Presence Of Template Molecule Research Articles

Preparation of Magnetic Molecularly Imprinted Polymer for Methylene Blue Capture

Hybrid magnetic molecularly imprinted polymers (MMIPs) have the advantages of the technology of molecularly imprinted material and magnetic nanoparticles. The magnetic properties of MMIPs allow easy magnetic separation of various pollutants and analytes. A convenient and simple approach has been developed for the preparation of MMIPs based on polyamide (nylon-6) and magnetic nanoparticles. The polymer matrix was formed during the transition of nylon-6 from a dissolved state to a solid state in the presence of template molecules and Fe3O4 nanoparticles in the initial solution. Methylene blue (MB) was used as a model imprinted template molecule. The MMIPs exhibited a maximum adsorption amount of MB reached 110 µmol/g. The selectivity coefficients toward MB structural analogs were estimated to be 6.1 ± 0.6 and 2.1 ± 0.3 for 15 μM hydroxyethylphenazine and toluidine blue, which shows high MMIP selectivity. To prove the MMIPs’ specificity in MB recognition, magnetic nonimprinted polymers (MNIPs) were synthesized without the presence of a template molecule. MMIPs exhibited much higher specificity in comparison to MNIPs. To show the remarkable reusability of the MMIP sorbent, more than four MB absorption and release cycles were carried out, demonstrating almost the same extraction capacity step by step. We believe that the proposed molecular imprinting technology, shown in the MB magnetic separation example, will bring new advances in the area of MMIPs for various applications.

Raclopride-Molecularly Imprinted Polymers: A Promising Technology for Selective [11C]Raclopride Purification.

In this work, we developed a novel approach to purify [11C]Raclopride ([11C]RAC), an important positron emission tomography radiotracer, based on tailored shape-recognition polymers, with the aim to substitute single-pass HPLC purification with an in-flow trap & release process. Molecular imprinting technology (MIT) applied to solid phase extraction (MISPE) was investigated to develop a setting able to selectively extract [11C]RAC in a mixture containing a high amount of its precursor, (S)-O-Des-Methyl-Raclopride (DM-RAC). Two imprinted polymers selective for unlabeled RAC and DM-RAC were synthesized through a radical polymerization at 65 °C using methacrylic acid and trimethylolpropane trimethacrylate in the presence of template molecule (RAC or DM-RAC). The prepared polymer was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy and tested in MISPE experiments. The polymers were used in testing conditions, revealing a high retention capacity of RAC-MISPE to retain RAC either in the presence of similar concentrations of RAC and DM-RAC precursor (96.9%, RSD 6.6%) and in the presence of a large excess of precursor (90%, RSD 4.6%) in the loading solution. Starting from these promising results, preliminary studies for selective purification of [11C]Raclopride using this RAC-MISPE were performed and, while generally confirming the selectivity capacity of the polymer, revealed challenging applicability to the current synthetic process, mainly due to high backpressures and long elution times.

Three-dimensional ordered macroporous imprinted polymer for bisphenol A recognition.

A novel kind of three-dimensional ordered macroporous molecular imprinted polymer (3DOM MIP) was prepared and studied. Monodisperse silica microspheres were used to form silica crystal template via simple centrifuge. In the presence of template molecule, acrylamide and trimethylolpropane trimethacrylate were co-polymerized in the interstices of crystal template bisphenol A (BPA). Hydrofluoric acid were employed to etch silica crystal and the mixed solvent of methanol with acetic acid were employed to extract template molecule. The results of SEM and FTIR confirmed the successful synthesis of 3DOM MIP. The obtained 3DOM MIP exhibited a rapid adsorption kinetics and a specific adsorption capacities toward template molecule because of the small size of MIP wall, which possessed much more effective imprinted cavies. Meanwhile, 3DOM MIP could selective recognized BPA from its structural analogues.

