Optimizing Formulation Conditions of PLGA Microparticles to Enhance Indomethacin Encapsulation

Abstract Drug delivery systems can avoid the drawbacks of Indomethacin (IND), a non‐steroidal anti‐inflammatory drug used to treat osteoarthritis and arthritis, which requires high doses to reach therapeutic plasma levels leading to significant systemic side effects. This study aims to optimize poly(lactic‐co‐glycolic acid) (PLGA) microparticles (MPs) for intra‐articular IND administration. MPs are prepared by solvent evaporation and freeze‐dried for stability. Initial formulations with Tween 80 yield rubbery samples with low drug loading (1%); replacement of Tween 80 with Gelatin produces a stable powder with syringable MPs (particles size: 7 µm), although, DL (3%) and EE (30%) remain suboptimal, due to IND polymorphic transformation. Differential Scanning Calorimetry and Fourier‐Transform Infrared spectroscopy demonstrate a molecular dispersion of IND in PLGA. Adjusting the aqueous phase to pH 3 in the formulation process, i.e below IND pKa, significantly enhances EE (90%) due to the reduction of drug solubility in the external aqueous phase. In vitro release study shows prolonged IND release over several days, confirming an effective drug encapsulation. This study provides a foundational framework toward the optimization of the successful encapsulation of IND in PLGA MPs, potentially advancing future clinical applications of such drug delivery systems.