## 3 Results
### In Vitro Release of MG-Loaded Mesoporous Silica and Analysis of MG Release Kinetics  
In vitro dissolution tests revealed a prolonged release of MG from both functionalized and un-functionalized mesoporous silica, compared to the dissolution profile of unloaded MG (Figure 4).  
Furthermore, study results have shown that the capacity for extended release of silica is enhanced by functionalization. Thus, in the first 10 h of the test, Cf-MG released 31.16% of the MG loaded, while the C-MG unfunctionalized matrix caused a release of 63.36%. Thus, the un-functionalized matrix  
Figure 4: In vitro dissolution release of MG form mesoporous silica.  
Figure 3: Comparative representation of Fourier Transform Infrared Spectroscopy (FTIR) spectra recorded.  
achieved a prolonged release of MG over 15 h, whereas the functionalized SBA-15 showed capabilities for retardation of release covering over 20 h. These results are consistent with other published results that evidenced an increase in the drug loading capacity of SBA-15 silica. It is important to note that the rate of drug release decreases proportionally with the increase of the loading capacity due to the electrostatic interactions that occur between the functional groups and the drug molecule [23; 41]. These results are additionally confirmed by the release kinetics analysis of the mesoporous silica (Table 2). The sigmoid-shaped drug delivery model best defines the release of MG from both C-MG and Cf-MG. Basically, the release rate of MG presents three phases, with a slow first phase which is more pronounced for Cf-MG because the amine groups of SBA-15 interact with the hydroxyl groups in the structure of MG (Figure 5) [54].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Kinetic Model**} & \multirow{2}{*}{**Model Coefficients**} & \multicolumn{2}{c}{**Mesoporous Silica**} \\  & & **C-MG** & **Cf-MG** \\ \hline \multirow{3}{*}{**Zero-order**} & \(K_{0}\) & 5.2110 & 4.3009 \\  & \(R^{2}\) & 0.9068 & 0.9563 \\  & **AIC** & 119.7224 & 99.7687 \\ \hline \multirow{3}{*}{**First-order**} & \(K_{1}\) & 0.3389 & 0.1586 \\  & \(R^{2}\) & 0.2499 & 0.2584 \\  & **AIC** & 169.7668 & 167.7206 \\ \hline \multirow{3}{*}{**Higuchi**} & \(K_{H}\) & 20.8929 & 16.6807 \\  & \(R^{2}\) & 0.8462 & 0.7343 \\  & **AIC** & 131.7288 & 143.0910 \\ \hline \multirow{3}{*}{**Korsmeyer-Peppas**} & \(n\) & 0.90 & 0.98 \\  & \(K_{P}\) & 6.9464 & 4.5512 \\ \cline{1-1}  & \(R^{2}\) & 0.9230 & 0.9524 \\ \cline{1-1}  & **AIC** & 117.1378 & 103.8153 \\ \hline \multirow{3}{*}{**Sigmoidal**} & \(M\) & 28.7 & 42.9 \\ \cline{1-1}  & \(K\) & 0.39 & 0.3 \\ \cline{1-1}  & \(R^{2}\) & 0.9963 & 0.9911 \\ \cline{1-1}  & **AIC** & 44.2082 & 63.7028 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Results of curve fitting of the in vitro release profile of magnolol (MG) from mesoporous silica SBA-15.  
Figure 5: Sigmoidal plot of MG release from C-MG (**a**) and Cf-MG (**b**).  
The second time-dependent stage of MG release has a duration of 15 h for the Cf-MG matrix and only 7-8 h for C-MG. The third phase of MG release begins once the steady-state concentration is reached, and eventually reveals the release of 100% of the MG loaded in the matrix.