Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Abstract

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.

Keywords: biosensors; chiral recognition; cyclodextrins; electrochemical sensors; inclusion complex.

Figure 1

Structures of α-, β-, and γ-CDs (cyclodextrins) and a schematic of the conelike structures.

Figure 2

Schematic of the formation of an inclusion complex between β-CD and dopamine and the corresponding ¹H NMR data, with an excess of the β-CD.

Figure 3

(a) Schematic of electron transfer for an included electroactive molecule and its exchange with a nonelectroactive target and the corresponding reduction in measured current; (b) the increasing current recorded following an accumulation period.

Figure 4

Schematic of (a) the solution-based fabrication of a CD/rGO sensor; (b) noncovalent π–π interactions with rGO coupled with a functionalized CD and (c) covalent attachment.

Figure 5

CD-linked multiwalled carbon nanotubes (MWCNTs-βCD) deposited onto screen printed electrodes (SPCE) and employed in the detection of Bisphenol A. Reproduced with permission from Ali et al. [92], Sens. Actuators B Chem.; published by Elsevier, 2020.

Figure 6

Cyclic voltammograms recorded during the electropolymerization of β-CD in an acidified phosphate buffer, I and II refer to oxidation waves and III to a reduction wave.

Figure 7

Synthetic route of the MXene/CNHs/β-CD-MOFs and the sensing strategy for carbendazim. Bulk Ti₃AlC₂ is etched and exfoliated, then combined with carbon nanohorns (CNHs), decorated with β-CD-MOF and drop casted onto a glassy carbon electrode (GCE). Reproduced with permission from Tu et al. [154], J. Hazard. Mater.; published by Elsevier, 2020.

Figure 8

Supramolecular assembly of β-CD tagged glucose oxidase (GOX) and an adamantine-modified electrode: (a) representation of mono-6-amino-β -CD, (b) electrogeneration of poly(adamantane-pyrrole), and (c) polymerized adamantane/β-CD complex. Reproduced with permission from Cosnier and coworkers [119], Biosens. Bioelectron.; published by Elsevier, 2009.

Figure 9

Illustration of the formation of magnetically anchored enzyme using CD-coated superparamagnetic Fe₃O₄ nanoparticles. Reproduced with permission from Diez et al. [161], J. Colloid Interface Sci.; published by Elsevier, 2012.

Figure 10

Schematic representation of the liquid-phase exfoliation of (a) black phosphorus (BP) to give (b) nanosheets of black phosphorus (BPNSs), shown in I, and fabrication of a Nafion (NF) BPNSs/β-CD modified electrode and its application in the electrochemical recognition of tryptophan enantiomers shown in II. Reproduced with permission from Zou and Yu [184], Mater. Sci. Eng. C; published by Elsevier, 2020.