Preparation and characterization of dual-template molecularly imprinted monolith with metal ion as 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).

Origin of macromolecular crowding: Analysis of recognition mechanism of dual-template molecularly imprinted polymers by in silico prediction

Multi-template imprinting is one of the challenge for molecular imprinting since the selectivity and binding affinity for each analyte decrease significantly compared with the corresponding molecularly imprinting polymers (MIPs) against single template. In this work, molecular crowding effect was tried to remedy the problem of imprinting reduction caused by the competition of two templates. Methacrylic acid (ACR) was used as functional monomer, ethylene dimethacrylate (EDMA) as crosslinker, and polystyrene (PS) as macromolecular crowding agent. With levofloxacin (S-OFX) as the first template, a number of compounds with varied chemical structure were chosen as the second template to investigate the imprinting effect of dual-template. When S-OFX and naproxen (S-NAP) was used as the dual-template, the imprinting factor (IF) of the resulting MIP for S-OFX was 20.1 and IF for S-NAP was 10.9. In contrast, for the single-template MIPs, IF for S-OFX was 22.4, and IF for S-NAP was 11.9. As a comparison, the IF of the DT-MIP prepared in absence of PS was only 2.3 for S-OFX and 1.0 for S-NAP. To analyze recognition mechanism of the molecular crowding-based imprinting system, molecular dynamics simulations to the chain structure of PS and binding modes between template and functional monomers was conducted by NAMD software. All the results displayed that molecular crowding is a promising method to improve the affinity of the dual-template imprinted polymer.

Selective adsorption and fluorescence sensing of tetracycline by Zn-mediated chitosan non-woven fabric

Nowadays, numerous studies have focused on the newly developed technologies for the thorough removal of tetracyclines (TCs). The efficient removal of trace-amount pollutants requires the development of improved materials with higher adsorption capacity and increased adsorption selectivity. Zn(II)-mediated chitosan nonwoven fabric (Zn-CSNW) adsorbent with coordination capability was explored for the effective and selective removal of TC. The adsorption of TC to Zn-CSNW could reach equilibrium in about 30 min with a maximum adsorption capacity of 195.9 mg/g. It exhibited high anti-interference performance for TC adsorption at low concentrations, with good regeneration and effective reuse. Except for citrate, organic materials similar in structure to TC or common ions in aqueous solutions did not show obvious competition for the adsorption of low concentrations of TC. Additionally, the inherent fluorescence of chitosan and the fluorescence sensitization effect of Zn²⁺ for TC enabled function of Zn-CSNW as an indicator of the adsorption of TC by changes in fluorescence color and intensity under UV light (365 nm). It can indicate the saturation state of the Zn-CSNW, which will bring convenience to the use of the adsorbent. The Zn(II)-mediated coordination interaction plays a vital role in both the selective recognition of TC and the fluorescence sensing of adsorption amount, demonstrating an affordable and effective strategy for the treatment of water containing low amounts of antibiotics.

Imprinting Technology for Effective Sorbent Fabrication: Current State-of-Art and Future Prospects

In the last 10 years, we have witnessed an extensive development of instrumental techniques in analytical methods for determination of various molecules and ions at very low concentrations. Nevertheless, the presence of interfering components of complex samples hampered the applicability of new analytical strategies. Thus, additional sample pre-treatment steps were proposed to overcome the problem. Solid sorbents were used for clean-up samples but insufficient selectivity of commercial materials limited their utility. Here, the application of molecularly imprinted polymers (MIPs) or ion-imprinted polymers (IIPs) in the separation processes have recently attracted attention due to their many advantages, such as high selectivity, robustness, and low costs of the fabrication process. Bulk or monoliths, microspheres and core-shell materials, magnetically susceptible and stir-bar imprinted materials are applicable to different modes of solid-phase extraction to determine target analytes and ions in a very complex environment such as blood, urine, soil, or food. The capability to perform a specific separation of enantiomers is a substantial advantage in clinical analysis. The ion-imprinted sorbents gained interest in trace analysis of pollutants in environmental samples. In this review, the current synthetic approaches for the preparation of MIPs and IIPs are comprehensively discussed together with a detailed characterization of respective materials. Furthermore, the use of sorbents in environmental, food, and biomedical analyses will be emphasized to point out current limits and highlight the future prospects for further development in the field.

