Analysis of imidacloprid residues in mango, cowpea and water samples based on portable molecular imprinting sensors.

Imidacloprid is a neonicotinoid insecticide widely used in the production and cultivation of crops. In recent years, the extensive use of imidacloprid in agricultural production has resulted in large amounts of pesticide residues in agricultural products and the environment. Therefore, it is necessary to establish a rapid, accurate, sensitive and convenient method for detecting imidacloprid pesticide residues to ensure the safety of agricultural products and the environment. To clarify how to use the molecular imprinting method for the electrochemical rapid residue detection of imidacloprid. This paper selected reduced graphene oxide and gold nanoparticles as modifiers modified on screen-printed carbon electrodes (SPCE) chitosan as a functional monomer, and imidacloprid as template molecule to prepare molecularly imprinted polymer, and applied this sensor to the residue detection of imidacloprid. The results showed that the concentration of imidacloprid showed a good linear relationship with the peak response current, and the detection limit of imidacloprid was 0.5 µM, while the sensor had good repeatability and interference resistance. The recoveries of imidacloprid spiked on three samples, mango, cowpea and water, were in the range of 90-110% (relative standard deviation, RSD<5%), which proved the practicality and feasibility of the assay established in this paper. The results of this paper can be used as a basis for the research on the detection of imidacloprid pesticide residues in food or environment.

Preparation and characterization of 96-well microplates coated with molecularly imprinted polymer for determination and biosimilarity assessment of recombinant human erythropoietin.

Synthesis and applications of molecularly imprinted polymers (MIP) are rapidly growing. In this study, a biomimetic MIP was prepared through silanes polymerization on the surface of 96-well microplates using recombinant human erythropoietin-alfa (rhEPO) as a template molecule. The rhEPO was immobilized onto the plate surface using bi-functional cross-linker and a thin imprinted layer following sol-gel procedure was constructed. After template extraction, uniform three-dimensional cavities compatible with the configuration of rhEPO were obtained. The rhEPO-MIP preparation was optimized using 2-level factorial design and response surface design where polymerization time and interactions between the different variable were found to be the most significant factors. Size-exclusion chromatography (SEC) was used to monitor the stability of the rhEPO under the investigated polymerization conditions. Determination of rhEPO using the MIP microplate showed good dynamic response fitting to the 4 PL regression model (0.9962) over a concentration range of 10.00 - 100.00 ng mL-1. Adsorption of rhEPO onto MIP followed the Langmuir isotherm model (r = 0.9957, χ2 =0.02786) with pseudo-second-order kinetics (r = 0.9984). The surface of the rhEPO-MIP was characterized using scanning electron microscopy (SEM) while step-by-step surface modification was tracked using Fourier transform infrared (FTIR) spectroscopy. The rhEPO-MIP was able to distinguish between the rhEPO-alfa template and modified rhEPO molecules; rhEPO-beta, hyperglycosylated and pegylated forms (imprinting factors < 2) and in the commonly used formulation additive human serum albumin (HSA) (R% = 113.96 -95.22%). The rhEPO-MIP was applied to compare the receptor-binding pattern to rhEPO and its biosimilars / structural analogues. The results were cross-validated using the conventional assay protocol (RP-HPLC and ELISA) and an acceptable correlation was observed with RP-HPLC (maximum deviation is 7.78%). This work confirmed the applicability of rhEPO-MIP with its unique binding features for batch release, stability and biosimilarity assessment as well as subsequent evaluation of batch-to-batch consistency during bioproduction of target analytes.

Determination of mold contamination using ergosterol imprinted particles.

Ergosterol is a key biochemical marker for fungal mycelial growth. In this study, molecularly ergosterol imprinted particles (Erg-MIPs) were newly synthesized for the selective detection of ergosterol in mold samples. Erg-MIPs were characterized via scanning electron microscopy, swelling studies, and surface area measurements. Maximum selective ergosterol adsorption achieved as 28.50 mg/g Erg-MIP. Selectivity studies showed that Erg-MIPs adsorbed Erg 2.01 and 3.27 times higher than that of cholesterol and stigmasterol, respectively. Erg adsorption from Aspergillus niger was found as 23.87 mg/g. Reusability of Erg-MIPs was studied and decrease in Erg adsorption capacity of the particles was negligible (3%). Erg-MIPs are good affinity materials for the selective Erg detection from food samples, prior to use in food industry.

