Imprinted Polymer Particles Research Articles

Microfluidic Approach for the Synthesis of Micro- or Nanosized Molecularly Imprinted Polymer Particles

Molecularly imprinted polymers (MIPs) have specific molecular recognition sites for chemical detection.High affinity receptors can increase the sensitivity of sensors/devices. The synthesis of micro- or nanosized MIP's particles is desirable to improve the sensitivity since MIP's particle sizes are inversely proportional to the affinity between receptors and template molecules. To synthesize nano- or microsized MIPs particles, we demonstrate here a novel microfluidic approach, which presents continuous and uniform MIP's particle generation.

Design of two-dimensional biomimetic uranyl optrode and its application to the analysis of natural waters

A two-dimensional biomimetic optrode for the detection and quantification of uranium in natural waters was fabricated. The sensing element was designed by the inclusion of uranyl ion imprinted polymer particles into polymethyl methacrylate followed by casting a thin film on a glass slide without any plasticizer. The ion imprinted polymer material was prepared via covalent immobilization of the newly synthesised ligand 4-vinyl phenylazo-2-naphthol by thermal polymerization. Operational parameters such as pH, response time and the amount of sensing material were optimized. The response characteristics of the imprinted and the corresponding non-imprinted polymer inclusion optrodes of uranium were compared under optimum conditions. The imprinted polymer inclusion optrode responds linearly to uranium in the concentration range 0–1.0 μg mL −1 with a detection limit of 0.18 μg mL −1, which is much better than the solution studies using 4-vinyl phenylazo-2-naphthol (1.5 μg mL −1). Triplicate determinations of 100 μg of uranium(VI) present in 250 mL of solution gave a mean absorbance of 0.018 with a relative standard deviation of 8.33%. The superior sensitivity of imprinted polymer inclusion optrode is exemplified by lower detection limits and broader dynamic range over non-imprinted polymer inclusion optrode. The developed imprinted polymer inclusion optrode was found to give stable and precise response for 3 months and can be used without any loss in sensitivity. The applicability for analysing ground, lake and tap-water samples collected in the vicinity of uranium deposits was successfully demonstrated.

A stoichiometric imprinted chelating resin for selective recognition of copper(II) ions in aqueous media

This work reports the preparation of a new copper(II) ion-imprinted polymer (IIP) material, using 5,6;14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadecane-5,14-diene (DBDA15C4) and 2-vinylpyridine (VP) as a non-vinylated chelating agent and a functional vinyl monomer, respectively. The Cu 2+ ion can form stable complexes with DBDA15C4 and VP. The stoichiometries of Cu 2+–DBDA15C4 and ternary Cu 2+–DBDA15C4-VP complexes were elucidated using conductometric and spectrophotometric methods, and found to be Cu 2+(DBDA15C4), Cu 2+(DBDA15C4) 2 and Cu 2+(DBDA15C4)(VP) 2. The results obtained from solution studies were also supported by ab initio theoretical calculations. The resulting ternary complex Cu 2+(DBDA15C4)(VP) 2 was copolymerized with ethyleneglycoldimethacrylate, as a cross-linking monomer, via bulk polymerization method. The imprinted copper ion was removed from the polymeric matrix by 0.1 M HNO 3. The Cu 2+-imprinted polymer particles were characterized by IR spectroscopy and elemental analysis. Optimum pH range for rebinding of Cu 2+ on the IIP and equilibrium binding time were 7.0–7.5 and 45 min, respectively. Sorbent capacity and enrichment factor for Cu 2+ were obtained as 75.3 ± 1.9 μmol g −1 and 100, respectively. In selectivity study, it was found that imprinting results in increased affinity of the material toward Cu 2+ ion over other competitor metal ions with the same charge and close ionic radius. The prepared IIPs were repeatedly used and regenerated for five times without a significant decrease in polymer binding affinities.

