Characterization and Validation of a Platinum Paper-Based Potentiometric Sensor for Glucose Detection in Saliva

Borràs-Brull, M.; Blondeau, P.; Riu, J.
Electroanalysis 2021, 33 (1), 181–187
doi: 10.1002/elan.202060221

A paper-based potentiometric sensor was constructed and characterized for the detection of glucose in saliva. Dilution of the samples was optimized to afford the optimum experimental conditions of measurements. The performance allows for detecting abnormal high glucose concentrations observed in diabetes patients. Repeatability data were presented and the performance of the sensor compared to literature examples showing suitable characteristics at a much lower cost. The validation in real saliva samples was performed against a commercial colorimetric kit showing that glucose could be effectively determined in the 4–10 mM range based on the comparison with a reference method.

Fabrication and Modification of Homemade Paper-Based Electrode Systems

Khan, M. A. R.; Vieira, C. A. C.; Riu, J.; Sales, M. G. F.
Talanta 2021, 224.
doi: 10.1016/j.talanta.2020.121861 

This work reports the simple and inexpensive fabrication of homemade paper-based carbon-printed electrodes (HP C-PEs), aiming to produce an alternative way to generate electrochemical biosensors to all and promoting their wide use. This is especially important in times of pandemics, considering the excellent features of electrochemical biosensing, which may ensure portability, low-cost and quick responses.

A Paper-Based Potentiometric Platform for Determination of Water Hardness

Bouhoun, M. L.; Blondeau, P.; Louafi, Y.; Andrade, F. J.
Chemosensors 2021, 9 (5) 96
Doi: 10.3390/chemosensors9050096

A novel paper-based potentiometric platform for the simple and fast monitoring of water hardness is presented. First, potentiometric ion-selective electrodes for calcium and magnesium printed on a paper substrate were built and optimized. These sensors, which display near-Nernstian sensitivity, were used for the determination of the concentration of these cations and the calculation of the water hardness. Second, the incorporation of a solid-state reference electrode allowed building an integrated paper-based potentiometric cell for the determination of the hardness of artificial and real samples (mineral waters). The validation of the results shows good ability to predict hardness in the conventional scale. Truly decentralized measurements were demonstrated by integration of a miniaturized instrument and dedicated software in a portable device. The measurements were able to be performed in just under two minutes, including a two-point calibration. Since the method is simple to use and cost-effective, it can be implemented in domestic and industrial settings

Simple Approach for Building High Transconductance Paper-Based Organic Electrochemical Transistor (OECT) for Chemical Sensing

Adil Ait Yazza, Pascal Blondeau, Francisco J. Andrade
ACS Applied Electronic Materials 2021, 3 (4), 1886-1895
doi: 10.1021/acsaelm.1c00116

Organic electrochemical transistors (OECTs) have attracted great interest in the last few years as biochemical sensors due to their outstanding analytical performance, versatility, stability, and easiness of fabrication. While thin-film OECTs have been studied extensively, their manufacturing still presents some challenges. This report presents a simple approach for developing OECT using a paper substrate and a thick-film approach that shows outstanding performance. The channel is hand-made by dip pen deposition of the conducting polymer poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS). This allows reproducible channel thickness in the order of 6 μm, well above the conventionally used values. This device displays a high transconductance that exceeds 40 mS and an on-to-off current ratio of 3.8 × 10³ comparable or superior to the state-of-the-art paper-based OECTs. The advantages of this approach are illustrated with the detection of H2O2 and glucose, obtaining sensitivities above 1.5 mA/dec. This simplified approach and high sensitivity may help to extend the use of the OECT-based sensors, particularly in the distributed and point-of need applications.

