Molecular imprinting micropolymerbeads having cooperative effect of both surfactant and inosine template

Molecular imprinted polymer (MIP) microbeads were prepared by emulsion copolymerization of divinylbenzene (DVB) and methacrylic acid (MAA) in the presence of inosine (INO) template and laurylbenzenesulfonic acid (LBSA) as surfactant. The polymerization was carried out at 55°C under ultrasound exposure. The resulting copolymer microbeads, having 0.1–0.4 μm diameter, were observed to have a binding behavior of INO and surfactant to the polymer which was strongly dependent of the bulk pH; for example, at pH 3, 6, and 10 values of binding for INO to the imprinted copolymer were 3.7 μmol/g, 2.1 μmol/g, and 0 μmol/g, respectively. It was found that LBSA surfactant bound to the MIP microbeads similarly depending on pHs. At pH 3, 6, and 10, the LBSA values of binding were 23 μmol/g, 1.3 μmol/g, and 4.8 μmol/g. It was also noted that the surfactant binding was enhanced in the presence of the INO template. This demonstrated that a cooperative binding with the surfactant was cooperatively occurred in the presence of INO. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Molecularly imprinted fluorescent polymers as chemosensors for the detection of mercury ions in aqueous media

This article describes the investigation of molecularly imprinted fluorescent polymer membranes as sensing receptors for Hg²⁺ detection by an optical approach. The polymers were synthesized with 4‐vinylpyridine as a functional monomer and Hg²⁺ as a template; 9‐vinylcarbazole was used as both a complex‐forming agent and a fluorescence probe. The free‐radical polymerization was performed within a semicylindrical Teflon mold and was initiated by 2,2′‐azobisisobutyronitrile at 60°C. The template, ion‐bonded to pyridine and carbazole groups in the polymer membrane, was removed by acid treatment. Attenuated total reflectance–Fourier transform infrared (FTIR) spectroscopic measurements and scanning electron microscopy images were used to compare the chemistry and surface morphology, respectively, of both imprinted and nonimprinted polymer materials. The final polymer membranes with semicylindrical shapes were used directly to determine Hg²⁺ concentration in aqueous solutions by the monitoring of the fluorescence intensity of the carbazole groups quenched upon complex formation with metal ions. The values of the Hg²⁺ binding ratio for the imprinted and nonimprinted polymeric membranes were compared, and the results indicate the superior sensitivity and selectivity of the imprinted membranes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rationally Designing Molecularly Imprinted Polymer Toward a High Specific Recognition by Using a Stoichiometric Self-Assembly

This article presents an original work aimed at rationally designing a molecularly imprinted polymer capable of a high specific recognition. Assembling with Bisphenol A as template and acrylamide as functional monomer, the imprinted polymer was prepared. The results indicate that the use of stoichiometric self-assembly plays an obvious role on significantly increasing the specificity of prepared material, so as to better discriminate the template from its analogue. A higher or lower extent of molecular self-assembly would result in a dramatic decrease in this specificity. Related information indicates that this, logically, can be a result of the increasing match between binding sites and the template, which makes the polymer capable of specifically recognizing the imprint species.     

Dummy template molecularly imprinted polymer for omeprazole and the study of its drug binding and release properties

In this study, we tried to prepare an omeprazole (OMP)‐imprinted polymer and study its binding and release properties in an aqueous media. Because of the instability of OMP under polymerization conditions and the inability of the molecule to form effective interactions with monomers, pantoprazole (PANTO) was used as a dummy template for the imprinting process. Different monomers and solvents were evaluated in polymerization. The optimized imprinted polymer was prepared in chloroform as a porogen. Also, 4‐vinylpyridine and ethylene glycol dimethacrylate were selected as a functional monomer and a crosslinker, respectively. The optimized imprinted polymer was evaluated in a binding study. The binding and release properties of the polymer were then investigated at different pHs. Our data indicated a higher affinity of the imprinted polymer to PANTO and OMP than that of nonimprinted polymer (NIP). The maximum percentage of OMP released from the imprinted polymer was 36–41%, whereas that for the NIP was 74–85%. These data were related to the 38–43 and 29–34 μg of OMP released from the imprinted polymer and NIP, respectively. Also, the protective effect of the imprinted polymer for OMP at pH 2 was greater than that of the nonimprinted one. This study revealed that the dummy template molecular imprinting was an effective method for preparing selective imprinted cavities in a polymeric matrix, especially for the molecules that were unstable during polymerization or unable to establish effective bonds with the monomers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4165–4170, 2013     

