Biomedical subjects

Magdalena Maj-Zurawska

Publications and source records attributed to Magdalena Maj-Zurawska.

9 recordsLinked to original sources

PubMed2006

Time-dependent phenomena in the potential response of ion-selective electrodes treated by the Nernst-Planck-Poisson model. 1. Intramembrane processes and selectivity.

The variability of selectivity coefficients, resulting from potential changes over time and the concentration ratio of primary to interfering ions, impedes many practical applications of ion-selective electrodes (ISEs). Existing theoretical interpretations of ISE selectivity are restricted by severe assumptions, such as steady state and electroneutrality, which hinder theorizing on this problem. For this reason, for the first time, the Nernst-Planck-Poisson equations are used to predict and visualize the selectivity variability over time and the concentration ratio. Special emphasis is placed on the non-Nernstian response in the measurements with liquid-ion-exchanger- and neutral-carrier-based ISEs. The conditions under which measured selectivity coefficients are true (unbiased) are demonstrated.

Journal Article↗

PubMed2006

Ion-selective electrode for measuring low Ca2+ concentrations in the presence of high K+, Na+ and Mg2+ background.

In this work, ion-selective electrodes for calcium ion were investigated. Two ionophores were used in the membranes: ETH 1001 and ETH 129. An internal filling solution buffered for primary ion was used that allowed the lower detection limit to be decreased down to 10(-8.8) M. Theoretical and experimental electrode characteristics pertaining to both primary and interfering ions are discussed. Better behavior was obtained with the electrode prepared with ETH 129 in the membrane. This electrode would be the most likely candidate for obtaining a low Ca(2+) detection limit in measurements performed with high K(+), Na(+), Mg(2+) background, which is found inside the cells of living organisms, for example. The potentiometric response of the electrode in solutions containing main and interfering ions is in good agreement with simulated curves obtained using the Nernst-Planck-Poisson (NPP) model.

Calcium↗

PubMed2005

DNA-based electrochemical biosensors for monitoring of bis-indoles as potential antitumoral agents, chemistry, X-ray crystallography.

Facile and practical electrochemical DNA bioassay, X-ray diffraction analysis, synthesis and 1H and 13C NMR data of the 5,5'-disubstituted-3,3'-methanediyl-bis-indoles are reported. On the basis of electrochemical measurements we have hypothesized that the analyzed bis-indoles have an effect on human tumor cells due to DNA binding at adenine-thymidine deoxynucleotides rich region in a concentration/substituent dependent manner. Interesting N-H...pi and hydrogen-bonding intermolecular interactions were observed which may differentiate their biological features. The 5,5'-dimethoxy-3,3'-methanediyl-bis-indole (2) was found to reduce considerably the growth of cancer cell lines HOP-92 (lung), A498 (renal) and MDA-MB-231/1TCC (breast). The results indicate that title compounds could be interesting as potential antitumoral chemotherapeutics.

Antineoplastic Agents↗

PubMed2004

Factors affecting the potentiometric response of all-solid-state solvent polymeric membrane calcium-selective electrode for low-level measurements.

An all-solid-state calcium-selective electrode was constructed with poly(pyrrole) solid-contact doped with calcium complexing ligand Tiron. The potentiometric response of this sensor can have a linear range down to 10(-)(9) M with a slope close to Nernstian and detection limit equal to 10(-)(9.6). The effects of pH and the activity of the interfering ion in the conditioning solution on the potentiometric behavior of the constructed sensors were examined. Potential stability, reproducibility, and impedance studies were performed. The selectivity of the constructed electrode is better than that of the conventional calcium-selective electrode with internal filling solution of 10(-)(2) M CaCl(2) and comparable to that of the best liquid-contact electrodes.

Calcium↗

PubMed2004

Ionized magnesium in erythrocytes--the best magnesium parameter to observe hypo- or hypermagnesemia.

