Preparation and characterization of β-cyclodextrin and poly(acrylic acid) microspheres

A method for the preparation of poly(acrylic acid) (PAA) microspheres cross-linked with beta-cyclodextrin (beta-CD) is described. The method is based on a water-in-oil (w/o) emulsion solvent evaporation technique which facilitates a condensation reaction between PAA and beta-CD. Aqueous solutions of PAA and beta-CD were used as the dispersed phase and food grade olive oil was used as the continuous phase. The effect of homogenization speed (used in the preparation of the emulsion), phase volume ratio and cyclodextrin-polymer load on the particle size of the microspheres produced was investigated in a replicated factorial design. Microspheres were sized by light microscopy. The particle size of the microspheres was influenced by all three variables with two significant first order interactions between the variables being observed (homogenization speed with phase volume ratio and homogenization speed with load). A second order interaction between the three principal factors was also observed. Particle size ranged from 16 to 150 mu m, depending on the production variables employed. The yield for the technique was 69.5 +/- 9.5%. Using selected conditions, microspheres of 15-25 mu m size were prepared from a range of PAA with different weight average molecular weights (Mw). These particles were then characterized for beta-CD, free carboxylic acid group content and residual oleic acid.