Micelles Self-assembled From Glucose-responsive Copolymer And The Controlled Release Of Insulin

A growing interest is focused on glucose-sensitive polymers because of their potential application in insulin delivery for the treatment of diabetes, a life-threatening disease showing an increased tendency around the world. Polymers containing phenylboronic acid have been of particular interest given for their selective glucose-responsiveness in aqueous milieu and the advantage of greater stability.The PAA segments of poly(ethylene glycol)-block-poly(acrylic acid) (PEG114-b-PAA170) is modified by 3-aminophenylboronic acid (APBA) with different modification degree such as PEG114-b-(PAA0.37-co-PAAPBA0.63)170 (PEG-A-PBA-1), PEG114-b-(PAA0.23-co-PAAPBA0.77)170 (PEG-A-PBA-2) and PEG114-b-(PAA0.02-co-PAAPBA0.9s)170 (PEG-A-PBA-3). Micelles self-assembled from these three copolymers possess glucose-responsiveness at varying pH values. Micelles self-assembled from (PEG-A-PBA-1), (PEG-A-PBA-2) and (PEG-A-PBA-3) obtain glucose-responsiveness at pH7.4,10.2 and 11.3, respectively. Moreover, the investigation of glucose-responsive behaviors at various pH values indicates that, the swelling and dissociation of micelles can be efficiently increased by increasing the glucose concentration.Micelles self-assembled from PEG-A-PBA-1, PEG-A-PBA-2 and PEG-A-PBA-3 swell and dissociate in aqueous solution at different pH values, such as pH 7.4,10.2 and 11.3 respectively. To further investigate this phenomenon,11B magic-angle spinning nuclear magnetic resonance (11B MAS NMR) and 2-dimesion 11B 3-quantum magic-angle spinning nuclear magnetic resonance (2D 11B 3Q MAS NMR) are employed to analyze the conformational changes of boron. The coordination between carboxylate anion of PAA segments and phenylboronic acid of PAAPBA segments triggers boron change from trigonal planar form to tetrahedral form, resulting the glucose-responsiveness of micelles at low pH values. Moreover, 11B 3Q MAS NMR experiements have been performed to research the structural changes of boron caused by the combination between phenylboronic acid and glucose.Glucose-responsive PEG-A-PBA-2 self-assembles into core-shell micelles with the hydrophobic core composed of PAAPBA and hydrophilic shell composed of PEG in aqueous solution. The swelling and disaggregating behaviors of micelles responding to glucose are investigated by using light scattering in aqueous solution at pH 7.4. Characterization of insulin-loaded micelles and their drug release in solutions with various glucose concentrations are further studied. The results demonstrate that the insulin-loaded micelles can swell and dissociate with the increasing glucose concentration, and the drug release rate can be controlled by varying glucose concentration.