Microparticle preparation by a propylene carbonate emulsification-extraction method

The use of various harmful organic solvents for microparticle formulations is still widespread. Here, an alternative low toxicity solvent (propylene carbonate; PC) is proposed for the preparation of poly(lactic-co-glycolic-acid) (PLGA) microparticles. Based on the classical emulsification-solvent extraction methodology, the use of PC offers the unique advantage of an additional solvent extraction step using hydrolytic solvent cleavage during microparticle preparation. Spherical, rough-surfaced microparticles were obtained with a volume median diameter range from 20 to 60 µm. The residual PC content has been identified to be the major factor for the solidification hindrance, leading to polymeric Tg shifting due to a plasticizing effect. When applying the enhanced PC extraction step, the residual PC content was lowered from 8.8% to 2.7% and subsequently Tg values shifted from 8.2 to 37.7 °C. Additionally, the hydrolytic solvent cleavage confirmed to have no impact on the PLGA stability. This method presents a significant advancement towards replacing of conventional solvents in the microparticle preparation due to more efficient solvent extraction.