Controlled insulin release from glucose-sensitive self-assembled multilayer films based on 21-arm star polymer

A glucose-sensitive multilayer film was fabricated by the layer-by-layer (LbL) assembly method with positively charged 21-arm poly[2-(dimethylamino)ethyl methacrylate] (star PDMAEMA) and negatively charged insulin and glucose oxidase (GOD) in the form of {(Star PDMAEMA/Insulin) 4  + (Star PDMAEMA/GOD) 4  + Star PDMAEMA}. The multilayer film shows an on-off regulation of insulin release in response to stepwise glucose challenge in vitro . It is found that the unique structure of star PDMAEMA and interdiffusion of charged insulin are the main factors to control the on-off status of the film. Reversible surface morphology transitions of the multilayer film were also observed, revealing a phase separation and large-scale reorganization process. Furthermore, the multilayer film could continuously release enough insulin in vivo after being subcutaneously implanted in streptocozotin-induced diabetic rats and reduce the blood glucose level for at least two weeks. It is indicated that such system may have substantial potential as a glucose-sensitive carrier for insulin due to its distinct mechanism.