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A novel molecularly imprinted ratiometric fluorescent probe was fabricated by simple sol-gel polymerization for selective and sensitive assay of C-type natriuretic peptide (CNP) in biosamples. Both the nitrobenzoxadiazole (NBD) and carbon dots (CDs) were located on the surface of silica, used as the detection signal and reference signal, respectively. For the turn-on-based probe, the fluorescence intensity of NBD could be quantitatively enhanced by CNP based on the strategy of photo-induced electron transfer (PET), while the fluorescence of CDs remained unchanged. The obtained probe exhibited excellent recognition selectivity and fast kinetics to CNP templates, and also showed good stability. The linear range of CNP determination was 5-80 pg mL -1 with a low detection limit of 2.87 pg mL -1 . Finally, the probe was successfully applied to determine CNP in human serum samples and attained high recoveries between 97.3 and 104% with precisions below 4.7%. The result indicates that the proposed method has promising potential for the assay of trace peptides in complex matrices. Schematic illustration for the formation and determination mechanism of the probe.

A novel molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization with baicalein (BAI) as the template and used as solid-phase extraction (SPE) adsorbent, aiming at the affinity isolation and selective knockout of BAI from Scutellaria baicalensis Georgi (SB). We used computational simulation to predict the optimal functional monomer, polymerization solvent and molar ratio of template to functional monomer. Characterization and performance tests revealed that MIP exhibited uniform spherical morphology, rapid binding kinetics, and higher adsorption capacity for BAI compared with nonimprinted polymer (NIP). The application of MIP in SPE coupled with high-performance liquid chromatography to extract BAI from SB showed excellent recovery (94.3%) and purity (97.0%). Not only the single BAI compound, but also the BAI-removed SB extract was obtained by one-step process. This new method is useful for isolation and knockout of key bioactive compounds from herbal medicines., (Copyright © 2015 John Wiley & Sons, Ltd.)

Penicilloic acid (PA) is a degraded byproduct of penicillin and often causes fatal allergies to humans, but its rapid detection in penicillin drugs remains a challenge due to its similarity to the mother structure of penicillin. Here, we reported a ligand-replaced molecularly imprinted monolayer strategy on a surface-enhanced Raman scattering (SERS) substrate for the specific recognition and rapid detection of Raman-inactive PA in penicillin. The bis(phenylenediamine)-Cu(2+)-PA complex was first synthesized and stabilized onto the surface of silver nanoparticle film that was fabricated by a bromide ion-added silver mirror reaction. A molecularly imprinted monolayer was formed by the further modification of alkanethiol around the stabilized complex on the Ag film substrate, and the imprinted recognition site was then created by the replacement of the complex template with Raman-active probe molecule p-aminothiophenol. When PA rebound into the imprinted site in the alkanethiol monolayer, the SERS signal of p-aminothiophenol exhibited remarkable enhancement with a detection limit of 0.10 nM. The imprinted monolayer can efficiently exclude the interference of penicillin and thus provides a selective determination of 0.10‰ (w/w) PA in penicillin, which is about 1 order of magnitude lower than the prescribed residual amount of 1.0‰. The strategy reported here is simple, rapid and inexpensive compared to the traditional chromatography-based methods.

