Biomedical subjects

Michael Keusgen

Publications and source records attributed to Michael Keusgen.

12 recordsLinked to original sources

PubMed2007

CRP determination based on a novel magnetic biosensor.

The c-reactive protein (CRP) is a very significant human blood marker for inflammatory processes and is routinely determined for many clinical purposes. The widespread and well established detection method for this approximately 115 kDa hepatic protein is the high-sensitivity ELISA assay (hsCRP-ELISA) in blood serum. New approaches in medical CRP diagnosis (e.g. for CVD, inflammatory bowel disease) require rapid quantification in native matrices. A novel CRP determination method based on magnetic detection is described and tested for human blood serum, saliva and urine. The detection principle is based on two different anti-CRP antibodies (monoclonal, IgG) for CRP trapment and labelling. The linear detection range of this immunosensor ranged from 25 ng/ml to 2.5 microg/ml and is therefore much more sensitive than typical hsCRP-ELISA-assays.

Biomarkers↗

PubMed2006

Rapid method for detection of Salmonella in milk by surface plasmon resonance (SPR).

The Plasmonic surface plasmon resonance (SPR) device was used to develop a rapid, simple and specific immunoassay for detection of Salmonella in milk. Rapid detection of Salmonella contamination is a major challenge for the food industry. Salmonella contamination is well known in all foods including pasteurised milk. The SPR assay was developed as a sandwich model using a polyclonal antibody against Salmonella as capture and detection antibody. Milk spiked with Salmonella typhimurium cells, killed by thimerosal (1%, w/w) treatment was used. Using the Plasmonic SPR assay it was possible to detect S. typhimurium down to a concentration of 1.25 x 10(5) cells ml(-1) in both milk and buffer system. The results obtained are comparable with existing, approved rapid Salmonella detection techniques. No negative effects on the sensitivity of the assay are encountered due to the milk matrix. Hence, no sample preparation or clean-up steps are required. The sample volume requirement for the assay is only 10 microl. Using the assay S. typhimurium was detected in milk within 1h, whereas the cultural techniques require 3-4 days for presumptive positive isolates and further time for confirmation. The rapid tests require at least 24h for the results. The Plasmonic SPR device operates on the Kretschmann configuration and is a cuvette-based system with the advantage of having eight channels on one single SPR chip.

Animals↗

PubMed2006

Magnetic biosensor for the detection of Yersinia pestis.

A novel type of magnetic-beads based magnetic biosensor is described for the detection of Yersinia pestis. Experiments were performed with the antigen fraction F1 of these bacteria. The magnetic sensor platform offers easy and reliable detection of Y. pestis by the use of magnetic beads for labelling and quantification in a single step due to their paramagnetic features. The system uses antiYPF1 antibodies as capture element on ABICAP columns as core element of the magnetic sensor. Several immobilization methods for antibodies on polyethylene were exploited. The established biosensor has a linear detection range of 25-300 ng/ml Y. pestis antigen F1 and a detection limit of 2.5 ng/ml in buffer and human blood serum. The presented sensor system is small, simple, portable and therefore usable as off-lab detection unit for medical and warfare analytes.

Animals↗

PubMed2006

Occurrence and taxonomic significance of cysteine sulphoxides in the genus Allium L. (Alliaceae).

Methiin was present in all investigated samples. In the genus Allium, methiin-dominated species (rarely used by man) were common, but the occurrence of the other cysteine sulphoxides was variable and was largely correlated with use as spices or vegetables. Two major chemical types (named according to the species where they occur) could be distinguished, and at least two more may be recognized. Isoalliin dominates in the widely used "onion-type", which includes chive (A. schoenoprasum) and top onion (A.xproliferum). Pearl onion and leek (A. ampeloprasum) have higher relative amounts of methiin and propiin, respectively. Alliin dominates in the widely used "garlic-type", which includes wild leek (A. obliquum) and sand leek (A. scorodoprasum). Alliin and isoalliin rarely co-dominate, being only found in the cultivated Chinese leek (A. tuberosum). A triple mix of almost equal amounts of methiin, alliin and isoalliin is present in ramson (A. ursinum). General trends in the three evolutionary lines of the genus Allium were apparent. In the first lineage, high amounts of methiin were more frequent, and propiin, although being a minor component in all three evolutionary lines, was present in the highest amounts. Most of the species in the second line showed only traces of cysteine sulphoxides. In the third line, the "onion-type" dominates, the "garlic type" is characteristic for subgenus Allium, and co-dominating alliin and isoalliin also occur. Generally, the total cysteine sulphoxide amount increased, and the complexity of cysteine sulphoxide patterns decreased in the transition from the first to the third evolutionary line.

