Robust and selective nano cavities for protein separation: An interpenetrating polymer network modified hierarchically protein imprinted hydrogel

Fundamentals, Synthetic Strategies and Applications of Non-Covalently Imprinted Polymers

Molecular imprinting has emerged as an important and practical technology to create economical and stable synthetic mimics of antibodies and enzymes. It has already found a variety of important applications, such as affinity separation, chemical/biological sensing, disease diagnostics, proteomics, bioimaging, controlled drug release, and catalysis. In the past decade, significant breakthroughs have been made in non-covalently imprinted polymers, from their synthesis through to their applications. In terms of synthesis, quite a few versatile and facile imprinting approaches for preparing MIPs have been invented, which have effectively solved some key issues in molecular imprinting. Additionally, important applications in several areas, such as sensors, proteomics and bioimaging, have been well demonstrated. In this review, we critically and comprehensively survey key recent advances made in the preparation of non-covalently imprinted polymers and their important applications. We focus on the state-of-art of this technology from three different perspectives: fundamentals, synthetic strategies, and applications. We first provide a fundamental basis for molecular imprinting technologies that have been developed, which is extremely helpful for establishing a sound understanding of the challenges in molecular imprinting. Then, we discuss in particular the major breakthroughs within the last ten years (2014-2024), with emphasis on new imprinting approaches, what strengths the breakthroughs can provide, and which new applications the properties of the prepared non-covalently imprinted polymers are fit for.

Peptide-crosslinked molecularly imprinted polymers for efficient separation of immunoglobulin G from human serum

Low-cost and highly effective methods are highly desirable to replace the costly ethanol fractionation and affinity chromatography in IgG isolation from human plasma. Molecularly imprinted polymers (MIPs) of IgG are potential candidates, however, they still suffer from severe problems such as difficult template removal and low imprinting efficiency. Here, a recently developed strategy was adopted to overcome these problems. The MIPs were synthesized using poly(L-glutamic acid) (PLGA) peptide crosslinkers instead of commonly used crosslinkers, such as N,N-methylenebisacrylamide (BIS). Because of the pH-induced helix-coil transition and the precise folding of the peptide segments in the polymers, the imprint cavities can be enlarged by adjusting the pH from 5.0 to 7.0, but their original size and shape are restored when the pH is adjusted back. Therefore, the IgG template can be eluted completely under mild conditions, and significantly improved imprinting efficiency can be achieved. Compared with BIS-crosslinked MIP, 8.6 times more binding sites can be created by molecular imprinting PLGA-crosslinked MIP. The factors influencing the performance of the MIP were studied systematically. An optimized MIP with a high adsorption capacity (612.5 mg g^-1), high IF (4.92), and high selectivity was obtained. The adsorption capacity and selectivity of the MIP are much higher than the previously reported IgG MIPs. Because of its high adsorption capacity and selectivity, it can separate IgG from human serum effectively, affording high purity products.

Rabbit IgG-imprinted nanoMIPs by solid phase synthesis: the effect of cross-linkers on their affinity and selectivity

Solid phase synthesis (SPS) of molecularly imprinted nanopolymers (nanoMIPs) represents an innovative method to prepare nanomaterials with tailor-made molecular recognition properties towards peptides and proteins. The synthesis of nanoMIPs by SPS usually involves a pre-polymerization formulation, where the cross-linker is invariably N,N'-methylen-bis-acrylamide (BIS). To date, the effect of cross-linkers on the binding properties of nanoMIPs prepared using cross-linkers other than BIS has never been reported. In this work, in order to investigate the effect of different cross-linkers in protein-imprinted nanoMIPs prepared by SPS, alongside BIS we considered other similar cross-linkers: N,N'-ethylene dimethacrylamide (EDAM), N,O-bis-methacryloylethanolamine (NOBE), ethylene glycol dimethacrilate (EDMA) and glycerol dimethacrylate (GDMA), replacing BIS with them in pre-polymerization mixtures. The synthetized nanoMIPs were homogeneous, with a polydispersity index of 0.24-0.30 and a mean diameter of 129-169 nm in water. The binding properties of the nanoMIPs were measured via equilibrium partition experiments with the template, rabbit IgG (RIgG), and the selectivity was evaluated with respect to bovine IgG (BIgG), bovine serum albumin (BSA) and hen egg lysozyme (LZM). The experimental results show that all the cross-linkers, with the exception of EDMA, endowed nanoMIPs with high binding affinities for the template (BIS: 16.0 × 10⁶ mol^-1 L, EDAM: 8.8 × 10⁶ mol^-1 L, NOBE: 15.8 × 10⁶ mol^-1 L, and GDMA: 12.8 × 10⁶ mol^-1 L), medium to high imprinting factors (BIS: 12.3, EDAM: 5.5, NOBE: 7.2, and GDMA: 11.6) and good selectivity towards other proteins but markedly dependent on the structure of the cross-linker, confirming the importance of the latter in the SPS of imprinted nanopolymers.

