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Biomedical subjects

R Hintsche

Publications and source records attributed to R Hintsche.

17 recordsLinked to original sources
PubMed1997

Miniaturized ion-selective chip electrode for sensor application.

The performance of miniaturized potentiometric cells, with multilayer, planar ion-selective sensors in aqueous electrolyte solutions, human serum, urine, and whole blood, is presented. The basic steps of the fabrication with silicon technology are summarized. The effect of the contact surface between the internal reference system and the ion-sensitive membrane on the analytical characteristics of potassium- and calcium-sensitive sensors is studied. Silicone rubber-, high molecular weight PVC-, carboxylated PVC and aliphatic polyurethane (Tecoflex)-based solvent polymeric membranes were dispensed into anisotropically etched wells on silicon wafers, and the resulted planar sensors were tested in terms of their ion sensitivity (slopes of the cell voltage-pK or pCa calibration curves), long-term stability, and reproducibility. For the assay of potassium in whole blood, the miniaturized potentiometric cell was built in a flow-through manifold. To achieve the required precision, the flow conditions were optimized and the sensors calibrated periodically. The results prove the feasibility of the new sensor design and satisfy the particularly difficult requirements for the analysis of biological samples.

Biosensing Techniques↗
PubMed1997

Microbiosensors using electrodes made in Si-technology.

The combination of electrochemical transducers made in silicon technology with chemical and biochemical components has been used to manufacture miniaturized sensor structures. Three different types of sensors have been developed and optimized for practical use; (i) an ion-selective sensor, (ii) a glucose enzyme sensor, (iii) a redox-amplifying sensor for immunosensing. The immunodetection based on the redox recycling of mediator molecules is shown for low and high molecular weight analytes. The sensors have been integrated with miniaturized fluidic components and combined with sensor-related electronics and a common microcontroller.

Antigen-Antibody Complex↗
PubMed1991

Second generation biosensors.

Enzyme-membrane electrodes using glucose oxidase in combination with peroxide detection dominate in the field of laboratory analyzers for diluted samples. Using the same indication principle, extremely fast responding glucose sensors have been fabricated by covering thin metal electrodes with a porous enzyme layer. In the second generation auxiliary enzymes and/or co-reactants are coimmobilized with the analyte converting enzyme in order to improve the analytical quality and to simplify the performance. Following this line oxidizable interferences are suppressed by using a glucose oxidase/peroxidase complex which communicates with the electrode at a low working potential. Furthermore, fluctuations of pH or buffer capacity are ineffective when using a glucose oxidase/peroxidase layer covered fluoride FET in the potentiometric glucose determination. Enzymatic recycling of the analyte and/or accumulation of intermediates increase the sensitivity by several orders of magnitude. Inclusion of NAD bound to PEG in the glucose dehydrogenase layer allows a reagentless glucose measurement.

Biosensing Techniques↗
PubMed1989

Glucose measurement in diluted blood.

The sensitivity, measuring range and lifetime of enzyme electrodes using glucose oxidase sandwiched between dialysis membranes or alternatively in a polyurethane layer directly on the surface of a platinum electrode are compared. The GOD modified electrode exhibits the highest sensitivity. However, the signal depends strongly on the stirring rate. Using the sandwich membranes up to 120 diluted blood samples per hour with a serial coefficient of variation below 1% can be analyzed.

Biosensing Techniques↗
PubMed1983

[1H-NMR study of the Naja naja oxiana neurotoxin II and its spin-labeled derivatives. Conformation of "short" neurotoxins].

In 1H NMR spectra of neurotoxin II N. n. oxiana the chemical shift pH-dependences in H2O and 2H2O solutions were studied, and also the deuterium exchange rates and chemical shift temperature gradients were measured for the amide protons. The spin probe method was applied to assess the degree of exposure into solvent of the amide and side chain protons. With the purpose of establishing mutual disposition of certain neurotoxin II groupings, nuclear Overhauser effect was studied in the 1H NMR spectra, along with the broadening of proton resonances induced by spin labels selectively attached to epsilon-amino groups of Lys26, Lys27, Lys45 or Lys47. The mobility of these labels was determined from the EPR spectra. The methyl resonances of Val and Leu residues were assigned to a definite position in the amino acid sequence. The following pKa were determined: alpha-NH2 Leu1 (9,2), gamma-COOH Glu2 (3,7), alpha-COOH Asn62 (1,3). The protonation of a carboxyl group(s) in neurotoxin II (alpha-COOH Asn62 seems to be involved) decreases the temperature stability of the neurotoxin II conformation. On the basis of studies on neurotoxin II and some other homologous neurotoxins, the model for the "short" neurotoxin folding in solution was proposed. Comparison of experimental data for the disposition of equivalent groups in homologous neurotoxins and in the X-ray structure of erabutoxin b Laticauda semifasciata revealed that the Val46 side chain in solution might change its orientation by 180 degrees with respect to polypeptide backbone. Binding of spin labeled neurotoxin II derivatives to the acetylcholine receptor was discussed in light of the obtained data.

Amino Acid Sequence↗
PubMed1975

[NMR spectroscopic characterization of deuterohemin complexes in aqueous media].

1H-NMR measurement and NMR susceptibility measurements were carried out with deuterohemin complexes in aqueous solution. The hydroxyaquo complex of deuterohemin, which is dimeric in weakly alkaline medium, turns into a low-spin dicyano complex on addition of cyanide. This reaction proceeds in two steps: whereas in the first, slow step a dimeric low-spin hydroxycyano complex is formed, in the second step the latter is converted quickly into the dimeric dicyano complex. The pK values for the overall reaction, the first and the second step were measured to be 23.25; 0.39 and 22.86, respectively. The values of free energy variation obtained therefrom suggest that conformational changes are decisive in the liganding of methemoglobin.

Cyanides↗