Boronate affinity surface imprinted polymers supported on dendritic fibrous silica for enhanced selective separation of shikimic acid via covalent binding

The preparation of a boronate affinity-based controlled oriented imprinting coating on a silica nanoparticle surface for the separation and purification of shikimic acid in herbal medicine

Shikimic acid (SA) is one of the most effective drugs against the A (H1N1) virus and has high medicinal value. Additionally, it has the ability to generate non-toxic herbicides and antimicrobial medications. The extraction from plants has proven to be the main route of production of SA with economic benefits and environmental efficiency. Therefore, it is necessary to perform purification of SA from these herbal medicines before quantifying it. In this study, researchers employed a boronate affinity-based controlled oriented surface imprinting technique to produce molecularly imprinted polymers (MIPs) as highly effective solid phase extraction (SPE) adsorbents for the isolation and purification of SA. 3-Fluoro-4-formylphenylboronic acid functionalized silica nanoparticles were used as supporting materials for immobilizing SA. Poly(2-anilinoethanol) with a higher hydrophilic domain can be used as an effective imprinting coating. The prepared SA-imprinted silica nanoparticles exhibited several significant results, such as good specificity, high binding capacity (39.06 ± 2.24 mg g-1), moderate binding constant (6.61 × 10-4 M-1), fast kinetics (8 min) and low binding pH (pH 5.0) toward SA. The replication of SA-imprinted silica nanoparticles was deemed satisfactory. The SA-imprinted silica nanoparticles could be still reused after seven adsorption-desorption cycles, which indicated high chemical stability. In addition, the recoveries of the proposed method for SA at three spiked level analysis in star aniseed and meadow cranesbill were 96.2% to 109.0% and 91.6% to 103.5%, respectively. The SA-imprinted silica nanoparticles that have been prepared are capable of identifying the target SA in real herbal medicines. Our approach makes sample pre-preparation simple, fast, selective and efficient.

Fabrication of double imprinted anchor points in cellulose nanocrystals-based hierarchical porous polyHIPEs for selective separation of flavoniods under physiological pH

Previous research had proved that molecular imprinted polymers can be used as separation material for removing Naringin (NRG) from agricultural pomelo wastes effectively. But the adsorption amounts of NRG molecules from traditional MIPs was quite low by using boronic acid as functional monomer because of single affinity interaction. Therefore, we developed the new combination of bifunctional monomers (i.e. low pKa boronate affinity monomer 2,4-difluoro-3-formylphenylboronic acid and dopamine) based on cellulose nanocrystals (CNCs) mixed with polymerized high internal phase emulsion (polyHIPE, PH) through an double layer surface imprinted method. The introduction of polyethylenimine (PEI) can offer abundant anchor units for the growth of more anchor sites to immobilization template molecules. Importantly, largely improved selective adsorption amounts (50.79 μmol g-1), which may be attribute to the fabrication of the uniform growth of double imprinted layers onto the polydopamine (PDA)/boronic acid-based surfaces. In addition, the resulting double recognition molecular imprinted polymers (MIPs) based on hypercrosslinked PH (DR-HCLPH@MIPs) not only exhibited fast adsorption kinetic of NRG molecule, but also possessed excellent selectivity and high adsorption capacities at physiological pH. Meanwhile, the coarse NRG from pomelo waste can be high selectively extracted to 94.74%. Overall, this study provides a versatile approach for fabrication of the sandwich-biscuit-like double imprinting layer porous MIPs for precise identification and ultrafast transport separation of NRG from complex samples.

The construction of highly selective surface molecularly imprinted polymers based on Cu(II) coordination for the detection of bisphenol A

Herein, we designed and constructed a highly selective MIPs for bisphenol A (BPA) named Cu-MIPs@CS based on Cu(II) coordination. The synthesis of Cu-MIPs@CS employed a dummy template strategy and surface imprinting technology, with chitosan (CS) as the substrate linked to imprinted layers via Cu2+ bridging. 4-vinylpyridine acted as the functional monomer, capable of forming a complex with the template ketoprofen, while ethylene glycol dimethacrylate served as the cross linker. Cu-MIPs@CS exhibited a significantly enhanced imprinting factor of 14.78 for BPA, which was approximately 6.6 times higher than that of imprinted materials without Cu2+ (MIPs@CS). Cu-MIPs@CS exhibited a selective factor of 12.74 towards resorcinol, which possessed identical functional groups but a smaller size than BPA, representing an enhancement of selectivity by 12.25-fold compared to MIPs@CS. More importantly, Cu-MIPs@CS exhibited a superior discrimination ability between BPA and its structural analogue, diphenolic acid, with an excellent selective factor of 2.93, highlighting its significance in distinguish the structural analogue of BPA. In contrast, MIPs@CS lack sufficient selectivity to differentiate between them. Through exploration of adsorption mechanism of Cu-MIPs@CS, it was demonstrated that the incorporation of Cu2+ significantly reduced nonspecific adsorption, but also facilitated the creation of more selective imprinted cavities by introducing metal coordination, thereby notably enhancing the selectivity of Cu-MIPs@CS. Finally, the developed Cu-MIPs@CS were applied as the solid phase extraction adsorbent and combined with HPLC-DAD detection to establish an analytical method towards BPA in drinking water samples. The limit of detection of the method was 0.14 μg L-1 and recoveries ranged from 95.6 % to 101 %. This work provided broad prospects for construction of highly selective MIPs and accurate quantification of trace amounts of BPA.