Swellable molecularly imprinted poly N-( N-propyl)acrylamide particles for detection of emerging organic contaminants using surface plasmon resonance spectroscopy

Lightly crosslinked theophylline imprinted poly N-( N-propyl)acrylamide particles (ca. 300 nm in diameter) that are designed to swell and shrink as a function of analyte concentration in aqueous media were spin coated onto a gold surface. The nanospheres responded selectively to the targeted analyte due to molecular imprinting. Chemical sensing was based on changes in the refractive index of the imprinted particles that accompanied swelling due to binding of the targeted analyte, which was detected using surface plasmon resonance (SPR) spectroscopy. Because swelling leads to an increase in the percentage of water in the polymer, the refractive index of the polymer nanospheres decreased as the particles swelled. In the presence of aqueous theophylline at concentrations as low as 10 −6 M, particle swelling is both pronounced and readily detectable. The full scale response of the imprinted particles to template occurs in less than 10 min. Swelling is also reversible and independent of the ionic strength of the solution in contact with the polymer. Replicate precision is less than 10 −4 RI units. By comparison, there is no response to caffeine which is similar in structure to theophylline at concentrations as high as 1 × 10 −2 M. Changes in the refractive index of the imprinted polymer particles, as low as 10 −4 RI units could be readily detected. A unique aspect of the prepared particles is the use of light crosslinking rather than heavy crosslinking. This is a significant development as it indicates that heavy crosslinking is not entirely necessary for selectivity in molecular imprinting with polyacrylamides.

Molecularly Imprinted Polymer Particles: Synthetic Receptors for Future Medicine

Molecular imprinting is a relatively new and rapidly evolving technique used to create synthetic receptors; it also possesses great potential in a number of applications in the life sciences. Traditionally, molecularly imprinted polymers are prepared by bulk polymerization, followed by crushing and sieving to obtain polymer beads. However, several methods can be used to synthesize polymer micro- and nano-particles directly, thereby avoiding the time- and labor-consuming process of crush sieving. Possible applications are foreseen in enhanced drug loading, controlled drug delivery and drug targeting. This review describes the different methods of synthesis of molecularly imprinted micro- and nano-particles and discusses how these methods challenge the outstanding issues that molecular imprinting is facing today, thereby facilitating biomedical applications in the future.

Molecularly imprinted polymer-based potentiometric sensor for degradation product of chemical warfare agents: Part I. Methylphosphonic acid

A biomimetic potentiometric sensor for the specific recognition of methylphosphonic acid (MPA), the degradation product of nerve agents sarin, soman, VX, etc., was designed. This involves the preparation of MPA imprinted polymer particles and removal of the template by soxhlet extraction. Subsequently, the leached MIP particles were dispersed in 2-nitrophenyloctyl ether (plasticizer) and embedded in polyvinyl chloride matrix. The sensor responds to MPA in the concentration range 5 × 10 −8 to 1 × 10 −4 and 1 × 10 −3 to 1 × 10 −1 M with a detection limit of 5 × 10 −8 M. The selectivity of the sensor has been tested with respect to chemical analogues such as phosphoric acid, sodium dihydrogen phosphate, organophosphorous pesticide and triazine herbicides. The utility of the sensor was tested for field monitoring of MPA in spiked ground water.

Ion imprinted polymer based sensor for monitoring toxic uranium in environmental samples

In view of the extreme toxicity of uranium and consequent stringent limits fixed by WHO and various national governments, it is essential to monitor the uranium content in the environment which is at ultratrace levels. Conventional ionophore based ion selective electrodes, barring a few, have limitations in terms of sensitivity and selectivity for the above mentioned purpose. We now propose an ion imprinted polymer (biomimetic) based potentiometric sensor by dispersing the uranyl ion imprinted polymer particles in 2-nitrophenyloctyl ether (plasticizer), which is embedded in polyvinyl chloride matrix. The sensor responds to uranyl ion over a wide concentration range of 2.0 × 10 −8 to 1.0 × 10 −2 M. The limit of detection was 2.0 × 10 −8 M. It showed a good selectivity for uranyl ion over alkali, alkaline earth, transition and heavy metal cations. The sensor is successfully tested for the monitoring of toxic uranium in tap and sea water samples.

Molecularly imprinted polymer (biomimetic) based potentiometric sensor for atrazine

A biomimetic potentiometric sensor was developed by dispersing the atrazine imprinted polymer particles in di- n-octyl phthalate plasticizer and then embedding in polyvinyl chloride matrix. The sensor responds to atrazine in the pH range 2.5–3.0 over a wide working range of 0.0001–10 mM with a detection limit of 0.5 μM (0.1 ppm). This sensor has a reasonably faster response time of ∼2 min and high selectivity with respect to other important classes of pesticides and herbicides. The utility of the sensor was successfully tested for field monitoring of atrazine in ground waters by spiking known amounts of atrazine.