Paper-based Potentiometric Biosensor for Monitoring Galactose in Whole Blood

Mohamed Bouri, Julio C. Zuaznabar-Gardona, Marta Novell, Pascal Blondeau, Francisco J. Andrade
Electroanalysis 2021, 33(1) 81-89, doi: 10.1002/elan.202060285

A filter paper sputtered with a layer of Pt and subsequently coated with a Nafion® membrane is used as working electrode. The mixed potential of the Pt electrode allows the detection of H2O2 generated by the oxidation of galactose in the presence of the galactose oxidase enzyme. This provides a simple and mediator‐free approach method. The system shows sensitivity values of −62.8±9.4 mV/decade of galactose in the range from 0.3 to 31.6 mM, well within the clinical relevant range. MnO2 nanoparticles were added to decrease the interference from ascorbic acid so that validation of the sensor in whole blood samples was performed with good recovery.

ATR-MIR spectroscopy to predict commercial milk major components: A comparison between a handheld and a benchtop instrument

Gorla, G.; Mestres, M.; Boqué, R.; Riu, J.; Spanu, D.; Giussani, B.
Chemom. Intell. Lab. Syst. 2020, 200.
doi:10.1016/j.chemolab.2020.103995

There is a growing need of measurement technologies that can be used close to the sample source and optical spectroscopy is an excellent example of this genre of technology: from the lab to the field. This study investigates the possibility to quantify the major components and to detect the presence or absence of lactose in commercial milks with ATR-MIR spectroscopy. We explored the possibility to use a portable and economical ATR-MIR instrument, comparing the results with a benchtop system. Commercial milk samples from Italy, Switzerland and Spain were chosen covering the maximum range of variation for protein, carbohydrate and fat content. The analytical protocol was optimized to make it as fast and useable as possible for both instruments, from the sample pretreatment to the instrumental parameters. Multivariate calibration was used to correlate the recorded spectra to the content of the major milk components, while a classification was done in order to classify samples with or without lactose. A comparison was performed between the predictive capabilities of the models built with different data pretreatments, different variable selection methods and different validation systems to obtain the best results and to assure robust models.

Rapid analysis of milk using low-cost pocket-size NIR spectrometers and multivariate analysis

J. Riu, G. Gorla, D. Chakif, R. Boqué, B. Giussani, Foods, 2020, 9
doi: 10.3390/foods9081090

The miniaturisation of analytical devices, reduction of analytical data acquisition time, or the reduction of waste generation throughout the analytical process are important requirements of modern analytical chemistry, and in particular of green analytical chemistry. Green analytical chemistry has fostered the development of a new generation of miniaturized near-infrared spectroscopy (NIR) spectrometric systems. However, one of the drawbacks of these systems is the need for a compromise between the performance parameters (accuracy and sensitivity) and the aforementioned requirements of green analytical chemistry. In this paper, we evaluated the capabilities of two recently developed portable NIR instruments (SCiO and NeoSpectra) to achieve a rapid, simple and low-cost quantitative determination of commercial milk macronutrients. Commercial milk samples from Italy, Switzerland and Spain were chosen, covering the maximum range of variability in protein, carbohydrate and fat content, and multivariate calibration was used to correlate the recorded spectra with the macronutrient content of milk. Both SCiO and NeoSpectra can provide a fast and reliable analysis of fats in commercial milk, and they are able to correctly classify milk according to fat level. SCiO can also provide predictions of protein content and classification according to presence or absence of lactose.

Electrochemical biosensors for the detection of pathogenic bacteria in food

J. Riu, B. Giussani
TrAC – Trends in Analytical Chemistry, 2020, 126
doi: 10.1016/j.trac.2020.115863

Biosensors for the detection of pathogenic bacteria in food are a promising alternative to conventional methods of analysis. This review focuses on the electrochemical biosensors reported in recent years for use with food samples. It highlights the performance parameters of these sensors, and provides a critical discussion of current and future trends, including future commercialization.

Modulating the mixed potential for developing biosensors: Direct potentiometric determination of glucose in whole, undiluted blood

Cánovas, R., Blondeau, P., Andrade, F.J.
Biosensors and Bioelectronics 2020, 163 article number 112302. Doi: 10.1016/j.bios.2020.112302

This work presents a novel strategy to control the mixed potential that allows the development of a potentiometric biosensor for the direct detection of glucose in whole, undiluted blood without any sample pretreatment. The accurate measurement of blood sugar levels in a single drop of whole blood with excellent recovery is presented.