A visible-light-responsive molecularly imprinted polyurethane for specific detection of dibenzothiophene in gasoline

Dibenzothiophene and its derivatives in gasoline and diesel would release sulfur oxides during combustion, and this is harmful to human health and the environment. This paper reports a method based on a visible-light-responsive molecularly imprinted polyurethane (VMIPU) to monitor trace dibenzothiophene in gasoline. The VMIPU was prepared by a polyaddition reaction using N,N-bis-(2-hydroxyethyl)-4-phenylazoaniline as the functional monomer, dibenzothiophene as the template molecule, diphenylmethane diisocyanate as the crosslinker and castor oil as the chain extender. The VMIPU showed good visible-light-response and specific adsorption for dibenzothiophene. The trans → cis photoisomerization rate constant of azobenzene chromophores in the VMIPU shows a linear relationship with the dibenzothiophene concentration in the range of 0-20 μmol L^-1. This was used to estimate trace dibenzothiophene in spiked gasoline with recoveries of 95.7-101.0% and relative standard deviations of 7.0-12.7%.

Molecularly imprinted polymer grafted on paper and flat sheet for selective sensing and diagnosis: a review

Molecularly imprinted polymers are efficient and selective adsorbents which act as artificial receptors for desired compounds with the ability to recognize the size, shape, and functional groups of the compounds simultaneously. A molecularly imprinted polymer is prepared by the polymerization of functional monomers around a template (analyte) molecule. Afterward, the removal of the template from the polymer matrix leaves a selective cavity behind. The fabrication and development of molecularly imprinted polymers grew rapidly, due to their low cost, simple preparation, selectivity, sensitivity, and stable physicochemical properties. Traditionally, molecularly imprinted polymers can be synthesized using two main methods, namely bulk and surface imprinting. For more efficient use of the latter method, researchers have developed molecularly imprinted polymers grafted on the solid-phase matrix (substrate). This grafting technique would be particularly useful for surface imprinting of macromolecules, such as proteins. Cellulose fibers of papers with unique properties such as being abundant, retaining a porous structure, having good adsorption properties, and possessing hydroxyl groups naturally have gained much attention as substrate. The goal of this review is to introduce molecularly imprinted polymer-grafted or molecularly imprinted polymer-coated paper, as an interesting, simple, and efficient method in the detection and separation of small and large molecules. Therefore, in the present paper, several recent preparation techniques and applications of molecularly imprinted polymer-grafted paper are reviewed and discussed in detail. Green, cost-effective, selective, and sensitive paper-based sensor prepared via grafting molecularly imprinted polymer on paper surface with the potential use for online detection trace of analytes in the point-of-care testing.

Amr AEG, Almehizia AA, Kamel AH. All-Solid-State Potentiometric Ion-Sensors Based on Tailored Imprinted Polymers for Pholcodine Determination

In recent times, the application of the use of ion-selective electrodes has expanded in the field of pharmaceutical analyses due to their distinction from other sensors in their high selectivity and low cost of measurement, in addition to their high measurement sensitivity. Cost-effective, reliable, and robust all-solid-state potentiometric selective electrodes were designed, characterized, and successfully used for pholcodine determination. The design of the sensor device was based on the use of a screen-printed electrode modified with multiwalled carbon nanotubes (MWCNTs) as a solid-contact transducer. Tailored pholcodine (PHO) molecularly imprinted polymers (MIPs) were prepared, characterized, and used as sensory receptors in the presented potentiometric sensing devices. The sensors exhibited a sensitivity of 31.6 ± 0.5 mV/decade (n = 5, R² = 0.9980) over the linear range of 5.5 × 10⁻⁶ M with a detection limit of 2.5 × 10⁻⁷ M. Real serum samples in addition to pharmaceutical formulations containing PHO were analyzed, and the results were compared with those obtained by the conventional standard liquid chromatographic approach. The presented analytical device showed an outstanding efficiency for fast, direct, and low-cost assessment of pholcodine levels in different matrices.

