148
20. Obtain the optimum conditions for the centrifugation by SEC
analysis of the supernatant and the solid (free Pacl) in the system running CHCl 3 /Et 3 N. Under these conditions only free
Pacl is precipitated leaving the vesicles with the encapsulated
Pacl in solution. The amount of Pacl in the vesicles is obtained
by SEC analysis, using an appropriate set of columns in order
to separate the polymer from the drug. Quantification is performed by setting calibration curves of Pacl in CHCl 3 /Et 3 N,
where the drug is soluble.
5 Results
A special set of size-exclusion columns was used in order to characterize the polymer and determine the concentration of Pacl in
polymersomes. As Pacl is a rather big molecule, compared to other
side species of the solvent, it can be clearly separated and quantified, by making a calibration curve. The polymer can also be quantified, since it can be separated from Pacl that has a much smaller
hydrodynamic volume. It is also obvious that Pacl has smaller polydispersity compared to the polymeric material.
The highest concentration achieved for Dox was 0.89 mg Dox
mL
−1
at pH = 7.4. The highest Dox loading efficiency achieved was
33.0% and loading content of 19.5%. The PLLDox vesicles
remained stable in storage for at least 12 h in a 10 vol% fetal calf
serum at 37 °C, while the PEODox vesicles in a 10 vol% fetal calf
serum at 37 °C were stable only for 2 h.
The highest Pacl concentration achieved was 0.4 mg Pacl
mL
−1
. The highest Pacl loading efficiency achieved was 25.0% and
a loading content of 13.0%. The PEOPacl nanoparticles remained
stable over storage at 37 °C for at least 12 h containing 10 vol%
fetal calf serum.
In all polymersomes formed by the PEO-b-PBLG-b-PLL (blank
and loaded), the zeta potential measured was between 3.2 and
5.4 mV, revealing that PEO is always in the outer periphery and
PLL is in the interior of the polymersome, since if PLL was in the
outer periphery, the zeta potential would be positive and much
higher. The dimensions of the nanoparticles were determined by
DLS, with an average diameter ranging from 100 to 300 nm.
The release is temperature and pH dependent. In case of PEOPacl,
the release is higher at higher pH values and temperatures. In case
of Dox-loaded polymers, the release increases at lower pH values
and higher temperatures. In all cases the release profiles show a
rather quick release in the beginning and a slower release after
15–20 h that continued for more than 3 days, revealing a slow
sustainable (controlled) drug release.
5.1 Synthesis and
Characterization of the
Polymers and
Determination of the
Concentration of Pacl
in Polymersomes [6]
5.2 Loading
and Stability
5.3 Polymersome
Characteristics
5.4 In Vitro Release
and Activity
Hermis Iatrou et al.
20. Obtain the optimum conditions for the centrifugation by SEC
analysis of the supernatant and the solid (free Pacl) in the system running CHCl 3 /Et 3 N. Under these conditions only free
Pacl is precipitated leaving the vesicles with the encapsulated
Pacl in solution. The amount of Pacl in the vesicles is obtained
by SEC analysis, using an appropriate set of columns in order
to separate the polymer from the drug. Quantification is performed by setting calibration curves of Pacl in CHCl 3 /Et 3 N,
where the drug is soluble.
5 Results
A special set of size-exclusion columns was used in order to characterize the polymer and determine the concentration of Pacl in
polymersomes. As Pacl is a rather big molecule, compared to other
side species of the solvent, it can be clearly separated and quantified, by making a calibration curve. The polymer can also be quantified, since it can be separated from Pacl that has a much smaller
hydrodynamic volume. It is also obvious that Pacl has smaller polydispersity compared to the polymeric material.
The highest concentration achieved for Dox was 0.89 mg Dox
mL
−1
at pH = 7.4. The highest Dox loading efficiency achieved was
33.0% and loading content of 19.5%. The PLLDox vesicles
remained stable in storage for at least 12 h in a 10 vol% fetal calf
serum at 37 °C, while the PEODox vesicles in a 10 vol% fetal calf
serum at 37 °C were stable only for 2 h.
The highest Pacl concentration achieved was 0.4 mg Pacl
mL
−1
. The highest Pacl loading efficiency achieved was 25.0% and
a loading content of 13.0%. The PEOPacl nanoparticles remained
stable over storage at 37 °C for at least 12 h containing 10 vol%
fetal calf serum.
In all polymersomes formed by the PEO-b-PBLG-b-PLL (blank
and loaded), the zeta potential measured was between 3.2 and
5.4 mV, revealing that PEO is always in the outer periphery and
PLL is in the interior of the polymersome, since if PLL was in the
outer periphery, the zeta potential would be positive and much
higher. The dimensions of the nanoparticles were determined by
DLS, with an average diameter ranging from 100 to 300 nm.
The release is temperature and pH dependent. In case of PEOPacl,
the release is higher at higher pH values and temperatures. In case
of Dox-loaded polymers, the release increases at lower pH values
and higher temperatures. In all cases the release profiles show a
rather quick release in the beginning and a slower release after
15–20 h that continued for more than 3 days, revealing a slow
sustainable (controlled) drug release.
5.1 Synthesis and
Characterization of the
Polymers and
Determination of the
Concentration of Pacl
in Polymersomes [6]
5.2 Loading
and Stability
5.3 Polymersome
Characteristics
5.4 In Vitro Release
and Activity
Hermis Iatrou et al.