Bioelectronic tongue for the simultaneous determination of urea, creatinine and alkaline ions in clinical samples

A paper-based organic electrochemical transistor array with a simplified configuration for simultaneous multi-ion detection

In recent years, organic electrochemical transistors (OECTs) have emerged as a promising tool to add to current analytical methods due to their high-amplification capacities, robust analytical performance, and versatility. The present work proposes a compact multi-analyte transistor array with outstanding analytical performance. The ion-selective organic electrochemical transistors (IS-OECTs) were developed by combining the thick-film technology with the optimum ion-selective membrane, resulting in highly sensitive and selective IS-OECTs. The system has then been simplified using only a power supply for each OECT and a single gate electrode. To prove these advantages, the IS-OECT array of sensors has been combined with multivariate models to simultaneously detect and quantify sodium, potassium and ammonium ions in human saliva. The results obtained have been validated against reference techniques, showing promising results and confirming the usefulness of the newly developed sensing array.

Multisensor Systems and Arrays for Medical Applications Employing Naturally-Occurring Compounds and Materials

The significant improvement of quality of life achieved over the last decades has stimulated the development of new approaches in medicine to take into account the personal needs of each patient. Precision medicine, providing healthcare customization, opens new horizons in the diagnosis, treatment and prevention of numerous diseases. As a consequence, there is a growing demand for novel analytical devices and methods capable of addressing the challenges of precision medicine. For example, various types of sensors or their arrays are highly suitable for simultaneous monitoring of multiple analytes in complex biological media in order to obtain more information about the health status of a patient or to follow the treatment process. Besides, the development of sustainable sensors based on natural chemicals allows reducing their environmental impact. This review is concerned with the application of such analytical platforms in various areas of medicine: analysis of body fluids, wearable sensors, drug manufacturing and screening. The importance and role of naturally-occurring compounds in the development of electrochemical multisensor systems and arrays are discussed.

Voltammetric analysis for distinguishing portal hypertension-related from malignancy-related ascites: A proof of concept study

Background

Serum-ascites albumin gradient (SAAG) remains the most sensitive and specific marker for the differentiation of ascites due to portal hypertension from ascites due to other causes. SAAG has some limitations and may fail in selected conditions. Voltammetric analysis (VA) has been used for the detection of electroactive species of biological significance and has proven effective for detection infections in biological fluids.

Aims

In this study, we compared the accuracy of voltammetric analysis (VA) with that of SAAG to differentiate ascites due to portal hypertension from that having a different origin.

Methods

80 ascites samples were obtained from patients undergoing paracentesis at the Campus Bio-Medico Hospital of Rome. VA was performed using the BIONOTE device. The ability of VA to discriminate ascitic fluid etiology and biochemical parameters was evaluated using Partial Least Square Discriminant Analysis (PLS-DA), with ten-fold cross-validations.

Results

Mean age was 68.6 years (SD 12.5), 58% were male. Ascites was secondary to only portal hypertension in 72.5% of cases (58 subjects) and it was secondary to a baseline neoplastic disease in 27.5% of cases (22 subjects). Compared to SAAG≥1.1, e-tongue predicted ascites from portal hypertension with a better accuracy (92.5% Vs 87.5%); sensitivity (98.3% Vs 94.8%); specificity (77.3% Vs 68.2%); predictive values (PPV 91.9% Vs 88.7% and NPV 94.4% Vs 83.3%). VA correctly classified ascites etiology in 57/58 (98.2%) of cases with portal hypertension and in 17/22 (77.2%) of cases with malignancy. Instead, VA showed poor predictive capacities towards total white blood count and polymorphonuclear cell count.

Conclusions

According to this proof of concept study, VA qualifies as a promising low-cost and easy method to discriminate between ascites secondary to portal hypertension and ascites due to malignancy.

