Molecularly Imprinted Polymer Micro- and Nano-Particles. A review

Abstract

In recent years, molecularly imprinted polymers (MIPs) have become an excellent solution to the selective and sensitive determination of target molecules in complex matrices where other similar and relative structural compounds could coexist. Although MIPs show the inherent properties of the polymers, including stability, robustness, and easy/cheap synthesis, some of their characteristics can be enhanced, or new functionalities can be obtained when nanoparticles are incorporated in their polymeric structure. The great variety of nanoparticles available significantly increase the possibility of finding the adequate design of nanostructured MIP for each analytical problem. Moreover, different structures (i.e., monolithic solids or MIPs micro/nanoparticles) can be produced depending on the used synthesis approach. This review aims to summarize and describe the most recent and innovative strategies since 2015, based on the combination of MIPs with nanoparticles. The role of the nanoparticles in the polymerization, as well as in the imprinting and adsorption efficiency, is also discussed through the review.

Keywords: hybrid sorbent; microextraction; molecularly imprinted polymer; monolith; nanomaterial; sensor.

Scheme 1

Main elements of the molecularly imprinted polymer stirring unit synthesized by interconnected carbon nanotube monolithic sorbent in a polypropylene cap using secbumenton as a template. Reproduced with permission from [60].

Scheme 2

(a) AFM images of the grafted fluorescent tetracycline-imprinted polymer (a1)/non-imprinted polymer (a2) nanoparticles. (The inset is a height profile of cross-section (white line)). (b) Profiles of a water drop on the films of the ungrafted and grafted fluorescent tetracycline-imprinted polymer/non-imprinted polymer nanoparticles. Photographs of nanoparticles dispersed in pure water (1 mg·mL⁻¹) (c) without irradiation and (d) under 365-nm light irradiation. The samples from left to right in each figure are the ungrafted tetracycline-imprinted polymer (1)/non-imprinted polymer nanoparticles (2) and grafted tetracycline-imprinted polymer (3)/non-imprinted polymer nanoparticles (4). Reproduced with permission from [69].

Scheme 3

Steps of attaching the nano-molecularly imprinted polymers (nanoMIPs) onto the gold working electrode surface (DPR C220AT, DropSens). (a) self-assembly monolayer formation; (b) carboxylic group activation by 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide/Hydroxysuccinimide; (c) nanoMIPs covalent attachment via amine coupling. (d) 3D scheme of the final nanoMIP sensor for cocaine determination. The scheme not in scale. Reproduced with permission from [79].

Scheme 4

Synthetic scheme for multi-walled carbon nanotube-MIP and application as an absorbent for SPE of Carbofuran. Reproduced with permission from [98].

Scheme 5

Schematic diagram of the construction of the (A) molecularly imprinted gold nanoparticles and (B) their use on the glassy carbon electrodes coating. Reproduced with permission from [106].

Scheme 6

Synthesis route of surface-imprinted core-shell magnetic beads and their application for extraction of bisphenol A. (a) Fe₃O₄ magnetite particles synthesis by a co-precipitation method followed by silica coating and functionalization with chloromethyl-phenyl groups; (b) β- cyclodextrin modified with an epoxy bond; (c) 4-vinylpyridine and β- cyclodextrin used as binary functional monomers for the synthesis of the MIP for bisphenol A. Reprinted with permission from [119].