Galactose monitoring in individuals allows the prevention of harsh health conditions related to hereditary metabolic diseases like galactosemia. Current methods of galactose detection need development to obtain cheaper, more reliable, and more specific sensors. Enzyme-containing amperometric sensors based on galactose oxidase activity are a promising approach, which can be enhanced by means of their inclusion in a redox polymer coating. This strategy simultaneously allows the immobilization of the biocatalyst to the electroactive surface and hosts the electron shuttling units. An additional deposition of capping polymers prevents external interferences like ascorbic or uric acid as well as biofouling when measuring in physiological fuels. This work studies the protection effect of poly(2-methacryloyloxyethyl phosphorylcholine-co-glycidyl methacrylate (MPC) and polyvinylimidazole-polysulfostyrene (P(VI-SS)) when incorporated in the biosensor design for the detection of galactose in human plasma.

The prevailing form of bacterial infection is within the urinary tract, encompassing a wide array of bacteria that harness the urinary metabolome for their growth. Through their metabolic actions, the chemical composition of the growth medium undergoes modifications as the bacteria metabolize urine compounds, leading to the subsequent release of metabolites. These changes can indirectly indicate the existence and proliferation of bacterial organisms. Here, we investigate the use of an electronic tongue, a powerful analytical instrument based on a combination of non-selective chemical sensors with a partial specificity for data gathering combined with principal component analysis, to distinguish between infected and non-infected artificial urine samples. Three prevalent bacteria found in urinary tract infections were investigated, Escherichia coli, Klebsiella pneumoniae, and Enterococcus faecalis. Furthermore, the electronic tongue analysis was supplemented with 1H NMR spectroscopy and flow cytometry. Bacteria-specific changes in compound consumption allowed for a qualitative differentiation between artificial urine medium and bacterial growth.

Managing blood glucose can affect important clinical outcomes during the intraoperative phase of surgery. However, currently available instruments for glucose monitoring during surgery are few and not optimized for the specific application. Here we report an attempt to exploit an enzymatic sensor in a vein replica that could continuously monitor glucose level in an authentic human bloodstream. First, detailed investigations of the superficial venous systems of volunteers were carried out using ocular and palpating examinations, as well as advanced ultrasound measurements. Second, a tubular glucose-sensitive biosensor mimicking a venous system was designed and tested. Almost ideal linear dependence of current output on glucose concentration in phosphate buffer saline was obtained in the range 2.2-22.0 mM, whereas the dependence in human plasma was less linear. Finally, the developed biosensor was investigated in whole blood under homeostatic conditions. A specific correlation was found between the current output and glucose concentration at the initial stage of the biodevice operation. However, with time, blood coagulation during measurements negatively affected the performance of the biodevice. When the experimental results were remodeled to predict the response without the influence of blood coagulation, the sensor output closely followed the blood glucose level.

This thesis is focused on developing electrochemical (bio-)sensors specifically designed to detect biomolecules and bacteria in human physiological fluids. A more comprehensive understanding of their performance can be obtained by exposing the sensors to real human physiological fluids. Thus, four biosensors were designed and tested in saliva, plasma, blood, and urine. Specifically, a voltammetric electronic tongue, integrating six different electrode materials, was developed to qualitatively assess SARS-CoV-2 in saliva samples using principal component analysis. A tubular enzyme-based sensor utilizing incorporated cellobiose dehydrogenase in an Os(bpy)PVI redox polymer was employed for continuous glucose sensing in human plasma and undiluted whole blood under homeostatic conditions. Two different sensing concepts were developed for the label-free detection of bacteria (Escherichia coli, Enterococcus faecalis, and Klebsiella pneumoniae) in artificial urine and human urine based on metabolic activity due to bacterial growth. The first sensor enabled continuous bacterial detection by reducing Prussian Blue deposited on screen-printed electrodes with wireless data transfer. The second bacterial-sensitive sensor utilized electrochemical characterization to identify three bacteria types based on artificial urine metabolic changes. For a qualitative investigation of the metabolic changes, nuclear magnetic resonance was utilized, and flow cytometry was used to quantify and correlate bacterial growth with electrochemistry. Multivariate statistical data analysis was applied to distinguish bacteria-free and bacteria-infected artificial urine. Finally, an overview of the recent advances in the field of non-invasive electrochemical biosensors operating in secreted human physiological fluids, viz., tears, sweat, saliva, and urine, was given.

