Molecularly Imprinted Polyresorcinol Based Capacitive Sensor for Sulphanilamide Detection

Electrochemical sensors based on molecularly imprinted polymers grafted onto gold electrodes using click chemistry

Electrochemical sensor for parabens based on molecular imprinting polymers with dual-templates

Development of Sudan II sensor based on modified treated pencil graphite electrode with DNA, o-phenylenediamine, and gold nanoparticle bioimprinted polymer

Fast, selective, sensitive and inexpensive detection techniques are highly required concerning the identification of planned terrorist attacks in- volving explosive, chemical or biological materials. State of the art are cost intensive equipments used e.g. in airport portal systems or swapping techniques (Imaging by X-ray, TeraHz-, MMwave, NQR, neutron activation techniques, electronic noses, IMS). We propose the development of substance specific low cost sensors, which can be installed as self reporting sensors in containers, compartments, wagons etc., used as hand held systems or sniffing devices which analyse the content of explosives in the gas phase. The basic sensor concept uses mass-sensitive devices coated with mole- cularly imprinted polymers (MIP). The components are cheap promising low- cost detection devices which could be applied for the passive as well as active sensing of explosives like TNT, DNT or TATP at short-range distances of about one meter. In the case of active sampling the MIP sensor will be combined with a suitable air-sucking system. Molecular imprinted polymers (MIPs) are highly cross-linked polymers. Like enzymes they possess a high affinity and selectivity for the adsorption of a special target substance (template molecule) which is present only during the MIP-synthesis and is afterwards extracted. This yields to a finished polymer with special and very selective binding sites for the former template. MIPs are very inexpensive, rapid to synthesise and they are already applied as substance specific solid phase extraction materials in the liquid phase. Preliminary results /1/ of synthesized particulate TNT-specific MIPs showed the effective adsorption capability of the material for TNT vapours. Moreover first experiments using direct UV-initiated polymerisation of TNT- MIPs produced thin films which can be used in combination with different sensor materials.

Chiral drugs exert pharmacological effects through strict matching with chiral biological macromolecules and chiral recognition. Each enantiomer has different pharmacological activities, metabolic processes and rates, as well as toxicity pharmacokinetic characteristics owing to the difference in its interactions with the chiral environment. Therefore, method development for the resolution of chiral drugs is of great significance for the synthesis of chiral drugs and for quality control during the production process. Molecularly imprinted polymers (MIPs) are prepared by using a target molecule as the template. MIPs demonstrate highly specific recognition properties toward the target molecule since they have specific spatial molecular structures and functional groups. Hence, MIPs are particularly suitable for the separation and purification of chiral drugs. Capillary electrochromatography (CEC) offers the advantages of high separation efficiency and high selectivity owing to the dual separation mechanisms including capillary electrophoresis and liquid chromatography. By using MIPs as the stationary phases for CEC, the advantages of the two technologies can be combined to achieve efficient separation of chiral drugs. MIPs were first applied to CEC for chiral resolution in 1994, and since then, there have been notable advances in this field. The four main chiral separation modes in CEC involve the use of MIPs as the stationary phases of open tubular, packed, and monolithic columns, and as the pseudostationary phase in the separation medium. This review summarizes the research progress of these four methods and reveals the potential of MIPs in chiral resolution by CEC. The advantages and disadvantages of these methods are commented. MIPs as the stationary phases of packed columns can allow for chiral separation. However, the preparation of packed columns in narrow capillaries is difficult. In addition, frits must be prepared at the ends of the capillaries to seal the MIPs. The frits lead to the formation of bubbles during the CEC analysis, thus resulting in poor repeatability and stability. These problems can be overcome by using MIP-based open tubular columns. Furthermore, conditioning of open tubular columns is easy and less time-consuming. However, open tubular columns have limited capacity. MIP-based monolithic columns have greater capacity than do open tubular columns, and frits are not required in this case. However, in situ preparation of MIPs monolith in narrow capillaries is still challenging. The application of MIPs to chiral CEC can also be realized by using them as pseudostationary phases (additives) in the separation medium, and this allows for ease of operation. Moreover, the amount of MIPs introduced into the capillary can be accurately controlled. Thus, the batch-to-batch reproducibility can be improved, but this has the disadvantage of increased MIP consumption. In order to further expand the potential of MIPs in chiral CEC, the following aspects must be considered. First, improvement of the preparation method. In most reported MIP-based-chiral CEC techniques, the peaks of the imprinted molecules show severe tailing, and this problem must be resolved. Improving the mass transfer rate of the prepared MIPs may be a suitable solution in this regard. Second, development of new functional monomers. A functional monomer is an indispensable component in the preparation of MIPs. New functional monomers can be prepared according to the "three-point interaction" rule. Third, selection of template molecules. A single enantiomer of chiral drugs is used as the template molecule to prepare chiral MIPs. The method is not suitable for the preparation of MIPs of chiral drugs for which a single enantiomer is difficult to obtain. Therefore, appropriate choice of the template molecules for these drugs is imperative. Fourth, discussion of chiral separation mechanism. The mechanism of interaction between the template molecules and MIPs needs to be explored further, in order to obtain theoretical guidance for the design and preparation of chiral MIPs.

