Contributions to the development of novel nanotechnological sensor chips for the detection of meat deterioration in special consideration of optimising the sensitivity with regard to chemical modification

Herkömmliche Nachweisverfahren für die Bestimmung und die Identifikation von mikrobiologischem Lebensmittelverderb sind zeitaufwändig, da sie auf üblichen Kultivierungstechniken beruhen oder die Veränderung von Umwelteinflüsse wie etwa die Temperatur oder den pH-Wert detektieren. Diese Parameter spiegeln jedoch nicht die reale Qualität des getesteten Fleisches wieder. Ziele dieser Arbeit waren Beiträge zur Entwicklung eines neuartigen nanotechnologischen Sensorchips zur Detektion von Fleischverderb unter besonderer Berücksichtigung von Sensitivitätsoptimierungen im Hinblick auf chemische Modifizierung der sensitiven Polymerschicht und Sensor Layout. Dieser biomimetrische Sensor nützt die Effekte der anormalen Absorption aus und kann den/die Konsumenten/Konsumentinnen im Supermarkt in Echtzeit den Frischegrad anzeigen. Weitreichende Verbesserungsansätze wurden auf der Ebene mehrerer Parameter, u.a. der Polymerkonzentration, der Vernetzerkonzentration und der Dicke der metallischen Beschichtung, dargebracht. Auch das Setup an sich wurde bei diesen Untersuchungen modifiziert. Ein Ergebnis dieser Entwicklung war ein neuartiger 2-Schicht-Biosensor, der keiner dritten metallischen Schicht bedarf und dennoch mit einem eindeutigen Farbumschlag den Zeitpunkt des Verderbs anzeigt. Dieser Sensor ist somit im Hinblick auf den Herstellungsprozess, die Fertigungskosten sowie gesundheitliche Aspekte dem ursprünglichen 3-Schicht-Setup klar überlegen.Standard methods for the detection and identification of microbiological spoilage of food are time-consuming as they use conventional culturing techniques or monitor environmental conditions like the increase of temperature or pH. These parameters do not reflect the real quality of the meat to be tested. Aim of this study was to make contributions to the development of a novel nanotechnological sensor chip for the detection of meat deterioration, in special consideration of optimising the sensitivity with regard to chemical modification of the sensitive polymer and the sensor layout. This biomimetic sensor utilises the effect of anormolous absorption and is able to show the consumer in the grocery store the rate of deterioration in real time. Numerous developmental approaches for several parameters, e.g. polymer concentration, linker concentration and thickness of the metallic layer, were examined. Even the sensor setup itself was modified within these studies. The result of this development was a novel 2-layer-biosensor with no need of a third metallic layer, which indicates the point of decay with a clearly visible colour shift. This sensor is superior to the original 3-layer-setup with regard of production process, costs as well as health aspects

Cell-Based Sensor System Using L6 Cells for Broad Band Continuous Pollutant Monitoring in Aquatic Environments

Pollution of drinking water sources represents a continuously emerging problem in global environmental protection. Novel techniques for real-time monitoring of water quality, capable of the detection of unanticipated toxic and bioactive substances, are urgently needed. In this study, the applicability of a cell-based sensor system using selected eukaryotic cell lines for the detection of aquatic pollutants is shown. Readout parameters of the cells were the acidification (metabolism), oxygen consumption (respiration) and impedance (morphology) of the cells. A variety of potential cytotoxic classes of substances (heavy metals, pharmaceuticals, neurotoxins, waste water) was tested with monolayers of L6 cells (rat myoblasts). The cytotoxicity or cellular effects induced by inorganic ions (Ni2+ and Cu2+) can be detected with the metabolic parameters acidification and respiration down to 0.5 mg/L, whereas the detection limit for other substances like nicotine and acetaminophen are rather high, in the range of 0.1 mg/L and 100 mg/L. In a close to application model a real waste water sample shows detectable signals, indicating the existence of cytotoxic substances. The results support the paradigm change from single substance detection to the monitoring of overall toxicity

Eukaryotic cell lines as a sensitive layer for direct monitoring of carbon monoxide

In the past years, whole cell gas toxicity assays have been developed in order to study the harmful effects of gaseous chemicals. Cells are incubated with nutrition medium supplemented with the gaseous substances to be tested. These methods are not feasible for the examination of toxic gases, which are insoluble in water. Carbon monoxide (CO), a poorly soluble and toxic gas (lethal dose 1vol% for some minutes) has been chosen as a model gas. Besides its binding to hemoglobin, it also leads to an inhibition of cytochrome c oxidase in the mitochondrial respiratory chain of living cells. Thus, a decrease in the respiratory behavior of eukaryotic cells indicates the presence of CO in a gaseous phase. Based on the Bionas® 2500 analyzing system, a device to measure the metabolic and morphological effects, caused by direct gas exposure on eukaryotic cells was established. The gaseous substances directly contact the eukaryotic cell line V79 (Chinese hamster lung fibroblast) without interfering liquid phase in between. Beside the measurement of oxygen consumption also acidification and impedance changes of the cell culture are detected by a metabolic sensor chip. In order to increase the stability different chip surface coatings like collagen A and poly-L-lysin (PLL) were used. Adhesion coating leads to a tighter junction of the cells to the sensor chip surface and thus enables higher stability of the confluent cell monolayer towards the gaseous flow during the gas exposure. The method reported here has the potential to become a valuable means for rapid monitoring of toxic compounds in gaseous phases. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.status: publishe

A critical comparison of cell-based sensor systems for the detection of Cr(VI) in aquatic environment

The toxicity of chromium ions was investigated using mammalian cell cultures on impedance sensors as well as physiological in vitro sensor systems. The performance of commercially available systems like the 2500 Analyzing System (Bionas), xCELLigence (Roche) and Cytosensor Microphysiometer (Molecular Devices) was compared with a novel CMOS-based impedance-to-frequency converter device. Cell-based sensor systems are shown to be powerful tools to detect Cr(VI) pollutions within several hours in the range of multinational drinking water regulations. The ability to distinguish between toxic Cr(VI) and non-toxic Cr(III) species is one advantage of these integral sensor systems. Impedance only devices are not sufficient for the fast detection of toxic chromium species as rapid cellular changes occur only in the respiration system and the cell physiology. © 2013 Elsevier B.V.status: publishe