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LAPS are field-effect-based potentiometric sensors which are able to monitor analyte concentrations in a spatially resolved manner. Hence, a LAPS sensor system is a powerful device to record chemical imaging of the concentration of chemical species in an aqueous solution, chemical reactions, or the growth of cell colonies on the sensor surface, to record chemical images. In this work, multi-chamber 3D-printed structures made out of polymer (PP-ABS) were combined with LAPS chips to analyse differentially and simultaneously the metabolic activity of Escherichia coli K12 and Chinese hamster ovary (CHO) cells, and the responds of those cells to the addition of glucose solution. [ABSTRACT FROM AUTHOR]

Light-addressable potentiometric sensors (LAPS) consisting of a p-Si-SiO2 and p-Si-SiO2-Au structure, respectively, have been tested for a label-free electrical detection of DNA (deoxyribonucleic acid) hybridization. Three different strategies for immobilizing single-stranded probe DNA (ssDNA) molecules on a LAPS surface have been studied and compared: (a) immobilization of thiol-modified ssDNA on the patterned Au surface via gold-thiol bond, (b) covalent immobilization of amino-modified ssDNA onto the SiO2 surface functionalized with 3-aminopropyltriethoxysilane and (c) layer-by-layer adsorption of negatively charged ssDNA on a positively charged weak polyelectrolyte layer of poly(allylamine hydrochloride). [ABSTRACT FROM AUTHOR]

The chemical imaging sensor, which is based on the principle of the light-addressable potentiometric sensor (LAPS), is a powerful tool to visualize the spatial distribution of chemical species on the sensor surface. The spatial resolution of this sensor depends on the diffusion of photocarriers excited by a modulated light. In this study, a novel hybrid fiber-optic illumination was developed to enhance the spatial resolution. It consists of a modulated light probe to generate a photocurrent signal and a ring of constant light, which suppresses the lateral diffusion of minority carriers excited by the modulated light. It is demonstrated that the spatial resolution was improved from 92 μm to 68 μm. [ABSTRACT FROM AUTHOR]

A novel design of the light-addressable potentiometric sensor (LAPS) for realisation of a portable multisensor device is presented. Light sources and electronics including an oscillator, a multiplexer, a pre-amplifier and a high-pass filter are encapsulated in a pen-shaped case, on which the sensor plate is mounted. This sensor device is capable of measuring up to four different ion species by integrating different ion-selective materials on the sensing surface, each illuminated with an independent light source. The novel design of the sensor system is expected to make the measurement easier and to enlarge the field of practical applications. [Copyright &y& Elsevier]

Nerve agents, like pesticides on the basis of organophosphates (OPs) are among the most toxic chemical species that are known. To determine such pesticides with high sensitivity, selectivity and reliability, a novel dual amperometric/potentiometric biosensor chip with the immobilized enzyme organophosphorus hydrolase (OPH) has been developed and examined. The amperometric and potentiometric transducers of the biosensor chip have been prepared by means of thin-film techniques. In addition, the enzyme OPH was immobilized by using a cystamine/glutaraldehyde coupling technique on the amperometric gold electrode, and by means of a silane modification preparation on the potentiometric field-effect (EIS: electrolyte–insulator–semiconductor) sensor. Arranged in a serial set-up, the two biosensors have been integrated in a flow-injection analysis (FIA) system. Due to the two combined, but different electrochemical transducer principles, the developed dual amperometric/potentiometric biosensor chip enables selective information for injections of different groups of organophosphorus pesticides, like paraoxon, parathion, dichlorvos and diazinon down to the lower μM concentration range. [Copyright &y& Elsevier]

The LAPS (light-addressable potentiometric sensor) platform is one of the most attractive approaches for chemical and biological sensing with many applications ranging from pH and ion/analyte concentration measurements up to cell metabolism detection and chemical imaging. However, although it is generally accepted that LAPS measurements are spatially resolved, the light-addressability feature of LAPS devices has not been discussed in detail so far. In this work, an extended electrical equivalent-circuit model of the LAPS has been presented, which takes into account possible cross-talk effects due to the capacitive coupling of the non-illuminated region. A shunting effect of the non-illuminated area on the measured photocurrent and addressability of LAPS devices has been studied. It has been shown, that the measured photocurrent will be determined not only by the local interfacial potential in the illuminated region but also by possible interfacial potential changes in the non-illuminated region, yielding cross-talk effects. These findings were supported by the experimental investigations of a penicillin-sensitive multi-spot LAPS and a metal-insulator-semiconductor LAPS as model systems. [ABSTRACT FROM AUTHOR]

