In vitro release of 9-β- d-arabinofuranosyladenine from thermo-responsive copoly(acryloyl- l-proline methyl ester/styrene) gels

Abstract

Hydrophobic styrene (St) was copolymerized with acryloyl- l-proline methyl ester (A-ProOMe) known as a characteristic thermo-responsive gel. The thermo-responsive function of this copolymer gel perfectly disappeared by the introduction of St > 20 mol% in the gel because of a strongly hydrophobic effect owing to pendant phenyl moiety. On thermo-responsive copolymer gels ranging in St composition from 1 to 10 mol%, the deswelling process proceeded faster than swelling process. This difference was explained from the results of activation energies (| ΔE|). The swelling-temperature curve of such a thermo-responsive gel was tried to investigate by a statistical moment analysis, e.g. the area under swelling-temperature curve (AUC), mean swelling transition temperature (MSTT), and variance of swelling transition temperature (VSTT), suggesting that these values corresponds very closely to St composition in the gel. 9-β- d-arabinofuranosyladenine (Ara-A) was incorporated into the thermoresponsive copoly(A-ProOMe/St) gels and, as a result, it was found that the in vitro release of Ara-A from the gel when cycled at different temperatures at 60-min intervals shows a typical pulsatile release such as a slight amount of drug release at 10°C and a good deal of drug release at 30°C.