Screening of Electrolyte Complexes Formed Between Dextran Sulfate and Amine Structures of Small-Molecule Drugs

Formation of an electrolyte complex using the electrostatic interactions between a polyanionic polymer and a cationic drug is a simple and efficient method of preparing a colloidal drug carrier system. Dextran sulfate, with a negatively charged sulfate group, was reacted in an acetate buffer solution of pH 3 with positively charged 1° amine, 2° amine, 3° amine, piperazine, and piperidine structures from 24 small-molecule drugs. The electrolyte complex was formed from 15 drugs, 63% of those tested. The tendency to form the electrolyte complex was in the order of piperazine and piperidine >3° amine >>2° amine. The drugs with the 1° amine structure failed to form an electrolyte complex. The mean particle sizes were in the range of 50-740 nm, and most of them showed a submicron colloidal dispersion of <400 nm. Regarding drug encapsulation efficiency (%), 11 drugs with piperazine, piperidine, and 3° amine structures showed 60-98% efficiency, which was fairly high. The results suggest that directly forming the electrolyte complex with dextran sulfate yields promising structural attributes as a submicron colloidal drug carrier system.