Imprinted polymer particles for selenium uptake: Synthesis, characterization and analytical applications

This work reports the preparation of molecularly imprinted polymer (MIP) particles for selective extraction and determination of selenium ions from aqueous media. Polymerization was achieved in a glass tube containing SeO 2, o-phenylenediamine, 2-vinylpyridine (VP), ethyleneglycoldimethacrylate (EDMA), 2,2′-azobisisobutyronitrile (AIBN). The polymer block obtained was ground and sieved (55–75 μm) and the Se- o-phenylenediamine complex was removed from polymer particles by leaching with 2 M of HCl, which leaves a cavity in the polymer particles. The polymer particles both prior to and after leaching have been characterized by IR and thermogravimetric (TG) studies. The effect of different parameters, such as pH, extraction time, type and least amount of eluent for elution of complex from polymer were evaluated. Extraction efficiencies >99% were obtained by elution of the polymers with 15 mL of methanol–acetonitrile mixture (1:2, v/v). The limit of detection of the proposed method followed by hydride generation atomic absorption spectroscopy (HG-AAS) was found to be 3.3 μg L −1 and a dynamic linear range (DLR) of 10–200 μg L −1 was obtained. The relative standard deviations (R.S.D.s) at 30.0 μg L −1 of Se were below than 8.1%. The influence of various cationic interferences on percent recovery of complex was studied. The method was applied to the recovery and determination of selenium in different real samples.

Magnetic Molecularly Imprinted Polymer Particles Synthesized by Suspension Polymerization in Silicone Oil

AbstractSummary: Magnetic nanoparticles have been prepared by a co‐precipitation method and modified with methacryloxypropyltrimethoxysilane. Magnetic molecularly imprinted polymer particles have been prepared by suspension polymerization in silicone oil. The particles possess a high affinity to the template molecules and are rapidly separated under a magnetic field.SEM photograph of magnetic MIP particles.magnified imageSEM photograph of magnetic MIP particles.

Ion imprinted polymer particles for separation of yttrium from selected lanthanides

Lanthanide(III) (Dy, Gd, Tb and Y) ion imprinted polymer (IIP) materials were synthesized via single pot reaction by mixing lanthanide imprint ion with 5,7-dichloroquinoline-8-ol, 4-vinylpyridine, styrene, divinylbenzene and 2,2'-azobisisobutyronitrile in 2-methoxyethanol porogen. The imprint ion was removed by stirring the above materials (after powdering) with 6 mol/L HCl to obtain the respective lanthanide IIP particles. Y-Dy, Y-Gd and Dy-Gd polymer particles were obtained by physically mixing equal amounts of the respective leached individual lanthanide(III) particles. Control polymer (CP) particles were similarly prepared without imprint ion. Application of the above synthesized polymer particles was tested for separation of Y from Dy, Gd and Tb employing batch and column SPE methods using inductively coupled plasma atomic emission spectrometry for the determination. Optimization studies show that Y present in 500 mL can be preconcentrated using Dy-Gd IIP particles and eluted with 20 mL of 1.0 mol/L of HCl, providing an enrichment factor of approximately 25. Dy-Gd IIP particles offer higher selectivity coefficients for Y over other lanthanides compared to other IIP particles and commercial liquid-liquid extractants. Selectivity studies for Y over other coexisting inorganic species (other than lanthanides) were also conducted and the results obtained show a quantitative separation of Y from other inorganics other than Cu(II) and Fe(III). Furthermore, both batch and column studies indicate the purification of yttrium concentrate from 55.0 +/- 0.2 to 65.2 +/- 0.2% in a single stage of operation.

