Potential Application of Poly(N-isopropylacrylamide) Gel Containing Polymeric Micelles to Drug Delivery Systems

摘要

We have investigated rapidly thermo-responsive NIPA gel containing polymer surfactant PMDP(NIPA-PMDP gel) as a potential drug carrier using (+)-L-ascorbic acid as a model drug. In theNIPA-PMDP gel system micelles of polymer surfactant PMDP are trapped by the entanglement ofpolymer chains inside the gel networks. Therefore, in principle the gel system tightly stores targeted drugin the micelles and rapidly releases controlled amount of the drug by switching on-off of external stimulisuch as temperature or infrared laser beam. In our investigation on release profile, the NIPA-PMDP gelsystem showed completely different releasing behavior from that of the conventional NIPA gel. TheNIPA-PMDP gel released rapidly all loaded (+)-L-ascorbic acid above the phase transition temperature(ca. 34 ℃), while slowly released the corresponding amount of the drug below the temperature. Incontrast, the conventional NIPA gel released more slowly limited amount of the drug above the phasetransition temperature while similarly did to the NIPA-PMDP gel below the temperature. The releaseprofile of the NIPA-PMDP gel seems to be governed by only kinetics of volume phase transition of thegel network but not by the hydrophobic domains of the micelles probably because of too hydrophilicnature of (+)-L-ascorbic acid.