Molecularly imprinted polymers (MIPs) are tailor-made polymers with high selectivity for a given analyte, or group of structurally related compounds. The influence of the process parameters (the moles of functional monomer and cross-linker, the selection of functional monomer and solvent) on the preparation of oseltamivir (OS)-imprinted polymers was investigated. A mathematical method for uniform design to optimize these selected parameters and to increase the MIP selectivity for template molecules was applied. The optimal conditions to synthesize MIP were 0.69 mmol 30% acrylamide (AA) + 70% 4-Vinylpyridine (4-VP) and 5.0 mmol ethylene glycol dimethacrylate (EGDMA) copolymerized in 5 ml toluene in the presence of 0.1 mmol OS. MIP showed high affinity and selectivity for separation of the template molecule from other compounds. In the present study, we have established an effective LC-MS/MS method to identify and quantify OS with good sensitivity, accuracy and precision.

After cochlear implant (CI) insertion, there is a possibility of postoperative inflammation, which may involve proinflammatory markers such as interleukin-6. Detecting this inflammation promptly is crucial for administering anti-inflammatory drugs, if required. One potential method for detecting inflammation is using molecular imprinted polymers (MIPs). These MIPs, which can be deposited on the CI electrode, provide readout employing impedance measurements, a feature already available on the CI circuit. MIPs designed for this purpose should possess biocompatibility, conductivity, and degradability. The degradability is crucial because there is a limitation on the number of electrodes available, and once the inflammation sensor degrades after the acute inflammation period, it should remain usable as a regular electrode. In this work, conductive poly(3,4-ethylenedioxythiophene) polystyrenesulfonate-based MIPs were synthesized against biotin as a surrogate target marker. Specific biotin binding with MIPs was determined before and after degradation using electrochemical impedance spectroscopy (EIS) and compared with the control nonimprinted polymers (NIPs). Subsequently, MIPs were electrochemically degraded by EIS with different potentials, wherein a potential dependence was observed. With decreasing potential, fewer dissolved polymers and more monomer molecules were detected in the solution in which degradation took place. At a potential of 0.205 V a negligible amount of dissolved polymer in addition to the dissolved monomer molecules was measured, which can be defined as the limiting potential. Below this potential, only dissolved monomer molecules are obtained, which enables renal clearance. Biocompatibility testing revealed that both the polymer and the solution with dissolved monomer molecules do not exceed the ISO 10993-5 cytotoxicity threshold. Based on these findings, we have developed conductive, biocompatible, and controllably degradable MIPs capable of detecting biotin. This research work paves the way for the advancement of CIs, where inflammation can be detected using molecular imprinting technology without compromising the stability and biosafety of the product.

Williamson etherifications of diethyl 3,4-dialkoxythiophene-2,5-dicarboxylate (DDTD) yielded the desired thiophene dicarboxylate derivatives (3) in up to 87% yield. Hydrolysis of these diethylesters afforded the diacids (4) in up to 96% yield. One pot synthesis by combining decarboxylation and bromination steps was carried out giving the dibromo product (7b) in 77% yield, higher than that was obtained from the corresponding separated steps. Molecularly Imprinted polymers (MIPs) based on PEDOT were prepared from monomer (7b) by solid state Polymerization (SSP) in the presence of templates molecules: 2,4,6-trinitrophenol (TNP) or 2,4,6-trinitrotoluene (TNT). The resulting conjugated MIPs exhibited the recognition of its template Molecules compared to non-imprinted polymers (NIPs) in the binding experiments monitored By UV-Vis spectroscopy. The result was found that the specific adsorption (ΔQ) of TNP and TNT molecules bound to the MIPs were 128.41 and 103.63 µmol/g, respectively. The rebinding capacities of the TNP MIPs were 38.64% for TNP-MIPs and 28.63% for TNT-MIPs. Cross binding experiments confirmed the selectivity of the MIPs only towards their template molecules. These result showed that PEDOT could be imprinted and developed to be sensors for specific detection of detected of selected template compounds.