Highly selective molecularly imprinted mesoporous silica polymer (SBA-15@MIP) for baicalein (BAI) extraction was synthesized using a surface molecular imprinting technique on the SBA-15 supporter. Computational simulation was used to predict the optimal functional monomer for the rational design of SBA-15@MIP. Meanwhile, high adsorption capacity was obtained when a suitable yield of molecularly imprinted polymers (MIPs) layer was grafted onto the surface of SBA-15. Characterization and performance tests of the obtained polymer revealed that SBA-15@MIP possessed a highly ordered mesoporous structure, reached saturated adsorption within 60 min, and exhibited higher sorption capacity to the target molecule BAI compared with non-imprinted mesoporous silica polymer (SBA-15@NIP) and SBA-15. Finally, SBA-15@MIP was successfully applied to solid-phase extraction (SPE) coupled with high-performance liquid chromatography and ultraviolet detection (HPLC-UV) for the determination of trace BAI in plasma samples. Mean recoveries of BAI through the molecularly imprinted solid-phase extraction (MISPE) sorbent, non-imprinted solid-phase extraction (NISPE) sorbent, and SBA-15 solid-phase extraction (SBA-15-SPE) sorbent were 94.4, 22.7, and 10.7 %, respectively, and the relative standard deviations were 2.9, 2.6, and 3.6 %, respectively. These results reveal that SBA-15@MIP as a SPE sorbent has good applicability to selectively separate and enrich trace BAI from complex samples.

Computational simulation and Doehlert experimental optimization were done for the rational design of a core-shell molecularly imprinted polymer (CS-MIP) for use in the highly selective separation of Tanshinone IIA (TSIIA) from the crude extracts of Salvia miltiorrhiza Bunge (SMB). The functional monomer layer of the polymer shells directed the selective occurrence of imprinting polymerization at the surface of silica through the copolymerization of vinyl end groups with functional monomers and also drove TSIIA templates into the formed polymer shells through the charge-transfer complex interactions between TSIIA and the functional monomer layer. As a result, the maximum rebinding capacity was achieved with the use of optimal grafting ratio by the Doehlert design. The CS-MIP exhibited high recognition selectivity and binding affinity to TSIIA. When the imprinted particles were used as dispersive solid phase extraction sorbents, the recovery yield of TSIIA reached 93% by a one-step extraction from the crude extracts of SMB, and the purity of TSIIA was larger than 98% by HPLC analysis. These results show the possibility of a highly selective separation and enrichment of TSIIA from the SMB using the TSIIA-imprinted core-shell molecularly imprinted polymers.

This paper reports the preparation of puerarin (PR) imprinted layer-coated silica microparticles toward selective recognition of PR and fast affinity-enrichment of the main isoflavonoid glycosides from the crude extract of Radix puerariae. Before the preparation, quantum mechanics (QM) method was applied to identify three kinds of common functional monomers capable of interaction with PR and then predicted optimal functional monomer (acrylamide, AA) and the relative molar ratio of template to functional monomer (PR/AA, 1:4). The obtained PR-imprinted silica microparticles were evaluated by transmission electron microscope (TEM) and rebinding experiments, exhibiting good morphology and high binding affinity to PR. Meanwhile, the rebinding amount of the imprinted microparticles to PR was nearly 2.1-folds that of non-imprinted microparticles. When the PR-imprinted microspheres were used as packing materials for solid-phase extraction, the recovery yields of PR, daidzin (DD) and genistin (GS) were simultaneously up to 90% by one-step extraction from the crude extract of Radix puerariae. Additionally, the PR-imprinted microparticles could be re-used for at least 5 times without losing any extraction efficiency. These results indicate that the PR-imprinted microparticles have highly selective adsorption capabilities to PR, DD and GS from the crude extract of Radix puerariae. The method of molecularly imprinted polymers (MIPs) coupled with solid-phase extraction (SPE) provides a good solution of the enrichment and separation of active extracts from complicated traditional Chinese medicine (TCM) with certain structures.

