Effect of Formulation Variables on the Performance of Doxycycline-Loaded PLA Microsphere

Polymeric materials are currently being investigated as potential drug carriers. However, their performance is highly influenced by various factors especially the formulation variables. Herein, doxycycline-loaded PLA microspheres were prepared using the double emulsion solvent evaporation method and the effects of formulation variables were investigated. Specifically, particle size distribution, encapsulation efficiency and in vitro drug release behavior were evaluated for different formulations. In addition, antimicrobial activity of the doxycycline-loaded PLA microspheres was studied through the agar well diffusion method. Results showed that the addition of 4% NaCl into the external aqueous phase helped to improve the encapsulation efficiency, which subsequently influenced the drug release behavior of the microspheres. Specifically, about 66% of the doxycycline was encapsulated within PLA microspheres. Notably, slower drug release behavior was obtained by increasing the aqueous/organic phase volume ratio, polymer concentration and NaCl concentration in the external aqueous phase. However, increase in the particle size of microspheres resulted in lower encapsulation and antibacterial efficiencies. This study reveals that through proper manipulation of formulation variables, high-performance PLA microspheres suitable for use as carrier for various drugs can be prepared.