Molecularly Imprinted Electrochemical Sensor for the Detection of Organophosphorus Pesticide Profenofos

AbstractThe presence of profenofos (PFF) in food has been strictly limited by legislation due to its genotoxic and toxic effects on health. It is therefore very important to establish simple and rapid analytical methods to detect traces of this insecticide. A reusable molecularly imprinted polypyrrole MIP(O‐PPy) on a glassy carbon electrode (GCE) has been developed to measure PFF. The PPy was polymerized by cyclic voltammetry (CV) in the presence of template molecules (PFF) in an acidic solution on a GCE. The various experimental parameters such as film thickness, analyte/monomer ratio, and removal/rebinding requirements were examined and optimized. The signal of the redox probe (ferrocyanide/ferrocyanide) was used for the electrochemical detections. All steps of the sensor manufacturing, removal/rebinding of template molecules, and response to different PFF concentrations were tested by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The MIP sensor was able to detect PFF in the linear ranges of 1.0×10−9 to 1.0×10−6 M and 1.0×10−9 to 5.0×10−6 M, with detection limits, a signal‐to‐noise ratio (S/N) of three was used to estimate LOD, of about 1 nM using DPV and EIS, respectively. The MIP (PPy) GCE provided excellent PFF recognition performance and was successfully used to quantify PFF in sweet pepper samples, yielding recoveries not greater than 108 %.

Molecularly Imprinted Polymers for Recognition of Engineered Nanoparticles

Introduction Engineered nanoparticles (ENPs) have found widespread use in modern technology, medicine and daily life. Ag-NPs for example are used as antimicrobials in several medical and cosmetic products, whereas Au-NPs have attracted great interest in medical applications, such as drug delivery systems. However, ENPs can potentially cause adverse toxic effects due to their small size and high surface to volume ratio and their increased utilization in different medical and consumer products leads to an increased exposure to humans. While a range of state-of-the-art technologies, such as ICP-MS, is available for the detection of ENPs, they usually require thorough sample preparation, highly trained personnel and expensive equipment. [1] To circumvent these limitations, the use of artificial recognition materials, as for instance molecularly imprinted polymers (MIPs), is a promising alternative. MIPs are synthesized via (radical) polymerization in the presence of template molecules. After template removal, cavities, which are complementary to the template in size, shape and chemical functionality, form in the material. These can rebind target molecules with high sensitivity and selectivity. [2] MIPs can be used as receptors for quartz-crystal microbalances (QCMs), which are mass-sensitive transducers that measure a change in mass via a change in resonant frequency of the oscillating quartz. [3] In this work, we report on developing an easy-to-use and low-cost MIP-based QCM sensor for the detection of ENPs in aqueous matrices. Method Stamps with immobilized metal-based NPs were used to imprint template material on poly(styrene-co-EGDMA) layers. Particle distribution and shape of NPs, immobilized on PDMS stamps, were analyzed using atomic force microscopy (AFM). MIPs were prepared by pressing NP-stamps onto poly(styrene-co-EGDMA) thin films. After polymerization overnight, stamps were removed from the polymers and MIPs were characterized via AFM and QCM. For QCM measurements, we utilized an in-house dual-electrode system. In this case, one of the two electrode pairs served as reference and was coated with the non-imprinted polymer (NIP) to compensate for unspecific binding and external effects, such as temperature changes. Results and Discussion Two different substrates were tested for fabrication of NP stamps: glass and PDMS. In both cases, APTES was used as linker for NP immobilization and let to desired cavity formation on MIPs as assed via AFM. However, removal of glass stamps was challenging, as a result of the strong interaction between glass NP stamp and the polymer, and required applying rather strong force to remove NP stamps. PDMS led to better outcomes and was easily removable from MIPs, which is especially useful for QCMs due to their fragility. QCM measurements of poly(styrene-co-EGDMA) MIPs, imprinted with Ag-NPs (75 nm, PVP-stabilized), led to high sensor responses of up to 1 kHz, whereas no binding was observed on the NIP. QCMs were analyzed via AFM before and after frequency measurements (figures 1a-d). As shown in figure 1a, cavities matching the template in size and shape were distributed evenly across the MIP surface, whereas the NIP did not reveal any binding sites (1c). After QCM measurement and exposure of MIPs and NIPs to the imprinted Ag-NPs, re-binding occurred exclusively on the MIP as visible in figures 1b and 1d, confirming successful NP imprinting. First selectivity studies of poly(styrene-co-EGDMA) MIPs seem promising: exposure to smaller Ag-NPs (50 nm) resulted in no re-incorporation of particles on sensing layers. However, measurement of Au-NPs on Ag-NP MIPs, imprinted with particles of the same size and stabilizer shell as the Au-NPs, led to re-binding on the MIP. Those results were not surprising since both NPs had the same size, shape and surface chemistry, and used Au-NPs fitted perfectly into the Ag-NP cavities. However, there is still room for improvement regarding batch-to-batch reproducibility. Further characterization of these sensing materials is necessary and still ongoing. Conclusion and Outlook Imprinting of thin polymer-films using metal-based ENPs is a novel concept with considerable potential in the field of sensor technology. Poly(styrene-co-EGDMA) Ag-NP MIPs were prepared by surface imprinting and characterized using AFM, revealing corresponding NP cavities on the polymer surface and thus confirming successful imprinting of NPs. Moreover, QCM measurements of MIPs led to sensor responses with high frequency shifts upon exposure to the imprinted particles with no cross-selectivity to smaller NPs. In the near future, selectivity studies will be completed in order to assess binding responses as a function of NP size, stabilizer and core material. Overall, this work demonstrates the potential use of MIPs for analysis of NPs in complex matrices, such as food, cosmetic or medical products. However, since biding occurred in an irreversible manner, MIPs would probably be more suitable as filtration materials rather than sensing layers, unless a way is found in order to remove NPs from the cavities again. Acknowledgements This work has been funded by the Austrian Science Fund FWF, project number I 3568-N28, which we gratefully acknowledge.

