Preparation and characterization of magnetic PLA-PEG composite nanoparticles for drug targeting

A series of biodegradable block copolymers of poly-d,l-lactide-co-polyethylene glycol (PLA-PEG) was prepared by ring-opening polymerization of d,l-lactide with stannous caprylate (Sn(Oct)2) as catalyst, then composite particles were prepared using PLA-PEG copolymers and magnetic Fe3O4 by a phase separation method. The average molecular weight and structure of PLA-PEG were determined by gel permeation chromatography (GPC), nuclear magnetic resonance (1H NMR) and differential scanning calorimeter (DSC). The sizes and its distributions of the composite particles were investigated by laser particle size analyzer. The morphologies of prepared particles were observed by transmission electron microscopy (TEM). The contents of Fe in the composite particles were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The magnetic susceptibilities were measured by nephelometery. The magnetic particles prepared were spherical with size range of 100-200 nm. The sizes of spheres were influenced by PLA, PEG chain length and block ratio. The magnetic properties of composite particles increased with increasing PEG chain length and PEG content. Particles with Fe content ranging from 0.5% to 5.2% were prepared. The properties of magnetic composite particles were controlled by altering the block ratio and the length of PLA-PEG copolymer to meet more requirements. The prepared Fe3O4/PLA-PEG particles with magnetic properties and biodegradable properties would provide practical applications in drug targeting and controlled drug release.