Advances in the development of molecularly imprinted polymers for the separation and analysis of proteins with liquid chromatography

This review documents recent advances in the design, synthesis, characterization, and application of molecularly imprinted polymers in the form of monoliths and particles/beads for the use in the separation and analysis of proteins with solid-phase extraction or liquid chromatography. The merits of three-dimensional molecular imprinting, whereby the molecular template is randomly embedded in the polymer, and two-dimensional imprinting, in which the template is confined to the surface, are described. Target protein binding can be achieved by either using the entire protein as a template or by using a protein substructure as template, that is, a peptide, as in the "epitope" approach. The intended approach and strategy then determine the choice of polymerization method. A synopsis has been provided on methods used for the physical, chemical, and functional characterizations and associated performance evaluations of molecularly imprinted and nonimprinted control polymers, involving a diverse range of analytical techniques commonly used for low and high molecular mass analytes. Examples of recent applications demonstrate that, due to the versatility of imprinting methods, molecularly imprinted monoliths or particles/beads can be adapted to protein extraction/depletion and separation procedures relevant to, for example, protein biomarker detection and quantification in biomedical diagnostics and targeted proteomics.

Review on recent progress in chitosan-based hydrogels for wastewater treatment application

Recently, chitosan has been used as a raw material for synthesis of hydrogels in a wide range of potential and practical applications like wastewater treatment, drug delivery, and tissue engineering. This review represents an overview of the application of chitosan-based hydrogels for wastewater treatment and helps researchers to better understand the potential of these adsorbents for wastewater treatment. It covers recently used and prospected methods for synthesis and modification of these hydrogels. Chitosan-based hydrogels are modified physically and chemically through crosslinking, grafting, impregnation, incorporating of hard fillers, blending, interpenetrating, and ion-imprinting methods to improve adsorption and mechanical properties. Understanding of these methods provides useful information in the design of efficient chitosan-based hydrogels and the select of appropriate pollutants for removal. This review provides a brief outlook on future prospects of chitosan-based hydrogels for wastewater application.

Fabrication of Hypericin Imprinted Polymer Nanospheres via Thiol-Yne Click Reaction

To fabricate molecularly imprinted polymer nanospheres via click reaction, five different clickable compounds were synthesized and two types of click reactions (azide-alkyne and thiol-yne) were explored. It was found that molecularly imprinted polymer nanospheres could be successfully synthesized via thiol-yne click reaction using 3,5-diethynyl-pyridine (1) as the monomer, tris(3-mercaptopropionate) (tri-thiol, 5) as the crosslinker, and hypericin as the template (MIP⁻NSHs). The click polymerization completed in merely 4 h to produce the desired MIP⁻NSHs, which were characterized by FTIR, SEM, DLS, and BET, respectively. The reaction conditions for adsorption capacity and selectivity towards hypericin were optimized, and the MIP⁻NSHs synthesized under the optimized conditions showed a high adsorption capacity (Q = 6.03 μmol•g-1) towards hypericin. The imprinting factors of MIP⁻NSHs towards hypericin, protohypericin, and emodin were 2.44, 2.88, and 2.10, respectively.