Molecularly imprinted label-free sensor platform for impedimetric detection of 3-monochloropropane-1,2˗diol

The fabrication of a molecularly imprinted overoxidized polypyrrole MIP(oPPy) on graphene oxide (GO) modified single-use pencil graphite electrode (PGE) for the quantitative analysis of 3˗monochloropropane˗1,2˗diol (3˗MCPD), an important food processing contaminant, was reported for the first time. In situ electropolymerization of oPPy in the presence of template molecules (3˗MCPD) onto GO/PGE was carried out via cyclic voltammetry method in a pH-controlled solution. To evaluate the most appropriate sensor response, various experimental conditions (such as film thickness, analyte/monomer ratio, desorption/adsorption time etc.) were discussed and optimized. The re-adsorption of 3-MCPD was screened by electrochemical impedance spectroscopy (EIS) on imprinted cavities capable of 3-dimensional recognition of the target molecule. The electrochemistry of a redox probe (ferrocyanide/ferricyanide) was utilized for the impedimetric detection of 3-MCPD with a dynamic linear range of 2−500 nM and low sensing limit as 1.82 nM. The combination of GO and oPPy to construct a MIP platform provided a superior recognition performance for 3-MCPD in a label-free, disposable and cost-effective way. In order to demonstrate the practical applicability, standard addition method was employed in soy sauce samples. The achieved high recovery rates displayed that MIP(oPPy)-GO/PGE hold significant promise for future on-site studies in real food matrices for food safety control purposes.