BACKGROUND: Almost 99% of the body magnesium is inside cells. The concentration of intracellular ionized magnesium (iMg) is physiologically relevant. iMg in erythrocytes is a new parameter that can help to establish reliable information on the functional magnesium status. METHODS: iMg concentration in erythrocytes and serum was measured by ion-selective electrode, in clinical analyzer Microlyte (KONE). Total magnesium (tMg) concentration was measured by atomic absorption spectrometry (AAS). Albumin and total protein concentration were measured colorimetrically. RESULTS: In critically ill postoperative patients, the mean of albumin, protein and hematocrit concentration was significantly lower compared to healthy individuals. Hypomagnesemia was found in 15.9% patients as tMgs, at 22.2% as iMgs and 36.5% as iMge. Significant correlations are between iMgs and tMgs or iMge and iMgs/tMgs. In dialyzed patients, the mean of hematocrit was significantly lower, iMge was significantly higher compared with healthy individuals. Significant negative correlations are between iMgs and tMge or iMge/tMge and tMge. CONCLUSIONS: iMge is the best magnesium parameter to observe hypo- or hypermagnesemia for both groups of patients. The function of magnesium is mainly intracellular and intracellular magnesium concentrations can be the method to evaluate the magnesium status.

Adolescent↗

PubMed2003

Improving the detection limit of anion-selective electrodes: an iodide-selective membrane with a nanomolar detection limit.

The lower detection limit and the selectivity behavior of anion-selective electrodes (ISEs) are improved by using optimized inner solutions and membrane compositions. With a membrane based on the recently described ionophore [9]mercuracarborand-3, a detection limit of 2 x 10(-9) M has been achieved for iodide. Nevertheless, the improvements are less pronounced than in the case of cation ISEs. This is mainly due to the fact that so far no anion ISE is known with the extremely high selectivities of cation ISEs. If the membrane does not contain an ionophore, leaching of the ion exchanger from the membrane into the sample is also a relevant limiting factor except for ion exchangers of very high lipophilicity.

Anions↗

PubMed2003

All-solid-state calcium solvent polymeric membrane electrode for low-level concentration measurements.

An all-solid-state calcium-selective electrode with a plastic membrane phase containing a calcium ionophore ETH-1001 placed on poly(3-methylthiophene) ion-to-electron transducting layer functionalized to bind calcium cations has been constructed. The obtained potentiometric sensors were characterized with a calibration line of slope close to Nernstian within the activity from 10(-5) to 0.1 M. For Ca2+ activity lower than 10(-5) M, super-Nernstian behavior was observed. The super-Nernstian response that is observed for electrodes with an internal solution strongly binding primary ions was in this case attributed to incorporation of calcium ions in the modified solid-contact phase. With this arrangement, the evaluation of selectivity coefficients much closer to those that depend on the properties of the ion-selective membrane itself was possible.

Journal Article↗

PubMed2003

Carbonate ion-selective electrode with reduced interference from salicylate.

A carbonate ion-selective electrode for determination of total carbon dioxide species such as carbon dioxide, bicarbonate and carbonate with reduced interference from salicylate is described. Derivatives of trifluoroacetophenone were used as neutral carriers for carbonate. A polymer-free liquid carbonate-selective membrane with a cellophane outer membrane was found to give a carbonate-selective electrode with a negligible response to salicylate. The electrical contact was obtained by insertion of a silver/silver chloride electrode directly into the liquid membrane. The electrode does not require any aqueous filling solution and is therefore maintenance-free. The response to carbon dioxide species was found to be highly reproducible with a response time of 1-2 min at total carbon dioxide concentrations in the range from 5 to 50 mM. The lifetime of the electrode was at least 3 months. The electrode is regarded as very promising for clinical analysis of carbon dioxide species in body fluids such as plasma and serum.

Artifacts↗

PubMed2002

Comparison of the potentiometric, (31)P NMR, and zero-point titration methods of determining ionized magnesium in erythrocytes.

A simple and rapid method of determining ionized magnesium in erythrocytes using a potentiometric clinical analyzer, Microlyte 6 (Kone, Finland), was investigated. The erythrocyte cell membranes were destroyed using ultrasound. The results were compared with those obtained with the (31)P nuclear magnetic resonance spectroscopy method and the zero-point titration method using atomic absorption spectrometry. The results obtained from potentiometry and from the other methods did not differ significantly (Student t test, alpha = 0.01). Total magnesium concentration was determined using atomic absorption spectrometry.

Adult↗