Preparation and characterization of poly(methyl methacrylate)—iron (III) oxide microparticles using a modified solvent evaporation method

Abstract

At present, there is widespread interest in developing new, biocompatible microparticles made from polymers such as poly(methyl methacrylate) (PMMA) that could have applications ranging from diagnostic imaging to drug delivery. In these experiments, there were two primary objectives: (1) to stabilize a suspension of iron (III) oxide (α-Fe₂O₃; mean diameter = 100 nm) nanoparticles in a solution of PMMA by using an emulsifier and different mixtures of two miscible solvents; and (2) to fabricate PMMA-α-Fe₂O₃ microparticles by using an oil-in-water (o/w) solvent evaporation method. By accomplishing the first objective, it was hypothesized that the encapsulation efficiency of α-Fe₂O₃ within PMMA microparticles would improve and induce the clustering of α-Fe₂O₃ along the circumferential edges of the microparticles. Of the seven emulsifiers tested, Tween 80 was selected primarily for its hydrophilicity and its ability to produce a stable α-Fe₂O₃ dispersion. As a result, 22 batches of microspheres (11 with Tween 80 and 11 without) were made and the solvent (dichloromethane) to co-solvent (ethyl acetate) ratios were varied. Particles made with solvent mixtures of >50% ethyl acetate (<50% dichloromethane) were more likely to be hollow and had larger mean volumetric particle diameters (>5 microns) than particles made with mixtures containing >50% dichloromethane. Particles made with Tween 80 were larger, more porous, and had α-Fe₂O₃ aligned along the circumferential edges of the particles. The use of solvent mixtures did not improve the encapsulation efficiency of α-Fe₂O₃ but the use of ethyl acetate helped to induce the clustering of α-Fe₂O₃ along the peripheries of the microparticles.

Key Words: :

• PMMA
• iron (III) oxide
• microsphere
• ICP-MS
• SEM
• TEM