Quartz crystal microbalance for the determination of daminozide using molecularly imprinted polymers as recognition element

As the daminozide (DM) and its metabolite have been identified to be potentially carcinogenic, rapid detection method for them is necessary for food safety. A type of piezoelectric crystal sensor has been prepared by using a molecularly imprinted polymer (MIP) as recognition element. The molecularly imprinted polymer was prepared by hot-induced precipitation polymerization, and then the polymer particles were fixed on the surface of the electrode. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to evaluate the obtained imprinted polymer particles and the MIP sensitive film coated on the electrode. The results showed that a typical time-response curve of the MIP-coated crystal to the DM solution had been given, frequency shifts versus logarithm changes of DM showed good linear correlation within the concentration range of 1.0x10(-9) to 10(-6) mg/mL (y=11.38 lg x+115.45, r=0.9872) and 1.0x10(-6) to 10(-1) mg/mL (y=25.22lgx+209.44, r=0.9938), respectively. The detection limit was 5.0x10(-8) mg/mL (S/N=3), which is lower than that of conventional methods. Further, computer simulation technology was employed to investigate the interaction between methacrylic acid and DM for elucidating the recognition mechanism. The influencing factor pH has also been investigated. The injection experiments of DM structurally related compounds indicated that the obtained sensor has high sensitivity, excellent selectivity, low cost, good reproducibility, and reusable property by combining with piezoelectric crystal and molecularly imprinted polymer.

Removal of Toxic Uranium from Synthetic Nuclear Power Reactor Effluents Using Uranyl Ion Imprinted Polymer Particles

Major quantities of uranium find use as nuclear fuel in nuclear power reactors. In view of the extreme toxicity of uranium and consequent stringent limits fixed by WHO and various national governments, it is essential to remove uranium from nuclear power reactor effluents before discharge into environment. Ion imprinted polymer (IIP) materials have traditionally been used for the recovery of uranium from dilute aqueous solutions prior to detection or from seawater. We now describe the use of IIP materials for selective removal of uranium from a typical synthetic nuclear power reactor effluent. The IIP materials were prepared for uranyl ion (imprint ion) by forming binary salicylaldoxime (SALO) or 4-vinylpyridine (VP) or ternary SALO-VP complexes in 2-methoxyethanol (porogen) and copolymerizing in the presence of styrene (monomer), divinylbenzene (cross-linking monomer), and 2,2'-azobisisobutyronitrile (initiator). The resulting materials were then ground and sieved to obtain unleached polymer particles. Leached IIP particles were obtained by leaching the imprint ions with 6.0 M HCl. Control polymer particles were also prepared analogously without the imprint ion. The IIP particles obtained with ternary complex alone gave quantitative removal of uranyl ion in the pH range 3.5-5.0 with as low as 0.08 g. The retention capacity of uranyl IIP particles was found to be 98.50 mg/g of polymer. The present study successfully demonstrates the feasibility of removing uranyl ions selectively in the range 5 microg - 300 mg present in 500 mL of synthetic nuclear power reactor effluent containing a host of other inorganic species.

Catalysis of a β-elimination applying membranes with incorporated molecularly imprinted polymer particles

Molecularly imprinted membranes are known to be applicable as recognition elements in separation, extraction and sensors, however, not as catalysts. In this paper, two different formats of molecularly imprinted membranes were generated and used as catalysts in a dehydrofluorination reaction. The first format was based on cellulose filter membranes which were coated with a polymer imprinted with a transition-state analogue of the chosen reaction. Alternatively, ground bulk polymers have been incorporated in polyvinyl alcohol (PVA) matrices on cellulose membranes. Both types of membranes were evaluated in membrane reactors. Either the substrate solution was pumped once only through the membrane, or the substrate solution was recirculated through the membrane. The coated membranes did not show any specific catalytic effect when comparing the molecularly imprinted with a non-imprinted control polymer membrane. Nevertheless, the PVA membranes containing the imprinted polymer particles showed specific catalytic effects, compared to PVA membranes with incorporated non-imprinted control polymer particles.