Precipitation polymerization of molecularly imprinted polymers for recognition of melamine molecule

Molecular imprinted polymer microspheres (MIPs) were prepared by precipitation polymerization using melamine as template molecule, methacrylic acid (MAA) as functional monomer, trimethylol‐propane trimethacrylate (TRIM) as crosslinking agent, acetonitrile as solvent and dispersion medium. Release of the template was performed by continuous extraction with methanol containing 10% acetic acid. The microspheres were observed by scanning electron microscopy (SEM). The perfect microspheres were produced when the addition of crosslinker was 7.48 mmol. The binding capacity of MIPs was examined, Q_max = 68.36 μmol g^?1, and the dissociation constant at binding site of MIPs, K_d = 0.761, was estimated. Compared with the performance of conventional imprinted polymer, the imprinted microspheres showed high selectivity in special binding to template molecule. The imprinted microspheres could be used as the stationary phase in HPLC or SPE for selective extraction of melamine in daily products. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of molecularly imprinted microspheres for recognition of trans‐aconitic acid

In the presence of a template molecule, trans‐aconitic acid and, using acetonitrile as solvent and dispersing medium, monodispersed microspheres with a diameter of 600–700 nm bearing molecularly imprinted binding sites were prepared by precipitation polymerization. It was found that the concentrations of template, monomer, and crosslinking agent as well as the chemical structure of the template greatly affect the polymer configuration. Microspheres are produced only when the concentration of the template molecule and the functional monomer are finely tuned. Comparison with the performance of a conventional imprinted polymer monolith showed that the imprinted microsphere had obvious advantages in specific binding to template molecule. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 542–547, 2004     

Crosslinking diversity on network morphology,template binding,and template transport of molecularly imprinted polymers prepared via living radical polymerization

The objective of this work is to study the effects of altering the chain building blocks and the reaction on template binding and transport parameters of imprinted polymer gels. The characterization of imprinted poly(diethylaminoethylmethacrylate‐co‐hydroxyethylmethacrylate‐co‐polyethyleneglycol(n)dimethacrylate) polymer gels prepared via free (FRP) or living (LRP) radical polymerization with varying crosslinking monomer lengths (number of ethylene glycol repeat units of 1, ～4.5, ～9) and concentrations (1, 5, 10, 50%) is presented. All imprinted networks prepared via LRP exhibited significantly higher template binding affinities and capacities as well as significantly lower template diffusion coefficients compared to those prepared via FRP. Synthesizing imprinted polymers via LRP results in much smaller and relatively constant dispersities of polymer chains compared to imprinted polymers prepared via FRP. Therefore, LRP has a profound structural effect on the imprinted polymer network leading to increased homogeneity in the mesh structure which enhances the molecular imprinting effect. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3588–3599, 2013     

3,3′‐Diindolylmethane imprinted polymers: synthesis,characterization and analytical procedure for template isolation from biological matrix

A novel sorbent for the separation of 3,3′‐diindolylmethane (DIM) has been developed. DIM was used as a template molecule to prepare twelve imprinted polymers from seven different functional monomers in six various porogens in the presence of ethylene glycol dimethacrylate as a crosslinker. The binding capacity showed that the highest binding specificity was achieved when allylamine as the monomer and carbon tetrachloride as the porogen were used to form bulk polymers. Binding capacities were 130.4 ± 2.8 µg g^?1 for imprinted MIP7_a polymer versus 49.03 ± 0.44 µg g^?1 for non‐imprinted NIP7_a polymer. An imprinting factor of 3.12 reflected the high specificity of MIP7_a. A solid‐phase extraction protocol was fully optimized. Two methanol–water systems were selected as the most effective for loading and washing steps, while acetonitrile was chosen as the most efficient eluent suitable for recovery of 91.7 ± 3.8% of DIM. Optimal concentration of DIM and volume of loaded sample were also examined. A loaded volume of 2.5 mL was the most appropriate for 0.625 and 1.25 mg L^?1. The use of MIP7_a for the separations of DIM from spiked bovine serum albumin was evaluated, showing a total recovery of 87.7 ± 3.5%. The commercial sorbent C18 was not suitable for such an application. © 2013 Society of Chemical Industry     

Characterization and quality assessment of binding properties of the monocrotophos molecularly imprinted microspheres prepared by precipitation polymerization in toluene

