Toward Rational Design of Electrogenerated Molecularly Imprinted Polymers (eMIPs): Maximizing Monomer/Template Affinity

Abstract

Molecularly imprinted polymers (MIPs) may be used to confer specific recognition properties to a variety of practical sensors and sorbents. However, the synthetic parameters (monomer species, template/monomer ratio, etc.) used to generate MIPs significantly impact their sensitivity and selectivity, generally requiring arduous empirical optimization to obtain materials with maximal target affinity. We present a MIP synthesis strategy that prioritizes the optimization of the pre-polymerization complex as a predictive model for the final polymer properties and demonstrate how greater target affinity may be obtained without iterative analysis of the polymer film. 2,4-Dichlorophenoxyacetic acid (2,4-D), a prevalent herbicide, was chosen for detection using electrogenerated molecularly imprinted polymers (eMIPs). eMIPs were rationally designed using molecular simulations to down-select an ideal functional monomer with a maximal affinity for 2,4-D. Following monomer selection, proton-based nuclear magnetic resonance ( 1 H NMR) titrations were used to verify the simulation results and optimize the monomer/2,4-D ratio by tracking the chemical shift associated with monomer/target binding. Following optimization, eMIPs were synthesized by the anodic electropolymerization of the selected monomer, o-phenylenediamine, onto gold substrates in the presence of 2,4-D, which was subsequently stripped away via solvent washing to reveal 2,4-D-specific binding sites. Surface sites were blocked upon 2,4-D association with the eMIP when placed in contaminated water, which was tracked electrochemically. The ability of molecular simulations and 1 H NMR titrations to predict optimal monomer/2,4-D ratios was evaluated by fitting the experimental data to a Langmuir−Freundlich isotherm, revealing a significant increase in target affinity (K a ) and binding site homogeneity (m) related to the chemical shifts exhibited by the prepolymerization complex for o-phenylenediamine (o-PD). The two techniques, when evaluated on o-PD, predicted ideal monomer/ template ratios with remarkable agreement. Thus, the synthetic strategy outlined herein represents a streamlined approach for the rapid prototyping and design of eMIP-based sensing elements essential for the realization of next-generation polymeric sensors and sorbents.

Determination of aflatoxin B1 by biomass derived porous carbon modified electrode with molecularly imprinted polymer

“…Considering the very low solubility of aflatoxin B 1 in aqueous solution, the monomer to template molar ratio used here is 1 mM phenol to 250 nM aflatoxin B 1 , which is 4000 : 1. The monomer/template molar ratio of other molecules sensing MIPs is found to be 4 : 1 [15], 1 : 1 [16] and 10 : 1 [17], which is much smaller than this study ratio of 4000 : 1. Therefore, the template cavities in the phenol MIP matrix is much less, which could result a small signal response and restrict the MIP sensor sensing range.…”

Design of molecularly imprinted polymers (MIP) using computational methods: A review of strategies and approaches

“…These interactions, occurring between the template and the polymer matrix, are the driving forces behind the sensitivity and selectivity of MIP. 22,23 Another key factor in the development of a selective and highly sensitive MIP is to determine the optimal ratio of the template to monomer. The composition of the pre-polymerization mixture significantly influences the properties of MIP.…”

PFAS Electroanalysis in Low-Oxygen River Water Using Electrogenerated Dioxygen

“…Previously, our group and others have used a molecularly imprinted polymer (MIP) approach to PFAS detection. ,− A polymer is electrogenerated on the conductive electrode in the presence of a PFAS molecule of interest (the template molecule). When the template molecule is extracted, binding sites remain that are specific to the molecule of interest due to intermolecular interactions . Therefore, PFAS molecules will selectively bind to the MIP and block access of a mediator to the electrode surface, providing a turn-off sensing modality.…”

“…When the template molecule is extracted, binding sites remain that are specific to the molecule of interest due to intermolecular interactions. 26 Therefore, PFAS molecules will selectively bind to the MIP and block access of a mediator to the electrode surface, providing a turn-off sensing modality.…”