| 1. |
- Boija, Elisabet, et al.
(författare)
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Bilayer disk capillary electrophoresis : a novel method to study drug partitioning into membranes
- 2008
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835 .- 1522-2683. ; 29:16, s. 3377-3383
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Tidskriftsartikel (refereegranskat)abstract
- CE in the presence of lipid bilayer disks was introduced as a new approach in membrane partitioning studies. The disks were used as a pseudostationary phase in the partial-filling mode of CE and the partitioning of cationic drugs was determined. The migration times of the analytes increased linearly with the lipid amount in the system. An appropriate algorithm for the calculation of a partition coefficient is presented. In the disk-shaped bilayers, which have excellent stability and shelf life, all of the lipids are readily available for interaction and the disks can be used as realistic cell membrane models.
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| 2. |
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| 3. |
- Boija, Elisabet, et al.
(författare)
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Effects of ions and detergents in drug partition chromatography on liposomes
- 2004
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Ingår i: Journal of chromatography A. - : Elsevier BV. - 0021-9673. ; 1030, s. 273-278
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Tidskriftsartikel (refereegranskat)abstract
- We have determined drug partitioning into phospholipid bilayers by immobilized-liposome chromatography. Electrostatic effects on the drug partitioning were observed on neutral bilayers at low ionic strength. The size of the counterions affected the partitioning. When liposomes were supplemented with ionic detergents the partitioning of charged drugs was strongly affected, allowing complete separation of drugs of different charges which showed similar retention on neutral bilayers. Partial separation was obtained on bilayers containing fatty acid. Detergent ions or fatty acid inserted into phospholipid bilayers affected the partitioning of drugs much more than did free ions or phospholipid head group charges.
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| 4. |
- Boija, Elisabet, et al.
(författare)
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Evaluation of bilayer disks as plant cell membrane models in partition studies
- 2007
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Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 364:2, s. 145-152
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the partitioning of a set of phenolic compounds used as lignin precursor models into lipid bilayer disks and liposomes. The bilayer disks are open bilayer structures stabilized by polyethylene glycol-conjugated lipids. Our results indicate that disks generate more accurate partition data than do liposomes. Furthermore, we show that the partitioning into the membrane phase is reduced slightly if disks composed of 1,2-distearoyl-sn-glycero-3-phosphocholine and cholesterol are exchanged for disks with a lipid composition mimicking that of the root tissue of Zea mays L.
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| 5. |
- Boija, Elisabet, et al.
(författare)
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Interactions between model membranes and lignin-related compounds studied by immobilized liposome chromatography
- 2006
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Ingår i: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier BV. - 0005-2736 .- 1879-2642. ; 1758:5, s. 620-626
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Tidskriftsartikel (refereegranskat)abstract
- In order to elucidate the modes of interaction between lignin precursors and membranes, we have studied the influence of temperature, lipid composition and buffer composition on the partitioning of monolignol and dilignol model substances into phospholipid bilayers. The partitioning was determined by immobilized liposome chromatography, which is an established method for studies of pharmaceutical drugs but a new approach in studies of lignin synthesis. The temperature dependence of the retention and the effect of a high ammonium sulfate concentration in the mobile phase demonstrated that the interaction involved both hydrophobic effects and polar interactions. There was also a good correlation between the partitioning and the estimated hydrophobicity, in terms of octanol/water partitioning. The partitioning behavior of the model substances suggests that passive diffusion over the cell membrane is a possible transport route for lignin precursors. This conclusion is strengthened by comparison of the present results with the partitioning of pharmaceutical drugs that are known to pass cell membranes by diffusion.
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| 6. |
- Boija, Elisabet, 1977-
(författare)
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Partitioning of Drugs and Lignin Precursor Models into Artificial Membranes
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main aim of this thesis was to characterize membrane-solute interactions using artificial membranes in immobilized liposome chromatography or capillary electrophoresis. The partitioning of a solute into a cell membrane is an essential step in diffusion across the membrane. It is a valid parameter in drug research and can be linked to the permeability as well as the absorption of drugs. Immobilized liposome chromatography was also used to study partitioning of lignin precursor models. Lignin precursors are synthesized within plant cells and need to pass the membrane to be incorporated into lignin in the cell wall. In immobilized liposome chromatography, liposomes or lipid bilayer disks were immobilized in gel beads and the partitioning of solutes was determined. Capillary electrophoresis using disks as a pseudostationary phase was introduced as a new approach in drug partitioning studies. In addition, octanol/water partitioning was used to determine the hydrophobicity of the lignin precursor models. Electrostatic interactions occurred between bilayers and charged drugs, whereas neutral drugs were less affected. However, neutral lignin precursor models exhibited polar interactions. Moreover, upon changing the buffer ionic strength or the buffer ions, the interactions between charged drugs and neutral liposomes were affected. Hydrophobic interactions were also revealed by including a fatty acid or a neutral detergent into the bilayer or by using a buffer with a high salt concentration. The bilayer manipulation had only a moderate effect on drug partitioning, but the high salt concentration had a large impact on partitioning of lignin precursor models. Upon comparing the partitioning into liposomes and disks, the latter showed a more pronounced partitioning due to the larger fraction of lipids readily available for interaction. Finally, bilayer disk capillary electrophoresis was successfully introduced for partitioning studies of charged drugs. This application will be evaluated further as an analytical partitioning method and separation technique.
