Modulation of redox reactivity of resazurin through host-guest complexation with Cucurbit[ n]uril (n = 7, 8)

Jia Liu; Su-Hang He; Hugues Lambert; Tung-Chun Lee

doi:10.3389/fchem.2023.1295715

Modulation of redox reactivity of resazurin through host-guest complexation with Cucurbit[ n]uril (n = 7, 8)

Front Chem. 2023 Dec 14:11:1295715. doi: 10.3389/fchem.2023.1295715. eCollection 2023.

Authors

Jia Liu^{1

2

3}, Su-Hang He⁴, Hugues Lambert^{1

2}, Tung-Chun Lee^{1

2}

Affiliations

¹ Department of Chemistry, University College London (UCL), London, United Kingdom.
² Institute for Materials Discovery, University College London (UCL), London, United Kingdom.
³ Xiamen Institute of Rare-earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, China.
⁴ Center of Single-Molecule Sciences, College of Electronic Information and Optical Engineering, Nankai University, Tianjin, China.

Abstract

Resazurin (Alamar Blue, RZ) is a widely utilized fluorescent probe for biological sensing, whose fluorescent intensity can be modulated by changing its redox states; thereby, electrochemical reactivity of RZ is of significance when designing a sensing assay. Herein, we report novel two-way electrochemical reactivity modulation of RZ using host-guest complexation with rigid molecular containers cucurbit[n]uril (CBn, n = 7, 8). The complexation between CBn and RZ is confirmed by ¹H NMR measurements and supported by computational simulation, and the binding constants are determined via UV-vis titration. Notably, the voltametric data highlights that the redox reactivity of RZ can be activated or deactivated upon encapsulation by CB8 or CB7, respectively. This two-way reactivity modulation is hypothesized to be mediated by the difference in cavity volume that favors or hinders the approach of water molecules to the encapsulated reaction center during the reduction process. Despite the similar cavity size to CB, molecular containers such as cyclodextrins (CDs) exhibit considerably weaker modulation effects. Our approach can potentially be applied to other redox processes that involve proton transfer, and open new possibilities in supramolecular electrochemistry.

Keywords: cucurbituril; host-guest complexes; reactivity modulation; resazurin; supramolecular electrochemistry.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This project is funded by EPSRC (Grant EP/P020194/1) and Leverhulme Trust Grant (RPG-2016-393) of T-CL. HL and T-CL are grateful to the Studentship funded by the A^*STAR-UCL Research Attachment Programme through the EPSRC M3S CDT (EP/L015862/1).