Effect of amino acids on the dispersion of disodium cromoglycate powders

Modified disodium cromoglycate powders were prepared by co-spray drying with different concentrations of leucine, phenylalanine, tryptophan, methionine, asparagine, and arginine. Amorphous spherical particles of the same size and density where obtained which, however, exhibited different surface properties as measured by the inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy (XPS) techniques. The surface energy parameters, such as the dispersive component of surface free energy of the sample, γ _S^D, and the total solubility parameter, γ, were significantly lower in the presence of nonpolar chain amino acids, particularly with leucine and phenylalanine, than pure DSCG. However no quantitative relationship between these parameters, the additive concentrations, and the fine particle fractions, FPF, determined for different inhalers and air flow rates, was observed. The FPF significantly increased with addition of leucine and this effect was attributed to reduced intermolecular interactions between leucine and disodium cromoglycate molecules, as indicated by the difference in corresponding Hansen solubility parameters. Decrease of interparticle interactions for leucine-containing powders also led to a lesser dependence of FPF on the flow rate and inhaler type.