Electronic Tongues for Inedible Media

“Electronic tongues”, “taste sensors”, and similar devices (further named as “multisensor systems”, or MSS) have been studied and applied mostly for the analysis of edible analytes. This is not surprising, since the MSS development was sometimes inspired by the mainstream idea that they could substitute human gustatory tests. However, the basic principle behind multisensor systems—a combination of an array of cross-sensitive chemical sensors for liquid analysis and a machine learning engine for multivariate data processing—does not imply any limitations on the application of such systems for the analysis of inedible media. This review deals with the numerous MSS applications for the analysis of inedible analytes, among other things, for agricultural and medical purposes.

Advances in the Detection, Mechanism and Therapy of Chronic Kidney Disease

Chronic Kidney Disease (CKD) is characterized by the gradual loss of renal mass and functions. It has become a global health problem, with hundreds of millions of people being affected. Both its incidence and prevalence are increasing over time. More than $20,000 are spent on each patient per year. The economic burden on the patients, as well as the society, is heavy and their life quality worsen over time. However, there are still limited effective therapeutic strategies for CKD. Patients mainly rely on dialysis and renal transplantation, which cannot prevent all the complications of CKD. Great efforts are needed in understanding the nature of CKD progression as well as developing effective therapeutic methods, including pharmacological agents. This paper reviews three aspects in the research of CKD that may show great interests to those who devote to bioanalysis, biomedicine and drug development, including important endogenous biomarkers quantification, mechanisms underlying CKD progression and current status of CKD therapy.

Biosensing methods for determination of creatinine: A review

Creatinine is a metabolic product of creatine phosphate in muscles, which provides energy to muscle tissues. Creatinine has been considered as indicator of renal function specifically after dialysis, thyroid malfunction and muscle damage. The normal level of creatinine in the serum and its excretion through urine in apparently healthy individuals is 45-140 μM and 0.8-2.0 gm/day respectively. The level of creatinine reaches >1000 μM in serum during renal, thyroid and kidney dysfunction or muscle disorder. A number of conventional methods such as colorimetric, spectrophotometric and chromatographic are available for determination of creatinine. Besides the advantages of being highly sensitive and selective, these methods have some drawbacks like time-consuming, requirement of sample pre-treatment, high cost instrumental set-up and skilled persons to operate. The sensors/biosensors overcome these drawbacks, as these are fast, easy, cost effective and highly sensitive. This review article describes the classification, operating principles, merits and demerits of various creatinine sensors/biosensors, specifically nanomaterials based biosensors. Creatinine biosensors work optimally within 2-900 s, potential range 0.1-1.0 V, pH range 4.0-10.0, temperature range 25-35 °C and had linear range, 0.004-30000 µM for creatinine with the detection limit between 0.01.01 µM and 520 µM. These biosensors measured creatinine level in sera and urine samples and had storage stability between 4 and 390 days, while being stored dry at 4 °C. The future perspective for further improvement and commercialization of creatinine biosensors are discussed.

Determination of urea with special emphasis on biosensors: A review

Urea is the major end product of nitrogen metabolism in humans, which is eliminated from the body mainly by the kidneys through urine but is also secreted in body fluids such as blood and saliva. Its level in urine ranges from 7 to 20 mg/dL, which drastically rises under patho-physiological conditions thus providing key information of renal function and diagnosis of various kidney and liver disorders. Increase in urea levels in blood, also referred to as azotemia or uremia. The chronic kidney disease (CKD) or end stage renal disease (ESRD) is generally caused due to the progressive loss of kidney function. Hence, there is an urgent need of determination of urea in biological fluids to diagnose these diseases at their early stage. Among the various methods available for detection of urea, most are complicated and require time-consuming sample pre-treatment, expensive instrumental set-up and trained persons to operate, specifically for chromatographic methods. The biosensing methods overcome these drawbacks, as these are simple, fast, specific and highly sensitive and can also be applied for detection of urea in vivo. This review presents the principles of various analytical methods for determination of urea with special emphasis on biosensors. The use of various nanostructures and electrochemical microfluidic paper based analytical device (EμPAD) are suggested for further development of urea biosensors.

