Figure 4

Effect of PLGA polymer composition on the properties of resultant nanospheres. PLGA (50:50) at molecular weights of 72 kDa, 50 kDa, and 17 kDa was used to encapsulate AO. The 50 kDa and 17 kDa polymers did not have lauryl ester end groups but unmodified carboxylic acid end groups instead. Measurements were done on unloaded and PEG-PEI-AO polyplex loaded nanospheres. The following properties of the nanospheres were evaluated: (A) Mean diameters measured by DLS. No statistical difference was observed between the nanospheres formulated using the three different PLGA polymers for either loaded or unloaded nanospheres (P > 0.05). (B) Surface charge (evaluated by zeta potential analysis) was determined by light scattering. A significant difference in zeta potential was seen between nanospheres formulated using each of the three different PLGA polymers for both polyplex loaded and unloaded nanospheres (P < 0.05). A significantly less negative zeta potential was observed for polyplex loaded compared to unloaded nanopsheres formulated using 72 kDa endcapped PLGA (*P = 0.027). No difference in zeta potentials were seen between polyplex loaded and unloaded groups for 50 kDa and 17 kDa PLGA. (C) Encapsulation efficiency (EE) of unloaded nanospheres and PEG-PEI-AO loaded nanospheres. Non-endcapped 50 kDa and 17 kDa PLGA polymers showed significantly higher encapsulation efficiencies compared to endcapped 72 kDa PLGA (**P < 0.05). (D) Polymer yield for the unloaded nanospheres and PEG-PEI-AO loaded nanospheres. The yield for 72 kDa PLGA was moderately higher than for 50 kDa and 17 kDa PLGA polymers for both unloaded and loaded samples (***P < 0.05). All measurements were repeated in triplicate from independently prepared samples.