To obtain the desired specific adsorbents for monocrotophos (MCP) to enrichment, separation, and analysis of trace pesticides residue in soils and foods, molecularly imprinted polymer microspheres were prepared by precipitation polymerization using MCP, methacylic acid (MAA), ethylene glycol dimethacrylate, azobisisobutyronitrile, and toluene as template, functional monomer, crosslinker, initiator, and porogen, respectively. Computer simulation was employed to demonstrate the mechanism of the interaction between MCP and MAA in toluene. It was found that one MCP was entrapped by two MAAs in toluene through hydrogen bond. The binding properties of MCP in toluene for imprinted microspheres were evaluated by equilibrium rebinding experiments. Scatchard plot analysis revealed that there were two classes of binding sites populated in the imprinted polymer microspheres with dissociation constants of 0.0019 and 0.12 mmol/L, respectively. The specificity of the imprinted microspheres was investigated by binding analysis using MCP and structurally related organophosphorous pesticides. The results indicated that the obtained imprinted microspheres showed a good selectivity for MCP. POLYM. ENG. SCI., 47:1302–1308, 2007. © 2007 Society of Plastics Engineers     

Rationally Designing Molecularly Imprinted Polymers Toward a Highly Specific Recognition by Using a Stoichiometric Molecular Self-assembly

This article presents work on designing a highly specific imprinted polymer for molecular recognition. Based on a stoichiometric molecular self-assembly, the imprinted material was prepared using adenine as the template and methacrylic acid as the functional monomer. The result indicates that the stoichiometric molecular self-assembly plays a positive role in increasing the specificity of prepared materials, so as to adsorb more for the template but less for its analogue. Furthermore, the results indicate that higher or lower extents of self-assembly cause a dramatic decrease in the specificity. Related information indicates that these changes can be an increase in the match of template and the binding framework, which thereby makes the polymer capable of specifically recognizing the imprint species.     

Molecularly imprinted stimuli-responsive hydrogels for protein recognition

Temperature-responsive poly(N-isopropylacrylamide)-based (PNIPAAm) hydrogels were imprinted with lysozyme via in situ photo-initiated crosslinking polymerization. The three-dimensional network of the hydrogels was tailored by tuning the ionic content through methacrylic acid as template-binding comonomer while keeping the ratio between crosslinker (N,N′-methylenebisacrylamide) and N-isopropylacrylamide fixed. Moderate salt concentrations (0.3 m NaCl) were found to be suited for template removal without phase separation of the hydrogel. Swelling and protein (lysozyme and cytochrome C) binding were investigated for imprinted and nonimprinted gels at temperatures below and above the lower critical solution temperature of PNIPAAm (32 °C). Imprinted gels showed a much higher affinity, selectivity and binding capacity for lysozyme compared to the nonimprinted reference materials. Protein binding capacity was strongly reduced above 32 °C, to zero for nonimprinted and to small values for imprinted gels. Most important, specific lysozyme binding to the imprinted gels caused a large concentration dependent deswelling. This effect was much smaller for nonimprinted gels, and the response could be modulated by the content of the comonomer methacrylic acid. Overall, this approach is interesting for the development of novel sensors or materials for controlled release applications.     

Preparation of molecularly imprinted polymers in supercritical carbon dioxide

Molecularly imprinted polymer nanoparticles were prepared in supercritical carbon dioxide using a noncovalent imprinting approach. In the present work, propranolol was used as a model template, methacrylic acid as a functional monomer, and divinylbenzene as a crosslinker. Under a high dilution condition, the heterogeneous polymerization resulted in discrete crosslinked polymer nanoparticles. Compared with the nonimprinted polymers, the imprinted nanoparticles displayed much higher propranolol uptake in a low polarity organic solvent. The use of a single enantiomer (S)‐propranolol as the template clearly demonstrated that the imprinted binding sites are chiral‐selective, with a cross‐reactivity towards (R)‐propranolol of less than 5%. The overall binding performance of the imprinted nanoparticles was comparable to imprinted polymers prepared in conventional organic solvents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2863–2867, 2006     

Selective removal of Cu(II) from contaminated water using molecularly imprinted polymer

A synthetic molecularly imprinted polymer (MIP) was prepared by noncovalent imprinting technique for the selective removal of Cu²⁺ from aqueous solutions. In the preparation of imprinted polymer, Cu²⁺ was used as the template, oleic acid as the functional monomer and divinylbenzene as the cross-linker. The surface morphologies and characteristics of the MIP were determined by BET, scanning electron microscopy (SEM), FTIR and energy dispersive X-ray spectrometer (EDS). The proper adsorption and selective recognition ability of the MIP were studied by an equilibrium-adsorption method. In general, the removal efficiency of Cu²⁺ increased rapidly with pH from 2 to 7 and decreased at a pH 8. The removal efficiency of Cu²⁺ increased with temperature from 25°C to 50°C. Competitive adsorption studies showed that the coexisting cations have no obvious influence on the adsorption of Cu²⁺. In addition, the variation in the adsorption ability of the MIP that was repeatedly used was investigated, and it showed excellent reproducibility.     

