Self-consistent field modelling of poly(lactic acid)-poly(ethylene glycol)particles

Self-consistent field (SCF) modelling studies on a series of varying molecu lar weight poly(lactic acid):poly(ethylene glycol) (PLA:PEC) particles (2:5 -15:5 kDa) that form micelles in aqueous solutions have been performed usin g the formalism of Scheutjens and Fleer. The parameters were chosen to repr esent a central core made from collapsed hydrophobic PLA blocks, and PEG bl ocks, which form a corona layer extended into the solvent. These different phases have been confirmed in H-1 and C-13 NMR experiments. From the analys is of the relevant thermodynamic data of the series, particle radii and agg regation numbers varying from 12.6 to 24.9 nm and from 17 to 280, respectiv ely, have been predicted, which agree well with those obtained experimental ly. The actual thickness of the PEG corona is fairly constant at approximat ely 11 nm For the whole particle series indicating that the size of the PLA core has little effect on the thickness of the PEG corona layer. Another i mportant consideration of these particles is the PEG density at the surface , which is related to the in vivo properties of these particles. The surfac e area available to each PEG block at the central PLA core has been obtaine d in order to compare the members of the particle series. It has been shown that the surface area available to each PEG block decreases and then incre ases throughout the PLA:PEG series. (C) 2000 Elsevier Science B.V. All righ ts reserved.