Michael Addition Based Chemodosimeter for Serum Creatinine Detection Using ( E)-3-(Pyren-2-yl)-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one Chalcone

First, a simple and highly emissive fluorescent chalcone ( E)-3-(pyren-2-yl)-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one (PTP) was synthesized via simple shaking along with an excellent quantum yield of 0.85, and proved as a stable, highly sensitive, and selective biosensor for creatinine. Owing to its unique photophysical interaction with creatinine through Michael adduct formation, PTP was utilized as a Chemodosimeter for the selective recognition of creatinine in blood serum. Under optimized conditions, a broad range of creatinine detection was achieved  from 0.00000113 mg/dL to 15.8 mg/dL along with an excellent limit of detection of 0.00000065 mg/dL (0.058 nM). This biosensor is highly reproducible even for different concentration levels of creatinine. It is the very first creatinine biosensor possessing a wider linear range for clinical applications for creatinine. To ensure its clinical application, blood serum samples of people of different age groups were collected from Alpha Hospital and analyzed for creatinine by using our chemodosimeter method and compared with data obtained using a commercial method in the Alpha hospital. Our data show very good agreement with clinical data. Because clinical protocol involves trienzymes and tedious sample preparation, no doubt, our chemodosimeter will be a cheap and sensitive option compared to the existing clinical methods.

Voltammetric analysis for fast and inexpensive diagnosis of urinary tract infection: a diagnostic study

BACKGROUND

Dipstick test is widely used to support the diagnosis of urinary tract infections (UTI). It is effective in ruling out UTI, but urine culture is needed for diagnosis confirmation. In this study we compared the accuracy of voltammetric analysis (VA) with that of DT to detect UTI (diagnosed using urine culture), and its usefulness as a second-stage test in people with positive DT.

METHODS

142 patients were enrolled with no exclusion criteria. VA was performed using the BIONOTE device. Partial Least Square Discrimination Analysis was used to predict UTI based on VA data; diagnostic performance was evaluated using sensitivity, specificity, positive and negative predictive values (PPV and NPV, respectively), positive and negative likelihood ratios (LR), accuracy, diagnostic odds ratio (DOR).

RESULTS

Mean age was 76.6 years (SD 12.6), 57% were male. VA had a better overall performance respect to DT in detecting UTI with accuracy 81.7% vs 75.9%, specificity 90.8% vs 82.5%, PPV 75% vs 61.4%, positive LR 6.68 vs 3.5, DOR 17.7 vs 7.47; sensibility, NPV and negative LR of the two tests were similar. VA had an accuracy of 82.4% in discriminating bacterial from fungal infections. When added as a second-stage test, VA identified 9 of the 17 false positive patients, with a net specificity of 91.7%, sensitivity 54%, PPV 75% and NPV 81%.

CONCLUSIONS

VA is a quick and easy method that may be used as a second stage after DT to reduce the number of urine culture and of inappropriate antibiotic prescriptions.

Prediction of wastewater quality using amperometric bioelectronic tongues

Wastewater samples from a Swedish chemi-thermo-mechanical pulp (CTMP) mill collected at different purification stages in a wastewater treatment plant (WWTP) were analyzed with an amperometric enzyme-based biosensor array in a flow-injection system. In order to resolve the complex composition of the wastewater, the array consists of several sensing elements which yield a multidimensional response. We used principal component analysis (PCA) to decompose the array's responses, and found that wastewater with different degrees of pollution can be differentiated. With the help of partial least squares regression (PLS-R), we could link the sensor responses to the Microtox® toxicity parameter, as well as to global organic pollution parameters (COD, BOD, and TOC). From investigating the influences of individual sensors in the array, it was found that the best models were in most cases obtained when all sensors in the array were included in the PLS-R model. We find that fast simultaneous determination of several global environmental parameters characterizing wastewaters is possible with this kind of biosensor array, in particular because of the link between the sensor responses and the biological effect onto the ecosystem into which the wastewater would be released. In conjunction with multivariate data analysis tools, there is strong potential to reduce the total time until a result is yielded from days to a few minutes.

