The adsorption effect of proteins on liposomal bilayer membranes plays a noticeable role in the use of liposomes as drug delivery systems. To explain thìs behaviour and correlate it with the protein properties, the thermal behaviour the hydrated multilamellar vesicles (liposomes) of dimyristoylphosphatidylcholine (DMPC) in the presence of increasing amounts of both lysozyme (Lyso) and bovine serum albumine (BSA) at pH = 7.0 was studied by means of Differential Scanning Calorimetry (DSC) technique. Liposomes were prepared mixing DMPC with the protein/water mixtures to a final lipid concentration of about 20% w/w and then incubated 1h at 37°C. DSC scans were performed by a Mettler-Toledo DSC 821C calorimeter at a heating rate of 2.0°C/min. In the samples with the lower Lyso concentrations (up to 2% w/w), a small decrease of about 0.2°C on the main transition temperature (Tm) was observed, whereas Tm increased from 23.3 up to 24.1°C by further addition of the Lyso amount (up to 15%). Contemporaneously, a increase of about 25% on the AH of the transition was observed. The pretransition was affected in a greater extent by the protein presence. Indeed, Tpr, after a small decrease of about 0.5 °C in the 2% Lyscontaining sample, increased from 12.8 to U.4°C in the 15% Lyso-containing samples, with a contemporary 35% increase in the associated AH value. In the presence of BSA a smaller increase (from 23.3 to 23.6°C) in the Tm values was observed, in addition to a contemporary increase of about 10% in the associated AH. On the contrary, at the same conditions, a greater Tpr increase (from 12.8 to 15.2'C) took place. The data suggest that the interaction BSA-liposome involve only the external surface of the bilayer, excluding thus any penetration into the liposomial hydrophobic core. On the contrary, in the presence of Lyso, a partial penetration into the bilayer cannot be excluded, as suggested from the low Tm and Tpr decrease observed in the lower Lyso-containing samples. In the presence of both considered protein the overall bilayer structure of DMPC liposomes is strengthened, suggesting a decrease in the membrane permeability.
M. Di Foggia, S. Bonora, A. Torreggiani (2007). Effect of lysozime and bovine serum albumine on the thermal behaviour of DMPC liposomes.. MILANO : Biomedia.
Effect of lysozime and bovine serum albumine on the thermal behaviour of DMPC liposomes.
DI FOGGIA, MICHELE;BONORA, SERGIO;
2007
Abstract
The adsorption effect of proteins on liposomal bilayer membranes plays a noticeable role in the use of liposomes as drug delivery systems. To explain thìs behaviour and correlate it with the protein properties, the thermal behaviour the hydrated multilamellar vesicles (liposomes) of dimyristoylphosphatidylcholine (DMPC) in the presence of increasing amounts of both lysozyme (Lyso) and bovine serum albumine (BSA) at pH = 7.0 was studied by means of Differential Scanning Calorimetry (DSC) technique. Liposomes were prepared mixing DMPC with the protein/water mixtures to a final lipid concentration of about 20% w/w and then incubated 1h at 37°C. DSC scans were performed by a Mettler-Toledo DSC 821C calorimeter at a heating rate of 2.0°C/min. In the samples with the lower Lyso concentrations (up to 2% w/w), a small decrease of about 0.2°C on the main transition temperature (Tm) was observed, whereas Tm increased from 23.3 up to 24.1°C by further addition of the Lyso amount (up to 15%). Contemporaneously, a increase of about 25% on the AH of the transition was observed. The pretransition was affected in a greater extent by the protein presence. Indeed, Tpr, after a small decrease of about 0.5 °C in the 2% Lyscontaining sample, increased from 12.8 to U.4°C in the 15% Lyso-containing samples, with a contemporary 35% increase in the associated AH value. In the presence of BSA a smaller increase (from 23.3 to 23.6°C) in the Tm values was observed, in addition to a contemporary increase of about 10% in the associated AH. On the contrary, at the same conditions, a greater Tpr increase (from 12.8 to 15.2'C) took place. The data suggest that the interaction BSA-liposome involve only the external surface of the bilayer, excluding thus any penetration into the liposomial hydrophobic core. On the contrary, in the presence of Lyso, a partial penetration into the bilayer cannot be excluded, as suggested from the low Tm and Tpr decrease observed in the lower Lyso-containing samples. In the presence of both considered protein the overall bilayer structure of DMPC liposomes is strengthened, suggesting a decrease in the membrane permeability.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
