Parameters influencing the determination of liposome lamellarity by 31P-NMR

Fröhlich, Margret; Brecht, Volker; Peschka‐Süss, Regine

doi:10.1016/s0009-3084(00)00220-6

Cited by 81 publications

(51 citation statements)

References 33 publications

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“…The phosphoinositide-containing and control liposomes gave an average radius of 60.4 and 65.9 nm, respectively, with high homogeneity (low % polydispersity, 100% intensity, and 100% mass). The lamellarity of prepared liposomes was calculated as reported previously (37), and for the phosphoinositide-containing and control liposomes, the lamellarities were estimated to be 0.8 and 0.72, respectively. The stability of the liposomes during the interactions with proteins was evaluated by Dynamic Light Scattering experiments, in which the size of the liposomes was recorded over time.…”

Section: Sample Preparation-the Human P47mentioning

confidence: 99%

Atypical Membrane-embedded Phosphatidylinositol 3,4-Bisphosphate (PI(3,4)P2)-binding Site on p47 Phox Homology (PX) Domain Revealed by NMR

Stampoulis

Ueda

Matsumoto

et al. 2012

Journal of Biological Chemistry

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Section: Sample Preparation-the Human P47mentioning

confidence: 99%

Atypical Membrane-embedded Phosphatidylinositol 3,4-Bisphosphate (PI(3,4)P2)-binding Site on p47 Phox Homology (PX) Domain Revealed by NMR

Stampoulis

Ueda

Matsumoto

et al. 2012

Journal of Biological Chemistry

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“…Others have reported that lamellarity determined by cryo-electronmicroscopy is higher than suggested by 31 P-NMR measurements 26) ; mean lamellarity determined by cryo-electronmicroscopy and by 31 P-NMR was 1.9 and 1.35, respectively. 26) Cryo-electronmicroscopy shows the actual native structure of vesicles whereas 31 P-NMR only determines the ratio of the outer to inner phospholipids. Thus, it is likely that the lamellarity data determined by NMR reported here is an underestimate of the actual value.…”

Section: Discussionmentioning

confidence: 74%

“…26 Lϭpeak area of both peaks/(2ϫpeak area of shifted peak) (2) Drug Release Experiments Samples (50 mg/ml, 65 mmol/l EPC) were diluted 1 : 9 with FBS and incubated at 37°C. Aliquots were removed at various times and, after removal of unencapsulated drug by size exclusion chromatography (Sepharose CL-6B columns), the concentrations of encapsulated drugs were determined as described before.…”

