Chiral separation of racemic mandelic acids by use of an ionic liquid-mediated imprinted monolith with a metal ion as self-assembly pivot

Cobalt (II)-Mediated Molecularly Imprinted Polymer as a Monolithic Stationary Phase for Separation of Racemic Citronellal by Liquid Chromatography

A metal-mediated molecularly imprinted polymer (MMIP) monolithic column was prepared as the stationary phase for high-performance liquid chromatography (HPLC) and applied to the enantiomeric separation of rac-citronellal. MMIP column was prepared through in situ copolymerizations with the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate/[BMIM][BF₄] as the primary pore-forming agent and cobalt(II) acetate as the metal pivot. Interactions between polymer components in the synthesized monolith were assessed by FTIR to identify the functional groups. The monolith morphology was characterized with SEM, and the template removal was detected by UV Spectrophotometry at 253 nm. In this study, (R)-(+)-citronellal was used as a template, whereas 4-vinylpyridine (4-VP) was employed as the functional monomer with two monomer crosslinkers, trimethylolpropane trimethacrylate (TRIM), and ethylene glycol dimethacrylate (EDMA). The ternary mixture of porogenic solvent consisted of [BMIM][BF₄], dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) with the applied ratio of 1 : 1:1 (v/v) and 10 : 1:5 (v/v) for the preparation of MMIP using TRIM and EDMA crosslinkers, respectively. Co(II) ion was added to the porogenic solvent before being mixed with the functional monomer and the crosslinker mixtures. Separating the rac-citronellal was achieved on the synthesized MMIP, showing better selectivity than the monolithic metal-mediated nonimprinted polymer (MNIP), nonimprinted polymer (NIP), and molecularly imprinted polymer (MIP).

Green molecularly imprinted polymers for sustainable sample preparation

The use of molecularly imprinted polymers in sample preparation as selective sorbent materials has received great attention during the last years leading to analytical methods with unprecedented selectivity. However, with the progressive implementation of Green Analytical Chemistry principles, it is necessary to critically review the greenness of synthesis and further use of molecularly imprinted polymers in sample preparation. Accordingly, in the present review, the different steps and strategies for the preparation of molecularly imprinted polymers, the used reagents, as well as their incorporation to microextraction techniques are reviewed from a green perspective and recent alternatives to make the use of molecularly imprinted polymers more sustainable are provided.

Perspectives of Molecularly Imprinted Polymer-Based Drug Delivery Systems in Cancer Therapy

Despite the considerable effort made in the past decades, multiple aspects of cancer management remain a challenge for the scientific community. The severe toxicity and poor bioavailability of conventional chemotherapeutics, and the multidrug resistance have turned the attention of researchers towards the quest of drug carriers engineered to offer an efficient, localized, temporized, and doze-controlled delivery of antitumor agents of proven clinical value. Molecular imprinting of chemotherapeutics is very appealing in the design of drug delivery systems since the specific and selective binding sites created within the polymeric matrix turn these complex structures into value-added carriers with tunable features, notably high loading capacity, and a good control of payload release. Our work aims to summarize the present state-of-the art of molecularly imprinted polymer-based drug delivery systems developed for anticancer therapy, with emphasis on the particularities of the chemotherapeutics’ release and with a critical assessment of the current challenges and future perspectives of these unique drug carriers.

An insight into chiral monolithic stationary phases for enantioselective high-performance liquid chromatography applications

In this review, three main classes of chiral monolithic stationary phases, namely silica-, organic polymer-, and hybrid-based monolithic stationary phases, are covered. Their preparations, applications, and advantages compared with the conventional-packed and open-tubular capillary columns are discussed. A detailed description of the different types and techniques used for the introduction of chiral selectors into the monolithic matrices such as immobilization, functionalization, coating, encapsulation, and bonding. Special emphasis is given to the recent developments of chiral selectors in HPLC monolithic stationary phases during the past 18 years.

