Molecularly Imprinted Polymer Film Research Articles

A molecular imprinting electrochemical sensor for detection of anticancer drug amsacrine

PurposeThe purpose of this study is to develop a molecular imprinting electrochemical sensor for the specific detection of the anticancer drug amsacrine. The sensor used a composite of bacterial cellulose (BC) and silver nanoparticles (AgNPs) as a platform for the immobilization of a molecularly imprinted polymer (MIP) film. The main objective was to enhance the electrochemical properties of the sensor and achieve a high level of selectivity and sensitivity toward amsacrine molecules in complex biological samples.Design/methodology/approachThe composite of BC-AgNPs was synthesized and characterized using FTIR, XRD and SEM techniques. The MIP film was molecularly imprinted to selectively bind amsacrine molecules. Electrochemical characterization, including cyclic voltammetry and electrochemical impedance spectroscopy, was performed to evaluate the modified electrode’s conductivity and electron transfer compared to the bare glassy carbon electrode (GCE). Differential pulse voltammetry was used for quantitative detection of amsacrine in the concentration range of 30–110 µM.FindingsThe developed molecular imprinting electrochemical sensor demonstrated significant improvements in conductivity and electron transfer compared to the bare GCE. The sensor exhibited a linear response to amsacrine concentrations between 30 and 110 µM, with a low limit of detection of 1.51 µM. The electrochemical response of the sensor showed remarkable changes before and after amsacrine binding, indicating the successful imprinting of amsacrine in the MIP film. The sensor displayed excellent selectivity for amsacrine in the presence of interfering substances, and it exhibited good stability and reproducibility.Originality/valueThis study presents a novel molecular imprinting electrochemical sensor design using a composite of BC and AgNPs as a platform for MIP film immobilization. The incorporation of BC-AgNPs improved the sensor’s electrochemical properties, leading to enhanced sensitivity and selectivity for amsacrine detection. The successful imprinting of amsacrine in the MIP film contributes to the sensor's specificity. The sensor's ability to detect amsacrine in a concentration range relevant to anticancer therapy and its excellent performance in complex sample matrices add significant value to the field of electrochemical sensing for pharmaceutical analysis.

Green Synthesis of a Molecularly Imprinted Polymer Based on a Novel Thiophene-Derivative for Electrochemical Sensing.

An environmentally friendly and sustainable approach was adopted to produce a molecularly imprinted polymer (MIP) via electropolymerization, with remarkable electrochemical sensing properties, tested in tyrosine (tyr) detection. The 2,2'-bis(2,2'-bithiophene-5-yl)-3,3'-bithianaphtene (BT2-T4) was chosen as functional monomer and MIP electrosynthesis was carried out via cyclic voltammetry on low-volume (20 μL) screen-printed carbon electrodes (C-SPE) in ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ((BMIM) TFSI). An easy and rapid washing treatment allowed us to obtain the resulting MIP film, directly used for tyr electrochemical detection, carried out amperometrically. The sensor showed a linear response in the concentration range of 15-200 μM, with LOD of 1.04 µM, LOQ of 3.17 μM and good performance in selectivity, stability, and reproducibility. Tyrosine amperometric detection was also carried out in human plasma, resulting in a satisfactory recovery estimation. The work represents the first use of BT2-T4 as a functional monomer for the production of a molecularly imprinted polymer, with a green approach afforded by using a few microliters of a room temperature ionic liquid as an alternative to common organic solvents on screen-printed carbon electrodes, resulting in a valuable system that meets the green chemistry guidelines, which is today an essential criterion in both research and application field.