This work reports on the selective multi-analyte detection of neurotransmitters using polypyrrole based molecularly imprinted polymer (MIP) sensors. A LabVIEW-based differential pulse voltammetry (DPV) method is designed for the simultaneous detection of multiple analyte. Two types of MIP-based sensors, namely the dopamine (DA)-imprinted and the norepinephrine (NE)-imprinted polymers, were prepared using pyrrole as a functional monomer. The ability to detect multiple neurotransmitters simultaneously can provide the critical information about many psychiatric disorders such as Parkinson's Disease and Alzheimer's Disease. Electrochemical detection method is one of the most effective techniques for neurotransmitter sensing because of the high sensitivity and portability. However, the similar redox potential among the neurotransmitters cause poor selectivity in detection. Molecularly imprinting technique provides a highly selective method for neurotransmitters sensing. Figure 1 illustrates the basic principle for MIP technique. Polypyrrole (PPy) was used as a functional polymer because of the good conductivity and ease of synthesis. Multi-walled carbon nanotubes (MWCNTs) were introduced as a platform (or a template) for PPy growth because of the strong affinity between MWCNTs and the PPy as well as the excellent electrical property. DA and NE molecules served as templates, and each type of MIP was synthesized in a similar way. The template molecule was embedded inside the PPy layers. After being overoxidized with several cyclic voltammetry (CV) cycles, the templates were removed from the PPy layer which created cavities corresponding to the shape and size of the analyte. Therefore, the MIPs are able to enhance the sensitivity and selectivity of the sensor. Although there have been recent work on MIP-based sensors, most of them have focused on single analyte detection. Therefore, a novel method for multi-analyte sensing is urgently needed for commercial applications. In order to achieve this goal, this work presents a LabVIEW-based multi-species detection system. Figure 2 shows the design of the circuit for the potentiostat system. The sensor consists of two working electrodes (WE1 and WE2), a reference electrode (RE), and a counter electrode (CE). The generated DPV signal was connected to the two working electrodes, and MIPs were deposited on the working electrode for detection. The MIP synthesis method was designed as follows, H2O2 was added to the mixture of pyrrole monomer, CNT, FeCl2, and template solutions (either DA,or NE) at room temperature. After the MIPs was fully synthesized, deionized water was used to wash out the unreacted substance. Finally, the MIPs were overoxidized in phosphate buffered saline (PBS 1X) solution to remove the embedded template molecules. Figure 3 shows the DPV responses for (a) DA-imprinted device (DA-MIP) and (b) NE-imprinted device (NE-MIP) when exposed to various concentrations of DA. DA-MIP and NE-MIP were connected to WE1 and WE2, respectively. Although oxidation peaks were observed in both sensors, the DA-MIP device produced a greater sensitivity at 0.02V. However, NE-MIP device exhibited better performance at 0.26V when two types of MIP device (c), (d) were exposed to various concentrations of NE solutions. Figure 4 shows a set of calibration curves for both DA-MIP and NE-MIP incubated in DA figures (a – c), and NE (d – f) solutions. Each sensor exhibited higher sensitivity for their respective target analyte. Also, the sensitivity of the sensor can be affected by the present of other species, the performance of the sensors varies when exposed to different mixtures. Figure 5 summarizes the multi-analyte performance for two MIP devices simultaneously exposed to a mixture of two analyte. The slope of the calibration curve was obtained for each combination of mixtures, where the slope indicated its sensitivity. The response of DA-MIP device was significantly higher than the NE-MIP device for all cases when the concentration of DA was varied. On the other hand, NE-MIP device usually possesses better sensitivity than the DA-MIP device when the concentration of NE was varied. In summary, the selectivity of both MIP devices toward their own species have been confirmed, and the results demonstrate that the molecularly imprinted cavities inside the PPy nanofibers can selectively measure the quantity of the target analyte even in the presence of other interfering molecules. We envision that a highly selective multi-analyte detection of a large number of analytes is also possible by implementing multiple types of MIP-based electrochemical sensors on a single chip. Figure 1

