Layer-by-layer Ultrathin Hydrogel Films Linked With Phenylboronate Ester Bonds And Their Applications In Biosensing And Drug Release

Most hydrogel-based biosensors have been hindered in their practicalapplications due to the slow response. In this dissertation we designed hydrogelsensors with quick response from ultrathin hydrogel films, by using layer-by-layer(LBL) assembly technique, which is a simple but versatile approach for filmfabrication. Specifically, with formation of reversible covalent phenylboronate esterbond as the driving force, glucose-responsive hydrogel films can be facilelyfabricated by layer-by-layer assembly, and their thickness is controlled on submicronor micron scale, which is2orders of magnitude thinner than films used in ordinaryhydrogel sensors. In the presence of glucose, these films swell to a larger degree,which infers good glucose-responsive performance. Furthermore, the response islinear and reversible. Glucose-induced swelling can be reported via the shift ofFabry-Perot fringes. Most importantly, the response is quite fast, making it possible tobe used for continuous glucose monitoring.In the later work, in order to enhance the sensors’ performance,N,N-Dimethylaminopropyl acrylamide (DMAPAA) and acrylic acid (AAc) areintroduced into LBL films. Under this experiment setup, the pKa of phenylboronicacid is reduced by B-N interaction. Besides, the cross-link of PVA and acrylic acidincreases the stability of the films. Therefore, in this way, stable glucose-sensorscapable of using under phycological pH are prepared.Under proper conditions, layer-by-layer films may disintegrate as a result of thebreakage of the bonds, which makes them suitable for controlled drug release.Therefore, the films fabricated using reversible phenylboronate ester bonds as drivingforces also disintegrate gradually in aqueous solutions. In this work, insulin canrelease from LbL films fabricated from insulin-PVA (PVA: polyvinyl alcohol)conjugate and poly[acrylamide-co-3-(acrylamido)-phenylboronic acid]. Whenimmersed in an aqueous solution, the films disintegrate gradually, thus insulin isreleased into the media. Specifically, the release rate can be tuned by pH, ionicstrength and glucose concentration, making this system potential for self-regulated insulin release.