Preparation and characterization of magnetic PLA–PEG composite particles
Introduction
Polymer magnetic microsphere is a new type of functional material which has been recently applied to enzyme immobilization [1], drug targeting [2], cell separation [3] and immunoassay [4], etc. Many researches have described the preparation of particles containing inorganic magnetic nanoparticles such as monomer polymerization method–emulsion polymerization [5], dispersion polymerization [6], suspension polymerization [7], microemulsion polymerization [8] and polymer hybrid method–emulsion technology [9] and solvent evaporation [10].
Gómez-Lopera et al. [9] produced mixed colloidal particles (average diameter 0.16 ± 0.06 μm) with approximately spherical geometry by double-emulsion technique. The particles they prepared were composed of a magnetite nucleus and a biodegradable poly (d,l-lactide). They found that the synthetic new material displays a behavior intermediate between that of magnetite and poly(d,l-lactide) spheres. In this paper, biodegradable PLA–PEG block copolymers were used as magnetite carriers. The magnetic Fe3O4/PLA–PEG composite particles were prepared by a phase separation method. Furthermore adequate control of magnetic properties, such as particle size and magnetic responsibility, were researched in this paper. This paper also involves the synthesis and characterization of PLA–PEG block copolymers with different block ratio and different block length by a ring-opening polymerization between d,l-lactide and PEG, for the structure of copolymer plays an important role in the properties of magnetic composite particles.
We try to control the properties of magnetic composite particles by alternating the block ratio and length of PLA–PEG copolymer. The prepared Fe3O4/PLA–PEG particles with magnetic properties and biodegradable properties would provide useful applications in drug targeting and drug controlling release.
Section snippets
Materials
Poly(ethylene glycol)s (PEGs) with weight average molecular weights of 2000, 4000, 6000, 8000, and 10,000 g mol− 1 were used after drying under vacuum at 80 °C for over 10 h. d,l-lactide was used after further purification. Fe3O4 with particle size of 20∼30 nm was provided by Huaming Group, Shanghai, China and it was used after modified by KH-570. PEGs, stannous caprylate (Sn(Oct)2), acetone, ethyl acetate, n-heptane and other solvents used were of analytical grade and were purchased from
Particle morphology
Fig. 1 is a representative image taken for the sample obtained by Fe3O4 and copolymer, which was synthesized by d,l-lactide and PEG-4000 with a ratio of 5 : 1. The prepared magnetic particles were spherical with a size range of 100–200 nm as shown in Fig. 1. The particles in Fig. 1 can be divided into three kinds—PLA–PEG copolymer particles (white particles), PLA–PEG magnetic composite particles with Fe3O4 absorbed on the surface (black particles and white particles circled by black ring) and
Acknowledgements
This work was supported by the project of Nano Science and Technology of Shanghai (Number: 0452 nm 059) and the track project of Rising Star for Youthful Scholar of Shanghai (Number: 04QMH1406).
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