Drug microencapsulation by PLA/PLGA coacervation in the light of thermodynamics. 1. Overview and theoretical considerations

  • Thomasin C
  • Nam-Trân H
  • Merkle H
 et al. 
  • 58

    Readers

    Mendeley users who have this article in their library.
  • 72

    Citations

    Citations of this article.

Abstract

Phase separation (frequently called coacervation) of poly(lactide) (PLA) and poly(lactide-co-glycolide) (PLGA) is a classical method for drug microencapsulation. Here, attempts have been made to describe this process in the light of thermodynamics. Different PLA/PLGAs were dissolved in either dichloromethane or ethyl acetate, phase separated by addition of the coacervating agent silicone oil (PDMS), and hardened in either octamethylcyclotetrasiloxane or hexane. Various stages of phase separation were defined microscopically, and the coacervate and continuous phases characterized with respect to volume, composition, polymer molecular weight, and rheological behavior. The optimal amount of PDMS was inversely proportional to the polymer molecular weight and hydrophilicity, and a coacervate viscosity of above 5-10 Pa s was required for stable coacervate droplets. The composition and, consequently, viscosity of the coacervate and continuous phases depended on the polymer-solvent-PDMS interactions, as analyzed by the parameters chi (Flory), delta (Hildebrand), and delta(int)E (Hô). In general, the lattice model of FIory and Scott describing polymer-polymer incompatibility best explained the results. The interaction parameters and viscosity of the phases were also helpful to explain microsphere characteristics such as residual solvent and particle size. The data suggest that microsphere formation by polyester coacervation is primarily driven by molecular interactions between polymer, solvents, and coacervating agent.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Get full text

Authors

  • Claudio Thomasin

  • Hô Nam-Trân

  • Hans P. Merkle

  • Bruno Gander

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free