Rational design and tailoring of imprinted polymeric enantioselective sensor layered on multiwalled carbon nanotubes for the chiral recognition of d-mandelic acid

Attempts have been made to investigate the feasibility of fabricating an enantiomeric sensor for the specific detection of d-mandelic acid layered on vinyl-MWCNT using molecular imprinting technology.

A star-shaped molecularly imprinted polymer derived from polyhedral oligomeric silsesquioxanes with improved site accessibility and capacity for enantiomeric separation via capillary electrochromatography

A star-shaped molecularly imprinted coating was prepared starting from octavinyl-modified polyhedral oligomeric silsesquioxanes (Ov-POSS). It possesses a relatively open structure and has good site accessibility and a larger capacity even at lower cross-linking. The imprinted coating was prepared from S-amlodipine (S-AML) as the template and analyte, Ov-POSS as the cross-linker, and methacrylic acid as the functional monomer. The preparation and chromatographic parameters were optimized, including ratio of template to functional monomer, apparent cross-linking degree, pH value, ACN content and salt concentration in the mobile phase. The best resolution in enantiomer separation by means of capillary electrochromatography reaches a value of 33. A good recognition ability (α = 2.60) was obtained and the column efficiency for S-AML was 54,000 plates m^-1. The use of Ov-POSS as a cross-linker significantly improves the column capacity and thus the detection sensitivity. The results show that Ov-POSS is an effective cross-linker for the preparation of imprinted polymers with good accessibility and large capacity. Graphical abstract Schematic presentation of the preparation of star-shaped imprinted polymer using octavinyl-modified polyhedral oligomeric silsesquioxanes (Ov-POSS) and by using methacrylic acid (MAA) as functional monomer. The best enantiometric resolution (33) for amlodipine (AML) can be achieved in capillary chromatography (CEC).

Improved Enantioselectivity for Atenolol Employing Pivot Based Molecular Imprinting

In the last few decades, molecular imprinting technology went through a spectacular evolution becoming a well-established tool for the synthesis of highly selective biomimetic molecular recognition platforms. Nevertheless, there is still room for advancement in the molecular imprinting of highly polar chiral compounds. The aim of the present work was to investigate the favorable kosmotropic effect of a ternary complex involving a polar chiral template (eutomer of atenolol) and a functional monomer, bridged by a central metal ion through well-defined, spatially directional coordinate bonds. The efficiency of the chiral molecular recognition was systematically assessed on polymers obtained both by non-covalent and metal-mediated molecular imprinting. The influence on the chromatographic retention and enantioselectivity of different experimental variables (functional monomers, cross-linkers, chaotropic agents, metal ions, porogenic systems, etc.) were studied on both slurry packed and monolithic HPLC columns. Deliberate changes in the imprinting and rebinding (chromatographic) processes, along with additional thermodynamic studies shed light on the particularities of the molecular recognition mechanism. The best performing polymer in terms of enantioselectivity (α = 1.60) was achieved using 4-vinyl pyridine as functional monomer and secondary ligand for the Co(II)-mediated imprinting of S-atenolol in the presence of EDMA as cross-linker in a porogenic mixture of [BMIM][BF₄]:DMF:DMSO = 10:1:5, v/v/v.

Recent advances in green reagents for molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) are tailor-made materials with special binding sites.