Section: Determination Of Trap Volumementioning

confidence: 99%

Release of Drugs from Liposomes Varies with Particle Size

Yamauchi

Tsutsumi

Abe

et al. 2007

Biological & Pharmaceutical Bulletin

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Administration of liposomes loaded with active drugs can result in enhanced therapeutic activity 1,2) and reduced toxic side effects. [3][4][5] For example, liposomes are widely used to improve the delivery of many anticancer, antibiotic and antifungal drugs, such as doxorubicin, epirubicin, vincristine and ciprofloxacin. [6][7][8][9][10] The effectiveness of this formulation approach is dependent on the rate of drug release from the liposomes. Liposomes that rapidly release their contents in vivo will not improve delivery of drugs to target sites 2); for therapeutic value, it is important that drugs are retained in liposomes in vivo for an appropriate time.11,12) Weakly basic drugs can be actively concentrated inside liposomes using a transmembrane pH gradient [13][14][15] or an ammonium sulfate gradient.16) However, the retention of drugs in liposomes is drug-dependent and can vary dramatically. For example, the anticancer drugs doxorubicin and epirubicin are well retained inside liposomes, [17][18][19] whereas the anticancer drug vincristine and the antibiotic ciprofloxacin tend to leak out rapidly. 14,19,20) In order to obtain homogenous preparations, liposomes are often extruded through polycarbonate filters of 0.4, 0.2 and 0.1 mm pore size. A high proportion of liposomes that are passed through 0.2 mm filters remain as multilamellar vesicles. On the other hand, extrusion of liposomes through 0.1 mm filters produces mainly unilamellar vesicles.21) Zhang et al. 22) reported that the release of the amphiphilic drug 5-carboxyfluorescein (CF) was greater from unilamellar liposomes than from multilamellar liposomes of similar particle size. The curvature of small unilamellar vesicles (SUVs) is greater, and packing between lipids in the membranes is looser, compared with large unilamellar vesicles. For this reason, SUVs are believed to release drugs more readily. 23,24) The aim of the present study was to identify the causes of the rapid release of drugs, such as vincristine, from liposomes and then to apply this knowledge to the development of more stable formulations. Initially, we investigated the effect of particle size on the leakage of drugs from liposomes incubated in fetal bovine serum (FBS); for these studies, doxorubicin and vincristine were used as examples of wellretained and readily released drugs, respectively. MATERIALS AND METHODS MaterialsEgg yolk phosphatidylcholine (EPC) was purchased from Nippon oil and fat (Tokyo, Japan). Vincristine and doxorubicin were acquired from Sigma-Aldrich (St. Louis, MO, U.S.A.) and Kyowa Hakko (Tokyo, Japan), respectively. FBS was obtained from GIBCO BRL (Grand Island, NY, U.S.A.). Nuclepore polycarbonate filters and Sepharose CL-6B were purchased from Corning (Acton, MA, U.S.A.) and Amersham Pharmacia Biotech (Uppsala, Sweden), respectively. All other chemicals were of analytical grade quality.Preparation of Liposomes EPC liposomes were formed by hydrating the lipid with the following buffers: (i) 100 mmol/l citric acid (pH 4.0), (ii) 10 mmol/l Tris-HCl (pH 7.3...

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“…The size of the liposomes was found to be between 95 and 108 nm, and the polydispersity was between 0.055 and 0.085. The average lamellarity was estimated with 31 P-NMR using Pr(NO 3 ) as a shift reagent (25)(26)(27) and the mean lamellarity was found to be 1.20-1.28. Since Laurdan is photosensitive, all experiments were performed under light protection.…”

Section: Liposome Preparationmentioning

confidence: 99%

Membrane/Water Partition Coefficients of Bile Salts Determined Using Laurdan as a Fluorescent Probe

Strohmeier

Först

Tauber

et al. 2016

Biophysical Journal

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The interaction of liposomal membranes composed of soybean phosphatidylcholine with the bile salts (BSs) cholate (Ch), glycocholate (GC), chenodeoxycholate (CDC), and glycochenodeoxycholate (GCDC) was studied. The BSs differed with regard to their lipophilicity, pKa values, and the size of their hydrophilic moiety. Their membrane interactions were investigated using Laurdan as a membrane-anchored fluorescent dye. The apparent membrane/water partition coefficient, D, at pH 7.4 was calculated from binding plots and compared with direct binding measurements using ultracentrifugation as a reference. The Laurdan-derived LogD values at pH 7.4 were found to be 2.10 and 2.25 for the trihydroxy BSs, i.e., Ch and GC, and 2.85 and 2.75 for the dihydroxy BSs, i.e., CDC and GCDC, respectively. For the membrane-associated glycine-conjugated GC and GCDC (pK a values of~3.9), no differences in the Laurdan spectra of the respective BS were found at pH 6.8, 7.4, and 8.2. Unconjugated Ch and CDC (pK a values of~5.0) showed pronounced differences at the three pH values. Furthermore, the kinetics of membrane adsorption and transbilayer movement differed between conjugated and unconjugated BSs as determined with Laurdan-labeled liposomes.

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Parameters influencing the determination of liposome lamellarity by 31P-NMR

Cited by 81 publications

References 33 publications

Atypical Membrane-embedded Phosphatidylinositol 3,4-Bisphosphate (PI(3,4)P2)-binding Site on p47 Phox Homology (PX) Domain Revealed by NMR

Atypical Membrane-embedded Phosphatidylinositol 3,4-Bisphosphate (PI(3,4)P2)-binding Site on p47 Phox Homology (PX) Domain Revealed by NMR

Release of Drugs from Liposomes Varies with Particle Size

Membrane/Water Partition Coefficients of Bile Salts Determined Using Laurdan as a Fluorescent Probe

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