Selective detection of salivary cortisol using screen-printed electrode coated with molecularly imprinted polymer

A novel electrochemical sensor was developed for the detection of salivary cortisol levels. The sensor employs a combination of a molecularly imprinted polymer (MIP) and gold nanoparticles (AuNPs) that are electrodeposited onto a screen-printed electrode (SPE). The study utilised density functional theory and molecular docking techniques to determine the geometry of molecular orbitals, electrostatic potential energies, and binding energy of cortisol and the polymers. The thin film of cortisol-imprinted polymer on the SPE was created by electro-polymerizing pyrrole and thiophene-3-carboxylic acid on the electrode surface along with cortisol as the template molecule. The MIP film was characterised using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and electrochemical techniques. The sensor exhibited a linear response in the concentration range of 0.05 nmol L−1 to 2.5 μmol L−1, with a limit of detection of 0.01 nmol L−1, as determined by differential pulse voltammetry. This method offers a simple yet efficient and sensitive approach to detecting cortisol levels in human saliva samples.

Photoelectrochemical sensor for the detection of Escherichia coli O157:H7 based on TPA-NO2 and dual-functional polythiophene films

The detection of Escherichia coli (E. coli) is of great significance for the environment and human health. Herein, a photoelectrochemical (PEC) detection strategy based on molecularly imprinted polymers (MIPs) was proposed for the sensitive detection of E. coli. 4,4′,4″-Trinitrotriphenylamine (TPA-NO2) was prepared using a simple nitration reaction. Subsequently, MIP films were polymerized on the surface of TPA-NO2 using 1,3-dihydrothieno[3,2-d]pyrimidine-2,4-dione as the functional monomer with the dual functions of specific recognition and sensitization. The linear range was 10–108 CFU/mL and the limit of detection was 10 CFU/mL. It showed favorable recoveries in real sample tests of milk, orange juice and tomato. Additionally, the ability of functional monomers to bind excellently with E. coli was verified using molecular docking techniques. This research provided broader possibilities for constructing MIPs-PEC sensors and analyzing the interaction mechanism between E. coli and functional monomers.

Single-monomer dual templated MIP based electrochemical sensor for tartrazine and brilliant blue FCF

In this study, a dual-templated molecularly imprinted polymer-based electrochemical sensor was developed for the simultaneous analysis of two food additive dyes, brilliant blue FCF and tartrazine. Using a 3-aminophenyl boronic acid (3-APBA) monomer and the dual templates of brilliant blue FCF (BB) and tartrazine (TZ), the molecularly imprinted polymer (MIP) layer was electropolymerized on the carbon fibre paper (CFP) electrode. By using BB and TZ as template molecules along the electro-polymerization of 3-APBA, then removing both template molecules, the MIP film was generated on the surface of the CFP electrode. Due to the high surface area provided by modification, several complementary binding sites for template molecules are formed on the surface of the MIP sensor during this process of sensor fabrication. On the MIP/CFP electrode, the electrochemical behavior of BB and TZ was assessed. The monomer/template ratio, pH values, and influencing parameters like the electro-polymerization scanning cycles were all optimized. This sensor was applied to detect brilliant blue FCF and tartrazine in beverage and food samples using MIPAPBA/CFP electrode.

Mobile Point-of-Care Device Using Molecularly Imprinted Polymer-Based Chemosensors Targeting Interleukin-1β Biomarker.

Molecularly imprinted polymers (MIPs) have garnered significant attention as a promising material for engineering specific biological receptors with superior chemical complementarity to target molecules. In this study, we present an electrochemical biosensing platform incorporating MIP films for the selective detection of the interleukin-1β (IL-1β) biomarker, particularly suitable for mobile point-of-care testing (POCT) applications. The IL-1β-imprinted biosensors were composed of poly(eriochrome black T (EBT)), including an interlayer of poly(3,4-ethylene dioxythiophene) and a 4-aminothiophenol monolayer, which were electrochemically polymerized simultaneously with template proteins (i.e., IL-1β) on custom flexible screen-printed carbon electrodes (SPCEs). The architecture of the MIP films was designed to enhance the sensor sensitivity and signal stability. This approach involved a straightforward sequential-electropolymerization process and extraction for leaving behind cavities (i.e., rebinding sites), resulting in the efficient production of MIP-based biosensors capable of molecular recognition for selective IL-1β detection. The electrochemical behaviors were comprehensively investigated using cyclic voltammograms and electrochemical impedance spectroscopy responses to assess the imprinting effect on the MIP films formed on the SPCEs. In line with the current trend in in vitro diagnostic medical devices, our simple and effective MIP-based analytical system integrated with mobile POCT devices offers a promising route to the rapid detection of biomarkers, with particular potential for periodontitis screening.