The fabrication of molecularly imprinted polymer microspheres via Pickering emulsion polymerization stabilized with novel ferric hydroxide colloid

Micro-patterned molecularly imprinted polymer structures on functionalized diamond-coated substrates for testosterone detection

Molecularly imprinted Ni-polyacrylamide-based electrochemical sensor for the simultaneous detection of dopamine and adenine

Novel molecularly imprinted polymeric (MIP) micelles were prepared via macromolecule self-assembly of a photo-crosslinkable copolymer, combined with molecular imprinting technique using 4-acetaminophenol as the template molecule. First, an acrylic copolymer poly(DMA-co-HEA-co-EHA-co-St) was synthesized via free radical polymerization using (dimethylamino)ethylmethacrylate (DMA), 2-hydroxy ethylacrylate (HEA), 2-ethylhexyl acrylate (EHA) and styrene (St). Further post functionalization introduced a cross-linkable acrylate side groups into the polymer to form the photo-crosslinkable copolymer using isophorone diisocyanate (IPDI) as bridges. The photo-crosslinkable copolymer and 4-acetaminophenol were dissolved to give copolymer mixed solution. Water as a non-solvent, was added to the mixed solu- tion to induce the self-assembly micellization of the photo-crosslinkable copolymer, during which the template molecules (4-acetaminophenol) was entrapped in the micelles through the interactions between 4-acetaminophenol and the copolymer chain. The properties and morphology of MIP micelles were characterized by dynamic light scattering (DLS), zeta potential and transmission electron microscope (TEM). DLS results showed that the average hydrodynamic diameter was about 70 nm, which was supported by the result from the TEM measurements. The MIP micelle solution prepared was used as a bath solu- tion for electrodeposition. A MIP film was formed in situ on the electrode surface by electrodeposition of the MIP micelles and then crosslinked by UV radiation to lock the structure and improve the stability of the film. Finally the template mole- cules were removed from the film by extraction, leading to 4-acetaminophenol imprinted electrode. The electrochemical per- formance of the MIP electrode was evaluated by cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV). The resulting MIP sensor showed good response and selectivity towards 4-acetaminophenol. In addition, this MIP sensor showed excellent selectivity to 4-acetaminophenol, and the interferences from structurely similar analogues were ef- fectively avoided. The linear range was from 1×10

A novel capacitive sensor based on molecularly imprinted nanoparticles as recognition elements

The dendritic effect of nano mesoporous molecular sieve was first used to enhance molecular recognition of molecularly imprinted polymers (MIPs)-based polyhedral oligomeric silsesquioxanes (POSS). In this study, the MIPs were made using S-naproxen (S-NAP) as template molecule, 4-vinylpyridine (4-VP) as functional monomer, ethylene glycol dimethacrylate as cross-linker, 1-butyl-3-methylimidazoliumtetrafluoroborate ([BMIM]BF4)/DMSO as binary porogens, 1-propylmethacrylate-heptaisobutyl substituted as POSS monomer, and mesoporous molecular sieve (Mobil composition of matter No. 41, MCM-41) as dendritic scaffold. The influence of synthesis parameters on the imprinting effect, including the content of POSS monomer and derivatized MCM-41-MPS, the ratio of template to monomer, and the ratio of binary porogens were also investigated, respectively. The morphology of the polymers was characterized by scanning electron microscopy, nitrogen adsorption, and X-ray powder diffraction. The results showed that POSS&MCM-41-MPS MIP had a stronger imprinting effect with an imprinting factor 6.86, which is approximately 2.4, 2.3, and 3 times than that of POSS MIP, MCM-41-MPS MIP, and conventional MIP, respectively. The increase of affinity might be attributed to impediment of the chain motion of polymer due to improved POSS aggregation and the dipole interaction between the POSS units by introduce of MCM-41-MPS as scaffolds. The resulting POSS&MCM-41-MPS MIP was used as adsorbent for the enrichment of S-NAP in solid-phase extraction with a high recovery of 97.65% and the value of RSD was 0.94%.