Imprinted Photonic Hydrogels for the Size- and Shell-Selective Recognition of Nanoparticles

Sensors based on responsive photonic hydrogels have recently attracted considerable attention for visual medical diagnostics, pharmaceutical bioassays, and environmental monitoring. However, the use of these promising materials for the detection of nanoparticles (NPs) has never been explored so far, although the sensing of nanoobjects is a rapidly evolving area of research. To address this issue, we have combined the concepts of inverse-opal hydrogels and nanoparticle-imprinted polymers. In this way, we could obtain a NP-imprinted photonic hydrogel consisting of a three-dimensional, highly ordered poly(methacrylic acid) macroporous array, in which nanocavities complementary to the target NPs, in this case colloidal quantum dots, are distributed. This novel type of NP-imprinted photonic hydrogel sensor was shown to display high sensitivity and selectivity, thus opening new prospects for the development of equipment-free and cost-efficient sensing devices for NPs.

Ultrasensitive Electrochemical Detection of Glycoprotein Based on Boronate Affinity Sandwich Assay and Signal Amplification with Functionalized SiO2@Au Nanocomposites

Herein we propose a multiple signal amplification strategy designed for ultrasensitive electrochemical detection of glycoproteins. This approach introduces a new type of boronate-affinity sandwich assay (BASA), which was fabricated by using gold nanoparticles combined with reduced graphene oxide (AuNPs-GO) to modify sensing surface for accelerating electron transfer, the composite of molecularly imprinted polymer (MIP) including 4-vinylphenylboronic acid (VPBA) for specific capturing glycoproteins, and SiO₂ nanoparticles carried gold nanoparticles (SiO₂@Au) labeled with 6-ferrocenylhexanethiol (FcHT) and 4-mercaptophenylboronic acid (MPBA) (SiO₂@Au/FcHT/MPBA) as tracing tag for binding glycoprotein and generating electrochemical signal. As a sandwich-type sensing, the SiO₂@Au/FcHT/MPBA was captured by glycoprotein on the surface of imprinting film for further electrochemical detection in 0.1 M PBS (pH 7.4). Using horseradish peroxidase (HRP) as a model glycoprotein, the proposed approach exhibited a wide linear range from 1 pg/mL to 100 ng/mL, with a low detection limit of 0.57 pg/mL. To the best of our knowledge, this is first report of a multiple signal amplification approach based on boronate-affinity molecularly imprinted polymer and SiO₂@Au/FcHT/MPBA, exhibiting greatly enhanced sensitivity for glycoprotein detection. Furthermore, the newly constructed BASA based glycoprotein sensor demonstrated HRP detection in real sample, such as human serum, suggesting its promising prospects in clinical diagnostics.

Selective extraction of proteins and other macromolecules from biological samples using molecular imprinted polymers

The accurate determination of intact macromolecules in biological samples, such as blood, plasma, serum, urine, tissue and feces is a challenging problem. The increased interest in macromolecules both as candidate drugs and as biomarkers for diagnostic purposes means that new method development approaches are needed. This review charts developments in the use of molecularly imprinted polymers first for small-molecular-mass compounds then for proteins and other macromolecules. Examples of the development of molecularly imprinted polymers for macromolecules are highlighted. The two main application areas to date are sensors and separation science, particularly SPE. Examples include peptides and polypeptides, lysozyme, hemoglobin, ovalbumin, bovine serum albumin and viruses.

A poly(2-(dimethylamino)ethyl methacrylate-co-methacrylic acid) complex induced route to fabricate a super-hydrophilic hydrogel and its controllable oil/water separation

Thermo and pH dual-controllable oil/water separation materials are successfully fabricated by free radical polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and methacrylic acid (MAA).

Aminoglutethimide-imprinted xerogels in bulk and spherical formats, based on a multifunctional organo-alkoxysilane precursor

The multifunctional alkoxysilane precursor, 2,6-bis(propyl-trimethoxysilylurelene)pyridine (DPS) was designed and synthesized, envisaging a multiple hydrogen-bond interaction in the molecular imprinting of the drug aminoglutethimide (AGT). Imprinted xerogels were obtained in bulk and spherical formats. The spherical format was achieved by pore-filling onto spherical mesoporous silica, as a straightforward technique to generate the spherical format. The bulk gels presented better selectivity for the template against its glutarimide (GLU) analogue (selectivity factor: bulk 13.4; spherical 4.6), and good capacity (bulk 5521μmol/L; spherical 2679μmol/L) and imprinting factor parameters (bulk 11.3; spherical 1.4). On the other hand, the microspherical format exhibited better dynamic properties associated to chromatographic efficiency (theoretical plates: bulk 6.8; spherical 75) and mass transfer, due mainly to the existence of a mesoporous network, lacking in the bulk material. The performance of the imprinted xerogels was not as remarkable as that of their acrylic counterparts, previously described. Overall it was demonstrated that the use of designed new "breeds" of organo-alkoxysilanes may be a strategy to achieve satisfactory imprints by the sol-gel processes. DPS may in principle be applied even more effectively to other templates bearing better-matching spatially compatible acceptor-donor-acceptor arrays.

