Microneedle based electrochemical (bio)sensing: towards decentralized and continuous health status monitoring

Microneedle (MN) based electrochemical (bio)sensing has become a growing field within the discipline of analytical chemistry as a result of its unique capacity for continuous, decentralized health status monitoring. There are two significant advantages to this exclusive feature: i) the ability to directly analyze interstitial fluid (ISF), a body fluid with a similar enough composition to plasma (and blood) to be considered a plentiful source of information related to biologically relevant molecules and biomarkers; and ii) the capacity to overcome some of the major limitations of blood analysis including painful extraction, high interferant concentrations, and incompatibility with diagnosis of infants (and especially newborns). Recent publications have demonstrated important advancements in electrochemical MN sensor technology, among which are included new MN fabrication methods and various modification strategies, providing different architectures and allowing for the integration of electronics. This versatility highlights the undeniable need for interdisciplinary efforts towards tangible progress in the field. In a context evidently dominated by glucose sensing, which is slowly being expanded towards other analytes, the following crucial questions arise: to what extent are electrochemical MN (bio)sensors a reliable analytical tool for continuous ISF monitoring? Which is the best calibration protocol to be followed for in vivo assays? Which strategies can be employed to protect the sensing element during skin penetration? Is there an appropriate validation methodology to assess the accuracy of electrochemical MN (bio)sensors? How significant is the distinction between successful achievements in the laboratory and the real commercial feasibility of products? This paper aims to reflect on those previous questions while reviewing the progress of electrochemical MN (bio)sensors in the last decade with a focus on the analytical aspects. Overall, we describe the current state of electrochemical MN (bio)sensors, the benefits and challenges associated to ISF monitoring, as well as key features (and bottlenecks) regarding its implementation for in vivo assays

Toward in vivo transdermal pH sensing with a validated microneedle membrane electrode

We present herein the most complete characterization of microneedle (MN) potentiometric sensors for pH transdermal measurements for the time being. Initial in vitro assessment demonstrated suitable analytical performances (e.g., Nernstian slope, linear range of response from 8.5 to 5.0, and fast response time) in both buffer media and artificial interstitial fluid (ISF). Excellent repeatability and reproducibility together with adequate selectivity and resiliency facilitate the appropriateness of the new pH MN sensor for transdermal ISF analysis in healthcare. The ability to resist skin insertions was evaluated in several ex vivo setups using three different animal skins (i.e., chicken, pork, and rat). The developed pH MN sensor was able to withstand from 5 to 10 repetitive insertions in all the skins considered with a minimal change in the calibration graph (<3% variation in both slope and intercept after the insertions). Ex vivo pH measurements were validated by determining the pH with the MN sensor and a commercial pH electrode in chicken skin portions previously conditioned at several pH values, obtaining excellent results with an accuracy of <1% and a precision of <2% in all cases. Finally, pH MN sensors were applied for the very first time to transdermal measurements in rats together with two innovative validation procedures: (i) measuring subcutaneous pH directly with a commercial pH microelectrode and (ii) collecting ISF using hollow MNs and then the pH measurement of the sample with the pH microelectrode. The pH values obtained with pH MN sensors were statistically more similar to subcutaneous measurements, as inferred by a paired sample t-test at 95% of confidence level. Conveniently, the validation approaches could be translated to other analytes that are transdermally measured with MN sensors

E-Tongues/Noses Based on Conducting Polymers and Composite Materials: Expanding the Possibilities in Complex Analytical Sensing

Conducting polymers (CPs) are extensively studied due to their high versatility and electrical properties, as well as their high environmental stability. Based on the above, their applications as electronic devices are promoted and constitute an interesting matter of research. This review summa- rizes their application in common electronic devices and their implementation in electronic tongues and noses systems (E-tongues and E-noses, respectively). The monitoring of diverse factors with these devices by multivariate calibration methods for different applications is also included. Lastly, a critical discussion about the enclosed analytical potential of several conducting polymer-based devices in electronic systems reported in literature will be offered

DENSIDAD POBLACIONAL E HISTORIA NATURAL DEL PAVO DE CACHO (OREOPHASIS DERBIANUS) EN LA RESERVA DE BIOSFERA SIERRA DE LAS MINAS, GUATEMALA

