Double affinity based molecularly imprinted polymers for selective extraction of luteolin: A combination of synergistic metal chelating and boronate affinity

ZIF-based boronic acid modified molecular imprinted polymers in combination with silver nanoparticles/glutathione coated graphene oxide adsorbent for the selective enrichment of ellagic acid

This study focuses on the extraction of ellagic acid (EA), a valued phenolic compound, from agricultural waste chestnut shell samples. A novel approach is introduced using a combination of boronic acid-modified molecularly imprinted polymer (ZIF@B@MIP) and a nanocomposite of graphene oxide-coated silver nanoparticles (GO@Ag@GSH) to enhance EA enrichment. ZIF@B@MIP precisely captured EA through boronate affinity-based molecular imprinting recognition. ZIF@B@MIP employs boronate affinity-based molecular imprinting recognition to precisely capture EA, while GO@Ag@GSH provides ample adsorption sites. The synergistic effect of ZIF@B@MIP and GO@Ag@GSH demonstrates excellent enrichment capability and selectivity for EA. High-performance liquid chromatography (HPLC) is employed for sensitive EA detection, achieving a maximum adsorption capacity of 46.25 mg g-1 and an imprinting factor of 3.01. The adsorption capacity to different structural analogue was investigated, and the selectivity coefficient was used to evaluate the selectivity, and its value was 1.16-3.01. The method successfully enriches EA in chestnut shell samples with a recovery rate of 95.6 %-110.1 %. This research presents an innovative approach for effective phenolic components enrichment from natural resources for pharmaceutical and biochemical applications.

A boronate-affinity magnetic molecularly imprinted polymer for luteolin recognition

In this study, 3-carboxyphenylboronic acid (CP)-functionalized amino-modified Fe₃O₄ (Fe₃O₄@NH₂-CP, FNC) magnetic molecularly imprinted polymers (FNC@MIPs) were synthesized and applied for the quick identification and selective separation of luteolin (LTL). The structure and morphology were characterized in detail by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and vibrating specimen magnetometry (VSM) methods. The FNC@MIPs had a homogeneous shape, excellent magnetic characteristics, quick binding kinetics, a high adsorption capacity, acceptable selectivity, and stable reusability. The solid-phase extraction parameters and preparation conditions were both optimized. Under optimized conditions, the maximal adsorption capacity was 14.26 mg g^-1 and the imprinting factor was 3.62. Furthermore, the experimental kinetics data were best fitted with the pseudo-first-order model (R² = 0.9877), and the Langmuir model could describe the adsorption process (R² = 0.9979), suggesting a monolayer covering. The practical application of the sorbent for LTL detection in Lonicera japonica Thunb samples showed recoveries in the range of 84.5-108.7%. Therefore, the strategy offers a fresh avenue for the extraction and purification of LTL.

A recognition strategy combining effective boron affinity technology and surface imprinting to prepare highly selective and easily recyclable polymer membrane for separation of drug molecule

Cellulose acetate membrane (CAM) has become one of the most widely used membrane materials by virtue of stability and hydrophilicity. In this work, to achieve the aim of selective recognition and separation of drug molecule shikimic acid (SA), an effective recognition tactics was proposed by combining boron affinity technology with surface imprinting strategy based on cellulose acetate membrane with low price and biocompatibility. The supporting CAM material was prepared through the phase inversion technique by continuous adjustment of different factors including solvent type and kinds of pore-forming agents, and the optimal CAM with multistage structure and highly porosity was applied for the imprinting of SA. Then the imprinted polymer membrane (MIPs-CAM) was developed via boron affinity surface imprinting polymerization. Various methods (FT-IR, UV-vis, SEM, XPS, AFM and TGA) were used to characterize the structure, morphology, elemental composition, surface roughness and thermal property of the obtained membrane. The as-prepared MIPs-CAM showed homogeneous and abundant imprinted layer, good thermal stability. The batch adsorption results showed that the MIPs-CAM had fast adsorption kinetics, specific recognition ability, and the adsorption capacity could obtain 63.598 mg g^-1, which was two times higher than that of non-imprinted membrane (NIPs-CAM). The adsorption isotherms conformed to the Langmuir isotherm and the adsorption processes were spontaneous and endothermic. Additionally, the adsorption capacity of MIPs-CAM still reached 85% of the initial result after five cycles. The experimental results revealed that the molecularly imprinted membrane possessed the advantages of high selectivity and easy recovery compared with the traditional molecular imprinted polymers for SA separation. These results indicate that boron affinity MIPs-CAM with high performance will provide a promising platform for the separation and purification of other cis-diol drug molecules from environmental resources.

