Astrid Ortner

Biosensor for the characterisation of hMAO B inhibitors and the quantification of selegiline

A novel human monoamine oxidase B (hMAO B) based biosensor for inhibitory measurements was developed. It allows both the characterisation of the type of enzyme inhibition and the sensitive and simple determination of inhibitors like selegiline hydrochloride. The sensor consists of a screen printed carbon working electrode modified with 20% manganese dioxide (MnO2) and the enzyme hMAO B, which was immobilised on the electrode via a dialysis membrane (regenerated cellulose, molecular weight cut-off 14000). Inhibition of hMAO B is evaluated by adding different concentrations of the inhibitor selegiline hydrochloride to the enzyme and applying a defined amount of the hMAO B substrate phenylethylamine (PEA). The enzymatically formed H2O2 is amperometrically detected at 0.4V vs. Ag/AgCl in a flow injection analysis (FIA) system. With 100µM PEA the sensor showed a linear correlation between peak height and inhibitor concentration in a range of 0.51-3.25µg/mL selegiline hydrochloride. LOD and LOQ were determined to be 0.15 and 0.51µg/mL, respectively. The sensor showed a repeatability of 3.7% and an intermediate precision of 8.1%. The inhibition-based biosensor was successfully employed to quantify selegiline hydrochloride in pharmaceutical samples. Kinetic studies via Lineweaver-Burk plot and enzyme quantity vs. current plot revealed that the inhibition is irreversible.

Bis-pentafluorobenzyl derivatives of N-acetyl-L-methionine and N-acetyl-L-selenomethionine for the quantitative determination in human plasma by gas chromatography-negative ion chemical ionisation mass spectrometry.

Targeted anti-cancer combination therapy with infusion of N-acetyl-L-methionine (NALM) and N-acetyl-L-selenomethionine (NASeLM) shows promising results in cancer treatment. Selenium has been recognised as a valuable additive in cancer therapeutics due to its ability to minimise side effects of chemotherapy and its role in cancer prevention and therapy. Due to the promising results of this new therapeutic approach evaluation of pharmacokinetic data for NALM and NASeLM is of ultimate importance. We have therefore elaborated a method for the quantitative measurement of these compounds in human plasma based on GC-negative ion chemical ionisation-MS. The derivatisation sequence elaborated can be regarded as a novel strategy for the chemical modification of delicate sulphur- and selenium-containing compounds, and underlines the enhanced reactivity of selenium-analogues of sulphur-containing amino acids. The target compounds were extracted from plasma with ethyl acetate and converted to the S/Se-pentafluorobenzyl-homocysteine pentafluorobenzyl ester derivative. Reaction conditions were optimised for derivative yield. Calibration graphs were established in the range of 2.938-481.105 ng/0.5 mL plasma (NALM) and 0.233-59.543 ng/0.5 mL plasma (NASeLM). Accuracy, precision and stability data were elaborated. The method was applied to pharmacokinetic profiling of the compounds after infusion into human volunteers.

A review of factors associated with maintenance of sinus rhythm after elective electrical cardioversion for atrial fibrillation

Atrial fibrillation is the most common heart‐rhythm disorder, affecting about 1.5% to 2% of the population with an increased risk of mortality and morbidity due to stroke, thromboembolism, and heart failure. If the conversion back to sinus rhythm does not happen spontaneously, pharmacological or electrical cardioversion (ECV) is the next available treatment options for some patients. However, the long‐term success following ECV is variable. This review describes the factors that are associated with maintenance of sinus rhythm following ECV and proposes a clinical strategy based on the available evidence.