Molecularly Imprinted Polymers for Recognition of Engineered Nanoparticles

Introduction Engineered nanoparticles (ENPs) have found widespread use in modern technology, medicine and daily life. Ag-NPs for example are used as antimicrobials in several medical and cosmetic products, whereas Au-NPs have attracted great interest in medical applications, such as drug delivery systems. However, ENPs can potentially cause adverse toxic effects due to their small size and high surface to volume ratio and their increased utilization in different medical and consumer products leads to an increased exposure to humans. While a range of state-of-the-art technologies, such as ICP-MS, is available for the detection of ENPs, they usually require thorough sample preparation, highly trained personnel and expensive equipment. [1]To circumvent these limitations, the use of artificial recognition materials, as for instance molecularly imprinted polymers (MIPs), is a promising alternative. MIPs are synthesized via (radical) polymerization in the presence of template molecules. After template removal, cavities, which are complementary to the template in size, shape and chemical functionality, form in the material. These can rebind target molecules with high sensitivity and selectivity. [2] MIPs can be used as receptors for quartz-crystal microbalances (QCMs), which are mass-sensitive transducers that measure a change in mass via a change in resonant frequency of the oscillating quartz. [3]In this work, we report on developing an easy-to-use and low-cost MIP-based QCM sensor for detection of ENPs in aqueous matrices. Method Stamps with immobilized metal-based NPs were used to imprint template material on PU layers. Particle distribution and shape of NPs, immobilized on PDMS stamps, were analyzed using atomic force microscopy (AFM). MIPs were prepared by pressing NP-stamps onto PU layers. After polymerization overnight, stamps were removed and remaining NPs were washed off the surface. MIPs were characterized via AFM and QCM. In case of QCM, we utilized an in-house dual-electrode system. In that case, one of the two electrode pairs served as reference and was coated with the non-imprinted polymer (NIP) to compensate for external effects, such as temperature changes. Results and Discussion Two different imprinting strategies were tested for fabrication of NP MIPs: bulk and surface imprinting. Bulk imprinting did not result in cavity formation on the polymer surface as examined via AFM. Consequently, we could not observe any significant differences of sensor signals between MIP and NIP during QCM measurements. In contrast to this, surface imprinting led to more favorable outcomes. NP-stamps were used for that purpose and characterized using AFM to verify the presence of NPs on stamp surfaces. As shown in Figure 1a, NPs are distributed evenly across the surface. Figure 1b displays an AFM image of the corresponding imprinted PU layer, which clearly reveals cavities on the polymer surface, matching the template in size and shape, thus confirming successful NP imprinting. In addition, an image of the reference, the non-imprinted polymer (NIP), is given for comparison, bearing no binding sites on the polymer surface (Figure 1c).Frequency measurements of MIP and NIP coated QCMs resulted in reversible and concentration-dependent sensor responses with no cross-selectivity to larger NPs. Furthermore, frequency shifts of MIPs, caused upon injection of NP solution, were much higher than those of NIPs. Fist results on acrylate-based MIPs using self-initiating monomers seem promising. First QCM measurements revealed incorporation of NPs by MIPs, with a way higher sensor response compared to the NIP. However, there is still room for improvement regarding batch-to-batch reproducibility. Further characterization of these sensing materials is necessary and still ongoing. Conclusion and Outlook Imprinting of thin polymer-films using metal-based ENPs is a novel concept with considerable potential in the field of sensor technology. PU-based MIPs were prepared by surface imprinting and characterized using AFM, revealing corresponding NP cavities on the polymer surface and thus confirming successful imprinting of NPs. Moreover, frequency measurements of MIP coated QCMs led to sensor responses in a reversible and quantitative manner. In the near future, selectivity studies will be performed in order to assess binding responses as a function of NP size, stabilizer and core material. Moreover, surface morphology of MIPs will be further characterized using PeakForce QNM.Overall, this work demonstrates the potential use of MIPs for analysis of NPs in complex matrices, such as food, cosmetic or medical products. Acknowledgements This work has been funded by the Austrian Science Fund FWF, project number I 3568-N28, which we gratefully acknowledge.

Electrochemical sensor based on electropolymerized dopamine molecularly imprinted film for tetrabromobisphenol A

This work reported the simple and direct detection of 3,3′,5,5′‑tetrabromobisphenol A (TBBPA) by a polydopamine imprinted electrochemical sensor. The imprinted film was directly prepared by electropolymerization of dopamine on a glassy carbon electrode in the presence of template molecule, and then characterized using electrochemical probe of potassium ferricyanide, scanning electron microscopy and atomic force microscopy. It was found that the obtained sensing film greatly enhanced the oxidation signals of TBBPA due to strong accumulation ability. The influences of electropolymerization conditions (e.g. template concentration, scan cycles and scan rates), accumulation time and pH value were studied. The developed sensing platform exhibited good reproducibility, excellent sensitivity and selectivity, offering a low detection limit (0.27 nM) and a linear range from 1 to 50 nM. It was applied for TBBPA detection in plastic e-waste samples, and the results were consistent with those obtained by high-performance liquid chromatography.

