Molecularly Imprinted Polymer Membranes Research Articles

Wavelength-dependent photoelectrochemical response demonstrated by the determination of acetaminophen and rutin in differential molecularly imprinted polymers strategy

Herein, the excitation wavelength-dependent responses of the molecularly imprinted polymer (MIP) photoelectrochemical (PEC) sensors were investigated, using acetaminophen (AP), rutin (RT) and perfluorooctanoate (PFOA) as the model templates, pyrrole as functional monomer, CuInS2@ZnS/TiO2 NTs as the basic photoelectrode. With wavelength λ > 240 nm, the photocurrent of MIPPFOA enhanced at higher concentrations of PFOA. With increasing AP concentration, the photocurrents of MIPAP could decline with λ < 271 nm, not change at λ = 270 nm, or increase with λ > 270 nm. As RT concentration increased, the photocurrents of MIPRT could decrease (λ < 431 nm), not change (λ = 431 nm) or increase (λ > 431 nm). The PEC responses depend on the comprehensive interaction of two contrary mechanisms from the template molecules within the MIP membrane. The photocurrent is enhanced by the role of the electron donor for photo-generated holes but attenuated due to the steric hindrance effect and the excitation light intensity loss via absorption or scattering. The apparent molar absorption coefficient of AP and RT within MIP membranes are 9.1–19.4 folds of those measured from dilute solutions. By using a routine UV lamp as the light source, the photocurrents of MIPRT at 254 nm and MIPAP at 365 nm were used to determine RT and AP, with the detection limits of 5.3 and 16 nM, respectively. The interference from the non-specific adsorption of interferents on the surfaces of MIPAP and MIPRT was reduced by one order of magnitude via a differential strategy.

Fabrication of a surface molecularly imprinted polymer membrane based on a single template and its application in the separation and extraction of phenytoin, phenobarbital and lamotrigine.

An innovative molecularly imprinted polymer membrane (MIPM) was prepared with polyvinylidene difluoride (PVDF) as the support, phenytoin (PHT) as the single template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linking reagent, azobisisobutyronitrile as the initiator, and acetonitrile-dimethylformamide (1 : 1.5, v/v) as the porogen. These materials were characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller measurements and X-ray photoelectron spectroscopy. Their adsorption performances were evaluated through a series of experiments including isothermal adsorption, kinetic adsorption, selective adsorption, adsorption-desorption, reusability, and preparation reproducibility. Additionally, the application was explored by investigating the extraction recovery of MIPMs towards PHT, phenobarbital (PHB) and lamotrigine (LTG) in different matrices including methanol, normal saline (NS), phosphate buffer solution (PBS) and plasma. The results showed that MIPMs with rough and porous surfaces were successfully constructed, which offered good preparation reproducibility, reusability and selectivity. The adsorption capacities of MIPMs towards PHT, PHB and LTG were 2.312, 2.485 and 2.303 mg g-1, respectively, while their corresponding imprinting factors were 8.538, 12.122 and 4.562, respectively. The adsorption equilibrium of MIPMs was achieved within 20 min at room temperature without stirring or ultrasonication. The extraction recoveries of MIPMs for PHT, PHB or LTG in methanol, NS and PBS were more than 80% with an RSD% value of less than 3.64. In the case of plasma, the extraction recovery of MIPMs for PHT and PHB was more than 80% with an RSD% value of less than 2.41, while that of MIPMs for LTG was more than 65% with an RSD% value of less than 0.99. All the results indicated that the preparation method for MIPMs was simple, stable, and reliable, and the prepared MIPMs possessed excellent properties to meet the extraction application of PHT, PHB and LTG in different matrices.

