Sepia Melanin Bio-Inks on Paper-Based Laser-Induced Graphenic Electrodes for the Low-Cost, Sustainable Electrochemical Detection of Dopamine

Electrochemical methods allow for rapid, high-sensitivity detection of neurotransmitters. Unfortunately, the redox activity of dopamine, and many other neurotransmitters, can trigger polymerization reactions that are associated with the fouling of most electrode materials. Fouling degrades sensor performance by passivating its surface, which decreases signal quality and strength with sensor use. To mitigate this, novel antifouling coatings are being investigated [1].<br/><br/>With the aim to find antifouling coating materials for the <i>in vitr</i>o detection of dopamine, we considered Sepia melanin, an ubiquitous, bio-sourced eumelanin pigment that can be extracted from the ink of the common cuttlefish (<i>Sepia Officinalis</i>). Sepia melanin, made up of 200 nm-sized granules, has been studied for its biocompatibility [2] and sustainable electronic applications [3]. It results from the polymerization of (5,6)-dihydroxyindole and (5,6)- dihydroxyindole-2-carboxylic acid building blocks, which makes its molecular structure analogous to that of polydopamine. We hypothesize that this chemical similarity could limit electrode fouling by facilitating the reduction of oxidized dopamine and minimizing its polymerization at the surface of the electrode.<br/><br/>Laser-induced graphenization (LIG) of filter paper is a straightforward technique that can yield high-performance paper-based electrodes for low-cost bioanalytical quantitation [4]. While our ongoing research focuses on the antifouling properties of Sepia melanin coatings for <i>in vitro</i> sensing of neurotransmitters with live cell cultures, preliminary voltammetric data indicate that LIG paper electrodes, modified using the Sepia melanin, have an increased faradaic response to multiple analytes in solution (ruthenium hexaamine, dopamine) when compared to the unmodified LIG paper electrodes. We hypothesize that the Sepia melanin nano-granules enable redox cycling at the graphene-Sepia melanin interface, thanks to high electron transfer speeds between the analyte and the Sepia melanin.<br/><br/>References:<br/>[1] E. Peltola, S. Sainio, K.B. Holt, T. Palomäki, J. Koskinen, T. Laurila, Electrochemical Fouling of Dopamine and Recovery of Carbon Electrodes, Anal. Chem. 90 (2018) 1408–1416. https://doi.org/10.1021/acs.analchem.7b04793.<br/>[2] C.J. Bettinger, J.P. Bruggeman, A. Misra, J.T. Borenstein, R. Langer, Biocompatibility of biodegradable semiconducting melanin films for nerve tissue engineering, Biomaterials 30 (2009) 3050–3057. https://doi.org/10.1016/j.biomaterials.2009.02.018.<br/>[3] High conductivity Sepia melanin ink films for environmentally benign printed electronics | PNAS, (n.d.). https://www.pnas.org/doi/full/10.1073/pnas.2200058119 (accessed June 21, 2024).<br/>[4] L. Bezinge, J.M. Lesinski, A. Suea-Ngam, D.A. Richards, A.J. deMello, C.-J. Shih, Paper-Based Laser-Pyrolyzed Electrofluidics: An Electrochemical Platform for Capillary-Driven Diagnostic Bioassays, Adv. Mater. 35 (2023) 2302893. https://doi.org/10.1002/adma.202302893.<br/>[5] W. Harreither, R. Trouillon, P. Poulin, W. Neri, A.G. Ewing, G. Safina, Carbon Nanotube Fiber Microelectrodes Show a Higher Resistance to Dopamine Fouling, Anal. Chem. 85 (2013) 7447–7453. https://doi.org/10.1021/ac401399s.