Allium↗

PubMed2006

Wild Allium species (Alliaceae) used in folk medicine of Tajikistan and Uzbekistan.

BACKGROUND: Hitherto available sources from literature mentioned several wild growing Allium species as "edible" or "medicinally used" but without any further specification. METHODS: New data were gained during recent research missions: Allium plants were collected and shown to the local population which was asked for names and usage of these plants. RESULTS: Information was collected about current medical applications of sixteen wild species, nine of which belong to different sections of Allium subgenus Melanocrommyum. These plants are used against headache, cold, and stomach problems, and are mostly applied fresh or after boiling. CONCLUSION: Close taxonomic relatives of the common onion were used similar to cultivated onion species, but medical use like garlic was mostly reported for species taxonomically not related to garlic.

Allium↗

PubMed2006

Innovative analytical system for screening on lectins.

Lectins are proteins or glycoproteins from plants, animals or microorganisms, which typically bind specifically to sugar residues, e.g., those located in cell walls or membranes. This reaction might change the physiology of the cell wall and influences the metabolism inside the cell. Some lectins of plants stimulate the immune system by unspecific activation of T-cells or influence cell division; others cause agglutination of cells (e.g., erythrocytes) and are therefore from therapeutic interest. In a new approach, biomolecular interaction analysis (BIA) was utilized for a screening program on lectins. The BIA has been done by a new interferometric biosensor based on spectral-phase interference (SPI). The system can be used either for characterisation of lectin binding domains or for a screening on lectins obtained from natural sources. Several lectin binding surfaces on the basis of SPI have been established.

Biosensing Techniques↗

PubMed2005

SPR-based immunosensor for the CRP detection--a new method to detect a well known protein.

The c-reactive protein (CRP) is one of the significant human blood serum markers for inflammatory processes. The serum presence of this hepatic approximately 115 kDa protein of five identical subunits accompanies several diseases (e.g. CVD, inflammatory bowel diseases) and is nowadays detected by high-sensitivity ELISA assays in blood serum. To enable CRP detection in other matrices, an SPR-based (surface plasmon resonance) immunosensor for the CRP detection has been established. A linear detection range of 2-5 microg CRP per ml was found, using two different antiCRP antibodies (monoclonal, IgG) for CRP trapment and detection. Furthermore, the kinetic antibody association and dissociation constants of one antibody (antiCRP, clone C2) could be determined.

Antibodies↗

PubMed2005

Chemical characterization of Allium ursinum L. depending on harvesting time.

Sulfur-containing compounds of ramson (Allium ursinum L.) are responsible for its traditional use in terms of culinary and medicinal purposes. Leaves and bulbs were investigated for their contents of cysteine sulfoxides (volatile precursors) as well as volatile compounds released from minced plant material. Plants were analyzed during the whole vegetation period, focused on the months from March to June. Additionally, within the dormancy period bulbs were analyzed again and alliinase activity was determined. The pattern of volatile compounds was analyzed both by SPME/GC-MS and by SDE/GC-MS. Compared to each other, SDE exhibited a wider spectrum of detectable volatile compounds. The quality and quantity of volatiles significantly depended on the time of harvest. The highest amounts of volatile precursors can be gained in March and April, shortly before flowering time (up to 0.4% of total cysteine sulfoxides). The main cysteine sulfoxides were alliin and isoalliin. It has been found that alliinase of A. ursinum exhibited properties similar to those of alliinase of garlic (Allium sativum L.), but differing in terms of substrate specificity.

Allium↗

PubMed2004

Chemical characterization of interspecific hybrids between Allium cepa L. and Allium kermesinum Rchb.

Interspecific hybridization between wild and cultivated species of the genus Allium has been performed to generate plant material possessing biochemical properties of both parental plants. These cross-breeding experiments should lead to Allium plants with higher amounts of valuable constituents. The chemical characterization of interspecific hybrids between A. cepa and A. kermesinum is described on the basis of their sulfur-containing constituents and secondary metabolites. In addition, the hybrid character has been proven by random amplified polymorphic DNA (RAPD) analysis of the progenies obtained from the crosses. It has been shown that the distribution of the cysteine sulfoxides as well as the volatile secondary metabolites in the hybrids is not uniform. The profiles are mainly determined by the paternal wild species A. kermesinum. It has been ascertained that the gas chromatography profiles of the hybrids show increasing amounts of unsymmetrical substituted oligosulfides, which are known to be physiologically active substances. On the basis of statistical calculations, three different types of hybrids can be separated. The chemical analysis of cysteine sulfoxides and volatile sulfur-containing substances is shown to be a useful tool for breeding purposes as it allows an effective selection with regard to optimal distribution and amount of valuable constituents.

