Preparation and characterization of magnetic PLA–PEG composite particles

doi:10.1016/j.matlet.2005.04.013

Materials Letters

Volume 59, Issue 21, September 2005, Pages 2655-2658

https://doi.org/10.1016/j.matlet.2005.04.013 Get rights and content

Abstract

A series of biodegradable block copolymers of poly-d,l-lactide-co-polyethylene glycol (PLA–PEG) were prepared out by ring-opening polymerization of d,l-lactide with stannous caprylate (Sn(Oct)₂) as catalyst, then the PLA–PEG copolymers and magnetic Fe₃O₄ were made into composite particles by phase separation method. The sizes and distribution of composite particles were investigated by laser particle size analyzer. The morphologies of the prepared particles were examined by TEM. The contents of Fe in composite particles were detected by ICP. The magnetic susceptibilities were measured by nephelometery and VSM. The particles prepared were spherical with a size range of 100–200 nm. The sizes of the particles were influenced by PEG molecular weights and block ratio. The magnetic properties of composite particles increased with the increase of PEG molecular weights and block ratio. The properties of magnetic composite particles were controlled by altering the block ratio and the molecular weight 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.

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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Preparation and characterization of magnetic PLA–PEG composite particles

Abstract

Introduction

Section snippets

Materials

Particle morphology

Acknowledgements

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