Vesicle destabilization

Kirpotin D, et al. Liposomes with detachable polymer coating destabilization and fusion of dioleoylphosphatidylethanolamine vesicles triggered by cleavage of surface-grafted poly(ethylene glycol). FEBS Lett 1996 388 115. 

Foam destabilization is also a factor in the packing and orientation of mixed films, which can be determined from monolayer studies. It is worth mentioning that foam formation from monolayers of amphiphiles constitutes the most fundamental process in everyday life. The other assemblies, such as vesicles and BLM, are somewhat more complicated systems, which are also found to be in equilibrium with monolayers. 

The information provided by the 31P-NMR spectra of DOPE/16 as a function of temperature and the extent of polymerization was critical to the characterization of the nature of the lipid structures responsible for the destabilization of the photolyzed DOPE/16 vesicles [73]. The progressive appearance of an isotropic NMR signal at the expense of the lamellar signal (Fig. 14) indicated that a lipid structure with isotropic symmetry was associated with the photo-induced leakiness of DOPE/16 vesicles. The enriched domains of PE facilitates the interaction and formation of intermediate lipid structures between bilayers, with the eventual development of an ILA(s) that connect the bilayers of an... 

Figure 7.33 The renal accumulation and toxicity of gentamycin (G). Gentamycin is filtered in the glomerulus and enters the tubular lumen. Here, it is taken up by proximal tubular cells and in vesicles as part of the uptake process. These fuse with lysosomes (L) inside the cell. The accumulation of gentamycin inside the lysosome destabilizes it, causing it to rupture and release its hydrolytic enzymes (o). These cause damage within the cell. Also, gentamycin can directly damage mitochondria (M).

There are several methods to selectively open up closed polymeric membrane compartments in order to release entrapped substances (Fig. 37). For uncorking a polymerized vesicle, its membrane has to contain destabilizable areas which could possibly be opened up by variation of pH 70), temperature increase71), photochemical destabilization 72), or enzymatic processes. Such an enzymatic process is the hydrolysis of a natural phospholipid by phospholipase A2 (Fig. 38). This enzyme cleaves the ester bond in position two of a natural phosphoglyceride producing a lysophospholipid and a fatty acid which are both water soluble. This leads to complete destruction of the membrane. 

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