Coating of neutral liposomes with hydrophobically modified hydroxyethyl cellulose. The influence of hydrophobic chain length on the liposomes' properties and stability.

Abstract

In this study, gel phase (DPPC) and liquid phase (soy PC) neutral liposomes were coated with hydrophobically modified hydroxyethyl cellulose (HM-HEC). The chain lengths of the hydrophobic moieties of HM-HEC were C8 and C16.

The influence of the hydrophobic chain length of the polymer coating on the release of a fluorescence marker was studied at both 35 °C and 4 °C. I addition the size, zeta potential, transmittance and pH were investigated during storage at 4 °C during a period of 12 weeks.

Differential scanning calorimetry was used to study the interaction between the liposomal membrane and the hydrophobically modified polymers. Egg PC, DMPC and DOPC liposomes were included in these studies.

The release studies at 35 °C showed that the HM-HEC coating protected against release, however, with no significant difference between the HM-HEC with C8 and C16 chain lenght. No difference in leakage was found between the HM-HEC C8 and HM-HEC C16 coated liposomes at 4 °C. The HM-HEC C8 coated liposomes were larger than the liposomes coated with HM-HEC C16. The zeta potential was found to be slightly negative, with no differences between the HM-HEC coated liposomes with different chain lengths. The transmittance was slightly lower for the HM-HEC C8 than the HM-HEC C16 coated liposomes, however, with no significant difference.

Although it was shown that the liposomes were stabilized by the polymer coating, no interactions of HM-HEC alkyl chains with the liposome membrane could be verified by DSC. The HM-HEC coated liposomes with C8 and C16 chain lengths showed no differences in the stabilization properties.