Dynamic dialysis for the drug release evaluation from doxorubicin-gelatin nanoparticle conjugates

The drug release from doxorubicin (DXR)-gelatin nanoparticle conjugates was evaluated by means of a dynamic dialysis technique. The study was carried out in absence and in presence of a proteolytic enzyme (trypsin) able to de grade the carrier. In a preliminary study the apparent permeability constan t (K-cv) of the drug through the dialysis bag was evaluated in several medi a. On the basis of this screening, a saline solution (NaCl 0.9%, w/v) resul ted appropriate to carry out the dialysis study since, in this medium, the K-cv did not depend on the drug concentration in the donor solution. In abs ence of the enzyme only a little fraction (from 9 to 13%, w/w of the drug c ontent) was released from nanoparticles. This fraction was considered as th e evidence of the free drug fraction. After the addition of trypsin, the di ffusion of a further drug fraction was observed. This fraction is probably due to a fraction of the DXR-peptide conjugates characterised by a molecula r weight lower than membrane cut-off (3500 Da). (C) 1999 Elsevier Science B .V. All rights reserved.