Water-dispersible molecularly imprinted nanohybrids via co-assembly of carbon nanotubes with amphiphilic copolymer and photocrosslinking for highly sensitive and selective paracetamol detection

A novel kind of water-dispersible molecularly imprinted nanohybrids containing multi-walled carbon nanotubes (MWCNTs) was prepared via the combination of co-assembly and photocrosslinking, and employed to construct an electrochemical sensor. A photo-crosslinkable amphiphilic copolymer (Poly(AA-co-VMc-co-EHA), PDHES) was firstly synthesized, which could co-assemble with MWCNTs in the presence of template molecule (paracetamol, PCM) in aqueous solution, generating photo-crosslinkable molecularly imprinted nanohybrids (MIP-MWCNTs). A robust MIP-MWCNTs film was formed on the electrode surface via the deposition of MIP-MWCNTs nanohybrids and the subsequent photo-crosslinking. After extracting paracetamol molecules, an electrochemical MIP-MWCNTs sensor was successfully developed. The as-prepared MIP-MWCNTs sensor showed a significantly wide linear detection range (0.1–2500 μM) and low detection limit (0.02 μM), owing to the large surface area of MIP-MWCNTs nanohybrids and superior electrical conductivity of MWCNTs, which affords a direct channel for the electron transfer from the recognition cavities to the electrode surface and thus enhances the response signal. In addition, good selectivity toward paracetamol (the imprinting factor α is 7.5) and ultrafast response time (less than 180 s) of MIP-MWCNTs sensor have also been demonstrated. The MIP-MWCNTs sensor also exhibited satisfactory repeatability and stability, which has been successfully utilized to measure paracetamol in urine samples with good results, demonstrating a promising feature for applications in medical diagnostics.

Necklace-like Molecularly Imprinted Nanohybrids Based on Polymeric Nanoparticles Decorated Multiwalled Carbon Nanotubes for Highly Sensitive and Selective Melamine Detection.

In this study, molecularly imprinted nanohybrids with "necklace-like" nanostructures were developed based on self-assembled polymeric nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) by employing melamine as template molecules. An amphiphilic copolymer poly(acrylic acid- co-(7-(4-vinylbenzyloxy)-4-methyl coumarin)- co-ethylhexyl acrylate) (poly(AA- co-VMc- co-EHA), PAVE) containing photosensitive coumarin units was synthesized first. Then, the PAVE copolymers were co-assembled with MWCNTs in the presence of template molecules, generating photosensitive molecularly imprinted nanohybrids (MIP-MWCNTs) with necklace-like structures. Subsequently, the MIP-MWCNTs nanohybrids were used to modify electrode surface followed by photo-polymerization of the coumarin units in the nanohybrids, leading to a network architectured complex film. After extracting melamine molecules by electrolysis, a melamine MIP sensor was successfully developed. The as-prepared sensor exhibited a significantly wide linear range (1.0 × 10-12-1.0 × 10-6 mol L-1) and a low detection limit (5.6 × 10-13 mol L-1) for melamine detection. High selectivity of the sensor toward melamine was well demonstrated with respect to other melamine analogues and interferents. Furthermore, the MIP sensor showed high stability and reproducibility. The excellent performance of the MIP sensor can be attributed to the unique nanostructure of the complex film provided by these necklace-like nanohybrids. On the one hand, the nanosized polymeric MIP nanoparticles along the MWCNTs increase the effective electrode surface area and thus offer a high melamine-binding capacity. On the other hand, the MWCNTs in MIP-MWCNTs nanohybrids serve as "electronic bridges" to accelerate the electron transfer among the complex MIP film. More importantly, the MIP sensor was practically used to monitor melamine in milk samples, demonstrating a promising feature for applications in the analysis of food like milk and other food products including milk powder, infant formula, and animal feed. Considering the ease of polymeric nanoparticles functionalization, the necklace-like nanohybrids would be extended to wider applications in many other sensors and devices.

