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. 2009 May 20;20(5):1037-43.
doi: 10.1021/bc9000849.

Thermally gated liposomes: a closer look

Ravil R Petrov  1 , Wen-Hua Chen, Steven L Regen
Affiliations

Thermally gated liposomes: a closer look

Ravil R Petrov et al. Bioconjug Chem. .

Abstract

A homologous series of pore-forming amphiphiles (PFAs), derived from cholic acid, lysine, and spermine, have been used as "thermal gates" for releasing sucrose from liposomes made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) [DPPG]. Binding measurements have established that these PFAs are fully bound to these liposomes in their gel state and that their transfer to fluid phase membranes is negligible. Release experiments have shown that thermal gating is sensitive to both the size and the concentration of the PFA that are used. Increases in the extent of release of sucrose with increasing temperature that have been found in the gel/fluid coexistence region indicate the existence of heterogeneity among the liposomes.

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Figures

Figure 1
Figure 1
Stylized illustration showing two PFAs forming a pore in a melted bilayer.
Figure 2
Figure 2
Structures of pore-forming amphiphiles and permeant (sucrose) used in this study.
Figure 3
Figure 3
High-sensitivity differential scanning calorimetry data for extruded liposomes made from DPPC/DPPG (95/5, mol/mol) with (A) no PFA added, (B) 0.1 mol% of 1, (C) 0.15 mol% of 2, and (D) 0.3 mol% of 3.
Figure 4
Figure 4
Plot of percent of sucrose released as a function of time from liposomes made from DPPC/DPPG (95/5, mol/mol) with (A) no PFA added, (B) 0.1 mol% of 1, (C) 0.15 mol% of 2, and (D) 0.3 mol% of 3 at (▽) 37°C and (●) at 43°C.
Figure 5
Figure 5
Release of sucrose as a function of time from liposomes made from DPPC/DPPG (95/5, mol/mol) containing (A) 0.010 mol% of 1 and (B) 0.015 mol% of 2 at (▽)37°C and (●) 43°C.
Figure 6
Figure 6
Release of sucrose as a function of time from liposomes made from DPPC/DPPG (95/5, mol/mol) containing 0.3 mol% of 3 at (▽) 37°C, (○) 41°C, and (●) 43°C.
Figure 7
Figure 7
Release of sucrose from liposomes made from DPPC/DPPG (95/5, mol/mol) containing 0.3 mol% of 3 as a function of temperature using a 6 min incubation period.
Figure 8
Figure 8
Release of sucrose from liposomes made from DPPC/DPPG (95/5, mol/mol) containing 0.3 mol% of 3 as a function of the number of heating/cooling cycles at 41.5 °C (○), and from one heating period at 43 °C (●); in all cases 6 min incubation periods were used.
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