Reducing residual solvent levels in poly (D, L-lactic-co-glycolic acid) microspheres: a roadmap for scalable industrial production.

Objective: Poly (D, L-lactic-co-glycolic acid) (PLGA) microspheres have garnered significant attention as biocompatible and biodegradable carriers for sustained drug delivery. However, the production of PLGA microspheres typically involves organic solvents, such as ethyl acetate and benzyl alcohol. Residual solvents are undesirable given their potential toxicity and adverse effects on product stability. Effective solvent removal is critical for ensuring the safety and functionality of microspheres.

Method: In this study, 12 formulations were designed by altering the conditions of solvent extraction, washing, and solvent evaporation steps to reduce residual solvents and determine critical parameters in process. Microspheres were evaluated based on residual solvent content, drug loading, size, morphology, moisture content, injectability, and release kinetics.

Result: In five formulations (F06-F10), at least the residual amount of one organic solvent was significantly reduced. Prolonging the microspheres' residence time in ethanolic solution during the second extraction phase (F11) resulted in notable organic solvent reductions (ethyl acetate 93% and benzyl alcohol 60% compared to formulation F01). Further, these microparticles were spherical with a geometric diameter of 75.8 μm, a drug loading percentage of 33.7%, and a reasonable release profile, representing significant achievements.

Conclusion: This study highlighted the importance of some modifications in preparing PLGA microspheres that have not been reported previously. These modifications greatly affected the residual solvent amount as well as other physicochemical properties of microspheres including size, morphology, and release profile. Overall, some practical methods could be used for feasible industrial production of PLGA microspheres.