Electrochemically Stimulated Insulin Release from a Modified Graphene–functionalized Carbon Fiber Electrode

  • A graphene-functionalized carbon fiber electrode was modified with adsorbed polyethylenimine to introduce amino functionalities and then with trigonelline and 4-carboxyphenylboronic acid covalently bound to the amino groups. The trigonelline species containing quarterized pyridine groups produced positive charge on the electrode surface regardless of the pH value, while the phenylboronic acid species were neutral below pH 8 and negatively charged above pH 9 (note that their pKa=8.4). The total charge on the monolayer-modified electrode was positive at the neutral pH and negative at pH > 9. Note that 4-carboxyphenylboronic acid was attached to the electrode surface in molar excess to trigonelline, thus allowing the negative charge to dominate on the electrode surface at basic pH. Negatively charged fluorescent dye-labeled insulin (insulin-FITC) was loaded on the modified electrode surface at pH 7.0 due to its electrostatic attraction to the positively charged interface. The local pH in close vicinity to the electrode surface was increased to ca. 9–10 due to consumption of H+ ions upon electrochemical reduction of oxygen proceeding at the potential of −1.0 V (vs. Ag/AgCl) applied on the modified electrode. The process resulted in recharging of the electrode surface to the negative value due to the formation of the negative charge on the phenylboronic acid groups, thus resulting in the electrostatic repulsion of insulin-FITC and stimulating its release from the electrode surface. The insulin release was characterized by fluorescence spectroscopy (using the FITC-labeled insulin), by electrochemical measurements on an iridium oxide, IrOx, electrode and by mass spectrometry. The graphene-functionalized carbon fiber electrode demonstrated significant advantages in the signal-stimulated insulin release comparing with the carbon fiber electrode without the graphene species.

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Metadaten
Author:Elham Honarvarfard, Maria Gamella, Devika Channaveerappa, Costel C. Darie, Arshak PoghossianORCiD, Michael Josef SchöningORCiD, Evgeny Katz
DOI:https://doi.org/10.1002/elan.201700095
ISSN:1521-4109
Parent Title (English):Electroanalysis
Publisher:Wiley-VCH
Place of publication:Weinheim
Document Type:Article
Language:English
Year of Completion:2017
Volume:29
Issue:6
First Page:1543
Last Page:1553
Link:https://doi.org/10.1002/elan.201700095
Zugriffsart:campus
Institutes:FH Aachen / Fachbereich Medizintechnik und Technomathematik
FH Aachen / INB - Institut für Nano- und Biotechnologien
collections:Verlag / Wiley-VCH