Interfacial tension effects on the properties of PLGA microparticles

Abstract

Many types of long-acting injectables, including in situ forming implants, preformed implants, and polymeric microparticles, have been developed and ultimately benefited numerous patients. The advantages of using long-acting injectables include greater patient compliance and more steady state drug plasma levels for weeks and months. However, the development of long-acting polymeric microparticles has been hampered by the lack of understanding of the microparticle formation process, and thus, control of the process. Of the many parameters critical to the reproducible preparation of microparticles, the interfacial tension (IFT) effect is an important factor throughout the process. It may influence the droplet formation, solvent extraction, and drug distribution in the polymer matrix, and ultimately drug release kinetics from the microparticles. This mini-review is focused on the IFT effects on drug-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles.

Keywords: Interfacial tension; PLGA microparticles; Processing parameters; Solvent extraction.

Figure 1.

Three main types of w/o/w emulsions: microcapsule (a), multi-vesicular (b), and matrix or monolithic (c) structures.

Figure 2.

Potential phase configurations at equilibrium in relation to the spreading coefficient. (a) Full engulfment (i.e., core shell) (S₁ < 0, S₂ < 0, S₃ > 0); (b) Partial engulfment (i.e., Janus) (S₁ < 0, S₂ < 0, S₃ < 0); (c) No engulfment (i.e., individual particles) (S₁ < 0, S₂ > 0, S₃ < 0). Scanning electron microscopy (SEM) images of PLGA/polycaprolactone microparticles formed with the polymer weight ratio of 19:11, (d) without drug; with drugs, i.e. (e) glibenclamide (negatively charged); (f) rapamycin (no charge); and (g) lidocaine (positively charged). Reproduced with permission [64].