Noncovalent imprinted microspheres: Preparation,evaluation and selectivity of DBU template

1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) imprinted polymer was prepared as microspheres by precipitation polymerization method to obtain molecular recognition systems based on the noncovalent interactions between DBU template, methacrylic acid (MAA), and ethylene .glycol dimethacrylate (EDMA) in acetonitrile. ¹H NMR analysis of DBU/MAA mixture has been performed and hydrogen bonding interactions have been established. Microspheres have been characterized by FTIR studies with evidence of DBU linkage in polymer particles and by Scanning Electron Microscopy (SEM) to study their morphological properties. How pH values affect the binding capacity of imprinted polymer during the binding stage has been also discussed and results suggest that imprinted poly‐(MAA‐EDMA) behavior is related to the influence of DBU basicity during rebinding processes and the optimum pH value for binding has been found around neutral range. Binding ability of the imprinted polymer towards different concentration of DBU buffered solutions has been evaluated and compared with binding ability of the non‐imprinted polymer. A more sensitive response to the template in the imprinted system suggests that a reasonable number of specific binding sites is formed. Finally, differential selectivity towards other less strong than DBU nitrogen bases, such as pyridine, imidazole, and 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN) has been also discussed. Our results indicate that both specific sites and basic properties are involved in the rebinding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of novel three-dimensionally ordered macroporous molecularly imprinted microspheres and its recognition for proteins

A novel protein molecularly imprinted microsphere with three-dimensionally ordered macroporous (3DOM) structure has been successfully prepared with a combination of colloidal crystal template method and molecular imprinting technique by using bovine serum albumin as template, acrylamide as functional monomer, and N,N′-methylenebisacrylamide as crosslinker, respectively. SEM shows that the polymeric microspheres have a highly ordered three-dimensional interconnected macroporous structure with typical face-centered cubic lattice. The isothermal and kinetic adsorption behaviors of the polymer were investigated. Compared with the traditional bulk polymer, the 3DOM imprinted microspheres show higher binding rate constant, adsorption capability and specificity to template molecules.     

Selective removal of Cu(Ⅱ) from contaminated water using molecularly imprinted polymer

A synthetic molecularly imprinted polymer (MIP) was prepared by noncovalent imprinting technique for the selective removal of Cu²⁺ from aqueous solutions. In the preparation of imprinted polymer, Cu²⁺ was used as the template, oleic acid as the functional monomer and divinylbenzene as the cross-linker. The surface morphologies and characteristics of the MIP were determined by BET, scanning electron microscopy (SEM), FTIR and energy dispersive X-ray spectrometer (EDS). The proper adsorption and selective recognition ability of the MIP were studied by an equilibrium-adsorption method. In general, the removal efficiency of Cu²⁺ increased rapidly with pH from 2 to 7 and decreased at a pH 8. The removal efficiency of Cu²⁺ increased with temperature from 25°C to 50°C. Competitive adsorption studies showed that the coexisting cations have no obvious influence on the adsorption of Cu²⁺. In addition, the variation in the adsorption ability of the MIP that was repeatedly used was investigated, and it showed excellent reproducibility.     

Computer simulation and synthesis of stimuli‐responsive polymer by sol‐gel for selective recognition of (4‐chloro‐2‐methylphenoxy)acetic acid

A novel photoresponsive functional monomer bearing a siloxane polymerizable group and azobenzene moieties was synthesized, and then photoresponsive molecularly imprinted sol‐gel polymers were successfully fabricated from the synthesized functional monomer, using (4‐chloro‐2‐methylphenoxy)acetic acid (MCPA) as a molecular template. The photoisomerization properties of the functional monomer are retained after incorporation into the rigid three‐dimensional crosslinked polymer matrix. The template is then removed from the resulting polymer to generate pores, which are complementary to the template in shape, size and functionality. The substrate affinity of the molecularly imprinted polymer (MIP) receptor sites is photoswitchable. This can be attributed to the photoisomerization of azobenzene chromophores within the MIP receptors, resulting in alteration of their geometry and the spatial arrangement of their binding functionalities. The binding affinity of the imprinted recognition sites was switchable by alternate irradiation with UV and visible light, suggesting that azobenzene groups located inside the binding sites could be used as chemical sensors and the trans–cis isomerization could regulate the affinity for MCPA. To study the hydrogen bond interactions between template molecules and functional monomer, computational molecular modeling was employed. The data indicate that the design of the MIP is rational. Copyright © 2012 Society of Chemical Industry     