Characterization of Oxidative Stress in Chicken Heart Tissue by High-Performance Liquid Chromatography with Ultraviolet‐Visible (HPLC–UV–Vis) Detection

Abstract Oxidative stress can lead to tissue damage in the body, resulting in conditions that may lead to heart failure. Carbonyl proteins and malondialdehyde are common markers for determining oxidative stress. In this study, a high-performance liquid chromatography with ultraviolet‐visible (HPLC–UV–Vis) method was developed for both carbonyl proteins and malondialdehyde and compared with common spectrophotometric methods. The HPLC–UV–Vis method for determining carbonyl proteins showed a linear correlation in a range of 0.05–1.6 µg.mL−1 (correlation coefficient: 0.9939). The limits of detection and quantitation were determined to be 1.7 and 5.1 pmol on-column, respectively. The HPLC–UV–Vis method for malondialdehyde exhibited a linear correlation in the range of 0.04–13.6 µg.mL−1 (correlation coefficient: 0.9982) with limits of detection and quantitation of 1.5 and 4.5 pmol on-column, respectively. As a proof of concept, the applicability of the methods for both marker substances was investigated in chicken heart tissue as a complex matrix sample. To simulate oxidative stress, the tissue was treated with hydrogen peroxide as the oxidizing agent. Samples prepared with hydrogen peroxide showed increased carbonyl protein and malondialdehyde levels when compared to non-oxidized samples and samples treated additionally with the antioxidant Trolox. Regarding oxidative stress, similar results were achieved when compared with common spectrophotometric methods. However, HPLC–UV–Vis presented higher reproducibility and accuracy. The developed methods for both markers enable rapid and simple investigation of possible antioxidant effects on tissue samples.

Development of a cobalt(II) phthalocyanine- MWCNT modified carbon paste electrode for the detection of polyunsaturated fatty acids

In this work the development of an electrochemical sensor for the determination of polyunsaturated fatty acids (PUFAs), in particular linoleic acid, in commercially available safflower oil as complex matrix is described. The sensor consists of a carbon paste electrode with cobalt(II) phthalocyanine, Co(II)Pc, as mediator and multiwalled carbon-nanotubes (MWCNT) as nanomaterial. As carrier medium a sodium borate buffer (0.1 M, pH 9) was used. PUFAs were detected at a working voltage of 0.35-0.45 V (vs. Ag/AgCl). The sensor development was carried out in a batch system with differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Sensor specification was tested by using various fatty acids (stearic acid, oleic acid, linoleic acid, linolenic acid and arachidonic acid) as well as esterified fatty acids, resulting in a specific applicability towards PUFAs, especially linoleic acid (LAH). The optimized sensor was applied in a flow injection analysis system (FIA) for the analysis of PUFAs in complex matrix. Linoleic acid was used as standard substrate to determine the analytical parameters. The linearity ranges between 7.5 and 200 μg mL-1 LAH, while the limit of detection was determined to be 2.5 μg mL-1 and the limit of quantification is approximately 7.5 μg mL-1 LAH. The LAH content was successfully detected in commercially available safflower oil via standard addition method and the results could be confirmed by a reference method. The PUFA content was calculated as LAH-equivalent.

Unexpected deaths in cardiology outpatients – what can we learn from case review?

Objectives A proportion of cardiac patients managed at a cardiology outpatient clinic will die between clinic visits. This study aimed to identify the cause of death, to determine if case review occurred and if a formal review of such cases might be useful. Design Single-centre retrospective cohort study. Setting A remote regional centre in the North of Scotland. Participants All patients who had been removed from the cardiology outpatient clinic due to death in the community. Main outcome measures Cause of death, comorbidities and treatments were collected from hospital records and the national register of deaths. Chi-squared test and Student’s t-test were used with significance taken at the 5% level. Results Of 10,606 patients who attended the cardiology outpatient clinic, 75 (0.7%) patients died in the community. The majority (57.0%) died from a non-cardiac cause. Eleven patients (14.9%) died due to an unexpected cardiac death. A detailed case note review was undertaken. In only two (18.2%) cases was any note made as to the cause of death in the hospital records and in only one was there details of post mortem discussion between primary and secondary care. Conclusions A small proportion of patients attending a cardiology outpatient clinic died in the community. Documentation of the death in the hospital notes was very poor and evidence of post mortem communication between primary and secondary care was absent in all but one case. Better documentation and communication between primary and secondary care would seem desirable.