Synthesis, characterization, and analytical applications of erbium(III) ion imprinted polymer particles prepared via γ-irradiation with different functional and crosslinking monomers

Erbium(III) ion imprinted polymer (IIP) particles were synthesized by preparing erbium(III)–5,7-dichloroquinoline-8-ol–4-vinylpyridine prepolymer complex and then copolymerizing via γ-irradiation with different functional and crosslinking monomer combinations, viz. styrene–divinyl benzene, 2-hydroxyethyl methacrylate (HEMA)–ethylene glycoldimethacrylate (EGDMA), methyl methacrylate (MMA)–EGDMA. The erbium(III) imprint ion was removed by stirring the above particles with 6.0 mol l −1 HCl to obtain leached IIP particles. Control polymer (CP) particles were prepared without imprint ion. Again, CP, unleached and leached IIP particles were characterized by XRD, UV–vis spectrophotometric, pore size, SEM, and swelling ratio studies. The preconcentration of traces of erbium(III) during rebinding with leached IIP particles was studied as a function of pH, weight of polymer material, preconcentration and elution times, eluent concentration and volume, and aqueous phase volume. These studies indicate that as low as 2 μg of erbium(III) present in 500 ml can be preconcentrated into 20 ml of 1.0 mol l −1 HCl, and thus providing an enrichment factor of ∼25. Furthermore, the present study indicates that styrene–divinyl benzene-based IIP could be a better choice for the separation of erbium(III) from yttrium(III), dysprosium(III), holmium(III), and thulium(III) compared to HEMA–EGDMA and MMA–EGDMA-based IIPs.

An allosteric model for the binding of bilirubin to the bilirubin imprinted poly(methacrylic acid-co-ethylene glycol dimethylacrylate)

During liver failure, hyperbilirubinemia occurred and the bilirubin level can be very high. Bilirubin concentration for a healthy adult is approximately 0.3 mg/dL. The detection of bilirubin concentration can be important to indicate the liver function. Molecular imprinting technique was applied in this work using bilirubin molecule as the target template. Therefore, bilirubin imprinted poly(methacrylic acid-co-ethylene glycol dimethylacrylate) (poly(MAA-co-EGDMA)) was synthesized. The bilirubin imprinted polymer showed specific binding toward bilirubin rather than its analogue biliverdin. The binding results from bilirubin solution, biliverdin solution, and bilirubin/biliverdin mixture solution performed by bilirubin imprinted polymer particles were all obtained. The binding capacity of the target molecule, bilirubin, to the imprinted poly(MAA-co-EGDMA) was reduced because of the presence of biliverdin. On the contrary, the binding of bilirubin analogue, biliverdin, was slightly enhanced by the presence of bilirubin. The experimental results were further used for simulation to obtain the binding isotherms. The computational analysis proved that the binding kinetics could not be properly explained by Langmuir model as it was often reported to be. Instead, an allosteric model was proposed in this work. The simulation results showed that the binding kinetics was well described by the allosteric model. For the specific adsorption of bilirubin by the molecularly imprinted polymer (MIP) from the bilirubin/biliverdin mixture solution, a competitive allosteric model could well interpret the data. The maximum binding amount of bilirubin in single-compound solution, 0.476 mg/g MIP, was higher than that obtained in bilirubin/biliverdin mixture solution, 0.442 mg/g MIP. The binding constant of bilirubin in single solution, 170 mg/dL, was smaller than that in bilirubin/biliverdin mixture, 192 mg/dL. Instead, for the non-specific adsorption of biliverdin by the MIP from the bilirubin/biliverdin mixture solution, an enhanced allosteric model was proposed. Excellent simulation results were achieved. The binding parameters of the proposed models for this system were also obtained and discussed.

Amperometric detection of morphine based on poly(3,4-ethylenedioxythiophene) immobilized molecularly imprinted polymer particles prepared by precipitation polymerization

Molecular imprinting is a novel technique used for chiral separation, artificial antibodies, sensors, and assays. Typically, molecular imprinted polymers (MIPs) are monoliths with irregular shapes. However, microspherical shapes with more uniform size can be obtained by the method of precipitation polymerization, which offers a higher active surface area by manipulating its compositions. In this study, MIP particles for the target molecule, morphine, were synthesized using a precipitation polymerization method that is more facile than the previous one that produced a thermally polymerized bulk. The conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was utilized to immobilize the MIP particles onto the indium tin oxide (ITO) glass as a MIP/PEDOT-modified electrode. The sensitivity for the MIP/PEDOT-modified electrode with MIP particles was 41.63 μA/cm 2 mM, which is more sensitive than that with non-MIP particles or that of a single PEDOT film with no incorporated particles in detecting morphine ranging from 0.1 to 2 mM. The detection limit was 0.3 mM (S/N = 3). In addition, we presented that the modified electrode can discriminate codeine that plays an interfering species.

