Abstract
The objective of this study is to investigate a pulsatile drug release synchronizing with water outflow induced by fast deswelling changes of novel thermo-responsive polymer gels containing graft chains. We synthesized thermo-responsive poly (N-isopropylacrylamide) crosslinked gels having poly (ethylene glycol) graft chains with freely mobile ends. The graft-type gels demonstrate rapid deswelling changes in response to temperature increases. The graft chains form water release channels during the gel deswelling changes accompanying water outflow from inside the gels. In contrast, conventional normal-type gels without graft chains demonstrate a slow deswelling change due to formation of a dense skin layer at the surface which retards the water outflow from the gels. The difference is apparent in a drug release pattern between the normal-type gel and the graft-type gel. Upon temperature increase, the normal-type gel restricts drug release due to formation of the dense skin layer. In contrast, pulsatile drug release is achieved synchronizing with the water outflow during rapid deswelling change of the graft-type gel. The details of pulsatile drug release regulation using novel graft-type gels are studied as a function of drug molecular weight.