Bisphenol A detection based on nano gold-doped molecular imprinting electrochemical sensor with enhanced sensitivity.

A facile electrochemical sensor based on nano gold-doped molecularly imprinted polymer (MIP) was proposed to realize the selective detection of bisphenol A (BPA) with enhanced sensitivity. Initially, gold-doped MIP (Au@MIP) film was constructed by electropolymerizing p-aminobenzoic acid (PABA) and BPA with in situ gold reduction to distribute gold nanoparticles nearby the imprinted cavities. Subsequently, the template molecules were further extracted from the polymer film, then the MIP could rebind with the template molecules to achieve specific detection of BPA. The nano gold-doped MIP increased the effective surface area and promoted conductivity when BPA was oxidized in the imprinted cavities, which improved the determination sensitivity. Under optimal conditions, the prepared sensor displayed a linear range from 0.5 to 100μM for BPA detection with a detection limit of 52nM. The designed sensor was further used to detect BPA in food samples, obtaining satisfactory recoveries from 96.7% to 107.6%.

Molecularly imprinted electrochemiluminescence sensor based on flake-like Au@Cu:ZIF-8 nanocomposites for ultrasensitive detection of malathion

The combination of electrochemiluminescence (ECL) and molecularly imprinted polymer (MIP) techniques offers distinct for detecting organophosphorus pesticides (OPs). Herein, a novel flake-like nanocomposites Au@Cu:ZIF-8 was successfully synthesized, as to design a molecularly imprinted electrochemiluminescence (MIP-ECL) sensor for the detection of malathion (MAL). The doped Cu2+ as a co-reaction promoter facilitated the generation of the active intermediate SO4•− for the cathodic reaction system with K2S2O8 as the co-reactant, while AuNPs were used as an excellent catalyst, further enhancing the ECL strength of the overall reaction system. Subsequently, MIP film was formed by the electropolymerization of Benzo[1,2-b:4,5-b′]dithiophene-4,8-dione as a functional monomer and MAL as a template molecule on the electrode surface. Confirmation of this process was achieved through molecular docking technique, which indicated that template molecule and functional monomer were tightly bound through non covalent bonds. The ECL signal was controlled by the elution and incubation of MAL by the MIP, thus establishing a novel method for MAL detection. The sensor showed a good linear relationship in the range of 10 pg/mL to 0.1 μg/mL with a detection limit of 0.18 pg/mL (S/N = 3). Furthermore, the recoveries of MAL detection in apple, cabbage and tomato samples ranged from 91.94% to 104.50%, indicating that the sensor offers potential applications for trace analysis of OPs in food and agricultural products.

Improving the Selectivity of the C-C Coupled Product Electrosynthesis by Using Molecularly Imprinted Polymer─An Enhanced Route from Phenol to Biphenol.

