Nanofibrous Conductive Sensor for Limonene: One-Step Synthesis via Electrospinning and Molecular Imprinting.

Detecting volatile organic compounds (VOCs) emitted from different plant species and their organs can provide valuable information about plant health and environmental factors that affect them. For example, limonene emission can be a biomarker to monitor plant health and detect stress. Traditional methods for VOC detection encounter challenges, prompting the proposal of novel approaches. In this study, we proposed integrating electrospinning, molecular imprinting, and conductive nanofibers to fabricate limonene sensors. In detail, polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) served here as fiber and cavity formers, respectively, with multiwalled carbon nanotubes (MWCNT) enhancing conductivity. We developed one-step monolithic molecularly imprinted fibers, where S(-)-limonene was the target molecule, using an electrospinning technique. The functional cavities were fixed using the UV curing method, followed by a target molecule washing. This procedure enabled the creation of recognition sites for limonene within the nanofiber matrix, enhancing sensor performance and streamlining manufacturing. Humidity was crucial for sensor working, with optimal conditions at about 50% RH. The sensors rapidly responded to S(-)-limonene, reaching a plateau within 200 s. Enhancing fiber density improved sensor performance, resulting in a lower limit of detection (LOD) of 137 ppb. However, excessive fiber density decreased accessibility to active sites, thus reducing sensitivity. Remarkably, the thinnest mat on the fibrous sensors created provided the highest selectivity to limonene (Selectivity Index: 72%) compared with other VOCs, such as EtOH (used as a solvent in nanofiber development), aromatic compounds (toluene), and two other monoterpenes (α-pinene and linalool) with similar structures. These findings underscored the potential of the proposed integrated approach for selective VOC detection in applications such as precision agriculture and environmental monitoring.

Multiplexed neurochemical sensing with sub-nM sensitivity across 2.25 mm2 area.

Multichannel arrays capable of real-time sensing of neuromodulators in the brain are crucial for gaining insights into new aspects of neural communication. However, measuring neurochemicals, such as dopamine, at low concentrations over large areas has proven challenging. In this research, we demonstrate a novel approach that leverages the scalability and processing power offered by microelectrode array devices integrated with a functionalized, high-density microwire bundle, enabling electrochemical sensing at an unprecedented scale and spatial resolution. The sensors demonstrate outstanding selective molecular recognition by incorporating a selective polymeric membrane. By combining cutting-edge commercial multiplexing, digitization, and data acquisition hardware with a bio-compatible and highly sensitive neurochemical interface array, we establish a powerful platform for neurochemical analysis. This multichannel array has been successfully utilized in vitro and ex vivo systems. Notably, our results show a sensing area of 2.25 mm2 with an impressive detection limit of 820 pM for dopamine. This new approach paves the way for investigating complex neurochemical processes and holds promise for advancing our understanding of brain function and neurological disorders.

Cytochrome c electrochemical detection utilizing molecularly imprinted poly(3, 4-ethylenedioxythiophene) on a disposable screen printed carbon electrode.

Cytochrome c (cyt c) has been found to play a function in apoptosis in cell-free models. This work presents the creation of molecularly imprinted conducting poly(3, 4-ethylenedioxythiopene) (MIPEDOT) on the surface of a screen printed carbon electrode (SPCE) for cyt c. Cyt c was imprinted by electropolymerization due to the presence of an EDOT monomer hydrophobic functional group on SPCE, using CV to obtain highly selective materials with excellent molecular recognition ability. MIPEDOT was characterized by CV, EIS, and DPV using ferricyanide/ferrocyanide as a redox probe. Further, the characterization of the sensor was accomplished using SEM for surface morphological confirmation. Using CV, the peak current measured at the potential of +1 to -1 V (vs. Ag/AgCl) is linear in the cyt c concentration range from 1 to 1200 pM, showing a remarkably low detection limit of 0.5 pM (sensitivity:0.080 µA pM). Moreover, the applicability of the approach was successfully confirmed with the detection of cyt c in biological samples (human plasma). Similarly, our research has proven a low-cost, simple, and efficient sensing platform for cyt c detection, rendering it a viable tool for the future improvement of reliable and exact non-encroaching cell death detection.

Molecular imprinting electrochemiluminescence sensor based on nitrogen-doped carbon quantum dots /Ru(bpy)3@SiO2 for the determination of citrinin.