Molecularly imprinted polymers via living radical polymerization: Relating increased structural homogeneity to improved template binding parameters

This work examined imprinted polymer networks prepared via controlled/living radical polymerization (LRP) and conventional radical polymerization (CRP) on chain growth, network formation, and efficiency of producing molecularly imprinted, macromolecular memory sites for the template molecule, diclofenac sodium. LRP extended the reaction-controlled regime of the polymerization reaction and formed more homogeneous polymer chains and networks with smaller mesh sizes. In addition, LRP negated the effect of the template on polymer chain growth resulting in polymers with a more consistent PDI independent of template concentration in the pre-polymerization solution. Improved network homogeneity within imprinted poly(HEMA-co-DEAEM-co-PEG200DMA) networks prepared via LRP resulted in a 38% increase in template binding affinity and 43% increase in the template binding over imprinted networks prepared via CRP and a 97% increase in affinity and 130% increase in capacity over non-imprinted networks prepared by LRP. By varying certain parameters, it was possible to create imprinted networks with even higher template binding affinities (155% over non-imprinted) and capacities (261% over non-imprinted). This work is the first to conclusively demonstrate that the observed improvement in binding parameters in weakly crosslinked, imprinted polymer networks could be explained by the more uniform molecular weight evolution associated with the LRP mechanism and the longer lifetime of an active polymer chain relative to the total polymerization time, which allowed for the formation of a more homogenous imprinted polymer network.     

Influence of template/functional monomer/cross‐linking monomer ratio on particle size and binding properties of molecularly imprinted nanoparticles

A series of molecularly imprinted polymer nanoparticles have been synthesized employing various template/functional monomer/crosslinking monomer ratio and characterized in detail to elucidate the correlation between the synthetic conditions used and the properties (e.g., particle size and template binding properties) of the obtained nanoparticles. In brief, the presence of propranolol (template) in the polymerization mixture turned out to be a critical factor on determination of the size as well as the binding properties of the imprinted nanoparticles. The functional monomer/crosslinking monomer ratio significantly affects the binding capability of the imprinted nanoparticles, but its influence on the size of the nanoparticles was found to be rather limited. The results obtained provide valuable clues for designing molecularly imprinted nanoparticle preparation in future studies, where fine tuning of particle size and binding properties are required to fit practical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enhancing molecularly imprinted polymer binding properties via controlled/living radical polymerization and reaction analysis

Fractional double bond conversion and associated template binding parameters of molecularly imprinted polymers were explored in this study in relation to initiator type and concentration, crosslinking monomer length, temperature, and solvent concentration. Controlled/living polymerization techniques were used to synthesize recognitive poly(methacrylic acid-co-ethylene glycol dimethacrylate) (poly(MAA-co-EGDMA)) networks which resulted in a 63% increase in the number of binding sites at approximately equivalent average binding affinity while retaining selectivity of the target molecule, ethyladenine-9-acetate. This is hypothesized to be attributed to a decrease in kinetic chain length and/or a more narrow dispersity of kinetic chains which leads to increased structural homogeneity and increased stability and integrity of binding sites. Reaction analysis of a typical poly(MAA-co-EGDMA) molecularly imprinted network measured via differential scanning calorimetry revealed low double bond conversion (35 ± 2.3% at 0 °C to 54 ± 1.9% at 50 °C) which is due to severely constrained network formation; therefore, the final composition of imprinted polymers does not represent the initial formulation when using significant amounts of short bifunctional crosslinking monomer. Optimization of conventional photoinitiator was shown to lead to a small improvement in template selectivity at equivalent affinity and capacity. However, the use of controlled/living polymerization techniques within the field of imprinted polymers has the greatest potential to improve the structural homogeneity and drastically enhance the binding parameters. Polymerization reaction analysis and the use of controlled polymerization strategies will lead to a greater understanding of the imprinting mechanism, optimization of binding parameters, and an increase in the application potential of imprinted networks.