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S Drost

Publications and source records attributed to S Drost.

11 recordsLinked to original sources
PubMed2001

Ultrasensitive quartz crystal microbalance sensors for detection of M13-Phages in liquids.

Quartz crystal microbalance (QCM) sensors are widely used for determining liquid properties or probing interfacial processes. For some applications the sensitivity of the QCM sensors typically used (5-20 MHz) is limited compared with other biosensor methods. In this study ultrasensitive QCM sensors with resonant frequencies from 39 to 110 MHz for measurements in the liquid phase are presented. The fundamental sensor effect of a QCM is the decrease of the resonant frequency of an oscillating quartz crystal due to the binding of mass on a coated surface during the measurement. The sensitivity of QCM sensors increases strongly with an increasing resonant frequency and, therefore, with a decreasing thickness of the sensitive area. The new kind of ultrasensitive QCM sensors used in this study is based on chemically milled shear mode quartz crystals which are etched only in the center of the blank, forming a thin quartz membrane with a thick, mechanically stable outer ring. An immunoassay using a virus specific monoclonal antibody and a M13-Phage showed an increase in the signal to noise ratio by a factor of more than 6 for 56 MHz quartz crystals compared with standard 19 MHz quartz crystals, the detection limit was improved by a factor of 200. Probing of acoustic properties of glycerol/water mixtures resulted in an increase in sensitivity, which is in very good agreement with theory. Chemically milled QCM sensors strongly improve the sensitivity in biosensing and probing of acoustic properties and, therefore, offer interesting new application fields for QCM sensors.

Acoustics↗
PubMed1999

Protein detection with a novel ISFET-based zeta potential analyzer.

This publication presents a novel ISFET-based measurement concept for the determination of the zeta potential, which is known to be an efficient method for the detection of protein accumulations onto surfaces. The basic set-up consists of two monolithically integrated ISFET sensors arranged in a serial flow configuration together with a precoated fused silica capillary, which provides the reactive surface for the protein detection. In comparison with the state of the art, this novel biosensor system is characterized by a small size, an extremely low reagent consumption, a simple fluidic concept, a short analysis time, and a very effective noise suppression due to the differential ISFET set-up. In the following, an overview is given over the theoretical background of the measurement principle. In order to get deeper insight into the theoretical background of the measurement principle, a simulation model was developed which is based on the site-binding theory and takes into account the different proton dissociation equilibria of the surface groups as well as the influence of monovalent electrolyte ions. A quasi-Newton iteration after Broyden was used for the numerical solution of the formulated equation system. For an experimental confirmation of the simulation results, the calculated zeta potential vs. pH curves were compared with measured data for various modifications of the fused silica capillaries (in untreated state, after a hydrothermal activation, and after the deposition of several silanes) and it could be shown, that the chosen physical model represents a satifactory theoretical basis for the description of the occuring surface effects. Measurements before and after a covalent coupling of the model analyte lysozyme were performed in order to demonstrate the feasibility of an immunosensor based on the measurement of the streaming potential and showed a significant shift of the zeta potential vs. pH curves.

Biosensing Techniques↗
PubMed1998

Characterization of immobilization methods for African swine fever virus protein and antibodies with a piezoelectric immunosensor.

A direct piezoelectric flow injection analysis immunoassay for the detection of African Swine Fever virus and antibodies is presented. The peptide-specific monoclonal antibody 18BG3 and the virus protein 73 were used for detection with a quartz crystal microbalance. Accumulation of the analyte on the surface of this mass-sensitive biosensor resulted in a shift of the resonant frequency. Highly selective receptor layers were applied on the sensing electrode of the quartz crystal for detection of the complementary analyte. Different immobilization methods proved to be appropriate for coating of the monoclonal antibody 18BG3. A quartz crystal covalently coated with the antibody 18BG3 detected virus protein VP73 samples more than 20 times and was stable for more than 30 days. The coating of virus protein was performed by physisorption. A sensor with a virus protein receptor layer detected antibody 18BG3 samples 10 times within one day. The sensor device was able to perform one measurement cycle including blocking and regeneration within 30 min. With the help of a suitable carrier liquid, measurements with serum samples were performed. The calibration curves for measurements in buffer and in serum could be determined and the detection limits for virus protein detection were 0.31 and 1 microgram/ml, and for antibody detection 0.1 and 0.2 microgram/ml, respectively.

