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.