Towards Clean and Safe Water: A Review on the Emerging Role of Imprinted Polymer-Based Electrochemical Sensors

Abstract

This review critically summarizes the knowledge of imprinted polymer-based electrochemical sensors for the detection of pesticides, metal ions and waterborne pathogenic bacteria, focusing on the last five years. MIP-based electrochemical sensors exhibit low limits of detection (LOD), high selectivity, high sensitivity and low cost. We put the emphasis on the design of imprinted polymers and their composites and coatings by radical polymerization, oxidative polymerization of conjugated monomers or sol-gel chemistry. Whilst most imprinted polymers are used in conjunction with differential pulse or square wave voltammetry for sensing organics and metal ions, electrochemical impedance spectroscopy (EIS) appears as the chief technique for detecting bacteria or their corresponding proteins. Interestingly, bacteria could also be probed via their quorum sensing signaling molecules or flagella proteins. If much has been developed in the past decade with glassy carbon or gold electrodes, it is clear that carbon paste electrodes of imprinted polymers are more and more investigated due to their versatility. Shortlisted case studies were critically reviewed and discussed; clearly, a plethora of tricky strategies of designing selective electrochemical sensors are offered to "Imprinters". We anticipate that this review will be of interest to experts and newcomers in the field who are paying time and effort combining electrochemical sensors with MIP technology.

Keywords: bacteria; electrochemical sensors; imprinted polymers; metal ions; pesticides.

Figure 1

Principle of making MIPs (a), and illustration of the imprinting technique by digital photographs of a slice of cake before after removal of candied fruits (b). NIP: non-imprinted polymer.

Figure 2

Screenshot of Dickey’s paper: Chemical structure of methyl orange and results of its relative adsorption (Adapted from [33]; paper in public domain).

Figure 3

Simplified mechanism of imprinted vinylic polymer synthesis by radical polymerization. Example is given for methacrylic acid functional monomer and ethylene glycol dimethacrylate (EGDMA) crosslinker. I–J is the initiator and T the template.

Figure 4

Simple pathways for the synthesis of polypyrrole (a) and polyaniline (b). Figure 4b is reproduced from [48] with the permission of Elsevier.

Figure 5

Sol-gel methods for nanoparticle synthesis.

Figure 6

Three main methods to prepare MIP-based electrodes for electrochemical sensors, by direct surface initiated polymerization (SIP) on the electrode chemical (top), by preparation of MIP nanocomposite and coating it on the electrode surface (middle), and by preparing carbon paste electrode (CPE) using a mixture of MIP and carbon powders in mineral oil. MIP designates pure imprinted polymer or its corresponding composite containing nanostructures (clay, carbon, nanometal…). For the sake of simplicity, MIP means either a molecular, ion or pathogen-imprinted polymer.

Figure 7

Methods of bacteria imprinting: surface imprinting of bacteria. Reproduced with permission of Elsevier from [63].

Figure 8

Schematic representation of the most common electrochemical techniques used in the detection of pollutants in water sources. (a) Details of the application of pulses in the square wave voltammetry technique and the corresponding voltammograms for reversible (b) and irreversible systems (c).

Figure 9

Overall synthesis procedure of flower-likeGDM and its electrocatalytic and photocatalytic applications. Reproduced with permission of ACS from [94].

Figure 10

Schematic representation of the 3D-CNTs@-MIP preparation and further fabrication of the MIP sensor. Reproduced with permission of Elsevier from [105].

Figure 11

Different steps of fabrication of mancozeb-imprinted star polymer. Reproduced with permission of RSC from [107].

Figure 12

Illustration of the fabrication process of the NF/AChE/OH-POF/CPE biosensor. Reproduced with permission of Elsevier from [109].

Figure 13

Schematic diagram for the preparation of the copper(II)-ion-imprinted polymer. The acrylamide derivative bearing thiozyl group serves as monomer and ligand in the same time. Adapted with permission of Taylor and Francis from [122].

Figure 14

DPV output of 3.0 × 10⁻⁵ mol L⁻¹ Eu³⁺ on bare and differently coated SPE electrodes at pH 4.7. Adapted with permission of Elsevier from [124].

Figure 15

Preparation of Cu(II) imprinted poly(pyrrole-EDTA like) polymer for the selective detection of Cd²⁺. Step (i): preparation of the metallo-polymer by electropolymerization of pyrrole-EDTA like/Cd(II) metal ion complex; step (ii): template ion removal for generating artificial receptor sites within the poly(pyrrole-EDTA like) polymer matrix. Adapted with permission of John Wiley & Sons from [126].

Figure 16

Top: Schmatic illustration of the stepwise synthesis of mercury imprinted PPy wrapped around vertically aligned ZnO nanorods attached to diazonium-modified gold electrodes. Bottom: (80 × 80 μm²) 3D image of Au-diazo-ZnO NRs. Reproduced from [14].

Figure 17

Synthesis of copper imprinted TPDT-functionalized silica. Reproduced with permission of Elsevier from [128].

Figure 18

Synthesis of a cadmium ion imprinted sol-gel (a), and the use of its corresponding carbon paste for the highly sensitive detection of Cd(II). (b) Square wave voltammograms of Cu(II) detection and its further calibration curve. Reproduced with permission of Elsevier from [129].

Figure 19

Synthesis of IISG from quinolone-functionalized silane, TMOS and uranyl. Adapted with permission of Elsevier from [130].

Figure 20

Two step preparation (a) and electrochemical Eu(III) sensing performance (b) of screen printed electrode coated with polycatechol-IISG bilayer. Adapted with permission of Elsevier from [131].

Figure 21

SEM images of E.coli imprinting before (a) and after removal (b) of templates. Reproduced with permission of Elsevier from [137].

Figure 22

AFM image of bacteria imprinted polymer, before (a) and after (b) washing. Reproduced with permission of Elsevier from [63].

Figure 23

Impedance spectra obtained with bioimprinted sensor and the biosensor after incubation with 1.0 × 10⁸ cfu mL⁻¹ SRB, S. aureus, M. luteus, V. anguillarum, and V. alginolyticus in PBS containing 5 mM Fe(CN)₆^4−/3− as the probe (a).The comparison of Rct changes of the impedimetric biosensor based on SRB-mediated bioimprinted film to SRB, S. aureus, M. luteus, V. anguillarum, and V. alginolyticus (b). DRct is the change of charge transfer resistance of impedimetric sensor before and after incubation with different bacteria. Reproduced with permission of Elsevier from [63].

Figure 23

Impedance spectra obtained with bioimprinted sensor and the biosensor after incubation with 1.0 × 10⁸ cfu mL⁻¹ SRB, S. aureus, M. luteus, V. anguillarum, and V. alginolyticus in PBS containing 5 mM Fe(CN)₆^4−/3− as the probe (a).The comparison of Rct changes of the impedimetric biosensor based on SRB-mediated bioimprinted film to SRB, S. aureus, M. luteus, V. anguillarum, and V. alginolyticus (b). DRct is the change of charge transfer resistance of impedimetric sensor before and after incubation with different bacteria. Reproduced with permission of Elsevier from [63].

Figure 24

SWV voltammogram: result for MIP with different concentration of flagella ((a), left) and result for NIP ((b), right). Reproduced with permission of Elsevier from [139].

Figure 25

Mechanisms of quorum sensing from isolated bacteria to the formation of biofilms. Early detection of quorum sensing signaling molecules will require action to prevent biofilm formation. https://www.wikiwand.com/en/Quorum_sensing; last accessed 8 June 2021.