INFLUENCE OF DIFFERENT PHYSICOCHEMICAL CONDITIONS ON THE RELEASE OF INDIUM OXINE FROM NANOCAPSULES

The main purpose of this study was to determine the influence of facto rs (pH, enzymes, etc.) chosen partially to mimic in vivo conditions on the release of a model drug, indium oxine, from polyepsiloncaprolacto ne (PCL) nanocapsules in vitro. A nanocapsule suspension, an emulsion (O/W), and a solution in olive oil were prepared in order to compare t he release of a radioactive tracer, indium oxine, as a function of tim e by an in vitro dialysis method. Nanocapsules were prepared by interf acial deposition of PCL and characterized by particle size distributio n (laser light scattering) and determination of the polymer molecular weight by gel permeation chromatography (GPC). The results of this stu dy suggest that the partition coefficient between the medium and the o live oil is the major parameter governing the release of the isotope, at least in the absence of significant enzyme activity. The PCL wall o f nanocapsules is a barrier that does not seem to retard the release o f indium. The addition of porcine liver esterases accelerated the degr adation of PCL. This study confirms that the release of a drug from na nocapsules may be very different depending on the in vivo location, th at is, the administration site. (C) 1998 John Wiley & Sons, Inc.