We developed a procedure for selective 2,4-dimethylphenol, DMPh, direct electro-oxidation to 3,3',5,5'-tetramethyl-2,2'-biphenol, TMBh, a C-C coupled product. For that, we used an electrode coated with a product-selective molecularly imprinted polymer (MIP). The procedure is reasonably selective toward TMBh without requiring harmful additives or elevated temperatures. The TMBh product itself was used as a template for imprinting. We followed the template interaction with various functional monomers (FMs) using density functional theory (DFT) simulations to select optimal FM. On this basis, we used a prepolymerization complex of TMBh with carboxyl-containing FM at a 1:2 TMBh-to-FM molar ratio for MIP fabrication. The template-FM interaction was also followed by using different spectroscopic techniques. Then, we prepared the MIP on the electrode surface in the form of a thin film by the potentiodynamic electropolymerization of the chosen complex and extracted the template. Afterward, we characterized the fabricated films by using electrochemistry, FTIR spectroscopy, and AFM, elucidating their composition and morphology. Ultimately, the DMPh electro-oxidation was performed on the MIP film-coated electrode to obtain the desired TMBh product. The electrosynthesis selectivity was much higher at the electrode coated with MIP film in comparison with the reference nonimprinted polymer (NIP) film-coated or bare electrodes, reaching 39% under optimized conditions. MIP film thickness and electrosynthesis parameters significantly affected the electrosynthesis yield and selectivity. At thicker films, the yield was higher at the expense of selectivity, while the electrosynthesis potential increase enhanced the TMBh product yield. Computer simulations of the imprinted cavity interaction with the substrate molecule demonstrated that the MIP cavity promoted direct coupling of the substrate to form the desired TMBh product.

Novel dual-recognition electrochemical biosensor for the sensitive detection of AFM1 in milk

Aflatoxin M1 (AFM1) is a highly carcinogenic and toxic compound that is commonly found in dairy foods such as milk. We developed an electrochemical MIP (molecularly imprinted polymer) and aptamer (Apt) based aptasensor (Apt-Au@PEIM/AFM1/MIP–Apt/AuNPs)/GCE) with dual-recognition signal amplification to detect AFM1 in milk. The MIP–Apt/AuNP/GCE sensor was prepared by synthesizing an MIP film through the electropolymerization of resorcinol on gold nanoparticles-modified electrodes. The dropwise addition of our cApt-Au@PEIM signal amplification probe could enhance the current signal response and improve the sensitivity of the sensor to detect AFM1. The AFM1 present in milk could prevent the probe from binding to the sensor, thereby drastically reducing the current signal. Under optimal experimental conditions, the sensor exhibits a linear range of 0.01–200 nM and a limit of detection of 0.07 nM (S/N = 3). The developed dual-recognition aptasensor would provide a novel and rapid method for specific detection of AFM1 in milk.

Recognition of bovine hemoglobin protein on molecularly imprinted polymer surfaces using nonlinear vibrational spectroscopy

Advancement in molecularly imprinted biomimetics has aided in developing robust artificial recognition-based materials, which can be customized for bio/chemo-sensing of distinct molecules. The present study reports a simple one-step synthesis and analysis of protein-imprinted polymer thin films as a recognition element directly onto a solid support. Dopamine has been explored as a versatile functional monomer for a molecularly imprinted polymer (MIP) matrix to fabricate polydopamine (PDA) thin films with bovine hemoglobin as a template protein molecule. A detailed molecular-level insight into the recognition of the template molecule at each step has been investigated using vibrational sum frequency generation (VSFG) spectroscopy. A suitable PDA-coated thin film is selected based on the extent of polymerized intermediates formed after non-imprinted polymer fabrication at different time durations. An optimally prepared film of MIP is specified by observing the spectral signature of the methyl groups from protein molecules at the air–polymer interface. The template removal from MIP films after the washing procedure and subsequent re-binding of the protein molecules were evaluated by VSFG spectroscopy. The insightful molecular-level findings from SFG spectroscopy demonstrate the fabrication of an imprinted matrix as a label-free chemical sensor.

