Solvent Effect in PLA-PEG Based Nanoparticles Synthesis through Surfactant Free Polymerization

摘要

In this work one-pot synthesis of PEGylated PLA-based nanoparticles (NPs) without using any surfactant has been performed. Adopting ring opening polymerization of L,L-Lactide and 2-hydroxyethyl methacrylate (HEMA), vinyl end functionalized poly(lactic acid) macromonomers (HEMA-LA_n) have been produced with tunable number of lactic acid units (larger than 5) and a low molecular weight distribution. Macromonomers have been further copolymerized with modified PEG chains (HEMAPEG_m) through a monomer starved semi-batch emulsion polymerization performed without using any surfactant. In these conditions, small and monodispersed NPs of around 150 nm are obtained. Since macromonomers with n larger than 5 are highly viscous at room temperature, they have to be dissolved in a solvent before their injection in the reactor. In this work the effects in changing the solvent adopted in the starved process (water miscible or non-miscible) and its amount have been investigated. Moreover, the effect of both PEG chains concentration and MW on the final NPs properties has been elucidated. The colloidal stability of the NPs produced using different solvents has been verified in phosphate buffered saline (PBS) solution via dynamic light scattering measurements; in addition the critical coagulation concentration of these PEGylated NPs has been determined.