A novel bio-electronic tongue using different cellobiose dehydrogenases to resolve mixtures of various sugars and interfering analytes

A novel application of cellobiose dehydrogenase (CDH) as sensing element for a Bioelectronic Tongue (BioET) system has been tested. In this work CDHs from various fungi, which exhibit different substrate specificities, were used to discriminate between lactose and glucose in presence of the interfering matrix compound Ca(2+) in various mixtures. This work exploits the advantage of an electronic tongue system with practically zero pre-treatment of samples and operation at low voltages in a direct electron transfer mode. The Artificial Neural Network (ANN) used in the BioET system to interpret the voltammetric data was able to provide a correct prediction of the concentrations of the analytes considered. Correlation coefficients in the comparison of obtained vs. expected concentrations were highly significant, especially for lactose (R(2)=0.975) and Ca(2+) (R(2)=0.945). This BioET application has a high potential especially for the food and dairy industry and also, if further miniaturised in screen printed format, for its in-situ use.

Discrimination of Rice with Different Pretreatment Methods by Using a Voltammetric Electronic Tongue

In this study, an application of a voltammetric electronic tongue for discrimination and prediction of different varieties of rice was investigated. Different pretreatment methods were selected, which were subsequently used for the discrimination of different varieties of rice and prediction of unknown rice samples. To this aim, a voltammetric array of sensors based on metallic electrodes was used as the sensing part. The different samples were analyzed by cyclic voltammetry with two sample-pretreatment methods. Discriminant Factorial Analysis was used to visualize the different categories of rice samples; however, radial basis function (RBF) artificial neural network with leave-one-out cross-validation method was employed for prediction modeling. The collected signal data were first compressed employing fast Fourier transform (FFT) and then significant features were extracted from the voltammetric signals. The experimental results indicated that the sample solutions obtained by the non-crushed pretreatment method could efficiently meet the effect of discrimination and recognition. The satisfactory prediction results of voltammetric electronic tongue based on RBF artificial neural network were obtained with less than five-fold dilution of the sample solution. The main objective of this study was to develop primary research on the application of an electronic tongue system for the discrimination and prediction of solid foods and provide an objective assessment tool for the food industry.

Multidimensional mapping method using an arrayed sensing system for cross-reactivity screening

When measuring chemical information in biological fluids, challenges of cross-reactivity arise, especially in sensing applications where no biological recognition elements exist. An understanding of the cross-reactions involved in these complex matrices is necessary to guide the design of appropriate sensing systems. This work presents a methodology for investigating cross-reactions in complex fluids. First, a systematic screening of matrix components is demonstrated in buffer-based solutions. Second, to account for the effect of the simultaneous presence of these species in complex samples, the responses of buffer-based simulated mixtures of these species were characterized using an arrayed sensing system. We demonstrate that the sensor array, consisting of electrochemical sensors with varying input parameters, generated differential responses that provide synergistic information of sample. By mapping the sensing array response onto multidimensional heat maps, characteristic signatures were compared across sensors in the array and across different matrices. Lastly, the arrayed sensing system was applied to complex biological samples to discern and match characteristic signatures between the simulated mixtures and the complex sample responses. As an example, this methodology was applied to screen interfering species relevant to the application of schizophrenia management. Specifically, blood serum measurement of antipsychotic clozapine and antioxidant species can provide useful information regarding therapeutic efficacy and psychiatric symptoms. This work proposes an investigational tool that can guide multi-analyte sensor design, chemometric modeling and biomarker discovery.

Determination of urine ionic composition with potentiometric multisensor system

The ionic composition of urine is a good indicator of patient's general condition and allows for diagnostics of certain medical problems such as e.g., urolithiasis. Due to environmental factors and malnutrition the number of registered urinary tract cases continuously increases. Most of the methods currently used for urine analysis are expensive, quite laborious and require skilled personnel. The present work deals with feasibility study of potentiometric multisensor system of 18 ion-selective and cross-sensitive sensors as an analytical tool for determination of urine ionic composition. In total 136 samples from patients of Urolithiasis Laboratory and healthy people were analyzed by the multisensor system as well as by capillary electrophoresis as a reference method. Various chemometric approaches were implemented to relate the data from electrochemical measurements with the reference data. Logistic regression (LR) was applied for classification of samples into healthy and unhealthy producing reasonable misclassification rates. Projection on Latent Structures (PLS) regression was applied for quantitative analysis of ionic composition from potentiometric data. Mean relative errors of simultaneous prediction of sodium, potassium, ammonium, calcium, magnesium, chloride, sulfate, phosphate, urate and creatinine from multisensor system response were in the range 3-13% for independent test sets. This shows a good promise for development of a fast and inexpensive alternative method for urine analysis.