Molecularly imprinted ultrasensitive cholesterol photoelectrochemical sensor based on perfluorinated organics functionalization and hollow carbon spheres anchored organic-inorganic perovskite

In spite of organic-inorganic perovskite emerging as a novel efficient light-harvesting material owing to their superior optical properties, excitonic properties, and electrical conductivity, the related applications are severely limited for their poor stability and selectivity. Herein, we introduced hollow carbon spheres (HCSs) and 2-(perfluorohexyl) ethyl methacrylate (PFEM) based molecularly imprinted polymers (MIPs) to dual-functionalize CH3NH3PbI3. HCSs can provide perovskite load conditions, passivate perovskite defects, increase carrier transport and effectively improve its hydrophobicity. The perfluorinated organic compound based MIPs film can not only enhance the water and oxygen stability of perovskite, but also endow it specific selectivity. Moreover, it can reduce the photoexcited electron-hole pair recombination and prolong the electron lifetime. Benefiting from the synergistic sensitization of HCSs and MIPs, an ultrasensitive photoelectrochemical platform (MIPs@CH3NH3PbI3@HCSs/ITO) for cholesterol sensing was acquired with a very wide linear range of 5.0 × 10−14−5.0 × 10−8 mol/L and an extremely low detection limit of 2.39 × 10−15 mol/L. The designed PEC sensor exhibited good selectivity and stability, as well as practicality for real sample analysis. The present work extended the development of the high-performance perovskite and showed its broad application prospect for advanced PEC construction.

RETRACTED ARTICLE: Fabrication of Molecularly Imprinted Polymer Films Based on Graphene Oxide and Carbon Nanotubes for Nitrogenous Compound Sensing in Fuel Chemicals

RETRACTED ARTICLE: Fabrication of Molecularly Imprinted Polymer Films Based on Graphene Oxide and Carbon Nanotubes for Nitrogenous Compound Sensing in Fuel Chemicals

Determination of tumor necrosis factor-α in serum using extended-gate field-effect transistor-based chemosensors with molecularly imprinted polymer-coated gold dendrites

Here, we developed extended-gate field-effect transistor (EG-FET)-based chemosensors with molecularly imprinted polymers (MIPs) on a gold-dendritic (AD) electrode to detect tumor necrosis factor-α (TNF-α) in serum. The poly(β-cyclodextrin) film was electrochemically prepared on the AD electrode using a potentiodynamic technique, followed by TNF-α immobilization by host-guest interaction. The MIP film was formed via electropolymerization of thiophene-3-amidoxime (T3A) monomer in PBS solution with one scan cycle at an applied voltage of 0–1.2 V. After electrochemical optimization, the sensing behavior (based on drain current, Ids) of the MIP films was investigated to explore the validity of the sensors, resulting in excellent reproducibility, reusability, and stability. Based on the ΔIds – CTNF-α regression curves obtained in serum containing various analyte concentrations, the imprinting factor (IF) of MIP-based EG-FET sensor was 5.55. The selectivity was evaluated by comparing sensing property using analogous cytokine proteins (interleukin 1β [IL-1β] and interleukin-6 [IL-6]). The MIP-based EG-FET sensors exhibited high sensitivity (LOD: 0.55 pg/mL, LOQ: 1.82 pg/mL) and excellent selectivity (coefficient (α)> 3). Based on the excellent sensing performances, including high sensitivity and selectivity, excellent reproducibility, robustness, reusability, and stability, our (EG-FET)-based chemosensor with TNF-α-recognizing MIP film can be used for the early diagnosis and point–of–care of immune-related diseases.

Detection of clenbuterol in meat samples using a molecularly imprinted electrochemical sensor with MnFe2O4-CQDs composite material

Clenbuterol hydrochloride (CLB) is a β-adrenergic agonizts that can stimulate specific receptors in muscles, leading to an increase in protein synthesis and lipid solubility, and consequently muscle fiber growth. As a result, it is a prohibited substance in sports. In this study, an electrochemical sensor based on molecular imprinting technology was proposed for high-sensitivity detection of CLB. MnFe2O4-carbon quantum dots (CQDs) composite material was prepared by a one-step solvent-thermal method and used as the electrode modification material to prepare the modified electrode. MIP (molecularly imprinted polymer) film was electro-polymerized using 3-aminophenylboronic acid as the functional monomer and CLB as the template molecule with the CV (cyclic voltammetry) technique. After washing out the CLB template molecule with an acetic acid-sodium acetate buffer solution, an MIP/MnFe2O4-CQDs-CS/GCE sensor with specific recognition performance for CLB was obtained. The factors that affect the performance of the sensor were investigated, including sensitivity, selectivity, stability, reproducibility, and repeatability. The research results showed that under the optimal conditions, the constructed sensor could detect CLB in the concentration range of 10 nM to 10 mM, with a calculated LOD of 0.041 μM.

