InGaZnO based thin-film transistor (TFT) is presented. The resulting flexible TFT exhibits a channel length of 160 nm and an effective field effect mobility of 4 cm2V-1s-1. Furthermore, the optimized Ga+ beam milling does not damage the underneath Al2O3 gate insulator leading to a gate leakage current of

In this work, we realized a printed immunosensor based on a competitive enzyme-linked immunosorbent assay (ELISA) to allow histamine detection. We investigated the effect of modifying the immunosensor electrodes with spray-deposited poly(3,4-ethyldioxythiophene)poly(styrenesulfunate) (PEDOT:PSS) and single walled carbon nanotube (SWCNT) films. Cyclic voltammetry (CV) was used to characterize the sensor performance in terms of electron transfer kinetics and to prove an enhancement of the electrode active surface area up to 29.1%, due to the use of the additional PEDOT:PSS/SWCNT film. The calibration curve of the so-realized immunosensor (obtained by chronoamperometry measurements) shows a linear detection range of histamine from 0.05 to 50 ng/ml, with 95.03% coefficient of determination.

We present a portable impedance analyzer based on the AD5933 integrated circuit for fruit quality monitoring. The system, custom designed, allows a flexible tuning of parameters (i.e. excitation voltage, feedback resistor, settling time) in order to allow a precise system calibration over a frequency range from 10 Hz to 100 kHz. The employment of Low-Energy Bluetooth and USB communication, together with a micro SD data storage and a rechargeable battery, increases the system portability and its connectivity especially for precision and smart agriculture applications. The system (7.5×2×4cm in volume), runs MicroPython on an STM32 microcontroller and provides 300 mAh Li-Po battery storage with USB recharge. The developed system is validated by comparing it with a bench-top impedance analyzer, using two-terminal measurement, for the specific analysis of tomatoes and bananas, showing an average Root Mean Square Error (RMSE) as low as 0.6% and 4.1%, for impedance magnitude and phase, respectively.