Separation of chiral compounds using magnetic molecularly imprinted polymer nanoparticles as stationary phase by microchip capillary electrochromatography.

In this work, a simple and rapid approach was developed for separation and detection of chiral compounds based on a magnetic molecularly imprinted polymer modified poly(dimethylsiloxane) (PDMS) microchip coupled with electrochemical detection. Molecularly imprinted polymers were prepared employing Fe3 O4 nanoparticles (NPs) as the supporting substrate and norepinephrine as the functional monomer in the presence of template molecule in a weak alkaline solution. After extracting the embedded template molecules, Fe3 O4 @polynorepinephrine NPs (MIP-Fe3 O4 @PNE NPs) showed specific molecular recognition selectivity and high affinity towards the template molecule, which were then used as stationary phase of microchip capillary electrochromatography for chiral compounds separation. Mandelic acid and histidine enantiomers were used as model compounds to test the chiral stationary phase. By using R-mandelic acid as the template molecule, mandelic acid enantiomer was effectively separated and detected on the MIP-Fe3 O4 @PNE NPs modified PDMS microchip. Moreover, the successful separation of histidine enantiomers on the MIP-Fe3 O4 @PNE NPs modified microchip using L-histidine as template molecule was also achieved.

Room temperature synthesis and binding studies of solution-processable histamine-imprinted microspheres.

Accurate quantification of histamine levels in food and in biological samples is important for monitoring the quality of food products and for the detection of pathophysiological conditions. In this study, solution processable histamine-imprinted microspheres were synthesized at 30°C via dilute free radical phototochemical polymerization technique using ethylene glycol dimethacrylate (EGDMA) as the crosslinker and methacrylic acid (MAA) as the monomer. The processability of the resulting polymer is dictated by the monomer feed concentration (eg, 4 wt% 80:20 EGDMA:MAA formulation) and solvent (acetonitrile). Whereas, the particle size is influenced by the monomer feed concentration, the presence of template molecule, and independent of the crosslinker content. Evaluation of the binding performance of the photochemically imprinted polymers (PCP) with different crosslinker content (80 and 90 wt%) indicated that the selective binding capacity was notably higher in PCP-80 (N= 16.0 μmol/g) compared to PCP-90 (N= 10.1 μmol/g) when analyzed via frontal analysis capillary electrophoresis (FACE) using Freundlich isotherm. In addition, PCP-80 microspheres are more selective toward histamine than conventional thermal polymers (CTP-80) prepared at 60°C in the presence of structural analogs such as histidine, imidazole, and tryptamine under cross-rebinding and competitive conditions. These results demonstrated that histamine-selective imprinted polymers can be obtained readily using room temperature photochemical polymerization where these materials can be subsequently used as recognition element for optical-based histamine sensing.

Specific Fluorescence Probe for Direct Recognition of Dimethoate Using Molecularly Imprinting Polymer on ZnO Quantum Dots.

ZnO quantum dots (QDs) based molecularly imprinting polymer (MIP)-coated composite was described for specific detection of the dimethoate (DM) as a template. The MIP was synthesized by simple self-assembly of 3-aminopropyl triethoxysilane (APTES) monomers and tetraethyl ortho-silicate as cross linking agent in the presence of template molecules. The used imprinting course can improve the tendency of the prepared QDs toward the DM template molecules. The MIP-coated ZnO QDs showed a strong fluorescence emission which undergoes a quenching effect in the presence of DM. So, a selective probe could be designed based on these composites to recognize DM in water samples. Under optimized experimental conditions, a linear relationship between the emission intensity of MIP-coated ZnO QDs and concentration of DM, in the range of 0.02-3.2 mg L-1 with a detection limit of 0.006 mg L-1. Combination of high specificity of MIP element and distinct fluorescence features of ZnO QDs provides a sensitive and selective recognizing method for pesticide detection. The developed method was successfully applied for the determination of DM contamination in environmental water samples.