Preparation of Z- l-Phe-OH-NBD imprinted microchannel and its molecular recognition study

An integrated microchip was presented for selective recognition of Z- l-Phe-OH-NBD, using molecular imprinting technique. Molecularly imprinted polymer (MIP) were prepared by copolymerization in the presence of template molecule Z- l-Phe-OH-NBD, in which methacrylic acid and 4-vinylpyridine were used as functional monomers and ethylene dimethacrylate used as crosslinker. Imprinted polymer particles were introduced into a microchannel fabricated with a new material i.e. poly(methylvinylsiloxane) by simply rapid prototyping method. Imprinted effects were evaluated by laser-induced fluorescence (LIF) detection where the results indicated that good selective recognition for Z- l-Phe-OH-NBD in the imprinted polymer was obtained; the adsorption percentage of Z- l-Phe-OH-NBD was 61%. In contrast to conventional molecular imprinting analysis, integration shortened overall analysis time from 4 h to 10 min.

Selective recognition of neodymium (III) using ion imprinted polymer particles.

Neodymium (III) ion-imprinted polymer (IIP) materials were prepared by the copolymerization of neodymium (III)-5,7-dichloroquinoline-8-ol-4-vinylpyridine ternary complex with styrene(monomer), divinyl benzene (crosslinking monomer) in the presence of 2,2'-azobisisobutyronitrile (initiator). The synthesis was carried out in 2-methoxy ethanol medium (porogen) and the resultant material was filtered, washed, dried and powdered to form unleached IIP particles. The imprint ion was removed by stirring the above particles with 50% (v/v) HCl for 6 h to obtain leached IIP particles with cavities in the polymer particles. Control polymer (CP) particles were similarly prepared without imprint ion, i.e. neodymium (III). CP, unleached and leached IIP particles were characterized by TLC, IR, microanalysis, XRD and UV-visible spectrophotometric studies. The preconcentration of 5-150 microg of neodymium (III) ions present in 500 ml of solution was possible with as little as 40 mg of neodymium (III) IIP particles in the pH range 7.5-8.0 with a detection limit of 50 ng/l. Five replicate determinations of 25 microg of neodymium (III) present in 500 ml of solution gave a mean absorbance of 0.120 with a relative standard deviation of 2.65%. The imprinting effect of IIP particles was noticed in all preconcentration and selectivity studies when compared with CP particles. Furthermore, the selectivity coefficients of neodymium (III) IIP particles were much higher compared with the reported separation factors for the best liquid-liquid extractants, viz. di-2-ethylhexyl phosphoric acid and 2-ethylhexyl-ethylhexyl phosphonate. Kinetic and isotherm studies during rebinding of neodymium (III) onto IIP particles were also carried out.

Preconcentrative separation of erbium from Y, Dy, Ho, Tb and Tm by using ion imprinted polymer particles via solid phase extraction

Erbium(III) ion imprinted polymer particles were synthesized by preparing ternary complex of erbium imprint ion with 5,7-dichloroquinoline-8-ol (DCQ) and 4-vinylpyridine (VP) and then thermally copolymerizing with methyl methacrylate (functional monomer) and ethylene glycol dimethacrylate (cross linking monomer) in the presence of 2-methoxy ethanol (porogen) and 2,2′-azobisisobutyronitrile (initiator). The imprint ion was removed by stirring the above particles with 50% (v/v) HCl to obtain leached IIP particles. Control polymer (CP) particles were similarly prepared without imprint ion. CP and unleached and leached IIP particles were characterized by spectral, thermal, microanalysis and nitrogen adsorption studies. The preconcentration and selectivity studies for erbium and other selected lanthanides were carried out with leached CP and IIP particles. The preconcentration of 2.0–250 μg of erbium(III) present in 250 ml of solution was possible with as low as 50 mg of IIP particles in the pH range 7.3–7.8. Seven replicate determinations of 25 μg of erbium(III) present in 250 ml of solution gave a mean absorbance of 0.148 with a relative standard deviation of 2.5%. The detection limit corresponding to three times the standard deviation of the blank was found to be 2 μg/250 ml.