308
concentration-dependent manner. Moreover, the incorporation of highest polymer amounts caused the appearance
of new peaks, indicating the creation of new metastable
phases, as a result of lateral phase separation into PNIPAM
1-rich and PNIPAM 1-poor domains. Taking into account
the lack of sharp transitions and the LCST of the polymeric guest, authors concluded that the PNIPAM 1 is not
uniformly distributed in the DPPC liposomal membranes.
Taking into consideration the amphiphilic character of the
polymeric guest and the hysteresis on cooling (of ~2 °C)
that was observed, the authors suggested the formation of
an interdigitated phase. The incorporation of the second
form of polymer (called PNIPAM 2) (7 kDa) affected the
thermotropic behavior of the liposomal bilayers in a different way, indicating that the characteristics of the guest,
such as its composition and its molecular weight, can play
a key role in the thermal behavior of the final liposomal
system. As long as the loading of the indomethacin, the
presence of the aforementioned metastable phases due to
the PNIPAM-1, as revealed by DSC, was found to act as a
promoter, resulting in a burst drug release profile, due to
the inhomogeneous drug distribution inside the chimeric
liposomal membrane.
(c) In the last presented example, Ionov et al. [26] incorporated cationic phosphorus-containing dendrimers (CPDs)
into liposomes. This category of dendrimers can provide
special surface properties that are strictly associated with
the pharmacokinetic profile of the drug delivery system.
More specifically, they used DSC in order to investigate
the thermotropic behavior of chimeric liposomes, when
generation 3 (G3) and generation 4 (G4) CPDs were
incorporated into uncharged DMPC and negatively
charged DMPC:DPPG membranes. Authors stated that
the information obtained from this DSC study can be useful toward the rational design of new drug carriers combining liposomal and dendrimeric technology. Regarding
the results from DMPC membrane (Fig. 4), both CPDs
caused concentration- dependent alterations of the pretransition specific enthalpy ΔΗ m , while the other calorimetric
parameters of the pretransition remained unaltered, reflecting interactions of the positively charged dendrimer end
groups with the polar head groups of the phospholipid
membranes but not with the lipidic chains.
Maria Chountoulesi et al.
concentration-dependent manner. Moreover, the incorporation of highest polymer amounts caused the appearance
of new peaks, indicating the creation of new metastable
phases, as a result of lateral phase separation into PNIPAM
1-rich and PNIPAM 1-poor domains. Taking into account
the lack of sharp transitions and the LCST of the polymeric guest, authors concluded that the PNIPAM 1 is not
uniformly distributed in the DPPC liposomal membranes.
Taking into consideration the amphiphilic character of the
polymeric guest and the hysteresis on cooling (of ~2 °C)
that was observed, the authors suggested the formation of
an interdigitated phase. The incorporation of the second
form of polymer (called PNIPAM 2) (7 kDa) affected the
thermotropic behavior of the liposomal bilayers in a different way, indicating that the characteristics of the guest,
such as its composition and its molecular weight, can play
a key role in the thermal behavior of the final liposomal
system. As long as the loading of the indomethacin, the
presence of the aforementioned metastable phases due to
the PNIPAM-1, as revealed by DSC, was found to act as a
promoter, resulting in a burst drug release profile, due to
the inhomogeneous drug distribution inside the chimeric
liposomal membrane.
(c) In the last presented example, Ionov et al. [26] incorporated cationic phosphorus-containing dendrimers (CPDs)
into liposomes. This category of dendrimers can provide
special surface properties that are strictly associated with
the pharmacokinetic profile of the drug delivery system.
More specifically, they used DSC in order to investigate
the thermotropic behavior of chimeric liposomes, when
generation 3 (G3) and generation 4 (G4) CPDs were
incorporated into uncharged DMPC and negatively
charged DMPC:DPPG membranes. Authors stated that
the information obtained from this DSC study can be useful toward the rational design of new drug carriers combining liposomal and dendrimeric technology. Regarding
the results from DMPC membrane (Fig. 4), both CPDs
caused concentration- dependent alterations of the pretransition specific enthalpy ΔΗ m , while the other calorimetric
parameters of the pretransition remained unaltered, reflecting interactions of the positively charged dendrimer end
groups with the polar head groups of the phospholipid
membranes but not with the lipidic chains.
Maria Chountoulesi et al.