In vitro Release of AgNPs-PVP from the Hydrogel Formulations
with Reverse Thermal Gelation
The cumulative release of AgNPs-PVP was studied by quantifying the in
vitro diffusion of Ag from hydrogel formulations placed in a Transwell®.
Effect of initial drug loading amount on release kinetics of the
hydrogel formulations was investigated using two hydrogel formulations,
50µM[AgNPs-PVP]-18%[P407] and
100µM[AgNPs-PVP]-18%[P407]. Consistent with previous
reports51,70, lower initial drug loading amount
resulted in slightly greater cumulative release fraction by the end of
the 48 hour testing period (Figure 8). At 3 hours, the two formulations
had similarly low release fractions, i.e., 5.38 ± 2.32 % for
50µM[AgNPs-PVP]-18%[P407] and 2.79 ± 0.40 % for
100µM[AgNPs-PVP]-18%[P407]. The total amounts of Ag released
from the two formulations were comparable. At 6 hours, 49.49 ± 1.24 %
was released from 50µM[AgNPs-PVP]-18%[P407] and 44.64 ± 2.94 %
from 100µM[AgNPs-PVP]-18%[P407], where the amount of Ag
released from the latter exceeded that of the former by nearly two-fold,
implying that the release of Ag was dominated by passive diffusion.
Similar observations were made at 24 and 48 hours, i.e.,
50µM[AgNPs-PVP]-18%[P407] achieved cumulative release fractions
of 77.41 ± 1.60 % and 87.03 ± 1.25 % respectively, and
100µM[AgNPs-PVP]-18%[P407] achieved 74.37 ± 1.56 %, and 80.61
± 1.65 % respectively. The cumulative release fractions of
100µM[AgNPs-PVP]-18%[P407] were slightly less than two-fold
that of 50µM[AgNPs-PVP]-18%[P407] at 6, 24, and 28 hours, which
was likely a result of the aforementioned entanglement between PVP and
P407 chains that increased physical cross-linking and reduced rate of
passive diffusion.