A norepinephrine coated magnetic molecularly imprinted polymer for simultaneous multiple chiral recognition

A newly designed molecularly imprinted polymer (MIP) material was developed and successfully used as recognition element for enantioselective recognition by microchip electrophoresis. In this work, molecularly imprinted polymers were facilely prepared employing Fe3O4 nanoparticles (NPs) as the supporting substrate and norepinephrine as the functional monomer in the presence of template molecule in a weak alkaline solution. After extracting the embedded template molecules, the produced imprinted Fe3O4@polynorepinephrine (MIP–Fe3O4@PNE) NPs have cavities complementary to three dimensional shape of template molecules favoring high binding capacity and magnetism property for easy manipulation. The MIP–Fe3O4@PNE NPs prepared with l-tryptophan, l-valine, l-threonine, Gly-l-Phe, S-(−)-ofloxacin or S-(−)-binaphthol as template molecules were packed in the polydimethylsiloxane microchannel via magnetic field as novel stationary phase to successful enantioseparation of corresponding target analysts. The MIP–Fe3O4@PNE NPs-based microchip electrophoresis system exhibited strong recognition ability, excellent high-performance, admirable reproducibility and stability, which provided a powerful protocol for separation enantiomers within a short analytical time and opened up an avenue for multiplex chiral compound assay in various systems.

Molecularly imprinted electrochemical sensor for propyl gallate based on PtAu bimetallic nanoparticles modified graphene–carbon nanotube composites

A novel molecularly imprinted electrochemical sensor for propyl gallate (PG) determination was developed via electropolymerization of an o-phenylenediamine membrane in the presence of template molecules on glassy carbon electrode surface modified by PtAu bimetallic nanoparticles-capped graphene-carbon nanotubes composites (PtAu-GrCNTs). The modified electrodes were characterized by cyclic voltammetry, scanning electron microscope, x-ray diffraction and chronoamperometry. Moreover, experimental parameters such as scan cycles, incubation time, molar ratios of template molecules to functional monomers and extraction time were optimized. It was found that the PtAu-GrCNTs composite could effectively enhance the electron transfer efficiency and remarkably improve the sensitivity of the sensor. The results revealed the sensor displayed superb resistance to no-specific binding, very attractive detection limit as low as 2.51×10−8mol/L, and a wide linear range from 7×10−8mol/L to 1×10−5mol/L towards PG. Furthermore, the MIPs sensor was also successfully used for the detection of PG in food samples. Therefore, the MIPs-based electrochemical sensing strategy might provide a sensitive, rapid, and cost-effective method for PG determination and related food safety analysis.

Electrochemical sensor for bovine hemoglobin based on a novel graphene-molecular imprinted polymers composite as recognition element

A highly selective and sensitive electrochemical sensor for bovine hemoglobin (BHb) was developed based on a novel graphene-molecular imprinted polymers composite (GR-MIP) as recognition element. The GR-MIP composite was synthesized by oxide self-polymerization of dopamine on the surface of graphene in the presence of template molecules (BHb) in aqueous solution, which is a one-pot facile and green preparation procedure. The fabrication process of the GR-MIP sensor was characterized by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS), in which [Fe(CN)6]3−/4− was used as an electrochemical active probe. The as-prepared GR-MIP sensor was tested by DPV to investigate the relationship between the current response and BHb concentration. Under optimized experimental conditions, selective detection of BHb in a concentration range of 1.0×10−9mgmL−1 to 1.0×10−1mgmL−1 with detection limit of 2.0×10−10mgmL−1 was obtained, which outperformed the most of reported BHb detecting methods. This novel GR-MIP sensor also exhibited excellent selectivity and good reproducibility, and was used to the determination of BHb in real samples with satisfactory results. The outstanding sensing behavior of the target protein coupled to its low production cost and facile, green preparation procedure makes the GR-MIP sensor attractive in the sensitive and selective detection of target proteins in biological fluids.

