Beyond the Gold Electrode Standard: Using a Triazabutadiene-Maleimide Linker to Covalently Immobilize a...

Triazabutadiene-mediated diazonium electrografting is an electrode modification method that enables stable covalent bonds to be made to a versatile range of electrode materials. In biosensing, a challenge in utilizing diazonium electrografting for immobilizing biorecognition elements has been the chemical incompatibility between these biomolecules and the corrosive grafting conditions often required to generate diazonium cations in situ. This work presents a solution to this problem. We describe the utilization of a heterobifunctional linker molecule that possesses a thiol-reactive maleimide head group and a triazabutadiene tail group. The maleimide group allows us to robustly ligate to a thiol functionality on a polymer which acts as an anti-biofouling display platform for the glycan-based biorecognition element. Following ligation between the linker molecule and our biorecognition element, we convert the triazabutadiene tail groups into diazonium cations under biocompatible conditions, readily enabling electrografting of the polymer onto carbon electrodes, yielding a ten-fold higher coverage density of the glycan biorecognition element compared to gold-thiol self-assembly (170 pmol cm^-2 compared to 13 pmol cm^-2 using the geometric working electrode surface area) and a commensurate increase in sensitivity to galectin-3, a disease associated biomarker.