DIRECT EVALUATION OF INTRACELLULAR ACCUMULATION OF FREE AND POLYMER-BOUND ANTHRACYCLINES

Nanoparticulate carriers of anthracyclines are being developed with th e aim of improving the pharmacokinetic or pharmacodynamic behavior of these drugs. To understand how the drug reaches its nuclear targets, w e have developed two methods that allow the quantification of the inte raction between an anthracycline and cellular DNA: (1) by direct evalu ation of the quenching of anthracycline fluorescence due to the interc alation of the drug into DNA and (2) by the measurement of Hoechst 332 58 fluorescence associated with its displacement from DNA-binding site s for which it competes with the anthracycline. We show that the intra cellular accumulation and DNA binding of doxorubicin encapsulated in p olyisohexylcyanoacrylate nanospheres (dox-NS) and of daunorubicin boun d to polyglutamic acid are reduced by 30%-40% in comparison with those obtained for free doxorubicin (dox) and daunorubicin, respectively. T he results obtained with dox or NS-dox are not modified by prior incub ation with either of these compounds. The two methods yielded similar results, and we conclude that either technique is applicable to the ev aluation of the interaction of carrier-bound anthracyclines with cellu lar DNA.