ADSORPTION OF HEMATOPORPHYRIN ONTO POLYALKYLCYANOACRYLATE NANOPARTICLES - CARRIER CAPACITY AND DRUG RELEASE

Experimental conditions for the formulation of hematoporphyrin loaded nanoparticles are presented. The adsorption was performed by incubation of unloaded nanoparticles with hematoporphyrin and was found to be dependent on the pH of the incubation medium. The maximum loading was achieved at pH 5.9 with a carrier capacity of about 30-mu-g HP/mg polyisobutyl-cyanoacrylate nanoparticles. The pH effect was correlated to the degree of ionization of hematoporphyrin. A rapid drug release from nanoparticles was, however, observed following dilution in phosphate buffer at pH 5.9 and was more important at pH 7.4. This fast release reflected an equilibrium shift between adsorbed drug and free drug. The addition of esterases to nanoparticles suspension modified this equilibrium by solubilization of the polymeric sites of drug adsorption and led to an increase in drug release. The potential of photosensitizer loaded nanoparticles in photodynamic therapy is briefly discussed.