Fig. 9 Freeze fracture electron micrograph of ELimixed phosphoinositides (4:1) liposomes after 10 passes through a0.1 pirn polycarbonate filter. growth, particularly during storage, would be undesirable in most products. Fortunately the tendency of liposomes to aggregate and fuse can be controlled by the inclusion of small amounts of negatively charged lipids such as PS or PG or positively charged amphiphiles such as stearylamine in the formulation. Knowing the number and the sign of charged groups added and the valency and concentration of electrolytes in the me-dium, the magnitude of the electrostatic forces generated by these charged groups can be closely approximated by using the double layer theory. These results can then be correlated with physical stability of liposomes and used to guide formulation efforts. The amount of charged component and ionic conditions in a particular liposome dos-age form can be adjusted to produce a high-enough zeta potential to inhibit close ap-proach of vesicles and prevent their aggregation. In practice it is usually necessary to determine empirically the magnitude of the zeta potential required to prevent aggrega-tion in a particular system. However, once this has been done, it is possible to use the zeta potential as a quality control check to insure that each batch of liposomes contains sufficient charged groups to avoid aggregation during storage.

DOI link for Fig. 9 Freeze fracture electron micrograph of ELimixed phosphoinositides (4:1) liposomes after 10 passes through a0.1 pirn polycarbonate filter. growth, particularly during storage, would be undesirable in most products. Fortunately the tendency of liposomes to aggregate and fuse can be controlled by the inclusion of small amounts of negatively charged lipids such as PS or PG or positively charged amphiphiles such as stearylamine in the formulation. Knowing the number and the sign of charged groups added and the valency and concentration of electrolytes in the me-dium, the magnitude of the electrostatic forces generated by these charged groups can be closely approximated by using the double layer theory. These results can then be correlated with physical stability of liposomes and used to guide formulation efforts. The amount of charged component and ionic conditions in a particular liposome dos-age form can be adjusted to produce a high-enough zeta potential to inhibit close ap-proach of vesicles and prevent their aggregation. In practice it is usually necessary to determine empirically the magnitude of the zeta potential required to prevent aggrega-tion in a particular system. However, once this has been done, it is possible to use the zeta potential as a quality control check to insure that each batch of liposomes contains sufficient charged groups to avoid aggregation during storage.

Fig. 9 Freeze fracture electron micrograph of ELimixed phosphoinositides (4:1) liposomes after 10 passes through a0.1 pirn polycarbonate filter. growth, particularly during storage, would be undesirable in most products. Fortunately the tendency of liposomes to aggregate and fuse can be controlled by the inclusion of small amounts of negatively charged lipids such as PS or PG or positively charged amphiphiles such as stearylamine in the formulation. Knowing the number and the sign of charged groups added and the valency and concentration of electrolytes in the me-dium, the magnitude of the electrostatic forces generated by these charged groups can be closely approximated by using the double layer theory. These results can then be correlated with physical stability of liposomes and used to guide formulation efforts. The amount of charged component and ionic conditions in a particular liposome dos-age form can be adjusted to produce a high-enough zeta potential to inhibit close ap-proach of vesicles and prevent their aggregation. In practice it is usually necessary to determine empirically the magnitude of the zeta potential required to prevent aggrega-tion in a particular system. However, once this has been done, it is possible to use the zeta potential as a quality control check to insure that each batch of liposomes contains sufficient charged groups to avoid aggregation during storage.