Probing charge transfer through antifouling polymer brushes by electrochemical methods: The impact of supporting self-assembled monolayer chain length

• Published in: Analytica chimica acta Vol. 1276; p. 341640
• Main Authors: Anthi, Judita, Vaněčková, Eva, Spasovová, Monika, Houska, Milan, Vrabcová, Markéta, Vogelová, Eva, Holubová, Barbora, Vaisocherová-Lísalová, Hana, Kolivoška, Viliam
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 02.10.2023
• Subjects: 3D printed electrochemical cell; Antifouling; Cyclic voltammetry; Electrochemical impedance spectroscopy; Polymer brushes; Self-assembled monolayers; Cyclic voltammetry; Polymer brushes; 3D printed electrochemical cell; Self-assembled monolayers; Antifouling; Electrochemical impedance spectroscopy
• ISSN: 0003-2670; 1873-4324; 1873-4324
• DOI: 10.1016/j.aca.2023.341640

Ultrathin surface-tethered polymer brushes represent attractive platforms for a wide range of sensing applications in strategically vital areas such as medicine, forensics, or security. The recent trends in such developments towards “real world conditions” highlighted the role of zwitterionic poly(carboxybetaine) (pCB) brushes which provide excellent antifouling properties combined with bio-functionalization capacity. Highly dense pCB brushes are usually prepared by the “grafting from” polymerization triggered by initiators on self-assembled monolayers (SAMs). Here, multi-methodological experimental studies are pursued to elucidate the impact of the alkanethiolate SAM chain length (C6, C8 and C11) on structural and functional properties of antifouling poly(carboxybetaine methacrylamide) (pCBMAA) brush. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a custom-made 3D printed cell employing [Ru(NH3)6]3+/2+ redox probe were used to investigate penetrability of SAM/pCBMAA bilayers for small molecules and interfacial charge transfer characteristics. The bio-fouling resistance of pCBMAA brushes was characterized by surface plasmon resonance; ellipsometry and FT-IRRAS spectroscopy were used to determine swelling and relative density of the brushes synthesized from initiator-bearing SAMs with varied carbon chain length. The SAM length was found to have a substantial impact on all studied characteristics; the highest value of charge transfer resistance (Rct) was observed for denser pCBMAA on longer-chain (C11) SAM when compared to shorter (C8/C6) SAMs. The observed high value of Rct for C11 implies a limitation for the analytical performance of electrochemical sensing methods. At the same time, the pCBMAA brushes on C11 SAM exhibited the best bio-fouling resistance among inspected systems. This demonstrates that proper selection of supporting structures for brushes is critical in the design of these assemblies for biosensing applications. [Display omitted] •Poly(carboxybetaine methacrylamide) antifouling zwitterionic brush was synthesized on alkanethiolate self-assembled monolayers of varying chain length.•Characterization and antifouling capability evaluation of these assemblies was performed by FT-IRRAS, spectroscopic ellipsometry and SPR.•Mass transport and charge transfer properties of these assemblies were probed by EIS and CV in a custom-made 3D printed electrochemical cell, employing [Ru(NH3)6]3+/2+ redox probe.•Results show the importance of finding a balance between the suppression of (bio) fouling and requirements for dynamic range of electrochemical sensors employing such assemblies.•Multi-methodological approach and results of this work may be considered as guidelines for selecting the base layer bearing initiator in synthesis of antifouling zwitterionic brushes for label-free biosensing applications approaching real-world conditions.