Poly(D,L-lactide-co-glycolide) dispersions containing pluronics:: from particle preparation to temperature-triggered aggregation

In this work the preparation mechanism, properties and temperature-triggered aggregation Of poly(D,L-lactide-co-glycolide) (PLGA) dispersions are investigated. The dispersions were prepared by interfacial deposition in aqueous solution containing Pluronic L62 (EO6PO30EO6) or F127NF (EO101PO56EO101), where EO and PO are ethylene oxide and propylene oxide, respectively. PLGA dispersions were also prepared in the absence of added Pluronic for comparison. The PLGA particles were characterized using SEM, photon correlation spectroscopy and electrophoretic mobility measurements. It was found that the hydrodynamic diameter (d) increased with PLGA concentration used in the organic solvent phase (C-PLGA(o)). The value for d was proportional to C-PLGA(o)(1/3). The value for d increased upon addition of 0.04 M NaNO3 which demonstrated the importance of electrostatic interactions during particle formation. Electrophoretic mobility measurements were conducted as a function of pH and the data used to estimate the Pluronic layer thicknesses on the PLGA particles. The layer thickness was greatest for the PLGA particles prepared in the presence of Pluronic F127NF. PLGA dispersions containing Pluronic L62 exhibited temperature-triggered aggregation in the presence of 0.15 M NaNO3. It was found that the critical temperature for dispersion aggregation (T-crit) was comparable to the cloud point temperature (T-cp) for the parent Pluronic L62 solution. Conditions were established for achieving temperature-triggered aggregation at body temperature for PLGA particle/Pluronic L62 dispersions under physiological ionic strength and pH conditions. The PLGA/Pluronic L62 mixtures studied may have potential for use as injectable biodegradable implants for controlled release applications.