Controllable preparation of silver-doped hollow carbon spheres and its application as electrochemical probes for determination of glycated hemoglobin

Silver-doped hollow carbon spheres (Ag@HCS) were firstly introduced as electrochemical probes for glycated hemoglobin (HbA1c) sensing at a molecularly imprinted polymer (MIP)-based carbon cloth (CC) electrode. Herein, Ag@HCS was prepared using one-pot polymerization of resorcinol and formaldehyde with AgNO3 on the SiO2 template, subsequent carbonization, and template removal. Furthermore, poly-aminophenylboronic acid (PABA) as the MIP film was used as a sensing platform for recognition of HbA1c, which captured the Ag@HCS probe by binding of HbA1c with aptamer modified on the probe surface. Due to regular geometry, large specific surface area, superior electrical conductivity, and highly-dispersed Ag, the prepared Ag@HCS probe provided an amplified electrochemical signal based on the Ag oxidation. By use of the sandwich-type electrochemical sensor, the ultrahigh sensitivity of 4.365 μA (μg mL−1)-1 cm−2 and a wide detection range of 0.8–78.4 μg mL−1 for HbA1c detection with a low detection limit of 0.35 μg mL−1 were obtained. Excellent selectivity was obtained due to the specific binding between HbA1c and PABA-based MIP film. The fabricated electrochemical sensing platform was also implemented successfully for the determination of HbA1c concentrations in the serum of healthy individuals.

A Facile Surface-Imprinting Strategy for Trypsin-Imprinted Polymeric Chemosensors Using Two-Step Spin-Coating

Surface imprinting used for protein recognition in functional cavities is highly effective in imprinting biomacromolecules to avoid template encapsulation during the formation of a molecularly imprinted polymer (MIP) matrix. Herein, we introduce a facile surface-imprinting method based on two-step spin-coating and photopolymerization to design highly efficient imprinted sites on polymeric films to detect trypsin (TRY). Well-distributed template imprinting is successfully achieved for maximized sensing responses by controlling the composition of functional monomers and crosslinkers in the precursor solution and the concentration of TRY in the imprinting solution. The MIP film exhibits higher sensitivity (−841 ± 65 Hz/(μg/mL)) with a coefficient of determination of 0.970 and a higher imprinting factor of 4.5 in a 0.24 µg/mL TRY solution compared to the nonimprinted polymer (NIP) film. Moreover, the limit of detection and limit of quantification are calculated to be 25.33 and 84.42 ng/mL, respectively. Finally, the selectivity coefficient is within the range of 3.90–6.78 for TRY against other proteins. These sensing properties are superior to those of the corresponding nonimprinted polymer matrix. Thus, the proposed facile surface-imprinting method is highly effective for protein imprinting with high sensitivity and selectivity.

Preparation of surface-modified electrode of copper(ii) oxide mixed with the molecularly imprinted polymer for enhancement of melamine detection with photoelectrochemical technique.