Molecularly imprinted polymeric sensings layers grafted from aryl diazonium‐modified surfaces for electroanalytical applications. A mini review

We review our strategy to attach polymerization initiators to electrode surfaces by electroreduction of aryl diazonium salts. The ~5 nm‐thick aryl layers efficiently initiate the growth of crosslinked polymer grafts prepared in the presence of template molecules. We address the important parameters in obtaining highly sensitive molecularly imprinted vinylic polymer layers grafted on working electrodes such as glassy carbon, gold and indium tin oxide. Square wave voltammetry is the preferred electroanalytical tool while the limit of detection (LOD) of analytes can be decreased down to subnanomolar detection by synthesizing ultrathin layers in the 20–30 nm thickness. Further improvement can be achieved with molecularly imprinted polymer layers with embedded gold nanoparticles. Rebinding solvent is demonstrated to be another important parameter for lowering LOD. This work highlights XPS as a unique surface sensitive technique for monitoring the chemical composition changes occurring at the electrode surface during the building of the high performance sensing layers as well as for evidencing the reversible complexation of the template molecule by the molecularly imprinted recognition sites. Copyright © 2014 John Wiley & Sons, Ltd.

A simple approach to prepare molecularly imprinted polymers from nylon‐6

A convenient and simple approach for the preparation of molecularly imprinted polymers (MIPs) based on polyamide (nylon-6) was developed. The polymer matrix formation occurred during the transition of nylon from dissolved to solid state in the presence of template molecules in the initial solution. 2,2,2-Trifluoroethanol (TFE) was chosen as a main solvent for the polyamide. It provides a high solubility of nylon and does not significantly change the structure of biopolymers. The alteration of the polymer matrix structure after the addition of different types of porogens in the nylon/TFE solution was investigated. The structured polymers in the form of films and microparticles were prepared in the chosen optimal conditions. Different model biomolecular templates (of low- and high-molecular weight) were used for the preparation of MIPs, which were shown to specifically recognize these molecules upon binding experiments. The binding of the template molecules to MIPs was monitored using spectrophotometric, radioisotopic, or fluorometric detection. The selectivity coefficients of the MIPs were estimated to be 1.4-4.6 depending on the type of templates and conditions of the polymer matrix formation.

Synthesis of Surface Imprinted Polymer Microspheres with Ultrathin Polymer Shells via Surface-Initiated Iniferter Polymerization

A simple and effective approach was proposed to synthesize uniform surface imprinted polymer microspheres via surface-initiated iniferter polymerization. The chloromethyl groups were firstly introduced onto the surface of the polystyrene microspheres by a one-step dispersion polymerization. After that the photosensitive iniferter groups were modified by the reaction of the polystyrene microspheres surface-bound chloromethyl groups with N, N-diethyldithiocarbamate sodium. The grafting step was then carried out in a stirred solution of polystyrene microspheres containing surface-initiated iniferter in the presence of template molecules (glutathione, GSH), functional and cross-linking monomers. The synthesized surface imprinted polymer (GSH-MIP) microspheres were characterized using SEM and FT-IR. The GSH-MIP microspheres were spherical in shape, and showed homogeneous polymer layer and high encapsulation efficiency. The rebinding properties of GSH for GSH-MIP was evaluated by carrying out batch rebinding tests, the obtained GSH-MIP shows faster mass transfer and higher binding amounts rate toward template than non-imprinted polymer (NIP).

Sensing of glycoprotein via a biomimetic sensor based on molecularly imprinted polymers and graphene–Au nanoparticles

A novel strategy was proposed for preparing a highly sensitive glycoprotein sensor based on molecularly imprinted polymers (MIP), which was electropolymerized with o-phenylenediamine and 3-aminophenylboronic acid monohydrate in the presence of template molecules (bovine serum albumin (BSA)). Sensitivity improved dramatically owing to the application of a graphene-Au nanoparticles hybrid as the electrode modifier, and the immobilization of a large amount of 6-ferrocenylhexanethiol, as the electroactive species, onto nanoparticles. The quantification of BSA was realized by detecting the electrochemical oxidation signal of 6-ferrocenylhexanethiol, which was bonded onto the electrode. Under optimized conditions, a good relationship was obtained between the response current and logarithm of BSA concentration in the range of 1.0 × 10(-11) to 1.0 × 10(-5) g mL(-1) with a detection limit of 7.5 × 10(-12) g mL(-1) (S/N = 3). The resulting MIP sensor displayed good selectivity, reproducibility and stability.