For four decades, the development of biointerfaces has been the subject of increasing research efforts in the field of biosensors and energy conversion. In particular, the functionalization of electrodes by biomaterials based on electrogenerated polymers and / or carbon nanotubes or graphene is widely used for the design of biosensors and biofuel cells. These nano-objects were successfully functionalized by electropolymerization of pyrrolic monomers or pyrene derivatives exhibiting affinity or covalent binding interactions towards biomolecules. Various biomolecule immobilization strategies have been explored involving photografting process, affinity and host-guest interactions. Some new approaches for developing nanostructured biomaterials based on supramolecular assemblies will be illustrated. In particular, an original versatile methodology for molecular grafting on different surfaces via a new photoactivatable diazirine derivative is reported. This pyrene-diazirine, which was electropolymerized onto various electrodes, enabled, under UV irradiation, the photografting of redox mediators and enzymes.¹

Recent examples of electropolymerized films will be presented for the design of labeless immunosensors for dengue or cholera toxin antibody. ^2,3 In particular, an original impedimetric immunosensor for the detection of cholera antibody was developed based on carbon nanotube deposits with different controlled thicknesses. These nanotube deposits were functionalized via electrocoating of polypyrrole-nitrilotriacetic acid (poly-NTA) followed by the formation of a Cu (II) complex with the NTA functions. The bioreceptor unit, cholera toxin B subunit, modified with biotin, was then immobilized via coordination of the biotin groups with the NTA-Cu(II) complex. The resulting impedimetric cholera Ab sensor shows a very satisfying detection limit of 10⁻¹³ g mL⁻¹ and an exceptional linear range detection of 8 orders of magnitude. Following a similar elaboration strategy, an electrochemical highly sensitive aptasensor was developed based on electropolymerized poly-NTA film and a new aptamer functionalized by a pentahistidine peptide for the quantification of bisphenol A. A surface coverage of antibisphenol A aptamer of 1.84 10⁻¹⁰ molcm⁻² was estimated from the electrochemical signal of the [RuIII (NH₃ )₆ ]³⁺ complex bound by electrostatic interactions onto the aptamer-modified electrode. The binding of bisphenol A onto the polymer film was successfully characterized by electrochemical methods as square wave voltammetry and electrochemical impedance spectroscopy measurements. The designed label-free impedimetric aptasensor displayed a wide linear range from 10⁻¹¹ to 10⁻⁶ mol L⁻¹ with a sensitivity of 372 Ω per unit of log of concentration and an excellent specificity toward interfering agents such as 4,4′ -dihydroxybiphenyl and bisphenol P.⁴

Finally, a simple, versatile, and rapid method for the fabrication of optically-transparent large-area carbon nanotube films via flotation assembly, will be described. After solvent-induced assembly, floating films were transferred to a flat supporting substrate to form conductive and transparent nanotube film electrodes. A proof-of-concept nanostructured bioelectrode demonstrating high sensitivity for glucose was developed with an electropolymerized poly(pyrene-adamantane) layer for host–guest immobilization of active b-cyclodextrin tagged GOx enzymes.⁵

References:

1. O. Hosu, K. Elouarzaki, K. Gorgy, C. Cristea, R. Sandulescu, R. S. Marks, S. Cosnier. Electrochem. Commun. 80 (2017) 5-8.
2. Q. Palomar, C. Gondran, M. Holzinger, R. Marks, S. Cosnier. Biosens. Bioelectron.,97 (2017) 177-183.
3. Q. Palomar, C. Gondran, R. Marks, S. Cosnier, M. Holzinger. Electrochim. Acta., in press

4. Kazane, K. Gorgy, C. Gondran, N. Spinelli, A. Zazoua, E. Defrancq, S. Cosnier, Anal. Chem., 88 (2016) 7268-7273.
5. A. J. Gross, J. L. Hammond, M. Holzinger, S. Cosnier. Nanomaterials, 17 (2017) 342-353; doi:10.3390/nano7100342