This paper reports a surface molecular self-assembly strategy for molecular imprinting on magnetic nanoparticles for selective separation and detection of estrogens in feeds. First, γ-methacryloxypropyltrimethoxysilane (MEMO) was successfully assembled at the surface magnetic nanoparticles through simple free radical polymerization, and subsequently, the copolymerization was further assembled between methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) in the presence of templates 17β-estradiol (E2). The synthesized magnetic molecularly imprinted polymers for E2 (E2-MMIPs) showed quick separation, large adsorption capacity, high selectivity and fast binding kinetics for E2. Meanwhile, a dispersive solid-phase extraction (DSPE) based on E2-MMIPs has been established for efficient separation and fast enrichment of estrogens from the feeds. The assay exhibited a linear range of 0.1-4 μM for E2 and estriol (E3) with the correlation coefficient above 0.9996 and 0.9994, respectively. Recoveries of E2 from three kinds of feeds spiked at different concentration levels ranged from 92.7% to 97.0% with RSD<4.7%, and recoveries of E3 ranged from 71.9% to 83.1% with RSD<4.9%, respectively. The method is simple and sensitive, and can be used as an alternative tool to effectively separate and enrich the trace of estrogens in agricultural products by HPLC-UV., (Copyright © 2011 Elsevier B.V. All rights reserved.)

This paper reports the preparation of metsulfuron-methyl (MSM) imprinted polymer layer-coated silica nanoparticles toward analysis of trace sulfonylurea herbicides in complicated matrices. To induce the selective occurrence of surface polymerization, the polymerizable double bonds were first grafted at the surface of silica nanoparticles by the silylation. Afterwards, the MSM templates were imprinted into the polymer-coating layer through the interaction with functional monomers. The programmed heating led to the formation of uniform MSM-imprinted polymer layer with controllable thickness, and further improved the reproducibility of rebinding capacity. After removal of templates, recognition sites of MSM were exposed in the polymer layers. As a result, the maximum rebinding capacity was achieved with the use of optimal grafting ratio. There was also evidence indicating that the MSM-imprinted polymer nanoparticles compared with nonimprinted polymer nanoparticles had a higher selectivity and affinity to four structure-like sulfonylurea herbicides. Moreover, using the imprinted particles as dispersive solid-phase extraction (DSPE) materials, the recoveries of four sulfonylurea herbicides determined by high-performance liquid chromatography (HPLC) were 80.2-99.5%, 83.8-102.4%, 77.8-93.3%, and 73.8-110.8% in the spiked soil, rice, soybean, and corn samples, respectively. These results show the possibility that the highly selective separation and enrichment of trace sulfonylurea herbicides from soil and crop samples can be achieved by the molecular imprinting modification at the surface of silica nanoparticles., (2010 Elsevier B.V. All rights reserved.)

This paper reports the preparation of high density imprinted layer-coated silica nanoparticles toward selective recognition and fast enrichment of chlorpyrifos (CP) from complicated matrices. The molecularly imprinted polymers (MIPs) were successfully coated at the surface of modified silica through using the chemical immovable vinyl groups at the nanoparticles' surface, followed by the graft copolymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) in the presence of templates CP. It has been demonstrated that the space of end vinyl groups at the surface of silica can be controlled by changing the condition of chemical modification, regulating the thickness of imprinted shells and the density of efficient imprinted sites. After removal of templates by solvent extraction, the recognition sites of CP were created in the polymer coating layer. The CP-imprinted nanoparticles exhibited high recognition selectivity and binding affinity to CP analyte. When the CP-imprinted nanoparticles were used as dispersive solid-phase extraction (dSPE) materials, the high recovery yields of 76.1-93.5% from various spiked samples with only 1microg/mL analyte were achieved by one-step extraction. These results reported herein provide the possibility for the separation and enrichment of CP from complicated matrices by the molecular imprinting modification at the surface of common silica nanoparticles.

