Liposomal particles

Characterizing the resultant complex for the amount of protein per liposome is somewhat more difficult than in other protein conjugation applications. The protein-liposome composition is highly dependent on the size of each liposomal particle, the amount of protein charged to the reaction, and the mole quantity of reactive lipid present in the bilayer construction. An approach to solving this problem is presented by Hutchinson et al. (1989). In analyzing at least 17 different protein-liposome preparations, the ratio of proteindipid content (pg protein/pg lipid) in most of the complexes ranged from a low of about 4 to as much as 675. In some instances, however, up to 6,000 molecules of a particular protein could be incorporated into each liposome. 

The higher generation dendrimeric derivative proved more effective in its interaction with liposomes. This behaviour was attributed to multivalent effects, exhibited at a greater extent by this dendrimeric derivative. Under an equal concentration of functional moieties the reactivity is favoured when the groups are located in a smaller number of particles. Thus the dendrimeric materials act as molecular glue causing adhesion of liposomal particles. 

The liposome particle mean size and size distribution are observed using a Coulter N4 Plus submicron particle analyzer. 

The particle size of the liposomes varied with the volume ratio of ethanol to water. An increase in the ratio of ethanol in the system resulted in an increase in particle size of liposomes at 10-30 mg total lipid/ethanol mL. An increase in the volume of water in the system resulted in a decrease in liposome particle size (15). 

The encapsulation efficiency of a thalidasine liposome injection was studied using Sephadex G-50 column fluorimetry. The free alkaloid was separated from the liposome particles by the column, with satisfactory recovery of the liposome particles, as well as column reproducibility. The encapsulation efficiency of this particular liposome preparation (139-2) was approximately 93% due to the highly lipophilic property of the alkaloid. The authors concluded that the method was suitable for the quality control of encapsulation efficiency of this polyphase liposome injection [147]. 

Huang W, Zhang J, Dom HC, Geohegan D, Zhang C. Assembly of single-waUed carbon nanohom supported liposome particles. Bioconjugate Chem 2011 22 1012-6. 

Figure 9 The Pp phase of bovine brain sphingomyelin revealed by negative staining with uranyl acetate on (A) a multilammelar body and (B) a single bIlayer. Liposome particles are present on the surface of the larger lipid bilayer structures. Bars = 100nm. (Reproduced with permission from Harris JR (1986) Micron and Microscopica Acta 17 175-200.)...

---