Thermodynamic parameters on poly(d,l-lactide-co-glycolide) particle size in emulsification–diffusion process

The emulsification–diffusion method was thermodynamically studied for making poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles quantitatively considering the diffusion and the solvent–polymer interaction. The properties of various solvents and polymer were also evaluated on the formation of PLGA nanoparticles, such as diffusion coefficients (Dsw, Dws), exchange ratio (R=Dsw/Dws), and solvent–polymer interaction parameter (χ). R was found to be proportional to the size of the PLGA nanoparticles, while χ was inversely proportional to it. In the case of the higher value of R and lower value of χ, a small local supersaturation region was produced at the O/W interface and the small nanoparticles separated from the oil globule were formed in that region. This thermodynamic approach provides a rational basis for the selection of solvent to control the size of PLGA nanoparticles.