Insulin impregnated reduced graphene oxide/Ni(OH)2 thin films for electrochemical insulin release and glucose sensing

Electrophoretic deposition (EPD) of graphene-based nanomaterials has become an attractive strategy for the controlled deposition of thin films onto substrates for various applications. In this work, we demonstrate that application of an electrical potential to gold interfaces immersed in an aqueous suspension of graphene oxide (GO), loaded with nickel ions and insulin produces a continuous coating of an insulin impregnated reduced graphene oxide (rGO) matrix loaded with Ni(OH)2 nanostructures (rGO/insulin/Ni(OH)2). The rGO/insulin/Ni(OH)2 coated Au electrodes exhibit excellent electrocatalytic behaviour towards glucose oxidation in alkaline medium at +0.6 V. The sensitivity towards glucose is 18.9 ± 1.5 mA mM−1 cm−2 with a detection limit of ≈5 μM. In addition, the amount of insulin integrated into the electrophoretically deposited coating is as high as 48 μg mL−1, making the matrix of high interest for release studies. Electrochemical triggered release of the trapped insulin is achieved upon application of a negative potential to the interface. The possibility to form multifunctional coatings by EPD, incorporating catalytic nanostructures for diagnosis as well as drugs for therapy in one-step makes this approach a competitive alternative to other surface coating strategies.