Allium↗

PubMed2003

Development of a biosensor specific for cysteine sulfoxides.

S-Alk(en)yl cysteine sulfoxides have been observed in several plants, mainly belonging to the onion family (Alliaceae), which are of high commercial interest (e.g. garlic, Allium sativum). The quality of most garlic containing herbal remedies produced from garlic powder is determined by their content of the cysteine sulfoxide alliin. Therefore, a comprehensive method for the documentation of alliin amounts present in the fresh plant material through to the final remedy is desirable. The newly developed biosensoric method described in this paper was designed in order to fulfil these demands. In contrast to conventional HPLC-methods, neither a pre-column derivatization nor a chromatographic separation are required allowing a high throughput of samples. This technique is based on immobilized alliinase (EC 4.4.1.4), which was combined with an ammonia-gas electrode. The enzyme was either placed in a small cartridge or was immobilized in direct contact of the electrode surface giving detection limits of 3.7 x 10(-7) and 5.9 x 10(-6) M. Founded on these experiments, a pH-sensitive electrolyte/insulator/semiconductor (EIS) layer structure made of Al/p-Si/SiO(2)/Si(3)N(4) was also combined with immobilized alliinase. Measurements could be performed in a range between 1 x 10(-5) and 1 x 10(-3) M alliin. All sensors were operated in the flow-through modus. A high specificity for alliin could be demonstrated for the electrode and a number of garlic samples were analyzed. Results gained with the new method showed a good correlation with those obtained with conventional HPLC-methods. In addition, onion and a variety of wild Allium species were analyzed in order to determine the amount of isoalliin or total cysteine sulfoxides present, respectively.

Allium↗

PubMed2002

Biosensors: new approaches in drug discovery.

The development of biosensors for analytical purposes has attracted a great deal of attention in recent years. A biosensor is defined as an analytical device consisting of a biological component (e.g., enzyme, antibody, entire cell, DNA) and a physical transducer (e.g., electrode, optical device). Biosensors are mostly designed for routine analysis, such as clinical diagnosis, quality control of food, in-process control of fermentations, and in environmental analysis. Many of these sensors are also suitable for screening purposes in order to find new drugs. Such systems should yield information either about compounds with known bioactivity or about the bioactivity of samples with known or unknown chemical composition. Biosensors intended for the latter purpose are essentially based on whole cells carrying receptors and ion channels at their surfaces. Miniaturization of structures, primarily based on silicon, allows integration of many sensors into arrays, which may be suitable for the screening of natural and chemical products as well as combinatorial libraries. Until now, no commercially available sensors of this kind exist but they are expected in the near future. Different biosensors, based on enzymes, antibodies, cells, artificial membranes and entire animal tissues, which can be used in drug discovery and may lead to efficient screening systems in the future, are described in this review.

Animals↗

PubMed2002

Characterization of some Allium hybrids by aroma precursors, aroma profiles, and alliinase activity.

Various Allium hybrids, obtained by the crossbreeding of Allium cepa (onion) as the mother plant and six taxonomically distant wild species obtained by embryo rescue, were investigated with special respect to their individual profiles of cysteine sulfoxides as well as enzymically and nonenzymically formed aroma substances. Alliinase (EC 4.4.1.4) catalyzes the conversion of odorless (+)-S-alk(en)yl-L-cysteine sulfoxides into volatile thiosulfinates. These thiosulfinates were converted to a variety of sulfides by steam distillation. SPME-gas chromatography (GC) and high-performance liquid chromatography (HPLC) used for the analysis of aroma components and their precursors permitted a high sample throughput, so that numerous gene bank accessions and Allium breeding materials were analyzed within a comparatively short time. Cysteine sulfoxides as well as alliinase activity were found in all investigated samples at different levels, but (+)-S-methyl-L-cysteine sulfoxide (methiin) was the most abundant sulfoxide present. (+)-S-(trans-1-Propenyl)-L-cysteine sulfoxide (isoalliin) is typical for onion and was found in all investigated hybrids. The pattern of the other cysteine sulfoxides depended strongly on the parent plants used. The profile of aroma components corresponded with the related pattern of aroma precursors (cysteine sulfoxides). Successful hybridization was proven by randomly amplified polymorphic DNA analysis. Together with these established marker techniques, HPLC and SPME-GC analysis provide support to breeding projects designed to improve the health and aroma properties of Allium hybrids.

Allium↗