Potential of capillary electrophoresis for the monitoring of the stability of placental alkaline phosphatase

Alkaline phosphatase (AP) is a potential therapeutic agent in the treatment of sepsis. In this paper the potential of capillary zone electrophoresis (CZE) for the monitoring of the degradation of placental alkaline phosphatase (PLAP) was investigated. To induce degradation PLAP samples were exposed to high temperatures, low and high pH and freeze-drying. The samples were then analyzed by CZE and enzymatic activity assay. Upon exposure to temperatures above 65 degreesC, PLAP lost its activity exponentially over time, while CZE revealed both a linear decrease of the area of the main peak and a rise of degradation products. At acidic pH the enzyme appeared to lose its activity. CZE revealed a decrease of the area of the main peak, but no degradation products could be detected. At pH 12 the enzymatic activity and the area of the main peak both decreased linearly over time and, in addition, formation of degradation products could be detected by CZE. Activity and CZE profile of PLAP remained unchanged upon freeze-drying in the presence of inulin. Prolonged storage of freeze-dried samples at room temperature caused a slight decrease of enzymatic activity, while the potential formation of oligomers was revealed by CZE analysis. The examples in this study show that, in combination with activity assays, CZE can provide useful complementary information, especially on the status of the protein and the presence of degradation products. (C) 2003 Elsevier Science B.V. All rights reserved

Investigations into the stabilisation of drugs by sugar glasses:I. Tablets prepared from stabilised alkaline phosphatase

The aim of this study was to investigate the formulation of sugar glass stabilised alkaline phosphatase from bovine intestine (BIAP) into tablets. Two major subjects of tablet formulation were investigated. First, the compaction behaviour of the inulin sugar glass was investigated. Secondly, the effect of the compaction process on the physical stability of sugar glass stabilised BIAP was investigated, comparing inulin and trehalose glass. The tabletting properties of freeze-dried inulin without BIAP were studied first. Freeze-dried inulin conditioned at either 20°C/0% relative humidity (RH) or 20°C/45% RH was compacted at various pressures. As expected, the yield pressure of the material conditioned at 0% RH was higher (68 MPa) than after conditioning at 45% RH (39 MPa). Tablets made of the material stored at 0% RH showed severe capping tendency, especially at high compaction pressures. In contrast, material conditioned at 45% RH gave tablets without any capping tendency and a friability of less than 1%. Sugar glasses of BIAP and either inulin or trehalose were prepared by freeze-drying (BIAP/sugar 1/19 (w/w)). The material was subsequently compacted. Tablets and powders were stored at 60°C/0% RH. The activity of the incorporated BIAP was measured at various time intervals. It was found that inulin was by far superior to trehalose as stabiliser of BIAP in tablets. The poor stabilising capacities of trehalose after compaction are explained by crystallisation of trehalose induced by the compaction process and moisture in the material. The results clearly show that inulin is an excellent stabiliser for BIAP. The tabletting properties are adequate, showing sufficient tablet strengths and low friability. Furthermore, the good (physical) stability of inulin glass with respect to exposure to high relative humidities makes it practical to work with. © 2002 Elsevier Science B.V. All rights reserved

Investigations into the stabilisation of drugs by sugar glasses:II: Delivery of an inulin-stabilised alkaline phosphatase in the intestinal lumen via the oral route

In this study the possibility to deliver the acid-sensitive enzyme alkaline phosphatase (AP) from calf intestine (CIAP) to the intestinal system by oral administration was investigated. Tablets were prepared and in vitro evaluated. Final proof of concept studies were performed in rats. This acid labile enzyme is potentially useful in the treatment of sepsis, a serious condition during which endotoxins can migrate into the blood stream. The CIAP was freeze-dried with inulin and subsequently compacted into round biconvex tablets with a diameter of 4mm and a weight of 25-30mg per tablet. The tablets were coated with an enteric coating in order to ensure their survival in the stomach. In vitro evaluation of tablets containing alkaline phosphatase from bovine intestine (BIAP) was the first step in the development. It was found that tablets without enteric coating dissolved rapidly in 0.10M HCl with total loss of enzymatic activity of the alkaline phosphatase. Tablets that were coated were stable for at least 2h in 0.10M HCl, but dissolved rapidly when the pH was increased to 6.8. Furthermore, it was shown that the enzymatic activity of the released BIAP was fully preserved. The in vivo test clearly showed that the oral administration of enteric coated tablets resulted in the release of enzymatically active CIAP in the intestinal lumen of rats. The location of the enhanced enzymatic activity of AP in the intestines varied with the time that had passed between the administration of the tablets and the sacrificing of the rats. Also, the level of enzymatic activity increased with an increasing number of tablets that were administered. © 2003 Elsevier Science B.V. All rights reserved

Excitation of Alfven eigenmodes by fusion-born alpha-particles in D-He-3 plasmas on JET

Alfven eigenmode (AE) instabilities driven by alpha-particles have been observed in D-He-3 fusion experiments on the Joint European Torus (JET) with the ITER-like wall. For the efficient generation of fusion alpha-particles from D-He-3 fusion reaction, the three-ion radio frequency scenario was used to accelerate the neutral beam injection 100 keV deuterons to higher energies in the core of mixed D-He-3 plasmas at high concentrations of He-3. A large variety of fast-ion driven magnetohydrodynamic modes were observed, including the elliptical Alfven eigenmodes (EAEs) with mode numbers n = -1 and axisymmetric modes with n = 0 in the frequency range of EAEs. The simultaneous observation of these modes indicates the presence of rather strong alpha-particle population in the plasma with a 'bump-on-tail' shaped velocity distribution. Linear stability analysis and Fokker-Planck calculations support the observations. Experimental evidence of the AEs excitation by fusion-born alpha-particles in the D-He-3 plasma is provided by neutron and gamma-ray diagnostics as well as fast-ion loss measurements. We discuss an experimental proposal for the planned full-scale D-T plasma experiments on JET based on the physics insights gained from these experiments

Enhanced performance in fusion plasmas through turbulence suppression by megaelectronvolt ions

© 2022, The Author(s), under exclusive licence to Springer Nature Limited.Alpha particles with energies on the order of megaelectronvolts will be the main source of plasma heating in future magnetic confinement fusion reactors. Instead of heating fuel ions, most of the energy of alpha particles is transferred to electrons in the plasma. Furthermore, alpha particles can also excite Alfvénic instabilities, which were previously considered to be detrimental to the performance of the fusion device. Here we report improved thermal ion confinement in the presence of megaelectronvolts ions and strong fast ion-driven Alfvénic instabilities in recent experiments on the Joint European Torus. Detailed transport analysis of these experiments reveals turbulence suppression through a complex multi-scale mechanism that generates large-scale zonal flows. This holds promise for more economical operation of fusion reactors with dominant alpha particle heating and ultimately cheaper fusion electricity.N