Abstract: In this work, two different redox-sensitive glass materials have been fabricated for the development of a production friendly redox electrode. The specific glass targets have been prepared by glass pouring process. The transducer structure is fabricated via conventional silicon-based semiconductor technology. The glass bulk material was deposited for the first time by means of pulsed laser deposition process into the thin-film state on the sensor structures. The fabricated sensors have been physically and electrochemically characterized by X-ray photoelectron spectroscopy, determination of expansion coefficient, impedance and potentiometric measurements. [Copyright &y& Elsevier]

Abstract: The cross-sensitivity of chemical sensors for several metal ions resembles in a way the overlapping sensitivity of some biological sensors, like the optical colour receptors of human retinal cone cells. While it is difficult to assign crisp classification values to measurands based on complex overlapping sensory signals, fuzzy logic offers a possibility to mathematically model such systems. Current work goes into the direction of mixed heavy metal solutions and the combination of fuzzy logic with heavy metal-sensitive, silicon-based chemical sensors for training scenarios of arbitrary sensor/probe combinations in terms of an electronic tongue. Heavy metals play an important role in environmental analysis. As trace elements as well as water impurities released from industrial processes they occur in the environment. In this work, the development of a new fuzzy logic method based on potentiometric measurements performed with three different miniaturised chalcogenide glass sensors in different heavy metal solutions will be presented. The critical validation of the developed fuzzy logic program will be demonstrated by means of measurements in unknown single- and multi-component heavy metal solutions. Limitations of this program and a comparison between calculated and expected values in terms of analyte composition and heavy metal ion concentration will be shown and discussed. [Copyright &y& Elsevier]

Abstract: A novel design of a light-addressable potentiometric sensor (LAPS) for the realisation of an easy exchangeable and modular measurement set-up is presented in this work. The sensor chip for up to 16 independent sensor spots is integrated in a standard plastic card and the appropriate measurement cell allows a selection of different chip cards within seconds. The measurement cell contains an integrated electronic to control the measurement procedure and to read out the measurement signal from the LAPS-chip card to provide a stable signal for further data acquisition. This guarantees a high flexibility due to the use of different chip cards with the same measurement device on the one hand, and a high statistical prediction, because of the repeatable measurements with different sensor-chip cards of the same series under exact the same environmental conditions, on the other hand. Both the design and first measurements with this “LAPS cards” will be presented. [Copyright &y& Elsevier]

Cyanide (CN-) and its derivatives are widely used in the metal mining and metal plating industry. But also many medicinal and food plants are toxic for man because of their content of cyanogenic glycosides. In the present investigation, a cyanide-specific biosensor exploiting immobilized cyanidase (EC 3.5.5.1) has been developed. Enzymatically formed ammonia was either detected by a potentiometric sensor based on an ammonia electrode or by a pH-sensitive electrolyte/insulator/semiconductor (EIS) layer structure made of Al/p-Si/SiO2/Si3N4. It could be demonstrated with both methods that sensitivity of these biosensors is sufficient to detect cyanide in sub-toxic concentrations. The detection limit was determined to be in the micromolar concentration range. [Copyright &y& Elsevier]

A new type of light-addressable potentiometric sensor (LAPS) has been developed by elaboration of photocurable ion-sensitive membranes based on matrices of mono- and diacrylates in combination with a silicon-based electrochemical transducer for the purposes of chemical and biochemical analyses. The characteristics of the elaborated K-, Li-, Cs-, Ca- and Mg-LAPS are presented to indicate the potential of the technology developed. For example, the sensitivities of the K- and Li-LAPS were found to be 58±1 mV/pK and 59±1 mV/pLi, respectively, over concentration ranges of 10−5–10−1 mol/l. The detection limits were evaluated to be 2×10−6 mol/l of the primary ion. [Copyright &y& Elsevier]

A lithium-selective polymeric membrane has been immobilised on the surface of a semiconductor transducer. This light-addressable potentiometric sensor (LAPS) with the induced lithium selectivity has been prepared with the aim at further development of a Li+ assay in liquid media, including biological fluids. The sensor developed exhibits Nernstian response interval of 10−5 to 10−1 mol l−1 with an ionic sensitivity of (58±1) mV/pLi. The detection limit was found to be (3±1)×10−6 mol l−1 Li+. The sensor has high selectivity for lithium over sodium and potassium ions with selectivity coefficients of KLi/NaPOT=(7±2)×10−3 and KLi/KPOT=(5±1)×10−3, respectively, and a response time of less than 30 s. [Copyright &y& Elsevier]