Metal-organic frameworks for virus detection.

Virus severely endangers human life and health, and the detection of viruses is essential for the prevention and treatment of associated diseases. Metal-organic framework (MOF), a novel hybrid porous material which is bridged by the metal clusters and organic linkers, has become a promising biosensor platform for virus detection due to its outstanding properties including high surface area, adjustable pore size, easy modification, etc. However, the MOF-based sensing platforms for virus detection are rarely summarized. This review systematically divided the detection platforms into nucleic acid and immunological (antigen and antibody) detection, and the underlying sensing mechanisms were interpreted. The nucleic acid sensing was discussed based on the properties of MOF (such as metal ion, functional group, geometry structure, size, porosity, stability, etc.), revealing the relationship between the sensing performance and properties of MOF. Moreover, antibodies sensing based on the fluorescence detection and antigens sensing based on molecular imprinting or electrochemical immunoassay were highlighted. Furthermore, the remaining challenges and future development of MOF for virus detection were further discussed and proposed. This review will provide valuable references for the construction of sophisticated sensing platform for the detection of viruses, especially the 2019 coronavirus.

Fabrication of UMCM-1 based monolithic and hollow fiber - Metal-organic framework deep eutectic solvents/molecularly imprinted polymers and their use in solid phase microextraction of phthalate esters in yogurt, water and edible oil by GC-FID.

In this study, for the first time, hollow fiber and monolithic fiber were fabricated based on metal-organic framework deep eutectic solvents/molecularly imprinted polymers (MOF- DES/MIPs) and were used for microextraction of phthalate esters under termed hollow fiber liquid membrane-protected solid-phase microextraction (HFLMP-SPME) followed by gas chromatography- flame ionization detection. Several parameters influencing extraction recoveries of phthalate esters including adsorption and desorption parameters were investigated and optimized using fabricated MOF- DES/MIPs monolithic fiber. Under optimal conditions, detection limits (S/N = 3) of the method were in a range of 0.008-0.03 µg L-1 and limits of quantification (S/N = 10) were between 0.028 and 0.12 µg L-1. RSD (%) for intra-day and inter-day precisions were between 2.4-4.7% and 2.6-3.4%, respectively. Subsequently, this procedure was successfully applied with satisfactory results in the determination of phthalate esters in yogurt, water, and soybean oil samples. The R (%) ranged from 95.5 to 100.0% in different samples.

A novel electrochemical sensor based on ion imprinted polymer and gold nanomaterials for nitrite ion analysis in exhaled breath condensate.

Human Exhaled Breath Condensate (EBC) contains markers of several inflammatory diseases. Its analysis is of interest to a number of researchers. Nitrite ions (NO2-), which are widely used in our daily lives, are nevertheless among these indicators. In this study, a simple, fast, portable, non-invasive and cheap electrochemical sensor is developed for the analysis of the nitrite profile in EBC. In this regard, sodium nitrite (NaNO2) was first immobilized on self-assembled 2-aminothiophenol (2-ATP) on a screen-printed gold electrode (Au-SPE). Then, a polymer matrix composed of polyvinyl alcohol (PVA) crosslinked with glutaraldehyde (GA) was combined with gold nanoparticles (Au-NPs) to cover the modified Au-SPE and complete the fabrication of the Ion Imprinted Polymer (IIP) sensor. The electrochemical behaviour of the sensor was monitored using Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Differential Pulse Voltammetry (DPV) methods, while the morphology and chemical composition of its layers were observed by infrared Fourier transform (FTIR), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy coupled with energy dispersion X-Ray spectroscopy (SEM-EDS) techniques. In addition, after a successful control test using a Non-Imprinted Ion Polymer (NIIP) sensor, the obtained results demonstrated satisfactory sensitivity and selectivity to nitrite compared to co-existing interfering substances in EBC, such as nitrate, acetate and ammonium nitrate. Under improved experimental conditions, the nitrite IIP sensor exhibits responses proportional to nitrite concentrations (R2 = 0.96) over a concentration range of 0.5-50 µg mL-1 with a detection limit (LOD) of 4 µmol L-1 (signal-to-noise ratio S/N = 3). The proposed approach was well applied for the nitrite determination in EBC samples with a relative standard deviation (RSD = 4%) and could open clinical applications in respiratory medicine.