Resumen ∙ El Pavo de Cacho (Oreophasis derbianus) es una especie de crácido críticamente amenazada y endémica de México y Guatemala; sin embargo, su tamaño poblacional ha sido pobremente documentado en la mayor parte de su distribución. Se estimó su densidad poblacional en la Sierra de las Minas, Guatemala, mediante detecciones visuales y auditivas obtenidas durante el recorrido de trayectos lineales, con base en la teoría del muestreo de distancias. Tres trayectos (8 km de longitud total) fueron recorridos mensualmente para obtener un esfuerzo de muestreo de 72 km, de abril a diciembre de 2009. Los trayectos se ubicaron en el bosque nuboso y latifoliado de la zona núcleo “Las Cabañas” de la Reserva de Biosfera Sierra de las Minas, en la localidad de Albores, departamento de El Progreso, Guatemala. La densidad poblacional estimada fue de 3,04 ± 1,16 (± EE) ind/km². Esta densidad fue comparada con otras estimaciones en diferentes áreas de la distribución de la especie en México y Guatemala. La distribución de las estimaciones de densidad parece ajustarse a un patrón biogeográfico en donde una mayor densidad poblacional se encuentra al centro de la distribución geográfica de la especie, disminuyendo hacia la periferia. Si este es el caso, esto podría tener importantes implicaciones en la definición de estrategias para la conservación de la especie. Sin embargo, factores de perturbación humana como la cacería y captura también podrían ser la causa de la diferencia en las densidades poblacionales entre los sitios comparados. La mayoría de las detecciones ocurrieron en junio, mientras que una hembra y sus dos pollos fueron observados en agosto. Se observó que el Pavo de Cacho utilizó 22 especies de plantas en el área de estudio para alimentarse, vocalizar o posarse, de las cuales tres (Passiflora membranaceae, Prunus barbata y Oreopanax hederaceum) fueron nuevos registros en su dieta. Se reporta actividad de cacería en la zona núcleo del área protegida, lo que representa una amenaza para la viabilidad de esta población. Estudios sobre presión de cacería, requerimientos de hábitat, patrones de movimiento y variabilidad genética del Pavo de Cacho son clave para comprender a fondo su biología y establecer medidas de conservación adecuadas.Abstract ∙ Population density and natural history of the Horned Guan (Oreophasis derbianus) in the Sierra de las Minas Biosphere Reserve, Guatemala The Horned Guan (Oreophasis derbianus) is a critically endangered cracid species endemic to Mexico and Guatemala; nevertheless, its population size has been poorly documented throughout most of its distributional range. In the Sierra de las Minas, Guatemala, population density was estimated by visual and acoustic surveys in line transects, based on the distance sampling theory. Three transects (8 km total length) located in the cloud and mixed forest at "Las Cabañas" core area of the Sierra de las Minas Biosphere Reserve in the Albores locality, Department of El Progreso were monthly surveyed to total up 72 km of sampling effort from April to December 2009. Estimated population density was 3.04 ± 1.16 (± SE) ind/km², which was compared with other density estimates from different areas within the species distribution in Mexico and Guatemala. The distribution of density estimates seems to fit a biogeographic pattern where higher population densities are found at the center of the species distributional range tending to decrease towards the periphery. If this is the case, it may have important implications in the definition of the species conservation strategies. Nevertheless, human impacts, such as hunting and poaching, could also be the cause of differences in population density among sites. Most of the detections occurred in June, and a female with two chicks was observed in August. The Horned Guan was observed to use 22 plant species in the study area for feeding, vocalizing, and perching, of which three (Passiflora membranaceae, Prunus barbata, and Oreopanax hederaceum) were new records as food items. Hunting activity is reported within the core zone of the protected area, threating the viability of this population. Research on hunting pressure, habitat requirements, movement patterns, and genetic variability are key to further understand the biology of the Horned Guan and to establish appropriate conservation measures

Fast Analysis of Caffeic Acid-Related Molecules in Instant Coffee by Reusable Sonogel–Carbon Electrodes

Reusable Sonogel–Carbon electrodes containing carbon black (SNGC-CB) have been used for the electrochemical analysis of caffeic acid (CA) in real matrices. Measurements were firstly performed in standard solutions, in which SNGC-CB electrodes allowed the electrochemical determination of CA with high sensitivity and low limit of detection, equal to 0.76 μM. The presence of CB nanostructures in the formulation led to improved performances with respect to pristine SNGC electrodes. Then, measurements were performed in four instant coffees of different brands. A comparison between the results obtained by electrochemical, chromatographic and spectroscopic methods showed that SBGC-CB electrodes represent a simple and economic tool for the rapid assessment of caffeic acid-related molecules in instant coffees

What Is Left for Real-Life Lactate Monitoring? Current Advances in Electrochemical Lactate (Bio)Sensors for Agrifood and Biomedical Applications

Monitoring of lactate is spreading from the evident clinical environment, where its role as a biomarker is notorious, to the agrifood ambit as well. In the former, lactate concentration can serve as a useful indicator of several diseases (e.g., tumour development and lactic acidosis) and a relevant value in sports performance for athletes, among others. In the latter, the spotlight is placed on the food control, bringing to the table meaningful information such as decaying product detection and stress monitoring of species. No matter what purpose is involved, electrochemical (bio)sensors stand as a solid and suitable choice. However, for the time being, this statement seems to be true only for discrete measurements. The reality exposes that real and continuous lactate monitoring is still a troublesome goal. In this review, a critical overview of electrochemical lactate (bio)sensors for clinical and agrifood situations is performed. Additionally, the transduction possibilities and different sensor designs approaches are also discussed. The main aim is to reflect the current state of the art and to indicate relevant advances (and bottlenecks) to keep in mind for further development and the final achievement of this highly worthy objective

