## 3 Results
### In Vitro Drug Release Kinetics

Table 3: Parameters for in vitro drug release from PLGA-CS-PEG microspheres as a function of time and temperature. Data are mean \(\pm\) SD, \(n\) = 3. However, comparing the respective cumulative drug release, the results were significant with _p_-value < 0.05. Overall, these results suggest the potential of drug-loaded microspheres for controlled release of therapeutic levels of anticancer drugs were within clinically relevant durations [11]. To understand the in vitro drug release kinetics from PLGA-CS-PEG microspheres, four kinetic models were explored. These include the zeroth order model, the first order model, the Higuchi model, and the Korsmeyer-Peppas (K-P) model [30]. The kinetic constant (K) and correlation coefficients (R\({}^{2}\)) obtained for the release kinetics are presented in Table 4.  
It is clear from Table 4 that the release kinetics for the various PLGA-CS-PEG microsphere formulations with the highest correlation coefficients R\({}^{2}\) fit the K-P model the best. The release exponents, \(n\), were also found to be within the range of 0.45 < \(n\) < 0.89, signifying that the release mechanism was by anomalous non-Fickian diffusion. Table 5 presents the values for the thermodynamic parameters that were calculated from in vitro drug release data in this study. The \(\Delta G\) which is the most important thermodynamic parameter associated with the release process, was positive for PLGA-CS-PEG microspheres, indicating a nonspontaneous natural process. This nonspontaneous process could be attributed to the controlled release of drug from the PLGA-CS-PEG microspheres and probably aids controlled drug release over a one month period [11; 15]. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \multirow{2}{*}{**Formulations**} & \multirow{2}{*}{**Temperature \({}^{\circ}\)C**} & \multicolumn{2}{c}{**Zeroth Order**} & \multicolumn{2}{c}{**First Order**} & \multicolumn{2}{c}{**[PERSON]**} & \multicolumn{2}{c}{**Korsmeyer–Peppas**} \\ \cline{3-10}  & & **K** & **R\({}^{2}\)** & **K** & **R\({}^{2}\)** & **K** & **R\({}^{2}\)** & **K** & **R\({}^{2}\)** & **_n_** \\ \hline PLGA-CS-PEG\_PGS5 & 37 & 1.162 & 0.593 & 0.034 & 0.418 & 8.020 & 0.791 & 1.277 & 0.840 & 0.462 \\ \hline PLGA-CS-PEG\_PGS5 & 41 & 1.295 & 0.611 & 0.037 & 0.438 & 8.902 & 0.809 & 1.279 & 0.860 & 0.482 \\ \hline PLGA-CS-PEG\_PGS5 & 44 & 1.452 & 0.672 & 0.038 & 0.488 & 9.811 & 0.859 & 1.308 & 0.894 & 0.464 \\ \hline PLGA-CS-PEG\_PGS8 & 37 & 1.146 & 0.539 & 0.023 & 0.415 & 8.005 & 0.737 & 1.179 & 0.934 & 0.542 \\ \hline PLGA-CS-PEG\_PGS8 & 41 & 1.438 & 0.624 & 0.029 & 0.486 & 9.828 & 0.817 & 1.266 & 0.839 & 0.494 \\ \hline PLGA-CS-PEG\_PGS8 & 44 & 1.546 & 0.648 & 0.029 & 0.509 & 10.507 & 0.838 & 1.205 & 0.948 & 0.536 \\ \hline PLGA-CS-PEG\_PTX5 & 37 & 1.162 & 0.593 & 0.034 & 0.418 & 8.020 & 0.791 & 1.277 & 0.840 & 0.462 \\ \hline PLGA-CS-PEG\_PTX5 & 41 & 1.162 & 0.587 & 0.027 & 0.481 & 8.059 & 0.791 & 1.065 & 0.900 & 0.522 \\ \hline PLGA-CS-PEG\_PTX5 & 44 & 1.332 & 0.575 & 0.032 & 0.384 & 9.238 & 0.776 & 1.371 & 0.814 & 0.457 \\ \hline PLGA-CS-PEG\_PTX8 & 37 & 1.122 & 0.626 & 0.026 & 0.530 & 7.681 & 0.822 & 1.081 & 0.908 & 0.488 \\ \hline PLGA-CS-PEG\_PTX8 & 41 & 1.169 & 0.601 & 0.025 & 0.489 & 8.053 & 0.799 & 1.126 & 0.884 & 0.483 \\ \hline PLGA-CS-PEG\_PTX8 & 44 & 1.067 & 0.494 & 0.020 & 0.418 & 7.620 & 0.706 & 1.115 & 0.913 & 0.591 \\ \hline \end{tabular}
\end{table} 
Table 4: The kinetic constant (K), correlation coefficient (R\({}^{2}\)) and release exponent (_n_) of kinetic data analysis of drug released from drug-loaded PLGA-CS-PEG microsphere formulations.