Selective extraction of cocaine from biological samples with a miniaturized monolithic molecularly imprinted polymer and on-line analysis in nano-liquid chromatography.

We report the on-line coupling of a monolithic molecularly imprinted polymer to nano-liquid chromatography for the selective analysis of cocaine and its main metabolite, benzoylecgonine, in complex biological samples. After the screening of different synthesis conditions, a monolithic molecularly imprinted polymer was in situ synthesized into a 100 µm internal diameter fused-silica capillary using cocaine as template, methacrylic acid as functional monomer, and trimethylolpropane trimethacrylate as cross-linker. Scanning electron microscopy was used to assess the homogeneous morphology of the molecularly imprinted polymer and its permeability was measured. Its selectivity was evaluated by nano-liquid chromatography-ultraviolet, leading to imprinting factors of 3.2 ±â€¯0.5 and 2.2 ±â€¯0.3 for cocaine and benzoylecgonine, respectively, on polymers resulting from three independent syntheses, showing the high selectivity and the repeatability of the synthesis. After optimizing the extraction protocol to promote selectivity, the monolithic molecularly imprinted polymer was successfully on-line coupled with nano-liquid chromatography-ultraviolet for the direct extraction and analysis of cocaine present in spiked human plasma and saliva samples. The repeatability of the obtained extraction recovery, between 85.4 and 98.7% for a plasma sample spiked at 100 ng mL-1, was high with relative standard deviation values lower than 5.8% for triplicate analyses on each of the three independently synthesized molecularly imprinted polymers. A linear calibration range was achieved between 100 and 2000 ng mL-1 (R2 = 0.999). Limits of quantification of 14.5 ng mL-1 and 6.1 ng mL-1 were achieved in plasma and urine samples, respectively. The very clean-baseline of the resulting chromatogram illustrated the high selectivity brought by the monolithic molecularly imprinted polymer that allows the removal of a huge peak corresponding to the elution of interfering compounds and the easy determination of the target analyte in these complex biological samples.

A fluorescent molecularly imprinted device for the on-line analysis of AFP in human serum.

MIT is a promising strategy in antibody free analysis for tumour markers. Conventional nanosized MIPs with off-line analysis are beset by tedious operation and unsatisfactory analysis performance. In this work, an on-line analytical device to directly detect AFP, which is a typical tumour marker in cancer screening, was prepared for the first time. A microscope slide was chosen to be the basis of the device. APBA-PA, a polymerizable fluorescent boronic acid monomer, was synthesised and grafted on the surface of the microscope slide to act as the signal transduction pathway between the templates and the device. Along with the hydrolysis of TEOS and the elution of the templates, a portable, stable, easy to operate and low-cost analysis device for AFP with excellent repeatability was successfully prepared. Owing to the excellent selectivity and highly sensitive fluorescence response ability of the device towards the templates, the on-line detection of AFP in human serum was realized. A series of characterizations were applied to the device, and its analysis performance and possible detection mechanism were carefully studied. Furthermore, the device exhibited appropriate application prospects by comparing its analysis results with those of the commercially available ELISA. In our perception, this work is an important step towards MIPs for clinical applications.

An impedimetric molecularly-imprinted biosensor for Interleukin-1ß determination, prepared by in-situ electropolymerization on carbon screen-printed electrodes.

This work reports the first electrochemical molecularly imprinted polymer (MIP) sensor for Interleukin-1beta (IL-1ß) detection, based on modified commercial screen-printed carbon electrode (SPCE) was successfully demonstrated. For this purpose, the carbon support was modified with a PEDOT/4-aminothiophenol layer prior to the MIP film to enhance sensitivity and signal stability. The MIP layer was constructed on top of this by electropolymerization of Eriochrome black T (EBT) in the presence of IL-1ß. The several steps of the biosensor assembly was followed by Raman spectroscopy and electroanalytical techniques. Using electrochemical impedance spectroscopy (EIS), a linear response in the range of 60 pM to 600 nM, with a LOD of 1.5 pM with (S/N = 3) was obtained in neutral PBS. Selectivity tests of the MIP biosensor made in spiked synthetic serum samples as well as against other structurally related (Myoglobin, of similar shape and size) or competing compounds (Immunoglobulin G, also present in the human serum) confirmed the good selectivity of the biosensor. Overall, the biosensor described herein has the potential to provide a simple and quick way for on-site screening of IL-1ß, with low sample/reagent consumption and enabling direct serum analysis, which constitutes a valuable alternative to other conventional methods.

The strategy of antibody-free biomarker analysis by in-situ synthesized molecularly imprinted polymers on movable valve paper-based device.

In this work, we provided a novel strategy of antibody-free biomarker analysis by in-situ synthesized molecularly imprinted polymers (MIPs) on movable valve microfluidic paper-based electrochemical device (Bio-MIP-ePADs) for clinical detection of biomarkers. The newly movable valves on the device enable continuous and convenient delivery of fluid, which guarantee the performance for fabricating MIPs structure during long time electropolymerization. Moreover, this strategy can directly detect antigens by taking advantage of molecular imprinting on paper-based device, which greatly decreases the cost during clinical testing, reduces the tedious washing procedure and does not need to consider the preservation of the antibody in enzyme linked immunosorbent assay (ELISA). This feature makes the chip suitable for the on-site family treatment or commercial products. To further validate the applicability of this proposed method for clinical diagnostic testing, carcinoembryonic antigen (CEA) was applied as prototyping model target for the clinical analysis. The proposed Bio-MIP-ePADs were cheap, easy to prepare, disposable and provided reliable analysis by comparing with ELISA. We hope the application of this technology will open up a new avenue to the point-of-care testing (POCT).

Ratiometric fluorescence molecularly imprinted sensor based on dual-emission quantum dots hybrid for determination of tetracycline.

A novel ratiometric fluorescence molecularly imprinted sensor based on a dual-emission quantum dot hybrid was fabricated and used as an alternative analytical tool for the detection of tetracycline. In the synthesis process, red-emitting quantum dots (r-QDs) and green-emitting quantum dots (g-QDs) were modified by two different methods. Afterward, a stepwise precipitation polymerization imprinting reaction was performed to prepare the novel ratiometric fluorescence molecularly imprinted sensor (MIP-g/r-QD sensor). The MIP-g/r-QD sensor integrated the advantages of molecularly imprinted polymers and ratiometric fluorescence probes. The specific recognition sites in the polymer layers could adsorb tetracycline molecules, and then they caused fluorescence quenching behavior of g-QDs via an electron transfer process. Under the optimal conditions, a linear relationship was obtained covering the range from 10 to 160 µmol/L, with a correlation coefficient of 0.9976 and a high imprinting factor of about 3.3. Moreover, the novel MIP-g/r-QD sensor was successfully applied to detect tetracycline in milk samples. This work provides a new way to fabricate an efficient ratiometric fluorescence molecularly imprinted sensor based on quantum dots for convenient, fast, and highly selective and sensitive detection of organic molecules. Graphical abstract A novel ratiometric fluorescence molecularly imprinted sensor based on a dual-emission quantum dot hybrid was fabricated and used as an alternative analytical tool for the detection of tetracycline. AIBN azoisobutyronitrile, EGDMA ethylene glycol dimethacrylate, KH-570 3-(methacryloyloxy)propyltrimethoxysilane, OVDAC octadecyl-4-vinylbenzyldimethylammonium chloride, PDDA poly(diallyldimethylammonium chloride), QD quantum dot, TEOS tetraethoxysilane.

Recent advances of molecularly imprinted polymer-based sensors in the detection of food safety hazard factors.

With increasing economic globalization, food safety is becoming the most serious concern in the food production and distribution system. Food safety hazard factors (FSHFs) can be categorized into chemical hazards, biological hazards and physical hazards, with the detection of the former two having fascinated interdisciplinary research areas spanning chemistry, material science and biological science. Molecularly imprinted polymer (MIP) -based sensors overcome many limitations of traditional detection methods and provide opportunities for efficient, sensitive and low-cost detection using smart miniaturized equipment. With highly specific molecular recognition capacity and high stability in harsh chemical and physical conditions, MIPs have been used in sensing platforms such as electrochemical, optical and mass-sensitive sensors as promising alternatives to bio-receptors for food analysis. In this systemic review, we summarize recent advances of MIPs and MIP-based sensors, such as popular monomers, usual polymerization strategies, fresh modification materials and advanced sensing mechanisms. The applications of MIP-based sensors in FSHF detection are discussed according to sensing mechanisms, including electrochemistry, optics and mass-sensitivity. Finally, future perspectives and challenges are discussed.

Fully automated method based on on-line molecularly imprinted polymer solid-phase extraction for determination of lovastatin in dietary supplements containing red yeast rice.

A fully automated method for the determination of lovastatin in dietary supplements containing red yeast rice has been developed. It uses a sequential injection analysis system combined with solid-phase extraction applying highly selective molecularly imprinted polymer sorbent. A miniaturized column for on-line extraction was prepared by packing 4.5 mg of the sorbent in a 5.0 × 2.5-mm-i.d. cartridge, which was used in the flow manifold. Sequential injection analysis manifold enabled all steps of lovastatin extraction and continuous spectrophotometric detection at 240 nm. A limit of detection of 60 µg g-1, a limit of quantitation of 200 µg g-1, and a linear calibration range of 200-2000 µg g-1 were achieved. Intra-day and inter-day precision values (RSD) were ≤ 6.7% and ≤ 4.9%, respectively, and method recovery values of spiked red yeast rice extracts at 200, 1000, and 2000 µg g-1 concentration levels were 82.9, 95.2, and 87.7%. Our method was used for determination of lovastatin lactone in four dietary supplements containing red yeast rice as a natural source of lovastatin, also known as monacolin K. The extracted samples were subsequently analyzed by the reference UHPLC-MS/MS method. Statistical comparison of results (F test, t test, α = 0.05) obtained by both methods did not reveal significant difference. A substantial advantage of the new automated approach is high sample throughput thanks to the analysis time of 7.5 min, miniaturization via down-scaling the extraction column, and smaller sample and solvent consumption, as well as reduced generation of waste. Graphical abstract ᅟ.

Polyelectrolyte-Graphene Oxide Multilayer Composites for Array of Microchambers which are Mechanically Robust and Responsive to NIR Light.

Development of composite polymer/graphene oxide (GO) materials attracts significant attention due to their unique properties. In this work, highly ordered arrays of hollow microchambers made of composite polyelectrolyte/GO multilayers (PEGOMs) are successfully fabricated via layer-by-layer assembly on sacrificial or sustainable templates having imprinted patterns of microwells on their surface. Mechanical and optical properties of PEGOMs are studied by nanoindentation and near-infrared (NIR) absorption spectroscopy. Incorporation of three GO layers in between the polyelectrolyte multilayer stacks increases Young's modulus and critical stress of the microchambers by a factor of 5.6 and 2.6, respectively. Optical density of this PEGOM film is found to decrease gradually from 0.14 at λ = 800 nm to 0.06 at λ = 1500 nm. Remote opening of PEGOM microchambers with NIR laser beam is also demonstrated. One of the possible applications of the developed structures includes micropackaging and delivery systems in biological tissues with remote triggering.

Effect of Formulation on the Binding Efficiency and Selectivity of Precipitation Molecularly Imprinted Polymers.

This study investigated the effect of feed formulation: the template:functional monomer (T:fM) and functional monomer:crosslinker (fM:X) ratios as well as the initiator concentration, on the binding performance and selectivity of caffeine (CAF) and theophylline (THP) imprinted polymers obtained by precipitation polymerisation in acetonitrile at 60 °C using methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as functional monomer and crosslinker, respectively. Template incorporation, monitored by quantitative ¹H-NMR spectroscopy, ranged from 8 to 77% and was found to be more favourable at both high and low T:fM ratios, low fM:X ratio and high initiator concentration. The resulting T:fM ratio in most MIPs were found to be lower than their feed ratios. Incorporation of THP into the polymers was observed to be consistently higher than CAF and, for most MIPs, the observed binding capacities represent less than 10% of the incorporated template. Improved imprinting factors were obtained from molecularly imprinted polymers (MIPs) with high crosslinker content, i.e., fM:X ratio of 1:10, and high initiator concentration, i.e., initiator:total monomer (I:tM) ratio of 1:5, while T:fM ratio (1:2 to 1:8) was found not to influence binding capacities and imprinting factors (IF). The NIPs showed no preference for either CAF or THP in competitive selectivity studies while MIPs were observed to bind preferentially to their template with THP displaying higher selectivity (72⁻94%) than CAF (63⁻84%). Template selectivity was observed to increase with increasing initiator concentration, with MIPs from I:tM ratio of 1:5 shown to be the most selective towards CAF (84%) and THP (93%). The fM:X ratio only showed minimal effect on MIP selectivity. Overall, for the MIP systems under study, template incorporation, binding capacity, imprinting factor and selectivity are enhanced at a faster rate of polymerisation using an I:tM ratio of 1:5. Polymer particles obtained were between 66 to 140 nm, with MIPs generally smaller than their NIP counterparts, and have been observed to decrease with increasing T:fM and fM:X ratios and increase with increasing initiator concentration.

Electrochemosensor for Trace Analysis of Perfluorooctanesulfonate in Water Based on a Molecularly Imprinted Poly( o-phenylenediamine) Polymer.

This work is aimed at developing an electrochemical sensor for the sensitive and selective detection of trace levels of perfluorooctanesulfonate (PFOS) in water. Contamination of waters by perfluorinated alkyl substances (PFAS) is a problem of global concern due to their suspected toxicity and ability to bioaccumulate. PFOS is the perfluorinated compound of major concern, as it has the lowest suggested control concentrations. The sensor reported here is based on a gold electrode modified with a thin coating of a molecularly imprinted polymer (MIP), prepared by anodic electropolymerization of o-phenylenediamine (o-PD) in the presence of PFOS as the template. Activation of the sensor is achieved by template removal with suitable a solvent mixture. Voltammetry, a quartz crystal microbalance, scanning electron microscopy and elemental analysis were used to monitor the electropolymerization process, template removal, and binding of the analyte. Ferrocenecarboxylic acid (FcCOOH) has been exploited as an electrochemical probe able to generate analytically useful voltammetric signals by competing for the binding sites with PFOS, as the latter is not electroactive. The sensor has a low detection limit (0.04 nM), a satisfactory selectivity, and is reproducible and repeatable, giving analytical results in good agreement with those obtained by HPLC-MS/MS analyses.

Preparation of a molecularly imprinted sensor based on quartz crystal microbalance for specific recognition of sialic acid in human urine.

A novel molecularly imprinted quartz crystal microbalance (QCM) sensor was successfully prepared for selective determination of sialic acid (SA) in human urine samples. To obtain the QCM sensor, we first modified the gold surface of the QCM chip by self-assembling of allylmercaptane to introduce polymerizable double bonds on the chip surface. Then, SA molecularly imprinted polymer (MIP) nanofilm was attached to the modified QCM chip surface. For comparison, we have also characterized the nonmodified and improved surfaces of the QCM sensor by using atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. We then tested the selectivity and detection limit of the imprinted QCM sensor via a series of adsorption experiments. The results show a linear response in the range of 0.025-0.50 µmol L-1 for sialic acid. Moreover, the limit of detection (LOD) of the prepared imprinted QCM sensor was found to be 1.0 nmol L-1 for sialic acid, and high recovery values range from 87.6 to 108.5% with RSD < 8.7 (n = 5) for the spiked urine sample obtained. Overall, this work presents how a novel QCM sensor was developed and used to detect sialic acid in human urine samples. Graphical abstract Specific recognition of sialic acid by the MIP-QCM sensor system.

Heparin molecularly imprinted polymer thin flm on gold electrode by plasma-induced graft polymerization for label-free biosensor.

Heparin, a highly sulfated glycosaminoglycan, is an important biomaterial having biological and therapeutic functionalities such as anticoagulation, regeneration, and protein stabilization. This study addresses a label-free quartz crystal microbalance (QCM) biosensor for heparin detection based on a macromolecularly imprinted polymer (MIP) as an artificial recognition element. We demonstrate the novel strategy for MIP in the form of thin film on a gold (Au) electrode with the plasma-induced graft polymerization (PIP) technique. The procedure of PIP is as follows: (i) Hexamethyldisiloxane plasma-polymerized thin film (PPF) as a pre-coating scaffold of active species for PIP (post-polymerization) is deposited on an Au electrode. (ii) The PPF/Au electrode is soaked in an water solution containing heparin (template), (2-(methacryloxy)-ethyl)trimethylammonium chloride acrylamide (functional monomer), acrylamide, and N,N-methylenebisacrylamide (crosslinker). Double bonds of monomer and crosslinker attacked by residually active species in pre-coating PPF cause radical chain reaction. Consequently, a growing polymer network of 20 nm thickness of PIP-MIP thin film is formed and grafted on the PPF/Au surface. (iii) The PIP-MIP/PPF/Au is washed by sodium chloride solution so as to remove the template. Non-imprinted polymer (NIP) is carried out like the same procedure without a template. The AFM, XPS, and QCM measurements show that the PIP process facilitates macromolecularly surface imprinting of template heparin where the template is easily removed and is rapidly rebound to PIP-MIP without a diffusional barrier. The heparin-PIP-MIP specifically binds to heparin compared with heparin analog chondroitin sulfate C (selective factor: 4.0) and a detectable range of heparin in the presence of CS (0.1 wt%) was 0.001-0.1 wt%. The PIP-NIP does not show selectivity between them. The evaluated binding kinetics are association (ka = 350 ±â€¯100 M-1 s-1), dissociation (kd = (5.0 ±â€¯2.0) × 10-4 s-1), and binding (KD = 1.3 ±â€¯0.6 µM) constants, demonstrating that the PIP-MIP as a synthetic antibody can be applied to analytical chemistry.

Selective amperometric flow-injection analysis of carbofuran using a molecularly-imprinted polymer and gold-coated-magnetite modified carbon nanotube-paste electrode.

Herein, we propose a new approach for selective determination of carbofuran (CBF) in vegetables, based on a simple flow-injection system using a molecularly-imprinted amperometric sensor. The sensor design is based on a carbon-paste electrode decorated with carbon nanotubes and gold-coated magnetite (CNTs-Fe3O4@Au/CPE) coated with a molecularly-imprinted polymer (MIP) for CBF sensing. The MIP was synthesized on the electrode surface by electropolymerization using a supramolecular complex, namely 4-ter-butylcalix [8] arene-CBF (4TB[8]A-CBF), as the template. We used o-phenylenediamine as the functional monomer. Our results demonstrate that incorporation of the MIP coating improves the electrochemical catalytic properties of the electrode, increases its surface area, and increases CBF selectivity by modulating the electrical signal through elution and re-adsorption of CBF. The imprinted sensor (MIP-CNTs-Fe3O4@Au/CPE) was used in a flow-injection analysis (FIA) system. Experimental conditions were investigated in amperometric mode, with the following optimized parameters: phosphate buffer solution (0.1M, pH 8.0) as the carrier, flow rate 0.5mLmin-1, applied potential +0.50V. When used in the FIA system, the designed imprinted sensor yields a linear dynamic range for CBF from 0.1 to 100µM (r2 = 0.998) with a detection limit of 3.8nM (3Sb), and a quantification limit of 12.7nM (10Sb). The sensor exhibits acceptable precision (%RSD = 4.8%) and good selectivity toward CBF. We successfully applied the electrode to detect CBF in vegetable samples.

Recent advances and future prospects in molecularly imprinted polymers-based electrochemical biosensors.

Molecularly imprinted polymers (MIPs)-based electrochemical biosensors (ECBSs) have many advantages from MIPs and ECBSs, such as high selectivity and sensitivity, chemical/mechanical stability, reusability, low limit of detection, facile preparation and low cost. MIPs-based ECBSs attract much attention in medical diagnose, biological analysis, environmental monitoring, food safety evaluation, etc. Due to the capacity of highly specific recognition for target biomolecules, MIPs-based ECBSs have been smartly designed and extensively used for electrochemical sensing applications in recent years, exhibiting obvious superiority over other analytical techniques. In this review, firstly we systematically summarize the recent advances of MIPs-based ECBSs reported in recent years, referring to the preparation, structures and components of sensing systems. Secondly, we highlight the sensing applications for various significant biomolecules (proteins, antibiotics, pesticide, neurotransmitter, hormone, etc.), and demonstrate the sensing mechanism and detection performance. Finally, the rational summaries, present challenges and future prospects in the field of MIPs-based ECBSs have been discussed reasonably.