Development of Robust Redox-Active Lyotropic Liquid Crystal Structures for Bioelectrodes

The fabrication of stable and highly performing enzyme-based electrodes is key for the effective generation of biodevices and bioelectronics, such as electrochemical biosensors. In this context, redox-active lyotropic liquid crystals based on 3D nanomaterials, known as lipid cubic phases (LCP), hold great potential due to the large specific surface area and the possibility to be functionalized. In this study, we functionalized a monoolein (MO) LCP matrix by incorporating an amphiphilic redox shuttle within its matrix with the aim to enhance the electrochemical performance of a glucose oxidase (GOx) based electrode and we investigated the stability of the overall system. The use of dodecyl(ferrocenylmethyl)dimethylammonium bromide (Fc12-Br) resulted in an electroactivity loss with time of the resulting Fc12-Br/MO electrode, probably due to the formation of a passivating layer between the bromide counterions and the electrode surface. Hence, bromine (Br-) was replaced with hexafluorophosate (PF6-), leading to Fc12-PF6/MO. Both structures were used for GOx entrapment and the resulting electro-activity towards glucose was assessed. Though the sensitivity obtained with the Fc12-Br/MO/GOx and Fc12-PF6/MO/GOx systems was comparable, the latter showed superior stability over time, with more than 80% activity retained for > 20 days. Moreover, when the concentration of the Fc12 redox shuttle within the cubic phase was increased by 10, a 4 times greater current density was generated. Consequently, the Fc12-PF6/MO electrode shows superior stability and performance than previously reported redox lyotropic LCP systems, thus paving the way for promising applications in enzyme-based biodevices.