Denna avhandling är inriktad på utveckling av elektrokemiska (bio-)sensorer som är särskilt utformade för detektering av biomolekyler och bakterier i mänskliga fysiologiska vätskor. Genom att undersöka sensorerna i verkliga mänskliga fysiologiska vätskor, kan man få en mer omfattande förståelse för deras prestanda. Fyra olika biosensorer har utformats och testats i saliv, plasma, blod och urin. En voltammetrisk elektronisk tunga, som integrerar sex olika elektrodmaterial, utvecklades för kvalitativ bedömning av SARS-CoV-2 i salivprover med hjälp av principalkomponentanalys. En rörformad enzymbaserad sensor som använder inkorporerat Cellobiose Dehydrogenase i en Os(bpy)PVI redoxpolymer användes för kontinuerlig glukosmätning i humant plasma och outspätt helblod under homeostatiska förhållanden. Dessutom utvecklades två olika sensorkoncept för märkningsfri detektion av bakterier (Escherichia coli, Enterococcus faecalis och Klebsiella pneumoniae) i artificiell urin och humanurin baserat på metabolisk aktivitet till följd av bakterietillväxt. Den första sensorn möjliggjorde kontinuerlig bakteriedetektion genom reduktion av preussiskt blått elektroder med trådlös dataöverföring. Den andra bakteriekänsliga sensorn använde elektrokemisk karakterisering för att identifiera tre typer av bakterier baserat på metaboliska förändringar i artificiell urin. För en kvalitativ undersökning av de metaboliska förändringarna användes dessutom nukleär magnetisk resonans och flödescytometri för att kvantifiera och korrelera bakterietillväxt med elektrokemi. Multivariat statistisk dataanalys användes för att skilja mellan bakteriefri och bakterieinfekterad (artificiell) urin. Slutligen gavs en översikt över de senaste framstegen inom området för icke-invasiva elektrokemiska biosensorer som arbetar i utsöndrade mänskliga fysiologiska vätskor, dvs. tårar, svett, saliv och urin.

Diese Arbeit fokussiert sich auf die Entwicklung elektrochemischer (Bio-)Sensoren, die speziell für den Nachweis von Biomolekülen und Bakterien inmenschlichen physiologischen Flüssigkeiten konzipiert sind. Indem die Sensorenhumanen, physiologischen Flüssigkeiten ausgesetzt werden, kann einumfassenderes Verständnis ihrer Funktionalität gewonnen werden. Im Einzelnenwurden vier verschiedene Biosensoren entwickelt und in Speichel, Plasma, Blutund Urin getestet. Für die qualitative Bewertung von SARS-CoV-2 inSpeichelproben unter Verwendung der Hauptkomponentenanalyse wurde einevoltammetrische „elektronische Zunge“, die sechs verschiedeneElektrodenmaterialien integriert, entwickelt. Zur kontinuierlichenGlukosemessung in menschlichem Plasma und unverdünntem Vollblut unterhomöostatischen Bedingungen wurden tubuläre enzymbasierte Sensorenverwendet, die die eingebaute Cellobiose-Dehydrogenase in einem Os (bpy) -PVI-Redoxpolymer verwenden. Darüber hinaus wurden zwei verschiedeneSensorkonzepte für den Nachweis von Bakterien (Escherichia coli, Enterococcusfaecalis und Klebsiella pneumoniae) in synthetischem und menschlichem Urinentwickelt, basierend auf der Stoffwechselaktivität während bakteriellemWachstum. Der erste Sensor ermöglichte einen kontinuierlichen Nachweis vonBakterien durch die Reduktion von „Prussian Blue“-Elektroden mit drahtloserDatenübertragung. Der zweite Sensor nutzte eine voltammetrische „elektronischeZunge“ zur Identifizierung von drei Bakterientypen aufgrund von spezifischen,metabolischen Veränderungen in synthetischem Urin. Zur qualitativenUntersuchung dieser Veränderungen wurde die Kernspinresonanz eingesetzt. DieDurchflusszytometrie diente zur Quantifizierung und Korrelation desBakterienwachstums mit der Elektrochemie, wobei multivariate statistischeDatenanalysen zur Unterscheidung von bakterienfreiem und bakterieninfiziertem(synthetischen) Urin eingesetzt wurden. Abschließend wurde ein Überblick überdie aktuellen Fortschritte auf dem Gebiet der nicht-invasiven elektrochemischenBiosensoren gegeben, die mit den physiologischen Flüssigkeiten des Menschen,d. h. in Tränen, Schweiß, Speichel und Urin, arbeiten. 

