## 3 Results
### In Vitro Drug Release Kinetics  
Figure 4a-d illustrates the profiles for in vitro drug release from PLGA-CS-PEG microspheres in PBS (pH 7.4, 0.01% Tween 80) at 37, 41, and 44 \({}^{\circ}\)C. The four types of PLGA-CS-PEG microsphere formulations (PLGA-CS-PEG_PGS5, PLGA-CS-PEG_PGS8, PLGA-CS-PEG_PTX5, and PLGA-CS-PEG_PTX8) all exhibited controlled drug release with over 50% release by the end of day 30. After 48 h, the initial burst release for each microsphere formulation is presented in Table 3. The initial burst release depended on the drug type encapsulated. In the case of PGS loaded PLGA-CS-PEG microspheres, a lower burst release was observed. This could be as a result of the hydrophilic and hydrophobic moieties in the PGS drug [11; 12]. For PLGA-CS-PEG microspheres encapsulated with PTX drug, a higher release was noticed. Similar findings have been reported in previous studies [11; 12]. The results also revealed that PLGA-CS-PEG microspheres loaded with 8 mg/mL concentration of drug have an overall higher burst release than PLGA-CS-PEG microspheres loaded with a drug concentration of 5 mg/mL. On day 30, the overall cumulative drug release reveals a similar pattern for the respective drug-loaded microspheres. It is also important to note that the overall % CDR after the 30 day release was slightly lower for paclitaxel-loaded PLGA-CS-PEG microsphere than prodigiosin-loaded PLGA-CS-PEG microspheres, which could be ascribed to the hydrophobic moiety of PTX drug [11; 12]. Figure 4: _Cont._  
Figure 3: A representative FTIR spectrum for the respective PLGA-CS-PEG microspheres synthesized. Figure 4: _Cont._  
The drug encapsulation efficiencies for the PLGA-CS-PEG_PGS5, PLGA-CS-PEG_PGS8, PLGA-CS-PEG_PTX5, and PLGA-CS-PEG_PTX8 microspheres were determined to be 56.5%, 58.5%, 57.5%, and 56%, respectively, and are presented in Table 3. Furthermore, the drug release profiles were similar at the set temperatures (37, 41, and 44 \({}^{\circ}\)C), which implies that the variation in temperature used during the drug release do not significantly (\(p\)-value \(>\) 0.05) influence the drug release profiles for the PLGA-CS-PEG microspheres. Figure 4: In vitro drug release profile of drug-loaded PLGA-CS-PEG microspheres: (**a**) PLGA-CS-PEG_PGS5, (**b**) PLGA-CS-PEG_PGS8, (**c**) PLGA-CS-PEG_PTX5, and (**d**) PLGA-CS-PEG_PTX8 performed in phosphate-buffered saline (pH = 7.4, 0.01% Tween 80) at set temperatures (37, 41, and 44 \({}^{\circ}\)C). In all cases (\(n\) = 3, @ \(p\) > 0.05). Error bars represent the standard deviation for \(n\) = 3. \begin{table}
\begin{tabular}{p{71.1 pt} p{71.1 pt} p{71.1 pt} p{71.1 pt} p{71.1 pt}} \hline \hline
**Formulations** & \begin{tabular}{c} **Drug Release** \\ **Temperature (\({}^{\circ}\)C)** \\ \end{tabular} & \begin{tabular}{c} **Percentage Burst** \\ **Release after 48 h** \\ \end{tabular} & \
\begin{tabular}{c} **Encapsulation** \\ **Efficiency (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Percentage** \\ **Cumulative Drug** \\ **Release for 30 Days** \\ \end{tabular} \\ \hline PLGA-CS-PEG\_PGS5 & 37 & 27.290 \(\pm\) 2.074 & & 52.117 \(\pm\) 2.506 \\ \hline PLGA-CS-PEG\_PGS5 & 41 & 27.290 \(\pm\) 1.031 & 56.5 & 54.471 \(\pm\) 1.095 \\ \hline PLGA-CS-PEG\_PGS5 & 44 & 27.130 \(\pm\) 1.031 & & 59.151 \(\pm\) 2.084 \\ \hline PLGA-CS-PEG\_PGS8 & 37 & 28.910 \(\pm\) 1.082 & & 62.502 \(\pm\) 3.412 \\ \hline PLGA-CS-PEG\_PGS8 & 41 & 23.277 \(\pm\) 1.230 & 58.5 & 66.700 \(\pm\) 3.641 \\ \hline PLGA-CS-PEG\_PGS8 & 44 & 27.872 \(\pm\) 1.807 & & 71.153 \(\pm\) 3.103 \\ \hline PLGA-CS-PEG\_PTX5 & 37 & 28.055 \(\pm\) 1.157 & & 52.117 \(\pm\) 1.172 \\ \hline PLGA-CS-PEG\_PTX5 & 41 & 28.055 \(\pm\) 1.270 & 57.5 & 56.862 \(\pm\) 1.329 \\ \hline PLGA-CS-PEG\_PTX5 & 44 & 34.275 \(\pm\) 1.231 & & 62.300 \(\pm\) 1.309 \\ \hline PLGA-CS-PEG\_PTX8 & 37 & 30.400 \(\pm\) 1.310 & & 54.728 \(\pm\) 2.290 \\ \hline PLGA-CS-PEG\_PTX8 & 41 & 33.323 \(\pm\) 1.346 & 56.0 & 59.287 \(\pm\) 1.930 \\ \hline PLGA-CS-PEG\_PTX8 & 44 & 37.176 \(\pm\) 1.320 & & 62.300 \(\pm\) 1.300 \\ \hline \hline \end{tabular}
\end{table}