Potentiometric electronic tongues for foodstuff and biosample recognition--an overview

Potentiometric sensors are attractive tools for the fabrication of various electronic tongues that can be used in wide area of applications, ranging from foodstuff recognition to environmental monitoring and medical diagnostics. Their main advantages are the ability to modify their selectivity (including cross-sensitivity effects) and the possibility of miniaturization using appropriate construction methods for the transducer part (e.g., with the use of solid-state technology). In this overview various examples of the design, performance, and applications of potentiometric electronic tongues are presented. The results summarize recent research in the field conducted in the Department of Microbioanalytics, Warsaw University of Technology (WUT).

Monitoring of periodic anaerobic digestion with flow-through array of miniaturized ion-selective electrodes

In the last few years Electronic tongues (ETs) based on various sensor arrays were applied to the monitoring of various fermentation processes, as devices capable of fast, inexpensive, automated and on-line control. In this work a novel application of ET is proposed--flow-through array of miniaturized ion-selective electrodes (ISEs) was used for the analysis of samples obtained during anaerobic digestion (methane fermentation) performed in periodic conditions. The samples were classified according to their Chemical Oxygen Demand (COD) and Volatile Fatty Acid (VFA) content. Moreover, for this application a novel design of ISEs was developed, which is fully compatible with flow-through modules for sensor measurements.

Recent trends in potentiometric sensor arrays--a review

Nowadays there exists a large variety of ion sensors based on polymeric or solid-state membranes that can be used in a sensor array format in many analytical applications. This review aims at providing a critical overview of the distinct approaches that were developed to build and use potentiometric sensor arrays based on different transduction principles, such as classical ion-selective electrodes (ISEs) with polymer or solid-state membranes, solid-contact electrodes (SCE) including coated wire electrodes (CWE), ion-sensitive field-effect transistors (ISFETs) and light addressable potentiometric sensors (LAPS). Analysing latest publications on potentiometric sensor arrays development and applications certain problems are outlined and trends are discussed.

Dyes assay for measuring physicochemical parameters

A combination of selective fluorescent dyes has been developed for simultaneous quantitative measurements of several physicochemical parameters. The operating principle of the assay is similar to electronic nose and tongue systems, which combine nonspecific or semispecific elements for the determination of diverse analytes and chemometric techniques for multivariate data analysis. The analytical capability of the proposed mixture is engendered by changes in fluorescence signal in response to changes in environment such as pH, temperature, ionic strength, and presence of oxygen. The signal is detected by a three-dimensional spectrofluorimeter, and the acquired data are processed using an artificial neural network (ANN) for multivariate calibration. The fluorescence spectrum of a solution of selected dyes allows discreet reading of emission maxima of all dyes composing the mixture. The variations in peaks intensities caused by environmental changes provide distinctive fluorescence patterns which can be handled in the same way as the signals collected from nose/tongue electrochemical or piezoelectric devices. This optical system opens possibilities for rapid, inexpensive, real-time detection of a multitude of physicochemical parameters and analytes of complex samples.

State-of-the-art of (bio)chemical sensor developments in analytical Spanish groups

(Bio)chemical sensors are one of the most exciting fields in analytical chemistry today. The development of these analytical devices simplifies and miniaturizes the whole analytical process. Although the initial expectation of the massive incorporation of sensors in routine analytical work has been truncated to some extent, in many other cases analytical methods based on sensor technology have solved important analytical problems. Many research groups are working in this field world-wide, reporting interesting results so far. Modestly, Spanish researchers have contributed to these recent developments. In this review, we summarize the more representative achievements carried out for these groups. They cover a wide variety of sensors, including optical, electrochemical, piezoelectric or electro-mechanical devices, used for laboratory or field analyses. The capabilities to be used in different applied areas are also critically discussed.