Dendritic mesoporous nanoparticles for the detection, adsorption, and degradation of hazardous substances in the environment: State-of-the-art and future prospects

Equipped with hierarchical pores and three-dimensional (3D) center-radial channels, dendritic mesoporous nanoparticles (DMNs) make their pore volumes extremely large, specific surface areas super-high, internal spaces especially accessible, and so on. Other entities (like organic moieties or nanoparticles) can be modified onto the interfaces or skeletons of DMNs, accomplishing their functionalization for desirable applications. This comprehensive review emphasizes on the design and construction of DMNs-based systems which serve as sensors, adsorbents and catalysts for the detection, adsorption, and degradation of hazardous substances, mainly including the construction procedures of brand-new DMNs-based materials and the involved hazardous substances (like industrial chemicals, chemical dyes, heavy metal ions, medicines, pesticides, and harmful gases). The sensitive, adsorptive, or catalytic performances of various DMNs have been compared; correspondingly, the reaction mechanisms have been revealed strictly. It is honestly anticipated that the profound discussion could offer scientists certain enlightenment to design novel DMNs-based systems towards the detection, adsorption, and degradation of hazardous substances, respectively or comprehensively.

Construction of the molecularly imprinted adsorbent based on shaddock peel biochar sphere for highly sensitive detection of ribavirin in food and water resources

Ribavirin (RBV) that is not metabolically released into the environment can contaminate the environment and even make organisms resistant to it. Therefore, it is of great significance to establish a simple and effective method for adsorbing RBV in the environment. In this study, a novel biochar-based boronate affinity molecularly imprinted polymers (C@H@B-MIPs) were synthesized. This is the first time that shaddock peel biochar sphere was used as a carrier for specific recognition of RBV. The polymerization conditions were optimized and the binding properties of RBV were studied. Benefiting from the synergistic effect of boronate affinity and surface imprinting, the C@H@B-MIPs showed rapid equilibrium kinetics of 15 min, high adsorption capacity of 18.30 mg g-1, and excellent reusability for RBV. The linear range was 0.05-100 mg L-1, and the detection limit was 0.023 mg L-1. This method was triumphant applied to the selective adsorption of RBV in food and water resources with recovery rates of 81.4-97.7%. This study provides a practical platform for the manufacture of efficient biomass-based adsorbents.

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.

Selective capture of Pd(II) from aqueous media by ion-imprinted dendritic mesoporous silica nanoparticles and re-utilization of the spent adsorbent for Suzuki reaction in water

The development of highly efficient adsorptive material for the selective capture of Pd(II), and re-utilization of spent Pd(II)-loaded adsorbent as an efficient catalyst for organic synthesis are of great significance, but challenging. Particularly, the heterogeneous palladium-catalyzed Suzuki reaction in aqueous media is much more challenging than that of homogeneous. Herein, several novel Pd(II) ion-imprinted polymers (PIIPs) based on dendritic fibrous silica particles are constructed by surface ion imprinting technology (SIIT), using Schiff base and pyridine groups functionalized organosilicon as functional monomer. The PIIP-3 prepared by 3 g of functional monomer exhibits the best adsorption performance, and shows ultrafast (10 min) and selective capture of Pd(II) with high uptake capacity (382.5 mg/g). Moreover, the waste Pd(II) loaded PIIP-3 (PIIP-3-Pd) can serve as a catalyst towards the Suzuki reaction in water, affording 94.2 % yield of the desired product. Interestingly, the PIIP-3-Pd can be reused 12 times without an appreciable decrease in catalytic activity, which is probably due to the imprinted cavity and specific recognition site of PIIP-3 can match and recapture Pd active species in a complex catalytic environment. Thus, this work demonstrates huge potentials of SIIT to enhance the selectivity of adsorption process and increase the lifetime of catalysts.

N-(2-Arylethyl)-2-methylprop-2-enamides as Versatile Reagents for Synthesis of Molecularly Imprinted Polymers

The paper describes the formation of six aromatic N-(2-arylethyl)-2-methylprop-2-enamides with various substituents in benzene ring, viz., 4-F, 4-Cl, 2,4-Cl₂, 4-Br, 4-OMe, and 3,4-(OMe)₂ from 2-arylethylamines and methacryloyl chloride in ethylene dichloride with high yields (46–94%). The structure of the compounds was confirmed by ¹H NMR, ¹³C NMR, IR, and HR-MS. Those compounds were obtained to serve as functionalized templates for the fabrication of molecularly imprinted polymers followed by the hydrolysis of an amide linkage. In an exemplary experiment, the imprinted polymer was produced from N-(2-(4-bromophenyl)ethyl)-2-methylprop-2-enamide and divinylbenzene, acting as cross-linker. The hydrolysis of 2-(4-bromophenyl)ethyl residue proceeded and the characterization of material including SEM, EDS, ¹³C CP MAS NMR, and BET on various steps of preparation was carried out. The adsorption studies proved that there was a high affinity towards the target biomolecules tyramine and L-norepinephrine, with imprinting factors equal to 2.47 and 2.50, respectively, when compared to non-imprinted polymer synthesized from methacrylic acid and divinylbenzene only.

