Development and characterization of biodegradable nanospheres as delivery systems of anti-ischemic adenosine derivatives.

We report a preliminarystudy concerning the encapsulation modalities in nanoparticles of the anti-ischemic drug N6-cyclopentyladenosine (CPA) and its pro-drug 50-octanoyl-CPA (Oct-CPA). The release of these compounds and the related pro-drug stabilityeffects in human whole blood have been tested. Moreover, the influence of the delivery systems on CPA interaction toward human adenosine A1 receptor has been analysed. The nanospheres were prepared by nanoprecipitation or double emulsion solvent evaporation method using poly(lactic acid) and recovered by gel filtration or ultracentrifugation or dialysis. Free and encapsulated Oct-CPA was incubated in fresh blood and its stabilitywas analysed with HPLC. Quite spherical nanoparticles with mean diameters ranging between 210750 and 390790nm were obtained. No encapsulation occurred when CPA was used. Satisfactoryresults concerning drug content (0.1-1.1% w/w) and encapsulation efficiency(6-56%) were achieved when Oct-CPA was employed. The controlled release of the pro-drug was achieved, being released within a range of 1-4 h, or very slowly, depending on nanoparticle preparations. The hydrolysis rate of Oct-CPA in human whole blood appeared stabilized in human whole blood with modalities related to the release patterns. The presence of all nanoparticle preparations did not interfere with CPA interactionat its action site.