Boronate-modified polyethyleneimine dendrimer as a solid-phase extraction adsorbent for the analysis of luteolin via HPLC

Luteolin (LTL) is a flavonoid containing a cis-diol, which has significant anti-inflammatory, anti-allergic, anti-diabetic, anti-cancer and neuroprotective activities. In this work, a silver modified boric acid affinity polyvinyl imine (PEI) dendritic adsorbent (PPEI-Ag@CPBA) was prepared on polystyrene (PS) for the rapid recognition and selective separation of LTL. A thin layer of polydopamine (PDA) was formed on the surface of the substrate by self-polymerization, and a PDA-coated PS material (PS@PDA) was obtained. PEI with sufficient active amino groups was grafted onto PS@PDA to obtain a PEI-modified material (PS@PDA@PEI), then AgNO3 was reduced with NaBH4, and PS@PDA@PEI was embedded on Ag. Finally, PPEI-Ag@CPBA was obtained through the condensation reaction of PEI with 4-carboxyphenyl boric acid (CPBA). The adsorption conditions were optimized, the optimal pH and the optimum amount of adsorbent were determined, and the maximum adsorption capacity was found to be 2.49 mg g-1. This method has been successfully applied to the selective identification of LTL in peanut shell samples, and provides a practical platform for the detection of LTL in complex substrates.

ZIF-based boronic acid functionalized metal-organic frameworks for the enrichment of cis-diol-containing luteolin from food samples prior to HPLC

Zeolite imidazole framework-based boronic acid-functionalized metal-organic frameworks (ZIF-67@PDA@BA-Zr-MOFs) were developed as an adsorbent for solid phase extraction (SPE) of luteolin (LTL) from peanut shell samples. Herein, ZIF-67 as a support matrix, polydopamine (PDA) as a coating to introduce amino and hydroxyl groups on the matrix surface to fix metal-organic frameworks (MOFs), zirconium tetrachloride (ZrCl₄) as a precursor, terephthalic acid (TPA), and 3-carboxyphenylboronic acid (3-CPBA) as the mutual organic building blocks, and 3-CPBA was also a boronate affinity functional monomer. The effects of synthesis conditions, SPE conditions, selectivity, competitivity, reproducibility, and reusability were evaluated in detail. Under the optimal conditions, the maximum adsorption capacity is 71.4 mg g^-1. The utility of ZIF-67@PDA@BA-Zr-MOFs as an adsorbent for SPE of LTL is supported by the presence of the abundant pore structure, as well as the boronate affinity sites facilitated the rapid binding of the adsorbent to the template. The concentration of the extracted LTL was determined by the high-performance liquid chromatography-ultraviolet (HPLC-UV), with calibration plots being linear in the concentration range 0.05-100 mg L^-1 and a limit of detection (LOD) of 0.035 mg L^-1. The method was applied to determine the LTL in peanut shell samples and recovered the target analyte in the range 85.6% to 99.2% (the standard deviations are less than 3.3%, n = 3). In addition, we incorporated boronate affinity and MOFs material into an SPE system to provide a promising strategy to detect other cis-diol-containing analytes in the complex matrix.

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.