Spectrum-resolved photoelectrochemical molecularly imprinted sensors for simultaneous determination of ascorbic acid and uric acid in a differential mode

Herein, a spectrum-resolved differential strategy was proposed to enhance further the selectivity of photoelectrochemical (PEC) sensors, demonstrated by the simultaneous determinations of ascorbic acid (AA) and uric acid (UA). Molecularly imprinted polymer (MIP) membranes for AA (MIPAA) and UA (MIPUA) were fabricated on the surface of TiO2 nanotubes via electropolymerization, using pyrrole as functional monomer, AA and UA as templates, respectively. It was shown that the increase in absorbance from AA or UA within the MIP membranes resulted in an intense decrease in the photocurrent of the PEC sensors. In the spectrum-resolved differential mode, ΔRIAA= (IAA/IAA0−IUA/IUA0)310 and ΔRIUA= (IUA0/IUA −IAA0/IAA)275 were used in the simultaneous determinations of AA and UA, respectively. Where IAA, IAA0, IUA and IUA0 are the photocurrents of MIPAA and MIPUA in sample and blank, the subscripts of 275 and 310 stand for the excitation wavelength (nm), respectively. The interference levels in the differential mode were reduced by one order of magnitude compared with the normal MIP mode. The spectrum-resolved differential PEC MIP sensors were used in the simultaneous determination of AA and UA in serum and urine samples, with the detection limits of 0.019 and 0.036 μM, respectively.

Development of a molecularly imprinted photoelectrochemical sensor for enhanced detection of ciprofloxacin in milk

In this work, a molecularly imprinted polymer (MIP)-based photoelectrochemical (PEC) sensor for the detection of ciprofloxacin (CIP) was constructed. Carbon-modified ZnO (ZnO/C) nanocomposite with adjustable zinc content was prepared by a carbonaceous method, facilitating visible light absorption and electron transition. The structure, morphology, and surface chemistry of ZnO/C were well characterized. The MIP membrane was formed by electropolymerizing, with ZnO/C nanocomposite, o-phenylenediamine (C6H4(NH3)2,o-PD), and CIP as highly efficient photoactive materials, functional monomer, and template, respectively. The PEC properties of different photoactive electrodes were measured and analyzed. The MIP-based PEC sensor showed excellent sensitivity and selectivity towards CIP, displaying a broad linear range from 0.01 nM to 1000 nM, a low detection limit of 8.41 pM, and satisfied recovery rates within 96.8%103.2%. The sensor exhibited reliable reproducibility and stability, with a relative standard deviation (RSD) of 2.48% for the CIP in milk. The constructed MIP-based PEC sensor not only provides a powerful and reliable route for the detection of CIP, but also can be extended to detect other antibiotics in food and natural environment.

Molecularly imprinted polymer membranes based on single template for recognition and extraction of carbamazepine and its structurally analogues

In this work, a novel molecularly imprinted polymer membrane (MIPM) using oxcarbazepine (OXC) as the single template and polyvinylidene difluoride membrane as the subtract was fabricated for recognition and extraction of carbamazepine (CBZ) and its analogues including OXC, carbamazepine-10,11-epoxide (CBZE), and monohydroxy derivative 10, 11-dihydro-10-hydroxy carbamazepine (MHD). The prepared MIPMs were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, Brunaner-emmet-teller measurements and X-ray photoelectron spectroscopy, showing the successful construction of uniform and porous polymers on the surface of membranes. A series of adsorption affinity tests were investigated, indicating the prepared materials had specific recognition capacity and excellent stability as novel sorbents. The maximum static adsorption capacities of MIPMs towards OXC, CBZ, MHD or CBZE was 4.246, 3.621, 2.316, or 4.877 mg·g−1, respectively. The MIPMs showed reusability and reproducibility. The usability of MIPMs was evaluated by combining MIPMs extraction and high performance liquid chromatography detection for the determination of CBZ, CBZE, OXC and MHD in different matrices including methanol, normal saline, phosphate buffer solution, and plasma. The mean recovery of four target compounds in methanol, normal saline and phosphate buffer solution was more than 75 %, while the mean recovery of CBZ and CBZE in plasma was more than 80 %. The results demonstrated that the proposed MIPMs is very suitable for the determination of OXC, CBZ, MHD and/or CBZE in different matrices.

A differential strategy to enhance the anti-interference ability of molecularly imprinted electrochemiluminescence sensor with a semi-logarithmic calibration curve

The non-specific adsorption behaviors of various interferents on the surface of a molecularly imprinted polymer (MIP) are adverse for the selectivity of an MIP-based sensor, which can be overcome via a differential strategy by using the differential signal between MIP- and non-imprinted polymer (NIP)-based sensors. However, the normal differential mode is not suitable for the MIP-based sensors with non-linear calibration curves. Herein, an improved differential strategy is reported for an MIP-based sensor with a semi-logarithmic calibration curve, demonstrated by an electrochemiluminescence (ECL) sensor for dopamine (DA). Glassy carbon electrode (GCE) was modified by the mixture of g-C3N4, TiO2 nanoparticles (NPs) and carbon nanotubes (CNTs). MIP membrane for DA was fabricated on the surface of g-C3N4/TiO2NPs/CNTs/GCE using chitosan for film-forming, obtained MIP@GCE. To enhance the anti-interference ability of the MIP-based DA sensor, the difference between exponential functions ECL intensities of MIP@GCE and NIP@GCE is used as the analytical signal in the improved differential strategy. The differential signal was increased linearly with increasing DA concentration ranging from 10 pM to 0.10 μM, with the detection limit of 5.6 pM. The interference level of Cu2+ on DA determination in the improved differential mode is only 9.7% of that in the normal MIP mode. The improved differential strategy can be used in other MIP-based sensors with semi-logarithmic calibration curves.

Hybridization and Characterization of a Deep Eutectic Solvent Molecularly Imprinted Polymer Membrane for the Removal of Bisphenol A

Hybridization and Characterization of a Deep Eutectic Solvent Molecularly Imprinted Polymer Membrane for the Removal of Bisphenol A

A novel differential ratiometric molecularly imprinted electrochemical sensor for determination of sulfadiazine in food samples

Herein, we report a novel differential ratiometric molecularly imprinted polymer (MIP) electrochemical sensor for sulfadiazine (SDZ). An MIP membrane with double templates, SDZ and propyl gallate (PG), was fabricated on glassy carbon electrode (GCE) modified by CuInS2/ZnS nanocomposites. After adding PG in the samples as the reference, the current differences between MIP@CuInS2/ZnS/GCE and non-imprinted polymer@CuInS2/ZnS/GCE at the potentials of 0.18 V (ΔIPG) and 0.92 V (ΔISDZ) were measured. The ratio of ΔISDZ/ΔIPG was used for SDZ determination in the differential and ratiometric dual-mode. The influence of the variations in electrode modification and sample enrichment conditions on the determination of SDZ can be suppressed by 2.8 ∼ 13.2-fold, enhancing the reproducibility and stability of the MIP sensor. The interference level was reduced by one order of magnitude compared with the normal MIP mode. The proposed sensors were used to determine SDZ in food samples, with the detection limit of 2.1 nM.

Nanoarchitectonics of on–off ratiometric signal amplified electrochemical sensor for chlorpromazine with molecularly imprinted polymer based on Ni-MOF/Fe-MOF-5 hybrid Au nanoparticles

A novel and stable on–off ratiometric electrochemical sensing platform for chlorpromazine (CPZ) detection by combing the selective recognition of molecularly imprinted polymer (MIP) technology and ratiometric quantification strategy. Gold nanoparticles (AuNPs) were first electrodeposited on a bare glassy carbon electrode surface and then modified with a mixture of Ni-MOF/Fe-MOF-5 by drop-coating, and subsequently electropolymerization polythionine (pTHi) as an internal reference to achieve a ratiometric on–off response. The reference signal of pTHi was obtained by the boiling water-bath-assisted in-situ electropolymerization method for the first time. Ni-MOF/Fe-MOF-5 hybrid AuNPs (Ni-MOF/Fe-MOF-5/AuNPs) not only benefited the output signal amplification, but also provided the enlarged surface for immobilization of pThi and MIPs, and served as catalytic active centers to oxidation CPZ. Then, the MIPs membrane was fabricated through in-situ electropolymerization by using CPZ as the template molecule, nicotinamide as a functional monomer. Ratiometric identifying and quantitative sensing model has been proposed based on the combination of MIP membrane as molecular recognition receptor and pTHi used as an internal reference probe, which improves the sensitivity and selectivity of the sensor. Under the optimal conditions, the ratiometric signals of peak current (ICPZ/IpTHi) were linear to CPZ concentration in the range of 0.001–40 μM and 40–900 μM, with the ultralow detection limit of 0.025 μM (S/N = 3). Furthermore, this sensor exhibited high anti-interference ability, reproducibility, satisfactory stability, and outstanding measurement performance in biological samples with favorable recoveries in the range of 98.11–100.81%. Together, the constructed on–off ratiometric MIP sensing platform is a promising tool for the rapid and accurate determination of antipsychotic drugs with high selectivity and stability.

Characterization of Molecularly Imprinted Polymers (MIPs) as Cholesterol-Absorbing Materials

Molecularly Imprinted Polymer (MIP) membranes as cholesterol absorbers have been successfully synthesized. MIP membranes can absorb cholesterol molecules because they have cavite (pores) and active groups that are selective and sensitive to cholesterol molecules. MIP membranes are synthesized from butyl acrylate monomers, cross-linkers, ethylene glycol dimethacrilate (EGDMA), initiators of 2- 2-dimethoxy-2-phenylacetophenone (DMPP, sodium dodecyl sulfate (SDS) as surfactants, and cholesterol as templates. MIP membranes are synthesized using photopolymerization irradiated with UV light. The results obtained in the form of powder solids can be characterized using UV-Vis spectrophotometry. The results obtained by UV-Vis spectrophotometry showed that the MIP membrane prepared a standard curve with a linear regression equation y = 0.0054x-0.007 with a value of R2 = 0.9982. This suggests that MIP membranes are selective and sensitive to analytes. At optimum absorption of the MIP-cholesterol membrane can absorb cholesterol molecules in the amount of 0.020 grams of cholesterol composition within 20 minutes

Rationally designed molecularly imprinted polymer membranes as antibody and enzyme mimics in analytical biotechnology

The paper is a self-review of works on development of new approaches to formation of mimics of receptor and catalytic sites of biological macromolecules in the structure of highly cross-linked polymer membranes and thin films. The general strategy for formation of the binding sites in molecularly imprinted polymer (MIP) membranes and thin films was described. A selective recognition of a number of food toxins, endocrine disruptors and metabolites is based on the results of computational modeling data for the prediction and optimization of their structure. A strategy proposed for the design of the artificial binding sites in MIP membranes was supported by the research performed by the authors on development of a number of the MIP membrane-based affinity and catalytic biosensors for selective and sensitive measurement (detection limits 0.3–100 nM) of the target analytes. Novel versatile approaches aimed at improving sensitivity of the developed biosensor systems were discussed.

A facile electrochemical method for rapid determination of 3-chloropropane-1,2-diol in soy sauce based on nanoporous gold capped with molecularly imprinted polymer

3-monochloropropane-1,2-diol (3-MCPD) is a well-known heat-produced food contaminant, which has been reported to be carcinogenic, nephrotoxic, and reproductively toxic. In this study, a facile electrochemical sensor based on nanoporous gold (NPG) capped with molecularly imprinted polymer (MIP) was constructed for the rapid and selective determination of 3-monochloropropane-1,2-diol (3-MCPD). Firstly, NPG was fabricated on the electrode through coating the glass carbon electrode (GCE) surface with NPG film to provide an ideal substrate for polymerization of the MIP membrane and improve the electrocatalysis activity of the sensor. Then, the MIP membrane was constructed on the NPG surface via self-assembly by electropolymerization to realize selective recognition of target 3-MCPD molecules. As a consequence of the combined effect of NPG and MIP, the optimized molecularly imprinted polymer/nanoporous gold/glassy carbon electrode (MIP/NPG/GCE) sensor exhibited outstanding analytical performance towards 3-MCPD with a much wider linear range from 10 −16 to 10 −7 mol/L and fairly low detection limit of 3.5 × 10 −17 mol/L (S/N = 3). Meanwhile, the constructed electrochemical sensor presented outstanding specificity, anti-interference capability, and reproducibility. In order to demonstrate practical applicability, the MIP/NPG/GCE was applied for the detection of 3-MCPD in real soy sauce and satisfactory results were obtained with recovery rates ranging from 105.90% to 107.52%. • An electrochemical sensor was prepared for detecting 3-MCPD using NPG and MIP. • NPG improved the electrocatalysis activity of the sensor. • The structure of NPG provided an ideal substrate for polymerization of MIP film. • The MIP film self-assembled on NPG realized selective recognition of 3-MCPD. • The fabricated sensor showed outstanding analytical performance towards 3-MCPD.

Development of enzyme/titanate nanosheet complex coated with molecularly imprinted polydopamine for colorimetric quercetin assay.

A novel hybrid material, which is an enzyme/inorganic nanosheet complex coated by molecularly imprinted polymer (MIP), was developed, and applied to colorimetric quercetin assay. First, an enzyme/inorganic nanosheet complex was prepared from horseradish peroxidase (HRP) enzyme and titanate nanosheet (TiOx), using electrostatic interactions between them in acetate buffer. In the next place, dopamine self-polymerization was performed in the presence of HRP/TiOx complex with quercetin as a template, to prepare MIP membrane onto the HRP/TiOx complex. After washing process, a new hybrid material, MIP-coated HRP/TiOx complex (MIP-HT) was obtained. MIP-HT adsorbed quercetin efficiently, compared with NIP-HT that is an HRP/TiOx complex coated with non-imprinted polydopamine. MIP-HT showed enzymatic activity for an oxidation reaction of guaiacol, which is a chromogenic substrate of HRP, whereas the enzymatic activity of NIP-HT was significantly suppressed. The amount of brown product, formed by the color reaction, reduced owing to the presence of quercetin in sample solution, and a good liner relationship was observed between the concentration of quercetin and the increment of absorbance at 470nm. The investigation using several biomolecules indicates that MIP-HT has the ability to detect quercetin and its analogues with selectivity. Therefore, MIP-HT shows great promise as a new and attractive material for use in colorimetric assay of quercetin or quercetin analogues.

Impedimetric Sensors for Cyclocreatine Phosphate Determination in Plasma Based on Electropolymerized Poly(o-phenylenediamine) Molecularly Imprinted Polymers.

Cyclocreatine and its water-soluble derivative, cyclocreatine phosphate (CCrP), are potent cardioprotective drugs. Based on recent animal studies, CCrP, FDA-awarded Orphan Drug Designation, has a promising role in increasing the success rate of patients undergoing heart transplantation surgery by preserving donor hearts during transportation and improving the recovery of transplanted hearts in recipient patients. In addition, CCrP is under investigation as a promising treatment for creatine transporter deficiency, an X-linked inborn error resulting in a poor quality of life for both the patients and the caregiver. A newly designed molecularly imprinted polymer (MIP) material was fabricated by the anodic electropolymerization of o-phenylenediamine on screen-printed carbon electrodes and was successfully applied as an impedimetric sensor for CCrP determination to dramatically reduce the analysis time during both the clinical trial phases and drug development process. To enhance the overall performance of the proposed sensor, studies were performed to optimize the electropolymerization conditions, incubation time, and pH of the background electrolyte. Scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry were used to characterize the behavior of the developed ultrathin MIP membrane. The CCrP-imprinted polymer has a high recognition affinity for the template molecule because of the formation of 3D complementary cavities within the polymer. The developed MIP impedimetric sensor had good linearity, repeatability, reproducibility, and stability within the linear concentration range of 1 × 10–9 to 1 × 10–7 mol/L, with a low limit of detection down to 2.47 × 10–10 mol/L. To verify the applicability of the proposed sensor, it was used to quantify CCrP in spiked plasma samples.

Ni-Co-LDH and Zn-Co Prussian blue analogue derived hierarchical NiCo2O4@ZnO/ZnCo2O4 microspheres with enhanced electrochemical sensing performance towards pentachloronitrobenzene

In this work, we developed a hierarchical structure and multi-component synergistic metal oxide hybrid material, and explored its practical application in monitoring pentachloronitrobenzene (PCNB). We used the ZnO/ZnCo2O4, obtained by calcining Zn-Co Prussian blue analogue (PBA), as the substrate and integrated Ni-Co layered double hydroxide (LDH) on its surface and calcined to obtain hierarchical NiCo2O4@ZnO/ZnCo2O4 microspheres (MSs). Due to the p-n heterojunction characteristics of p-type semiconductor NiCo2O4 and ZnCo2O4 and n-type semiconductor ZnO and the high specific surface area of the microspheres supported by the hierarchical structure conductive network, when this material was used to modify the glassy carbon electrode (GCE), it significantly enhanced the electrochemical sensing performance towards PCNB. Therefore, a new type of electrochemical sensor was constructed based on NiCo2O4@ZnO/ZnCo2O4 MSs and molecularly imprinted polymer (MIP) for the sensitive and highly selective detection of PCNB. Among them, the MIP membrane was fabricated by cyclic voltammetry (CV), and differential pulse voltammetry (DPV) was used to detect PCNB. Under the optimum conditions, the reduction peak current density of PCNB was linearly related to the concentration from 0.05 to 5.5 μM with a detection limit of 8.33 nM and a good sensitivity of 6.118 μA⋅μM−¹⋅cm−². Furthermore, the proposed MIP sensor exhibited high selectivity, reproducibility, repeatability, and stability, and had been used for the detection of PCNB residues in licorice, river water, and soil samples with satisfactory results.

Micro-Solid Phase Extraction of Polycyclic Aromatic Hydrocarbons in Water using either C18 or Molecularly Imprinted Polymer Membranes: Analytical Merits and Limitations

Sample pre-treatment is often the bottleneck in an analytical process. Due to the drawbacks of conventional sample pre-treatment methods, microextraction utilizing lower amounts of adsorbents and organic solvents are therefore favoured. A micro-solid phase extraction (μ-SPE) technique coupled with gas chromatography-flame ionization detection (GC-FID) was successfully developed for the analysis of selected polycyclic aromatic hydrocarbons (PA Hs), namely phenanthrene, fluoranthene, and pyrene, in environmental water. In this study, μ-SPE techniques using C18 and molecularly imprinted polymer (MIP) membranes were optimized, validated, and applied to the analysis of selected PA Hs in environmental water samples. The analytical merits were compared, and the two methods were evaluated in terms of linearity, repeatability, and relative recovery. Under the optimal extraction conditions, both μ-SPE techniques using either C18 or MIP membranes as the adsorbents offered comparable ultratrace analysis of the selected PA Hs in the range of 0.003 to 0.01 μg L–1. The extraction strength of C18 membranes was superior to that of MIP membranes for the extraction of low molecular weights PA Hs from water in the presence of humic acid as a matrix factor. The C18membranes overcome the non-covalence interaction between PA Hs and humic acid and thus achieve better recovery.

Chiral molecular imprinted sensor for highly selective determination of D-carnitine in enantiomers via dsDNA-assisted conformation immobilization

In this paper, a novel approach was established on the basis of a molecularly imprinted technique with the aid of double-stranded deoxyribonucleic acid (dsDNA) embedded in a molecularly imprinted polymer (MIP) membrane as a new functional unit with chiral recognition for highly specific chiral recognition. The chiral molecules were immobilized and anchored in the cavities of the MIP membrane on the basis of the three-dimensional structure of a molecule determined by the functional groups, spatial characterization of the cavities of MIPs, and the spatial orientation with dsDNA embedded in MIPs. D-carnitine was selected as an example of a chiral molecular template, which intercalated into dsDNA immobilized on the gold electrode surface to form dsDNA-D-carnitine complex, and then the complex was embedded in the MIP during electropolymerization. After elution, the stereo-selective cavities were obtained. Our findings have shown that AAAA-TTTT base sequence had high affinity for D-carnitine intercalation. Combined with the electrochemical detection method, MIP sensor was prepared. The selectivity of the MIP sensor to ultratrace D-carnitine was significantly improved; the sensor had remarkable stereo-selectivity and highly chiral specific recognition to D-carnitine, and L-carnitine with a concentration of 10,000 times D-carnitine did not interfere with the detection of D-carnitine in the assay of raceme. The sensor also exhibited high sensitivity to ultratrace D-carnitine determination with a linear response to the concentration of D-carnitine in the range of 3.0 × 10−16 mol/L to 4.0 × 10−13 mol/L, with a detection limit of 2.24 × 10−16 mol/L. The mechanism of chiral recognition was studied, and result showed that apart from the recognition effect of imprinted cavities, dsDNA provided chiral selectivity to the spatial orientation of chiral molecules via the intercalation of chiral molecules with dsDNA and electrostatic interaction with groups of DNA base.

Sensor Based on Molecularly Imprinted Polymer Membranes and Smartphone for Detection of Fusarium Contamination in Cereals.

The combination of the generic mobile technology and inherent stability, versatility and cost-effectiveness of the synthetic receptors allows producing optical sensors for potentially any analyte of interest, and, therefore, to qualify as a platform technology for a fast routine analysis of a large number of contaminated samples. To support this statement, we present here a novel miniature sensor based on a combination of molecularly imprinted polymer (MIP) membranes and a smartphone, which could be used for the point-of-care detection of an important food contaminant, oestrogen-like toxin zearalenone associated with Fusarium contamination of cereals. The detection is based on registration of natural fluorescence of zearalenone using a digital smartphone camera after it binds to the sensor recognition element. The recorded image is further processed using a mobile application. It shows here a first example of the zearalenone-specific MIP membranes synthesised in situ using “dummy template”-based approach with cyclododecyl 2, 4-dihydroxybenzoate as the template and 1-allylpiperazine as a functional monomer. The novel smartphone sensor system based on optimized MIP membranes provides zearalenone detection in cereal samples within the range of 1–10 µg mL−1 demonstrating a detection limit of 1 µg mL−1 in a direct sensing mode. In order to reach the level of sensitivity required for practical application, a competitive sensing mode is also developed. It is based on application of a highly-fluorescent structural analogue of zearalenone (2-[(pyrene-l-carbonyl) amino]ethyl 2,4-dihydroxybenzoate) which is capable to compete with the target mycotoxin for the binding to zearalenone-selective sites in the membrane’s structure. The competitive mode increases 100 times the sensor’s sensitivity and allows detecting zearalenone at 10 ng mL−1. The linear dynamic range in this case comprised 10–100 ng mL−1. The sensor system is tested and found effective for zearalenone detection in maize, wheat and rye flour samples both spiked and naturally contaminated. The developed MIP membrane-based smartphone sensor system is an example of a novel, inexpensive tool for food quality analysis, which is portable and can be used for the “field” measurements and easily translated into the practice.

Plasticizer-free polymer membrane potentiometric sensors based on molecularly imprinted polymers for determination of neutral phenols

Polymeric membrane potentiometric sensors based on molecularly imprinted polymers (MIPs) as the receptors have been successfully developed for detection of organic and biological species. However, it should be noted that all of the polymeric membrane matrices of these sensors developed so far are the plasticized poly(vinyl chloride) (PVC) membranes, which are usually suffered from undesired plasticizer leaching. Hence, for the first time, we describe a novel plasticizer-free MIP-based potentiometric sensor. A new copolymer, methyl methacrylate and 2-ethylhexyl acrylate (MMA-2-EHA), is synthesized and used as the sensing membrane matrix. By using neutral bisphenol A (BPA) as a model, the proposed plasticizer-free MIP sensor shows an excellent sensitivity and a good selectivity with a detection limit of 32 nM. Additionally, the proposed MMA-2-EHA-based MIP membrane exhibits lower cytotoxicity, higher hydrophobicity and better MIP dispersion ability compared to the classical plasticized PVC-based MIP sensing membrane. We believed that the new copolymer membrane-based MIP sensor can provide an appealing substitute for the traditional PVC membrane sensor in the development of polymeric membrane-based electrochemical and optical MIP sensors.

A signal on-off ratiometric electrochemical sensor coupled with a molecular imprinted polymer for selective and stable determination of imidacloprid

This work presents a signal on-off ratiometric electrochemical sensor coupled with a molecular imprinted polymer (MIP) for imidacloprid (IMI) determination. The ratiometric strategy corrects the detection results by setting 6-(Ferrocenyl)hexanethiol (FcHT) as an internal reference. The MIP membrane, as a molecular recognition receptor, has a three-dimensional structure and is complementary in the shape and chemical functionality to the template. The combination of a ratiometric strategy and MIP improves the sensitivity and selectivity of the sensors. The experimental parameters, such as monomer/template ratio, electropolymerization cycle and adsorption time, are optimized to improve the IMI sensing performance of the as-fabricated electrode. Under optimal electrochemical conditions, the proposed sensor is used to detect IMI in laboratory and real samples. In a range as wide as 5 × 10−7−1 × 10−4 mol L−1, a linear relationship is well established, and the value of the correlation coefficient is 0.9984. The limit of detection (LOD, S/N = 3) is well defined as 4.7 × 10−8 mol L−1. The recovery rates range from 97.4% to 103.5% while testing real samples. The fabricated electrode shows superior anti-interference ability for IMI determination in the presence of analogs at a higher level.