Melamine contamination in food and beverages affects short- and long-term health. In this work, enhanced sensitivity and selectivity in photoelectrochemical determination for melamine detection was achieved using copper(ii) oxide (CuO) combined with a molecularly imprinted polymer (MIP). A CuO nanomaterial was used to achieve MIP surface modification via co-precipitation synthesis. An MIP film was deposited by polymerizing the methacrylic acid monomer and a melamine template. The properties of the CuO nanomaterials, such as the surface morphology, chemical oxidation state, and crystalline structure, were characterized using field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction patterns (XRD), respectively. The diffuse reflection spectroscopy technique was applied to evaluate the optical properties of the CuO nanoparticles. The results indicated that the synthesized CuO nanomaterials had a monoclinic structure with an optical bandgap of 1.49 eV, which corresponds to absorbance in the visible light region. CPE electrodes with surface-modified CuO/MIP were measured using the photoelectrochemical techniques of cyclic voltammetry, differential pulse voltammetry (DPV), and amperometry. The modified CuO/MIP electrode for melamine detection in 7.4 pH PBS buffer solution exhibited a high sensitivity of 0.332 nA nM-1, with a linear range of 5.0-75.0 nM and a limit of detection of 2.45 nM. Moreover, real samples of various kinds of milk were applied to evaluate the sensing response of the prepared CuO/MIP electrode. The modified CuO/MIP electrodes could be reused seven times with good reproducibility and high selectivity for melamine detection.

Potentiometric MIP-Modified Screen-Printed Cell for Phenoxy Herbicides Detection

In this study, a molecularly imprinted polymer (MIP)-based screen-printed cell is developed for detecting phenoxy herbicides using 2-methyl-4-chlorophenoxyacetic acid (MCPA) as the template. MCPA is a phenoxy herbicide widely used since 1945 to control broadleaf weeds via growth regulation, primarily in pasture and cereal crops. The potentiometric cell consists of a silver/silver chloride pseudo-reference electrode and a graphite working electrode coated with a MIP film. The polymeric layer is thermally formed after drop-coating of a pre-polymeric mixture composed of the reagents at the following molar ratio: 1 MCPA: 15 MAA (methacrylic acid): 7 EGDMA (ethylene glycol dimethacrylate). After template removal, the recognition cavities function as the ionophore of a classical ion selective electrode (ISE) membrane. The detected ion is the deprotonated MCPA specie, negatively charged, so the measurements were performed in phosphate buffer at pH 5.5. A linear decrease of the potential with MCPA concentration, ranging from 4 × 10-8 to 1 × 10-6 mol L-1, was obtained. The detection limit and the limit of quantification were, respectively, 10 nmol L-1 and 40 nmol L-1. A Nernstian slope of about -59 mV/dec was achieved. The method has precision and LOD required for MCPA determination in contaminated environmental samples.

A ratiometric electrochemical sensing platform based on multifunctional molecularly imprinted polymer with catalytic activity for the detection of psychoactive substances

Molecularly imprinted polymers (MIPs) are widely used as artificial recognition element in sensing field, but their electrochemical sensing performances are generally affected by their poor catalytic activity and unruly condition change. In this work, an MIP film with catalysis (Fe-DMMIP) is constructed by electrodeposition of Fe-coordinated aminophenanthroline and 3,4-ethylenedioxythiophene on N, S doped C material, using cannabinoid (CBD) as template molecule. Due to the presence of Fe–N active sites, the obtained Fe-DMMIP possesses enzyme-like catalytic activity besides conventional recognition capability. Accordingly, the sensor exhibits high electrocatalytic activity and selectivity. Moreover, the Fe-DMMIP can produce a stable and well-defined signal as an internal reference around 0 V (vs. Ag/AgCl) for ratiometric sensing. Under the optimal conditions, the ratiometric signal is linear to CBD concentration in the range of 0.004–0.8 μmol L−1 (R2 = 0.9946) with a detection limit of 2.9 nmol L−1. The ratiometric sensor shows high reproducibility, stability and applicability. In addition, through replacing the template molecule, the resulting biomimetic sensor also exhibits good performance in sensing other psychoactive substances such as melatonin and 5-hydroxytryptophan, with LODs of 19 nmol L−1 and 8 nmol L−1for them, respectively. Therefore, the developed sensing platform has good prospects, and this work provides a new way for developing ratiometric electrochemical sensors with high sensitivity, reproducibility and anti-interference ability.