Investigation of the Relative Affinity of Doxorubicin for Neutral and Negatively Charged Particulate Carriers

Abstract Microparticles produced from polyisobutylcyano-acrylate (IBCA) and polyglutaraldehyde (PGA) were investigated for their relative affinity and surface characteristics using doxorubicin (DOX) as a model drug. IBCA microparticles have been reported to exhibit neutral hydrophobic surface features, whereas PGA microparticles have been shown to possess negatively charged carboxyl groups on their surface. The adsorption of DOX on the surface of these particles was studied by adding the drug to preformed microparticles. The amount of drug adsorbed was determined by centrifugation and analysis of the supernatant for the free drug by HPLC. The adsorption data was examined by Langmuir, Scatchard, and Hill equations. The results indicate that IBCA micropatricles have a higher adsorption capacity for DOX, however PGA microparticles demonstrated a higher relative affinity for the drug molecule. Additionally, both microparticles presented curvilinear Scatchard plots indicating the possibility of more than one type of binding sites for the drug on the surface of these particles. It appears that strong electrostatic attraction may exist between the positively charged amino group on DOX and the negatively charged carboxyl groups of PGA microparticles.