An electronic tongue is a powerful analytical instrument based on an array of non-selective chemical sensors with a partial specificity for data gathering and advanced pattern recognition methods for data analysis. Connecting electronic tongues with electrochemical techniques for data collection has led to various applications, mostly within sensing for food quality and environmental monitoring, but also in biomedical research for the analyses of different bioanalytes in human physiological fluids. In this paper, an electronic tongue consisting of six electrodes (viz., gold, platinum, palladium, titanium, iridium, and glassy carbon) was designed and tested in authentic (undiluted, unpretreated) human saliva samples from eight volunteers, collected before and during the COVID-19 pandemic. Investigations of 11 samples using differential pulse voltammetry and a principal component analysis allowed us to distinguish between SARS-CoV-2-free and infected authentic human saliva. This work, as a proof-of-principle demonstration, provides a new perspective for the use of electronic tongues in the field of enzyme-free electrochemical biosensing, highlighting their potential for future applications in non-invasive biomedical analyses.

Bacterial infections can affect the skin, lungs, blood, and brain, and are among the leading causes of mortality globally. Early infection detection is critical in diagnosis and treatment but is a time- and work-consuming process taking several days, creating a hitherto unmet need to develop simple, rapid, and accurate methods for bacterial detection at the point of care. The most frequent type of bacterial infection is infection of the urinary tract. Here, we present a wireless-enabled, portable, potentiometric sensor for E. coli. E. coli was chosen as a model bacterium since it is the most common cause of urinary tract infections. The sensing principle is based on reduction of Prussian blue by the metabolic activity of the bacteria, detected by monitoring the potential of the sensor, transferring the sensor signal via Bluetooth, and recording the output on a laptop or a mobile phone. In sensing of bacteria in an artificial urine medium, E. coli was detected in similar to 4 h (237 +/- 19 min; n = 4) and in less than 0.5 h (21 +/- 7 min, n = 3) using initial E. coli concentrations of similar to 10(3) and 10(5) cells mL(-1), respectively, which is under or on the limit for classification of a urinary tract infection. Detection of E. coli was also demonstrated in authentic urine samples with bacteria concentration as low as 10(4) cells mL(-1), with a similar response recorded between urine samples collected from different volunteers as well as from morning and afternoon urine samples.

Non-invasive healthcare technologies are an important part of research and development nowadays due to the low cost and convenience offered to both healthcare receivers and providers. This work overviews the recent advances in the field of non-invasive electrochemical biosensors operating in secreted human physiological fluids, viz. tears, sweat, saliva, and urine. Described electrochemical devices are based on different electrochemical techniques, viz. amperometry, coulometry, cyclic voltammetry, and impedance spectroscopy. Challenges that confront researchers in this exciting area and key requirements for biodevices are discussed. It is concluded that the field of non-invasive sensing of biomarkers in bodily fluid is highly convoluted. Nonetheless, if the drawbacks are appropriately addressed, and the pitfalls are adroitly circumvented, the approach will most certainly disrupt current clinical and self-monitoring practices.