Green synthesis of monolithic column incorporated with graphene oxide using room temperature ionic liquid and eutectic solvents for capillary electrochromatography

In this work, a hybrid monolith incorporated with graphene oxide (GO) was prepared in the first time with binary green porogens of deep eutectic solvents (DESs) and room temperature ionic liquids (RTILs). GO was modified with 3-(trimethoxysilyl) propylmethacrylate (γ-MPS), and the resultant GO-MPS can be incorporated into poly (methacrylic acid-co-butylmethacrylate-co-ethylene glycol dimethacrylate) monoliths covalently. A hybrid monolithic column with high permeability and homogeneity can be achieved due to good dispersion of GO-MPS in the green solvents. The GO-MPS incorporated monolith was characterized by transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis and nitrogen adsorption tests. The separation of small organic molecules of alkylphenones and alkylbenzenes was used to evaluate the performance of GO-MPS grafted monolith. The GO-MPS grafted monolith displayed the maximum column efficiency of 147,000 plates/m, about twice higher than the GO-free monolith. In addition, all of the retention and selectivity of small molecules of alkylphenones and alkylbenzenes increased due to the addition of GO-MPS. The results demonstrated that the use of DESs and RTILs is a powerful approach for the preparation of GO incorporated polymer monoliths. The monolith was further applied to the separation of tryptic digests from bovine serum albumin, and the result indicated its potential in the analysis of some complex samples.

Preparation of ionic liquid-mediated imprinted monolith for selective capture and purification of corilagin

A method for solid-phase extraction (SPE) of corilagin from natural plant extracts based on molecularly imprinted polymers (MIPs) was developed. For the preparation of corilagin-MIP monoliths, 4-vinylpyridine was used as functional monomer, and ethylene glycol dimethacrylate was used as cross-linking monomer, using a mixture of 1-butyl-3-methylimidazoliumtetrafluoroborate (ionic liquid)-N,N-dimethylformamide-dimethyl sulfoxide as a porogen. A morphological characteristic of the corilagin imprinted monolith was further studied by scanning electron microscopy and nitrogen sorption method. The greatest imprinting factor of COR was up to 9. The MIPs were used as solid-phase extraction (SPE) sorbents for purification of COR and the mean recoveries of corilagin was 78.0% with COR purity of 98.0% from the crude extract of phyllanthus urinaria L. The resulting COR-imprinted polymer also displayed the good performance of fragment imprinting polymer for gallic acid with the mean recoveries of 94.0% and purity of 99.7%.

Molecularly Imprinted Polymers for the Identification and Separation of Chiral Drugs and Biomolecules

Molecularly imprinting polymers (MIPs) have been extensively applied in chromatography for the separation of chiral drugs. In this review, we mainly summarize recent developments of various MIPs used as chiral stationary phases (CSPs) in high performance liquid chromatography (HPLC), capillary electrochromatography (CEC), and supercritical fluid chromatography (SFC). Among them, HPLC has the advantages of straightforward operation and high selectivity. However, the low separation efficiency, due to slow interaction kinetics and heavy peak broadening, is the main challenge for the application of MIPs in HPLC. On the other hand, CEC possesses both the high selectivity of HPLC and the high efficiency of capillary electrophoresis. In CEC, electroosmotic flow is formed across the entire column and reduces the heavy peak broadening observed in HPLC mode. SFC can modify the low interaction kinetics in HPLC when supercritical fluids are utilized as mobile phases. If SFC and MIP-based CSPs can be well combined, better separation performance can be achieved. Particles, monoliths and membrane are typical formats of MIPs. Traditional MIP particles produced by bulk polymerization have been replaced by MIP particles by surface imprinting technology, which are highly consistent in size and shape. Monolithic MIPs are prepared by in situ method in a column, greatly shortening the pre-preparation time. Some novel materials, such as magnetic nanoparticles, are integrated into the MIPs to enhance the controllability and efficiency of the polymerization. This review will be helpful to guide the preparation, development, and application of MIPs in chromatographic and electrophoretic enantioseparation.

Water-compatible molecularly imprinted polymers prepared using metal–organic gel as porogen

A novel water-compatible approach suitable for molecular imprinting was described by using metal–organic gel (MOG) as the porogenic solvent.

Synthesis of imprinted monolithic column with high content of monomers in ionic liquid

A MIP monolith with good permeability was successfully achieved using a strategy involving a high content of monomers in a [BMIM][BF₄]-based green solvent.