African Swine Fever Virus↗
PubMed1992

A quartz crystal biosensor for measurement in liquids.

The detection of anti-human immunodeficiency virus (HIV) antibodies by means of synthetic HIV peptide immobilized on a piezoelectric quartz sensor is demonstrated. The measurement set-up consists of an oscillator circuit, a suitably modified AT-cut thickness-shear-mode quartz crystal with gold electrodes, which is housed in a special reaction vessel, and a computer-controlled frequency counter for the registration of the measured frequency values. The quartz crystal is adapted for a steady operation in liquids at a frequency of 20 MHz. In phosphate-buffered saline solution the oscillator reaches a stability of about 0.5 Hz within a few seconds, of about 2 Hz within 10 min and about 30 Hz within 1 h. The frequency shift due to the adsorption of various proteins to the uncoated sensor surface has been investigated. It can be shown that a stable adsorptive binding of proteins to an oscillating gold surface is feasible and can be used for the immobilization of a receptor layer (e.g. HIV peptide). Specific binding of the anti-HIV monoclonal antibody to the HIV peptide immobilized on the quartz sensor is demonstrated. Control experiments show, however, additional unspecific binding. According to the experiments, the Sauerbrey formula gives a sufficiently accurate value for the decrease of the resonant frequency due to adsorption or binding of macromolecular proteins on the quartz crystal surface.

Biosensing Techniques↗
PubMed1982

[Sarcosporidia findings in chopped meat for consumption].

In a limited area 400 fresh samples of minced beef and minced pork were examined trichinoscopically for sarcocysts within a period of 6 months. In 102 samples (25.5%) the parasites were proved. Out of 200 samples of pork 18.5% were positive with an average intensity of 2.38 sarcocysts, out of 200 samples of beef 32.5% were positive with an average intensity of 2.91 sarcocysts. The proportion of sarcocysts in the 4 kinds of minced meat examined was calculated on the assumption of a constant distribution. The effect on human health of sarcosporidians is discussed in the light of the literature. Some measures to control this parasitosis are suggested.

Animals↗
PubMed1977

[Sarcosporidias of cloven-hoofed wild animals. Sarcosporidias in wild deer].

500 adult roes and 100 fawns were examined microscopically for the presence of Sarcocystis gracilis von Ratz, 1901. 95.80 per cent of the roes examined had Sarcosporidias. The parasites were noticed macroscopically in less than a third of them. The abdominal muscles were affected most frequently and most strongly. The leg muscles were affected least of all. Roe bucks were affected to a lesser extent than does. From the third month of life the fawns showed an incidence of parasites which increased with advancing age. During the period of research from May till November hardly any significant difference of parasitical attack occurred in adult roes.

Age Factors↗
PubMed1977

[Sarcosporidia of the cloven-hoofed game. III. Sarcosporidia in red deer and fallow deer].

The incidence of Sarcosporidia among red-deer and fallow-deer was investigated. The fallow-deer is less discussed because the low number of investigations. The red-deer shows with 15% the lowest incidence among the red-deer, fallow-deer and wild-boar investigated. The Sarcosporidia of the red-deer are smaller than those of the roe, therefore the identification in the trichinoscopic picture is more difficult. With regard to this it is recommended to name the Sarcosporidia of the red-deer Sarcocystis cervi (VON HESSLING, 1854), because their form is more similar to the cattle and not those of the roe. To be sure a greater number of investigations is necessary to detect all connections.

Animals↗