A new restricted access molecularly imprinted fiber for direct solid phase microextraction of benzodiazepines from plasma samples

Restricted access molecularly imprinted polymers (RAMIPs) are hybrid materials that present selective binding sites for a template (or similar molecules), and an external hydrophilic layer that avoids the binding of proteins to the material, making them appropriate for the sample preparation of protein fluids.

Synthesis of a molecularly imprinted polymer and its application in selective extraction of fenoprofen from wastewater

The presence of various classes of pharmaceutical drugs in different environmental compartments has been reported worldwide. In South Africa, the detection of pharmaceuticals especially the non-steroidal anti-inflammatory drugs is recent, and more studies are being done in order to fully understand their fate in the aquatic environment. With considerations for the need of better sample preparation techniques, this study synthesized a molecularly imprinted polymer for the selective extraction of a non-steroidal anti-inflammatory drug, fenoprofen in aqueous environmental samples. Batch adsorption studies showed that adsorption of fenoprofen onto the cavities of the polymer followed a Langmuir isotherm as well as a pseudo second order model implying formation of a monolayer on the surface through chemisorption. The polymer had a maximum adsorption capacity of 38.8 mg g^-1 and a Langmuir surface area of 1607 m² g^-1. The imprinted polymer was then used as the selective sorbent for solid phase extraction in the analysis of fenoprofen from wastewater followed by chromatographic determination. The analytical method gave a detection limit of 0.64 ng mL^-1 and recovery of 99.6%. The concentration of fenoprofen detected in influent and effluent samples from two wastewater treatment plants ranged from 24 to 58 ng mL^-1. The ability of the treatment plants to remove fenoprofen during wastewater processing based on the difference in concentrations in influent and effluent samples was found to be 41%. This work has shown that there is a possibility of release of fenoprofen from wastewater treatment plants into surface water sources.

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.

The Multi-Template Molecularly Imprinted Polymer Based on SBA-15 for Selective Separation and Determination of Panax notoginseng Saponins Simultaneously in Biological Samples

The feasible, reliable and selective multi-template molecularly imprinted polymers (MT-MIPs) based on SBA-15 (SBA-15@MT-MIPs) for the selective separation and determination of the trace level of ginsenoside Rb₁ (Rb₁), ginsenoside Rg₁ (Rg₁) and notoginsenoside R₁ (R₁) simultaneously from biological samples were developed. The polymers were constructed by SBA-15 as support, Rb₁, Rg₁, R₁ as multi-template, acrylamide (AM) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. The new synthetic SBA-15@MT-MIPs were satisfactorily applied to solid-phase extraction (SPE) coupled with high performance liquid chromatography (HPLC) for the separation and determination of trace Rb₁, Rg₁ and R₁ in plasma samples. Under the optimized conditions, the limits of detection (LODs) and quantitation (LOQs) of the proposed method for Rb₁, Rg₁ and R₁ were in the range of 0.63⁻0.75 ng·mL-1 and 2.1⁻2.5 ng·mL-1, respectively. The recoveries of R₁, Rb₁ and Rg₁ were obtained between 93.4% and 104.3% with relative standard deviations (RSDs) in the range of 3.3⁻4.2%. All results show that the obtained SBA-15@MT-MIPs could be a promising prospect for the practical application in the selective separation and enrichment of trace Panax notoginseng saponins (PNS) in the biological samples.

Applications of molecularly imprinted polymers for solid-phase extraction of non-steroidal anti-inflammatory drugs and analgesics from environmental waters and biological samples

The occurrence of pharmaceuticals used as non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics in the aquatic environment is a threat to humans and aquatic species at large. The primary route of these pharmaceuticals to aquatic environment is through human waste such as urine and faeces. The application of molecularly imprinted polymers (MIPs) in the solid-phase extraction (SPE) of such pollutants from environmental and biological samples is important for the pre-concentration of compounds and selectivity of the analytical methods. To date, there are still limited commercial suppliers of MIPs. However, it is easy to synthesize such polymers via non-covalent imprinting approach using easily available and affordable reagents. Therefore, the applications of MIPs in the SPE of NSAIDs and analgesics from environmental and biological samples are reviewed. This is very important because despite the fact that review articles on applications of MIPs for organic compounds have been reported, very little has focussed on NSAIDs and analgesics which are the major studied pharmaceuticals in the environment and biological samples. The review also brings out important aspects of common reagents used including the template molecules during MIP synthesis. Application and future trends are also discussed. Gaps such as little use of environmental friendly reagents such as ionic liquids have been identified. Also, the lack of MIP applications to some compounds such as fenoprofen has been observed which is likely to be developed in the near future.