engleski

In vitro methods for determining fusogenic activity of PEGylated pH sensitive liposomes

Like conventional, pH-sensitive liposomes are also rapidly cleared from the circulation by the reticuloendothelial system. The lack of their stability, which is the major drawback for their application in vivo, could be overcome by sterical stabilization. Incorporation of PEG-PE in the liposome membrane has been demonstrated to prolong the circulation time in vivo, but on the other side reduced thier pH sensitivity. Up to now it is still not confirmed what is really happening with the pH-sensitive liposomes inside the cell. There are several possible routes for for the cytoplasmic delivery of the liposomal content. The decrease of pH value induce the fusion of liposomes with endosome membrane and the susequent release of the liposomal content into the cytoplasm. The second possibility implies the primary release of the substance delivered from liposomes and then diffusion from the endosome following concentration gradient. The third way is endosome membrane permeabilization upon interaction with pH-sensitive liposomes. In order to find out the possible explanations for those processes inside the cells we have performed membrane fusion testing and in vitro release studies with liposomally encapsulated calcein. Ability of liposomes to undergo fusion was monitored by fluorescence resonance energy transfer (FRET).

pH sensitive liposomes; PEGylation; in vitro methods; Fusion

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