Incorporation of carbon black into a sonogel matrix: improving antifouling properties of a conducting polymer ceramic nanocomposite

A new electrochemical sensor device has been developed through the modification of a polyaniline-silicon oxide network with carbon black (CB). Enhanced electrical conductivity and antifouling properties have been achieved due to the integra- tion of this cheap nanomaterial into the bulk of the sensor. The structure of the developed material was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy tech- niques. Cyclic voltammetry was used to characterize electrochemically the Sonogel-Carbon/Carbon Black-PANI (SNG-C/ CB-PANI) sensor device. In addition, differential pulse voltammetry was employed to evaluate the analytical response of the sensor towards sundry chlorophenols, common environmental hazards in aqueous ecosystems. The modified sensor material showed excellent antifouling properties, which led to a better electroanalytical performance than the one displayed with the bare sensor. Notably, a sensitivity of 5.48 × 103 μA mM−1 cm−2 and a limit of detection of 0.83 μM were obtained in the determination of 4-chloro-3-methylphenol (PCMC) at a working potential of 0.78 V (vs. 3 M Ag/AgCl/KCl), along with proficient values of reproducibility and repeatability (relative standard deviation < 3%). Finally, the analysis of PCMC was carried out in multiple validated water samples using the synthesized SNG-C/CB-PANI sensor device, obtaining excellent results of recovery values (97–104%). The synergetic effect of polyaniline and carbon black leads to novel antifouling and electrocatalytic effects that improve the applicability of this sensor in sample analysis versus complex conventional devices

Rapid extraction and detection of ellagic acid in plant samples using a selective magnetic molecularly imprinted polymer coupled to a fluorescence method

A remarkable growth was noticed in the development of molecularly imprinted polymers (MIPs), which have used as efficient synthetic antibodies that contain selective cavities to the target molecule. Hereunder, a novel strategy using MIP as a sorbent in solid-phase extraction was coupled to a fluorescence method for ellagic acid (EA) purification and immediate detection. The synthesis of magnetic-MIP (MMIP) using a rapid and green ultrasound technology was assessed by central composite design to determine the optimal polymerization conditions for a high-imprinting polymer. The MMIP was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning/transmission electron microscopy, which accurately confirmed the functional, magnetic, and morphological features of MMIP. The prepared MMIP was demonstrated to be selective for EA compared to many similar phenols. The spectrofluorometric method showed a linear range from 0.05 to 2 μg·mL−1 of EA, and the limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.02 μg·mL−1, respectively. Besides, the novel proposed smartphone method using the ultraviolet lamp as the excitation source presented a linear range from 0.2 to 4 μg·mL−1, a LOQ of 0.2 μg·mL−1, and a LOD of 0.07 μg.mL−1. The proposed strategy revealed high efficiency in the extraction and detection of EA in grape, redberry, and green tea. Effectively, the calculated recoveries were ranging from 80 to 102% with low values of relative standard deviation ([removed]10 página

Production of HCl and LiOH from Lithium-ion Batteries Leaching Solution by Electrodialysis.

In this work, electrodialysis is proposed to produce HCl and LiOH from a LIBs leaching solution after metals precipitation. The experimental consists of an electrodialytic cell with four compartments divided by two cation exchange membranes (CEM) and one anion exchange membrane (AEM) arranged alternatively between the anode and cathode. The cell configuration results in the generation of an acidic and alkaline stream on both compartment sides of the feed compartment, which was allocated in the third compartment between the AEM and 2nd CEM. The application of an electrical current between the electrodes promotes the mobilization, on one hand of anions from the feed compartment through the AEM to the acid compartment, and on the other hand, of cations through the CEM to the alkaline channel. Both, acidic and alkaline compartment, were electrically balanced by H+ and OH- generated by water oxidation (anode) and reduction (cathode). Experiments were carried out using a feed solution composed of lithium (0.8M) and chloride ions (0.8M) with an initial pH of 7. That solution simulated the final solution once metals from LIBs were extracted using HCl (explain the presence of Cl- in the solution) and separated by precipitation (except Li+). Different parameters such as current density, compartment size and initial feed concentration were studied. Results indicate that the electrodialytic method could be a useful technique not only for concentrate LiOH, but also to generate HCl and LiOH stream that can be reuse for the extraction and precipitation steps, respectively, in the LIBs recycling process.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech