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- Bergqvist, Björn, 1965, et al.
(författare)
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Effect of microwave radiation on permeability of liposomes. Evidence against non-thermal leakage
- 1994
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Ingår i: Biochimica et Biophysica Acta - General Subjects. - : Elsevier BV. - 1872-8006 .- 0304-4165. ; 1201:1, s. 51-54
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Tidskriftsartikel (refereegranskat)abstract
- The effect of 2.45 GHz microwave radiation on the permeability of unilamellar phosphatidylcholine liposomes has been studied. Leakage of 5(6)-calboxyfluorescein from the liposomes was measured using spectrofluorimetry after exposure to either microwaves or thermal heating for 5-20 min intervals. The exposure temperature, 37.6 +/- 0.5 degrees C, was well above the phase transition temperature of the lipid membrane. The microwave exposure did not result in any non-thermal increase in permeability above that produced by thermal heating. This study refutes the results reported by Saalman et al. [1] in which an increased liposome permeability due to microwave exposure was reported. The refined analysis in the present study shows that this increased liposome permeability was not a non-thermal microwave effect.
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| 5. |
- Bergqvist, Yngve, et al.
(författare)
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In memory of Niklas Lindegardh
- 2012
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Ingår i: Bioanalysis. - 1757-6180 .- 1757-6199. ; 4:6, s. 751-751
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Blessborn, Daniel, et al.
(författare)
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A new approach to evaluate stability of amodiaquine and its metabolite in blood and plasma
- 2006
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Ingår i: Journal of Pharmaceutical and Biomedical Analysis. - : Elsevier BV. - 0731-7085 .- 1873-264X. ; 41:1, s. 207-212
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Tidskriftsartikel (refereegranskat)abstract
- A stability study for amodiaquine (AQ) and desethylamodiaquine (AQm) in whole blood and plasma is reported. AQ, AQm and chloroquine (CQ) were simultaneously analysed and the ratios AQ/CQ and AQm/CQ were used to ensure correct interpretation of the stability results. CQ was stable in whole blood and plasma at all tested temperatures enabling it to be a stability marker in stability studies. Simultaneous analysis of compounds, of which at least one is already known to be stable, permits a within sample ratio to be used as a stability indicator, The new approach significantly reduced bias when compared to the traditional approach. AQ and AQm were stable in plasma at -86 degrees C and -20 degrees C for 35 days, at 4 degrees C for 14 days and at 22 degrees C for 1 day. AQ and AQm were stable in blood at -86 degrees C and 4 degrees C for 35 days, at -20 degrees C and 22 degrees C for 7 days and at 37 degrees C for 1 day.
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| 7. |
- Blessborn, Daniel, et al.
(författare)
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Assay for screening for six antimalarial drugs and one metabolite using dried blood spot sampling, sequential extraction and ion-trap detection
- 2010
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Ingår i: Bioanalysis. - : Future Science Ltd. - 1757-6180 .- 1757-6199. ; 2:11, s. 1839-1847
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Tidskriftsartikel (refereegranskat)abstract
- Background: More parasites are becoming resistant to antimalarial drugs, and in many areas a change in first-line drug treatment is necessary. The aim of the developed assay is to help determine drug use in these areas and also to be a complement to interviewing patients, which will increase reliability of surveys.Results: This assay detects quinine, mefloquine, sulfadoxine, pyrimethamine, lumefantrine, chloroquine and its metabolite desethylchloroquine in a 100-mu l dried blood spot. Most of the drugs also have long half-lives that make them detectable at least 7 days after administration. The drugs are extracted from the dried blood spot with sequential extraction (due to the big differences in physicochemical properties), solid-phase extraction is used as sample clean-up and separation is performed with gradient-LC with MS ion-trap detection.Conclusion: Detection limits (S/N > 5:1) at 50 ng/ml or better were achieved for all drugs except lumefantrine (200 ng/ml), and thus can be used to determine patient compliance. A major advantage of using the ion-trap MS it that it will be possible to go back into the data and look for other drugs as needed.
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| 8. |
- Blessborn, Daniel, et al.
(författare)
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Assay for screening self medication of common antimalarial drugs using the dried blood spot technique
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Annan publikation (populärvet., debatt m.m.)abstract
- The aim of the developed assay is to determine drug use and self medication in areas where achange in treatment policy has taken place. The assay will be a complement to interviewing patients and will increase reliability of the survey. Several of the drugs included in this screening assay have long half-lifes e.g. chloroquine, sulfadoxine, mefloquine, andlumefantrine and are detectable at least 7 days after administration. The sample collection is very simple, using 100 μl capillary whole blood applied onto Whatman 31 ET Chr filter paper.The drugs are extracted from the dried blood spot with two different extraction methods (due to the big differences in physico-chemical properties). Solid phase extraction is used as sample clean-up and separation is performed with gradient-LC with MS ion-trap detection. Detection limits (S/N > 5:1) at 50 ng/ml or better were achieved for all drugs except lumefantrine (200 ng/ml)
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| 9. |
- Blessborn, Daniel, et al.
(författare)
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Determination of Lumefantrine after Capillary Sampling onto Sampling Paper
- 2007
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Ingår i: The Royal Society of Tropical Medicine and Hygiene. - London.
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Konferensbidrag (refereegranskat)abstract
- The antimalarial lumefantrine was first synthesised and registered in China and is now commercially available as a coformulated product together with artemether (Coartem®/Riamet®). This combination is well tolerated and has proven highly efficacious for treatment of uncomplicated falciparum malaria. Lumefantrine is highly lipophilic with an extensive protein binding (99.9%). The day 7 plasma lumefantrine level has been shown to be an important determinant of treatment efficacy. To date no method has been published for the determination of lumefantrine after capillary sampling onto filter paper for field use. The aim of this work was to develop a method with adequate sensitivity for quantification of lumefantrine in capillary blood sampled onto filter paper. The method has been validated according to the current FDA guideline for bioanalytical method validation. Method: Whatman 31 ET Chr filter paper was pre-treated with an organic acid before sampling capillary blood to enable a high recovery of lumefantrine. Lumefantrine was extracted from the filter paper, then further purified using solid phase extraction and finally quantified with HPLC. Results: The between day variation is below 10 % over the range 0.4 to 25 µmol/l. The lower limit of quantification is 0.25 µmol/l in 100 µl capillary blood. No decrease in Lumefantrine concentration in dried blood spot is seen after 3 months at 37o C. The field sampling for lumefantrine assay with pre-treated Whatman 31 ET Chr has been tested in Tanzania with good results. Discussion: The field sampling for lumefantrine concentration assay with pre-treated Whatman 31 ET Chr has been evaluated and proven to be a valid method for field studies. The day 7 level after treatment can lumefantrine be accurately estimated in capillary blood to follow up compliance and efficacy. Validation data will be presented.
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