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The determination of thyroid hormones has practical clinical significance for the diagnosis of hyperthyroidism and hypothyroidism diseases. Considering this aspect, a wide range of analytical methods for the detection of analytes, including immunoassay, chemiluminescence, mass spectroscopy and high-performance liquid chromatography, among others, has been developed. This type of analysis provides feasible results. Nevertheless, it requires qualified staff, special facilities and is time-consuming. For this reason, this paper relies on the fabrication of an electrochemical device developed with inkjet printing technology for the free detection of Thyroxine (T4). To manufacture our electrochemical device, several aspects were considered from the use of materials that amplify electrical signals, to finding a supramolecular scaffold that possess affinity towards the target analyte and the need of preconcentrating the analyte on the electrode’s surface. For this task, printed devices were modified with a hybrid nanomaterial consisting of reduced graphene oxide (rGO) tuned with Au nanoparticles (Au–NPs) and an entrapment agent and different thiolated cyclodextrins (x–CD-SH) as carrying agents. Analytes were preconcentrated via supramolecular chemistry due to the formation of an inclusion complex between the cyclodextrin and hormones. Morphological and electrochemical characterization of the final device was carried out to ensure the proper workability of the electrode, achieving excellent response, sensitivity and limit of detection (LOD).

In this work, the stability, electrical conductivity, and versatility of graphite-based inks were taken advantage of to fabricate a nitrate potentiometric sensor. One other key property that was exploited for the design of an ion-selective electrode was the hydrophobicity of graphite. This prevented the formation of a water layer between the solid contact and the polymeric selective membrane. Moreover, given the use of printing technologies for electrode fabrication, it was possible to easily miniaturize the sensors and achieve lower fabrication costs. In this article, a printed sensor, composed of a graphite working electrode and a Ag/AgCl reference electrode, is presented and thoroughly characterized. The working electrode was modified with a well-known PVC-ionophore membrane, and the reference electrode was protected with a PVB-NaCl saturated membrane. It showed almost-Nernstian sensitivity of −(55.4 ± 0.7) mV/dec to NO3−, stability of up to 25 days of operation, limit of detection of 0.204 ± 0.009 mM, and repeatability of 99.02 % (N = 3). Coupled with its high selectivity compared with other anions, this low-cost, mass-producible sensor is a great alternative for environmental and industrial applications.

Pòster amb el resum gràfic de la tesi doctoral en curs, que forma part de l'exposició "Doctorat en Recursos Naturals i Medi Ambient de la UPC Manresa. 30 anys formant en recerca a la Catalunya Central 1992-2022"., The authors acknowledge the Spanish Government, through the project RTI2018-099362-B-C21 MINECO/FEDER, EU, for the financial support provided to perform this research., Postprint (published version)

pH sensing for healthcare applications requires sensors with mechanically stable materials of high sensitivity and high reproducibility combined with low-cost fabrication technologies. This work proposes a fully printed pH sensor based on a specially formulated conducting polymer deposited on a microelectrode in a flexible substrate. A formulation, which combined polyaniline (PANI) and polypyrrole (PPy) with integrated polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS), was specially prepared to be printed by inkjet printing (IJP). The sensor has good sensitivity in the physiological region (pH 7-7.5) key for the healthcare biosensor. This mixture printed over a commercial gold ink, which has a singular chemical functionalization with phthalocyanine (Pc), increased the sensor sensitivity, showing an excellent reproducibility with a linear super-Nernstian response (81.2 ± 0.5 mV/pH unit) in a wide pH range (pH 3-10). This new ink together with the IJP low-cost technique opens new opportunities for pH sensing in the healthcare field with a single device, which is disposable, highly sensitive, and stable in the whole pH range.

Disposar de molts dispositius per a la medicina o el medi ambient a un preu assequible requereix noves tecnologies que ho facilitin, com l'electrònica impresa. En concret, l'estudi següent s'ha centrat a obtenir, per mitjà de la tècnica d'injecció de tinta, d'una banda, un elèctrode de referència d'estat sòlid. D'altra banda, una membrana protectora per evitar que, amb el temps, l'elèctrode quedi obsolet., Disponer de muchos dispositivos para la medicina o el medio ambiente a un precio asequible requiere nuevas tecnologías que lo faciliten, como la electrónica impresa. En concreto, el estudio siguiente se ha centrado en obtener, mediante la técnica de inyección de tinta, por un lado, un electrodo de referencia de estado sólido. Por otra parte, una membrana protectora para evitar que, con el tiempo, el electrodo quede obsoleto., New technologies are required in order to obtain many devices for medicine or the environment at an affordable price, such as printed electronics. Specifically, this study is focused on obtaining, through the inkjet printing technique of a solid-state reference electrode. In addition, a protective membrane to prevent the electrode from becoming obsolete over time is developed.

Developing new standardized tools to characterize brain recording devices is critical to evaluate neural probes and for translation to clinical use. The signal-to-noise ratio (SNR) measurement is the gold standard for quantifying the performance of brain recording devices. Given the drawbacks with the SNR measure, our first objective was to devise a new method to calculate the SNR of neural signals to distinguish signal from noise. Our second objective was to apply this new SNR method to evaluate electrodes of three different materials (platinum black, Pt; carbon nanotubes, CNTs; and gold, Au) co-localized in tritrodes to record from the same cortical area using specifically designed multielectrode arrays. Hence, we devised an approach to calculate SNR at different frequencies based on the features of cortical slow oscillations (SO). Since SO consist in the alternation of silent periods (Down states) and active periods (Up states) of neuronal activity, we used these as noise and signal, respectively. The spectral SNR was computed as the power spectral density (PSD) of Up states (signal) divided by the PSD of Down states (noise). We found that Pt and CNTs electrodes have better recording performance than Au electrodes for the explored frequency range (5-1500 Hz). Together with two proposed SNR estimators for the lower and upper frequency limits, these results substantiate our SNR calculation at different frequency bands. Our results provide a new validated SNR measure that provides rich information of the performance of recording devices at different brain activity frequency bands (<1500 Hz).