Review of the recent progress in photoresponsive molecularly imprinted polymers containing azobenzene chromophores

Photoresponsive molecularly imprinted polymers (PMIPs) containing azobenzene have received wide research attention in recent years and made notable achievements. This article reviews the recent developments on PMIPs containing azobenzene. Topics include the following: (i) brief introduction of azobenzene, molecularly imprinted polymers, and PMIPs containing azobenzene; (ii) progress in functional monomers, cross-linkers, and polymerization conditions; (iii) preparation methods, properties, applications, as well as advantages and disadvantages of conventional PMIPs; (iv) substrate, preparation method, and applications of photoresponsive surface molecularly imprinted polymers; and (v) some perspectives for further development of PMIPs containing azobenzene.

Preparation of the high purity gingerols from ginger by dummy molecularly imprinted polymers

In this work, a dummy molecularly imprinted polymers (MIPs) were developed as the selective sorbents for preparation of the high purity gingerols from ginger for the first time. The dummy template molecule with similar structural skeleton to gingerols, N-vanillylnonanamide, has been designed and synthesized. The performance of the MIPs and non-imprinted polymers (NIPs) were evaluated including selective recognition capacity, adsorption isotherm, and adsorption kinetics. Optimization of various parameters affecting dummy molecular imprinted solid phase extraction (MISPE), such as the type and flow rate of the loading solvent, the composition and volume of the eluting solvent, and the composition and volume of the washing solvent were investigated. Gingerols with the percent recovery of 80 and the percent purity of 99.1 were obtained from the extracts of ginger by MISPE. Besides, gingerols obtained by MISPE had more powerful activity of eliminating free radical compared with extracts before extraction with the MISPE column. Application of MIPs with a high affinity toward three gingerols provides a novel method for obtaining a group of compounds which have likely active groups from natural products.

Molecularly imprinted polymer for selective extraction and simultaneous determination of four tropane alkaloids from Przewalskia tangutica Maxim. fruit extracts using LC-MS/MS

A class-specific molecularly imprinted polymer (MIP) for selectively extracting four tropane alkaloids has been prepared using anisodine, methacrylic, and trimethylolpropane trimethacrylate as template, functional monomer and crosslinker, respectively.

Surface molecularly imprinted polymers with dummy templates for the separation of dencichine from Panax notoginseng

Surface molecularly imprinted polymers with dummy templates for the targeted separation of dencichine from Panax notoginseng.

Thermal preparation of lysozyme-imprinted microspheres by using ionic liquid as a stabilizer

Thermal preparation of lysozyme-imprinted microspheres was firstly investigated by using biocompatible ionic liquid (IL) as a thermal stabilizer. The imprinted microspheres made with IL could obtain the good recognition ability to template protein, whereas the imprinted polymer synthesized in the absence of it had a similar adsorption capacity to the non-imprinted one. Furthermore, the preparation conditions of imprinted polymers (MIPs) including the content of IL, temperature of polymerization, and types of functional monomers and crosslinkers were systematically analyzed via circular dichroism spectrum and activity assay. The results illustrated that using hydroxyethyl acrylate as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, 5 % IL as the stabilizer, and 75 °C as the reaction temperature could retain the structure of template protein as much as possible. The obtained MIPs showed excellent recognition ability to the template protein with the separation factor and selectivity factor value of 4.30 and 2.21, respectively. Consequently, it is an effective way to accurately imprint and separate template protein by cooperatively using circular dichroism spectroscopy and activity assay during the preparation of protein MIPs. The method of utilizing IL to stabilizing protein at high temperature would offer a good opportunity for various technologies to improve the development of macromolecules imprinting.