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| 7. |
- Eichenlaub, Manuel, et al.
(författare)
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Comparator Data Characteristics and Testing Procedures for the Clinical Performance Evaluation of Continuous Glucose Monitoring Systems
- 2024
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Ingår i: Diabetes Technology & Therapeutics. - : Mary Ann Liebert. - 1520-9156 .- 1557-8593. ; 26:4, s. 263-275
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Tidskriftsartikel (refereegranskat)abstract
- Comparing the performance of different continuous glucose monitoring (CGM) systems is challenging due to the lack of comprehensive guidelines for clinical study design. In particular, the absence of concise requirements for the distribution of comparator (reference) blood glucose (BG) concentrations and their rate of change (RoC), that are used to evaluate CGM performance, impairs comparability. For this article, several experts in the field of CGM performance testing have collaborated to propose characteristics of the distribution of comparator measurements that should be collected during CGM performance testing. Specifically, it is proposed that at least 7.5% of comparator BG concentrations are <70 mg/dL (3.9 mmol/L) and >300 mg/dL (16.7 mmol/L), respectively and that at least 7.5% of BG-RoC combinations indicate fast BG changes with impending hypo- or hyperglycemia, respectively. These proposed characteristics of the comparator data can facilitate the harmonization of testing conditions across different studies and CGM systems and ensure that the most relevant scenarios representing real-life situations are established during performance testing. In addition, a study protocol and testing procedure for the manipulation of glucose levels is suggested that enables the collection of comparator data with these characteristics. This work is an important step towards establishing a future standard for the performance evaluation of CGM systems.
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| 8. |
- Freckmann, Guido, et al.
(författare)
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Clinical Performance Evaluation of Continuous Glucose Monitoring Systems : A Scoping Review and Recommendations for Reporting
- 2023
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Ingår i: Journal of Diabetes Science and Technology. - : Sage Publications. - 1932-2968. ; 17:6, s. 1506-1526
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Forskningsöversikt (refereegranskat)abstract
- The use of different approaches for design and results presentation of studies for the clinical performance evaluation of continuous glucose monitoring (CGM) systems has long been recognized as a major challenge in comparing their results. However, a comprehensive characterization of the variability in study designs is currently unavailable. This article presents a scoping review of clinical CGM performance evaluations published between 2002 and 2022. Specifically, this review quantifies the prevalence of numerous options associated with various aspects of study design, including subject population, comparator (reference) method selection, testing procedures, and statistical accuracy evaluation. We found that there is a large variability in nearly all of those aspects and, in particular, in the characteristics of the comparator measurements. Furthermore, these characteristics as well as other crucial aspects of study design are often not reported in sufficient detail to allow an informed interpretation of study results. We therefore provide recommendations for reporting the general study design, CGM system use, comparator measurement approach, testing procedures, and data analysis/statistical performance evaluation. Additionally, this review aims to serve as a foundation for the development of a standardized CGM performance evaluation procedure, thereby supporting the goals and objectives of the Working Group on CGM established by the Scientific Division of the International Federation of Clinical Chemistry and Laboratory Medicine.
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| 9. |
- Helmersson, Johanna, et al.
(författare)
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Lower creatinine concentration values and lower inter-laboratory variation among Swedish hospital laboratories in 2014 compared to 1996 : results from the Equalis external quality assessment program
- 2019
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Ingår i: Clinical Chemistry and Laboratory Medicine. - : Walter de Gruyter GmbH. - 1434-6621 .- 1437-4331. ; 57:6, s. 838-844
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Tidskriftsartikel (refereegranskat)abstract
- Background:Creatinine measurement for estimation of glomerular filtration rate (GFR) is a frequently used laboratory test. Differences in analytic creatinine methods have caused large inter-laboratory variation. International and national standardization efforts have been made in the last decade.Methods:This study describes the results of the standardization efforts in Sweden by summarizing data for creatinine concentration in blood plasma in the Equalis quality assessment program during 1996-2014.Results:Non-compensated Jaffe methods dominated in 1996-2001 (91 of 103 laboratories; 90%) and were then gradually replaced by either compensated Jaffe methods or enzymatic creatinine methods. In 2014 a majority of Swedish hospital laboratories (139 of 159; 87%) used enzymatic methods. The reported mean creatinine value by the Swedish laboratories was about 10 mu mol/L higher than the isotope dilution mass spectrometry (IDMS) assured reference value in 2003, but consistent with the reference value from 2009 to 2014. The inter-laboratory CV was 7%-9% for creatinine values until 2007, and thereafter gradually decreased to about 4%-5% in 2014.Conclusions:The introduction of enzymatic methods in Swedish laboratories has contributed to achieving a low inter-laboratory variation. Also, the reported values are lower for enzymatic methods compared to Jaffe methods, and the values obtained with enzymatic methods were consistent with IDMS certified values established at reference laboratories. Thus, many Swedish hospital laboratories reported 10 mu mol/L lower, and more true, creatinine concentrations in 2012 than in 2003, which may cause bias in longitudinal studies.
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| 10. |
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