To study the release of
liposome-associated drugs into
hydrogels, we designed and synthesized two pH-sensitive
rhodamine derivatives to use as model compounds of different lipophilicities. The
dyes were fluorescent when in the free form released from
liposomes into the
chitosan hydrogel, but not when incorporated within
liposomes. The effect of liposomal composition, surface charge and vesicle size on the release of those incorporated
dyes was evaluated. The lipophilicity of the
rhodamine derivatives affected both the amount and rate of release. While
liposome size had only a minor effect on the release of
dyes into the
hydrogel, the surface charge affected the release to a greater extent. By optimizing the characteristics of
liposomes we could develop a
liposomes-in-
hydrogel system for application in
wound therapy. We further characterized
liposomes-in-
hydrogel for their rheological properties, textures and moisture handling, as well as their potential to achieve a controlled release of the
dye. The
polymer-dependent changes in the
hydrogel properties were observed upon addition of
liposomes. The charged
liposomes exhibited stronger effects on the textures of the
chitosan hydrogels than the neutral ones. In respect to the ability of the system to handle
wound exudates,
chitosan-based
hydrogels were found to be superior to
Carbopol-based
hydrogels.