pH Sensitive Liposomes (PSL)

Many formulations of pH-sensitive liposomes has been developed in the past few years. pH-sensitive liposomes are formed from lipids which adopt a lamellar phase at pH around 7.4 (physiological pH). When the pH is decreased to a critical value (around 5.5) the liposome will fuse with the endosomal membrane. Due to the fusion of the liposome with the endosomal membrane the content of the liposome (drugs) are released into the cytosol. The reason for the fusion at the lower pH is the transition from lamellar to hexagonal HII phase. Simultaneously membrane defect occurs which result in the release of the encapsulated substance into the liposome-surrounding compartment such as endosome.

The fusion of liposomes with cell membranes can be monitored by fluorescence resonance energy transfer (FRET).

pH-sensitive liposomes are powerful delivery systems for hydrophilic compounds such as proteins, oligonucleotides and proteins.

For making pH sensitive liposomes techniques such as reverse-phase evaporation and freeze-thawing followed by extrusion yield high encapsulation value.

Encapsula provides various types of custom-made formulations of pH-sensitive liposomes (various entrapped small molecules, proteins, oligonucleoides, proteins etc) for R&D laboratories. For more information send us an email at

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