Imprinted Polymer Monolith Research Articles

Via zinc(II) protoporphyrin to the synthesis of poly(ZnPP-MAA-EGDMA) for the imprinting and selective binding of bilirubin

Poly(zinc protoporphyrin-methacrylic acid-ethyl glycol dimethylacrylate) (poly(ZnPP-MAA-EGDMA)) imprinted with α-bilirubin can cause spectroscopic change in wavelength and absorption intensity due to the metal–ion coordination between ZnPP and bilirubin. The fluorescent imprinted polymer was able to selectively bind α-bilirubin. The corresponding imprinted polymer monolith was synthesized by using the functional monomer, methacrylic acid and the fluorescent monomer, zinc(II) protoporphyrin. Although the imprinted polymers (MIPs) using methacrylic acid, protoporphyrin, or zinc(II) protoporphyrin alone as the only functional monomer could bind bilirubin, the imprinting effects were all comparably inferior to the imprinted poly(ZnPP-MAA-EGDMA). Therefore, it revealed that via the combined utilization of ZnPP and MAA for the fluorescent and functional effect, the MIPs thus prepared were then able to create the highly selective cavities. The optimal condition for the heated polymerization of the imprinted poly(ZnPP-MAA-EGDMA) was found to be 60 °C for 6 h. The imprinting factor of 3.069 could be achieved from the fluorescent imprinted polymer by comparing the binding results obtained from the MIP and the NIP (non-imprinted polymer). The imprinting factor obtained from bilirubin/biliverdin mixture solution was reduced to 2.111 because of the presence of biliverdin. The selectivity toward bilirubin of 2.269 from the bilirubin/biliverdin mixture was obtained. Therefore, to utilize ZnPP for the preparation of the imprinted materials confirmed the selective binding and detection of bilirubin via the fluorescent approach.

Addition of N-carbobenzyloxy- l-tryptophan as a co-template molecule to molecularly imprinted polymer monoliths for (+)-nilvadipine

Molecularly imprinted polymer (MIP) monoliths for (+)-nilvadipine have been prepared using 4-vinylpyridine as a functional monomer and toluene/1-dodecanol as a porogen without or with addition of N-carbobenzyloxy- l-tryptophan (Cbz- l-Trp) as a co-template molecule. The MIP monoliths prepared with (+)-nilvadipine as a sole template molecule had no macro through-pores, while those could be formed by addition of Cbz- l-Trp as the co-template molecule. Furthermore, on the former nilvadipine enantiomers could not be separated, but on the latter they could. The presence of Cbz- l-Trp affected the polymerization process and resulted in forming macro through-pores of the MIP monoliths for (+)-nilvadipine and attaining separation of nilvadipine enantiomers. These results suggest that co-addition of Cbz- l-Trp could be effective for preparing MIP monoliths for (+)-nilvadipine, whose preparation is difficult.

Adsorption Isotherms and Sites Distribution of Caffeic Acid ? Imprinted Polymer Monolith from Frontal Analysis

The frontal analysis technique was successfully applied to the determination of the adsorption isotherms of the imprinted polymer monolith prepared by a in-situ synthesis method using caffeic acid as the template, and methacrylic acid, ethyl glycol dimethacrylate and2,2’-azobisisobutyronitrile as the functional monomer, cross-linker and initiator, respectively, with tetrahydrofuran-iso-octane (2:1, ν/ν) as a porogen. Adsorption isotherms of the monolith were measured at 25, 45 and 60°C using tetrahydrofuran containing 1, 3 and 5% acetic acid as mobile phase, respectively. The adsorption capacity of the monolith for the template was found to be much stronger than the other structurally related compounds. The column temperature significantly affected the adsorption capacity of the monolith. The acetic acid in the mobile phase showed some influence on the adsorption of the template on the stationary phase. The adsorption behavior of the template on the monolith is best described by the Freundlich isotherm. From the best coefficients of the Bi-Langmuir fit, the binding constant and saturation capacities of the molecularly imprinted polymer monolith were obtained.

Chiral separation of binaphthol enantiomers on molecularly imprinted polymer monolith by capillary electrochromatography.

A novel enantioseparational monolithic stationary phase for binaphthol based on a molecular imprinting method was introduced and evaluated in capillary electrochromatography (CEC). The monolithic stationary was prepared by the in situ copolymerization of methacrylic acid and ethylene glycol dimethacrylate in a porogenic solvent (toluene or toluene-isooctane) in the presence of an imprinting molecule, (R)-1,1'-bi-2,2'-naphthol. Such stationary phases could separate the enantiomers of binaphthol. The influence of several parameters on the column permeability was investigated. These parameters included the polymerization time, the molar ratio of the functional monomer to the imprinting molecule and the content of porogen. The influence of the polymerization condition and the electrochromatographic parameters on the enantiomer separation was also studied. Initial studies showed that a higher molecular ratio of the imprinted molecule to the functional monomer, a higher content of porogen, a higher content of acetonitrile, a higher pH, as well as the addition of Tween 20, gave a higher enantiomer selectivity.

Synthesis of molecularly imprinted microspheres for recognition oftrans-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

Molecularly Imprinted Anisotropic Polymer Monoliths

Anisotropic materials with selective binding properties may have potential as active components in optical sensors. A novel route for the synthesis of such materials is described and the validity of the concept has been demonstrated. To this end free radical polymerization of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol trimethacrylate (TRIM) in the presence of a template molecule [4,4‘-bis(dimethylamino)benzophenone (Michler's ketone)] and binding sites [2-(acrylamido)-2-methylpropanesulfonic acid (AMPSA) or methacrylic acid (MAA)] led to molecularly imprinted polymer monoliths. Upon irradiation using linearly polarized light, the template molecules reacted with the polymer networks to form transparent and anisotropic polymer monoliths. The origin of the dichroism is discussed and is believed to result from the incorporation of reactive template molecular species (radicals) into the polymer network. That the polymers are indeed imprinted was confirmed using competitive binding studies. The polymers are size...