Biomimetic Yeast Cell Typing—Application of QCMs

Artificial antibodies represent a key factor in the generation of sensing systems for the selective detection of bioanalytes of variable sizes. With biomimetic surfaces, the important model organism Saccharomyces cerevisiae and several of its growth stages may be detected. Quartz crystal microbalances (QCM) with 10 MHz fundamental frequency and coated with polymers imprinted with synchronized yeast cells are presented, which are able to detect duplex cells with high selectivity. Furthermore, a multichannel quartz crystal microbalance (MQCM) was designed and optimized for the measurement in liquids. This one-chip system based on four-electrode geometry allows the simultaneous detection of four analytes and, thus, provides a monitoring system for biotechnology and process control. For further standardization of the method, synthetic stamps containing plastic yeast cells in different growth stages were produced and utilized for imprinting. Mass-sensitive measurements with such MIPs resulted in the same sensor characteristics as obtained for those imprinted with native yeast cells

Combining Two Selection Principles: Sensor Arrays Based on Both Biomimetic Recognition and Chemometrics

Electronic noses mimic smell and taste senses by using sensor arrays to assess complex samples and to simultaneously detect multiple analytes. In most cases, the sensors forming such arrays are not highly selective. Selectivity is attained by pattern recognition/chemometric data treatment of the response pattern. However, especially when aiming at quantifying analytes rather than qualitatively detecting them, it makes sense to implement chemical recognition via receptor layers, leading to increased selectivity of individual sensors. This review focuses on existing sensor arrays developed based on biomimetic approaches to maximize chemical selectivity. Such sensor arrays for instance use molecularly imprint polymers (MIPs) in both e-noses and e-tongues, for example, to characterize headspace gas compositions or to detect protein profiles. Other array types employ entire cells, proteins, and peptides, as well as aptamers, respectively, in multisensor systems. There are two main reasons for combining chemoselectivity and chemometrics: First, this combined approach increases the analytical quality of quantitative data. Second, the approach helps in gaining a deeper understanding of the olfactory processes in nature

SAW RFID-Tags for Mass-Sensitive Detection of Humidity and Vapors

One-port surface acoustic wave (SAW) devices with defined reflector patterns give characteristic signal patterns in the time domain making them identifiable and leading to so-called RFID-Tags. Each sensor responds with a burst of signals, their timed positions giving the identification code, while the amplitudes can be related to the analyte concentration. This paper presents the first combination of such a transducer with chemically sensitive layer materials. These include crosslinked polyvinyl alcohol for determining relative humidity and tert-butylcalix[4]arene for detecting solvent vapors coated on the free space between the reflectors. In going from the time domain to the frequency domain by Fourier transformation, changes in frequency and phase lead to sensor responses. Hence, it is possible to measure the concentration of tetrachloroethene in air down to 50 ppm, as well as 1% changes in relative humidity

Solvent Vapour Detection with Cholesteric Liquid Crystals—Optical and Mass-Sensitive Evaluation of the Sensor Mechanism†

Cholesteric liquid crystals (CLCs) are used as sensitive coatings for the detection of organic solvent vapours for both polar and non-polar substances. The incorporation of different analyte vapours in the CLC layers disturbs the pitch length which changes the optical properties, i.e., shifting the absorption band. The engulfing of CLCs around non-polar solvent vapours such as tetrahedrofuran (THF), chloroform and tetrachloroethylene is favoured in comparison to polar ones, i.e., methanol and ethanol. Increasing solvent vapour concentrations shift the absorbance maximum to smaller wavelengths, e.g., as observed for THF. Additionally, CLCs have been coated on acoustic devices such as the quartz crystal microbalance (QCM) to measure the frequency shift of analyte samples at similar concentration levels. The mass effect for tetrachloroethylene was about six times higher than chloroform. Thus, optical response can be correlated with intercalation in accordance to mass detection. The mechanical stability was gained by combining CLCs with imprinted polymers. Therefore, pre-concentration of solvent vapours was performed leading to an additional selectivity

Künstliche Neuronale Netze: Einführung für AnwenderInnen

Univ.-Prof. Mag. Dr. Peter Lieberzeit spricht über künstliche neuronale Netze

Künstliche Neuronale Netze: Funktionsweise

Univ.-Prof. Mag. Dr. Peter Lieberzeit über Künstliche Neuronale Netze

A Review on Synthetic Receptors for Bioparticle Detection Created by Surface-Imprinting Techniques-From Principles to Applications

© 2016 American Chemical Society. The strong affinity of biological receptors for their targets has been studied for many years. Noncovalent interactions between these natural recognition elements and their ligands form the basis for a broad range of biosensor applications. Although these sensing platforms are usually appreciably sensitive and selective, certain drawbacks are associated with biological receptors under nonphysiological conditions in terms of temperature, pH, or ionic strength. Therefore, there are considerable efforts to mimic such molecular interactions with robust, synthetic receptors. Molecular imprinting is the best-known technique to obtain antibody mimics by synthesizing a polymer matrix in the presence of a template species, such as molecules or larger aggregates. Extraction of the template results in sterically and functionally adapted binding cavities in or on a porous matrix. Although in principle possible, the detection of larger bioparticles such as proteins, microorganisms, or cells remains challenging when using the classical MIP concept. To tackle inherent difficulties, extending the concept of molecular imprinting toward surface imprinting is a promising approach: Here, binding cavities are formed directly on the surface of a cross-linked polymer layer, thus facilitating the removal of the templates. This article reviews the main surface-imprinting techniques and focuses on the implementation of surface-imprinted polymers (SIPs) into various biomimetic sensors and related applications. In addition, we provide an outlook on emerging research on surface imprinting and the development of biomimetic tools for diagnostic purposes.status: publishe

Molecularly Imprinted Polymer Nanoparticles for Formaldehyde Sensing with QCM

Herein, we report on molecularly imprinted polymers (MIPs) for detecting formaldehyde vapors in air streams. A copolymer thin film consisting of styrene, methacrylic acid, and ethylene glycol dimethacrylate on quartz crystal microbalance (QCM) yielded a detection limit of 500 ppb formaldehyde in dry air. Surprisingly, these MIPs showed specific behavior when tested against a range of volatile organic compounds (VOCs), such as acetaldehyde, methanol, formic acid, and dichloromethane. Despite thus being a suitable receptor in principle, the MIPs were not useful for measurements at 50% humidity due to surface saturation by water. This was overcome by introducing primary amino groups into the polymer via allyl amine and by changing the coating morphology from thin film to nanoparticles. This led to the same limit of detection (500 ppb) and selectivity as before, but at the real-life conditions of 50% relative humidity

Aptamer-Based QCM-Sensor for Rapid Detection of PRRS Virus

Porcine reproductive and respiratory syndrome (PRRS) is caused by an RNA virus and has substantial economic impact on swine industry. Screening pigs for infection is the best way to prevent spreading the disease. For that purpose, we developed biosensors based on aptamers, i.e., short ss-DNA that can bind to porcine reproductive and respiratory syndrome virus (PRRSV). The present study, demonstrates selectivity and sensitivity of PRRSV aptamer (7R) by the means of quartz crystal microbalance (QCM) measurements. The respective results show that 7R aptamer indeed binds to samples containing around 1010 PRRSV virus particles, but not to Pseudorabies virus (PRV) and Classical swine fever virus (CSFV)