Teamed Boronate Affinity-Functionalized Zn-MOF/PAN-Derived Molecularly Imprinted Hollow Carbon Electrospinning Nanofibers for Selective Adsorption of Shikimic Acid

Electrospun micro-/nanofibers with tailor-made specific binding sites are extremely popular due to their tremendous potential in separation applications. In this work, teamed boronate affinity (TBA)-functionalized molecularly imprinted hollow carbon electrospun nanofibers (MI-HCESNFs) derived from ZIF-8/PAN fibers with selective binding sites toward shikimic acid (SA) are presented. Each ingredient used in this strategy plays its own part: HCESNFs with excellent structural characteristics as the highly porous electrospun substrate, KH560 as the grafting material for the follow-up polyethyleneimine (PEI) modification, PEI as the dendritic platform to approach more boronic acid owing to its long chain with abundant amino groups, and TBA molecular group as the functional monomer to specifically bind with SA under the neutral condition. Benefiting from the porous structure, the high density of boronic acid, and the highly accessible imprinted sites on the surface, MI-HCESNFs show strong affinity and selectivity to the SA molecules. The adsorption capacity of MI-HCESNFs can reach 127.8 mg g-1, which is 3.1 times larger than that of the non-imprinted material. Besides, MI-HCESNFs are stable when treated with continuous ultrasonication and can be recycled eight times with a slight loss of 8.615% on the adsorption quantity. This work presents a new strategy to prepare boronate affinity adsorbents based on the electrospinning technique for the capture of SA and also proposes a path for the integration of molecularly imprinted polymers and electrospinning.

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.

Tunable synthesis of dendritic fibrous nano silica using 1-pentanol-water microemulsion at low oil to water ratio

Dendritic fibrous nanosilica (DFNS) is a suitable nano-carrier for loading pesticides with radially oriented pores and a large surface area. The microemulsion method is standard method to prepare DFNS, and 1-pentanol is taken to replace cyclohexane as an oil solvent due to its high stability and nontoxic property. The results showed that the volume ratio of 1-pentanol (oil) to water (O/W) and the molar ratio of hexadecyltrimethylammonium bromide (CTAB) to tetraethylorthosilicate (TEOS) had effected on morphology and adsorption properties of DFNS in the water-CTAB-1-pentanol-ethanol-trimethylbenzene (TMB) microemulsion system. DFNS with bicontinuous concentric lamellar morphologies can be synthesized in this microemulsion at the meager O/W volume ratio (0.025-0.045). It features a tight mesoporous structure with a thin dendritic fibrous in 0.03 to 0.04 O/W volume ratio. The particle sizes, surface areas, and porosity of DFNS were positively correlated with the addition of the silica precursor TEOS. The size of DFNS increased from 123 to about 220 nm with the CTAB/TEOS molar ratio decreasing from 0.119 to 0.050. When the molar ratio of CTAB to TEOS  = 0.119, DFNS has a smaller particle size (123 nm) with a larger surface area and abundant honeycomb mesopores; the low O/W volume ratio strategy provides theoretical support for the industrialization development of DFNS and nano-pesticides, which plays a profound role in promoting the sustainable development of pesticide reduction, efficiency and green agriculture.

Metal oxide-based macroporous ordered double affinity molecularly imprinted polymer for specific separation and enrichment of glycoprotein from food samples: a co-modification of DMSA and boronate affinity

Metal oxide-based macroporous ordered double affinity molecularly imprinted polymers (D-MIPs) were developed as solid phase extraction (SPE) adsorbents for the specific identification of ovalbumin (OVA) under physiological pH conditions prior to ultraviolet visible (UV-vis) spectrophotometric detection. Herein, macroporous alumina (MA) was used as a matrix; dimercaptosuccinic acid (DMSA) and 3-aminophenylboric acid (APBA) were employed as dual-functional monomers; APBA is a self-polymerizing monomer. The effects of synthesis conditions, SPE conditions as well as selectivity, reproducibility, and reusability were studied. The co-modification of DMSA and boronate affinity renders the adsorbent exhibiting a high adsorption capacity (114.4 mg g^-1) and short equilibrium time (30 min). The surface imprinting technology causes the adsorbent to have high selectivity towards OVA. The OVA recovery range is 91.1-99.6%. This study provides a promising method for the enrichment of OVA and other cis-diol-containing analytes in complex biological samples. A novel metal oxide-based macroporous ordered nanoparticle with a combination of DMSA and boronate affinity was successfully prepared for specific separation and enrichment of glycoprotein from complex biological samples.