Figure 7 a and b showed ACV release profile in pH 1.2 (SGF) and pH 6.4 (SIF) respectively. Various kinetic models were employed for a comprehensive understanding of drug release mechanisms from the optimised formulation. Table VII shows the values of correlation coefficient (r2) and releasing model constant (k). Higuchi model showed the best fit with the highest r2 value and can be concluded that the PALN formulation showed modified release. This model corresponds to the sustained release properties of lecithin-chitosan nanoparticle. The drug release mechanism was identified based on the diffusion constant, n, from Korsmeyer-Peppas equation, as shown in Eq. (11). The mathematical adjustment of Eqs. (13) and (14) was obtained:13 Qt/QCR=KKPtn14 log10Qt/QCR=log10KKPnlog10twhere Qt and QCR indicate the amount of drug being released at time t and after time ∞ respectively. n represents the diffusional exponent and Kkp gives Korsmeyer release rate constant. Based on the equation, the slope of Korsemeyer-Peppas graph was the mechanism constant for Higuchi model. With n values reported to be 0.6185 and 0.6103 for SGF and SIF, respectively, it was concluded that PALN1 was following Higuchi drug releasing model with non-Fickian transport.
Fig. 7 ACV in vitro drug release profile in a pH 1.2, b pH 6.4, and c ACV intestinal permeation profile
Table 7 Coefficient of Determination r2 and Releasing Model Constant K for Drug Releasing Models
Model pH 1.2 pH 6.4
Coefficient of determination, r2 Release model constant, K Coefficient of determination, r2 Release model constant, K
Zero order 0.6184 3.1424 0.5605 3.0729
First order 0.9339 0.2588 0.7999 1.3440
Higuchi model 0.9341 25.4563 0.9199 26.5229
Korsmeyer-Peppas model 0.3101 18.6351 0.2953 19.8312
Hixson-Crowell model 0.0053 0.0131 0.0032 0.0100
The italicized is done to show the Nanoparticle release model is folloing Higuchi release model. It is done just to make it more visible