This paper reports the molecularly imprinted layer-coated silica nanoparticles toward highly selective separation of active diosgenin (DG) from the crude extracts of Dioscorea nipponica Makino (DNM). It has been demonstrated that DG templates were efficiently imprinted into the silica layer by the use of thermally cleavable urethane bonds between DG and 3-isocyanatopropyltriethoxysilane (IPTS), which was synchronously coated onto the surface of silica mother nanoparticles through a seed-directing surface condensation reaction between DG-IPTS and tetraethoxysilicane (TEOS). After removal of templates by simple thermal cleavage reaction, a high density of recognition sites of DG were created in the silica-coating layer. Afterwards, the DG-imprinted silica nanoparticles were evaluated by rebinding experiments and showed a higher selectivity and affinity to DG than commercial silica. When the imprinted particles were used as solid-phase extraction (SPE) sorbents, the recovery yield of DG was up to 90% by one-step extraction from the hydrolysate of DNM, and the purity of DG was larger than 98% by HPLC analysis. These results reported herein provide the possibility for the highly selective separation and purification of active DG from DNM by the molecular imprinting modification at the surface of common silica adsorbents.

A molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization with tanshinone IIA as the template and used as an adsorbent for solid-phase extraction (SPE). A simulation was employed to predict the most suitable polymerization solvent, the functional monomer, and the molar ratio of template to monomer. The obtained imprinted materials were evaluated by transmission electron microscopy, scanning electron microscopy, rebinding experiments, exhibiting good morphology, and high binding to tanshinone IIA. Compared with nonimprinted polymers, the imprinted material exhibited a higher sorption capacity, up to 34.09 µmol g−1, and better selectivity for tanshinone IIA and its structural analogs. The imprinted polymer was successfully employed for SPE coupled with high-performance liquid chromatography for the determination of tanshinone IIA, cryptotanshinone, and tanshinone I in fortified serum. The mean recoveries were between 91.5% and 95.1% with relative standard deviations less than 4.9%. These results demonstrate a highly selective isolation and determination of tanshinones. [ABSTRACT FROM PUBLISHER]

Molecularly imprinted hydrogel ( MIH) as drug delivery system has been studied. It still remains a challenge to construct the stimuli-responsive MIH. Here, we report a coordinate bond strategy for imprinting doxorubicin ( Dox) in hydrogel capable of p H-responsive and sustained drug delivery. The imprinting condition such as template-monomer interactions induced by metal ion was carefully investigated by spectroscopic methods. The obtained Dox- MIH was evaluated by absorption and in vitro release experiments. It has been demonstrated that the cupric ion mediated interaction between Dox and 4-vinyl pyridine via coordination and the optimal coordinate ratio of Dox/ Cu2+ was 2:1. The rebinding amount of MIH to Dox was 2.7-fold that of nonimprinted hydrogel and the Dox-loaded MIH showed a p H-responsive release property. Not more than 10% of loaded drug was released from Dox- MIH at p H 7.2 during a time course of 7 days. However, near to 60% of loaded drug was sustainedly released at p H 5.0 during the same period. These results indicated that Dox- MIH with p H-responsive behavior possessed great promising as sustained-release delivery system of anticancer drug. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:643-651, 2014 [ABSTRACT FROM AUTHOR]

Abstract: In this paper, highly selective core–shell molecularly imprinted polymers of 17β-estradiol on the surface of silica nanoparticles (SiO2@E2-MIPs) were prepared. The SiO2@E2-MIPs were characterized by Fourier transform infrared spectrometer (FT-IR), transmission electron microscope (TEM), dynamic adsorption and static adsorption tests. The sorption capacity of the SiO2@E2-MIPs were nearly 5 times that of the non-imprinted polymers (NIPs), and it only took 25min to achieve the sorption equilibrium. It indicated that the SiO2@E2-MIPs exhibited a high selectivity, large adsorption capacity and fast kinetics. When the SiO2@E2-MIPs were used as dispersive solid-phase extraction (dSPE) absorbents to selectively enrich and determine estrogens in duck feed, the average recoveries of E2 and estriol (E3) were higher than 96.74% and 72.07%, respectively, and the relative standard deviations (RSD) of E2 and E3 were less than 1.61% and 3.28%, respectively. The study provides an effective method for the separation and enrichment of estrogens in the complex matrix samples by the SiO2@E2-MIPs. [ABSTRACT FROM AUTHOR]