An electrochemiluminescence (ECL) sensor based on molecular imprinting polymer and SiO2 nanoparticles loaded Ru(bpy)3 and nitrogen-doped carbon quantum dots (NCQDs) is constructed for citrinin detection. The Ru(bpy)3 acts as ECL emitter, and the NCQDs cooperate with tri-n-propylamine (TPA) in solution as a coreactant to facilitate the luminescence. The citrinin imprinted poly(p-aminothiophenol) film is deposited on the surface of the luminophore by electrochemical method, which can immobilize the luminophore besides recognizing the target. The obtained ECL sensor exhibits high sensitivity, stability, and reproducibility. The change of ECL intensity and the logarithm of citrinin concentration display a good linear relationship in the range 1.0 to 100 pg mL-1, and the detection limit is 5 fg mL-1. When it is applied to the detection of citrinin contents in food sample (i.e., rice and millet) solutions, the RSD is less than 6.1%, and the recoveries for spiked standards range from 95.5 to 102.0%. Hence, this work provides a promising alternative for citrinin detection.

On-Demand, Reversible, Ultrasensitive Polymer Membrane Based on Molecular Imprinting Polymer.

The development of in vivo, longitudinal, real-time monitoring devices is an essential step toward continuous, precision health monitoring. Molecularly imprinted polymers (MIPs) are popular sensor capture agents that are more robust than antibodies and have been used for sensors, drug delivery, affinity separations, assays, and solid-phase extraction. However, MIP sensors are typically limited to one-time use due to their high binding affinity (>107 M-1) and slow-release kinetics (<10-4 µM/sec). To overcome this challenge, current research has focused on stimuli-responsive MIPs (SR-MIPs), which undergo a conformational change induced by external stimuli to reverse molecular binding, requiring additional chemicals or outside stimuli. Here, we demonstrate fully reversible MIP sensors based on electrostatic repulsion. Once the target analyte is bound within a thin film MIP on an electrode, a small electrical potential successfully releases the bound molecules, enabling repeated, accurate measurements. We demonstrate an electrostatically refreshed dopamine sensor with a 760 pM limit of detection, linear response profile, and accuracy even after 30 sensing-release cycles. These sensors could repeatedly detect <1 nM dopamine released from PC-12 cells in vitro, demonstrating they can longitudinally measure low concentrations in complex biological environments without clogging. Our work provides a simple and effective strategy for enhancing the use of MIPs-based biosensors for all charged molecules in continuous, real-time health monitoring and other sensing applications.

Novel biomimetic Prussian blue nanocubes-based biosensor for Tau-441 protein detection.

Tau protein is a promising biomarker for early diagnosis of Alzheimer's disease. Therefore, there is an urgent need to develop a simple and effective method for its detection. To this end, an innovative sensing device was developed using a carbon screen-printed electrode (C-SPE) decorated with graphene oxide/Prussian Blue nanocubes (GO/PBNCs) for the selective and sensitive determination of Tau-441 protein. The molecular imprinting polymer (MIP) was built on the GO/PBNCs/C-SPE by electropolymerizing 3-aminophenol (3-AMP) in the presence of the target protein using chronoamperometry, and the template was subsequently removed from the polymer matrix with oxalic acid. In parallel, a non-imprinted material (NIP) was also prepared in the absence of the target for comparison purposes. Scanning electron microscopy and transmission electron microscopy, were used to study the morphology of the modified electrode and electrochemical techniques were used to monitor the stepwise assembly of the sensor. Under optimized conditions, the sensing platform exhibited a linear range within 1.09 and 2.18 nmol/L and a detection limit of 0.01 pmol/L in spiked phosphate buffer solution (PBS). The MIP sensor showed minimal interference with uric acid and bovine albumin. The simplicity of production, affordable cost and promising performance make this sensor a potential strategic sensing platform for the detection of chemical and biological molecules.

Non-autofluorescence Detection of H5N1 Virus Using Photochemical Aptamer Sensors Based on Persistent Luminescent Nanoparticles.

Fluorescence sensing is limited in practical applications owing to multiple autofluorescent substances in complex biological samples such as serum. In this paper, the luminescence decay effect of persistent luminescent nanoparticles (PLNPs) was used to avoid the interference of autofluorescence in complex biological samples, and a non-autofluorescence molecularly imprinted polymer aptamer sensor (MIP-aptasensor) was designed to detect H5N1 virus. The proposed MIP-aptasensor consists of a magnetic MIP and aptamer-functionalized persistent luminescent nanoparticle Zn2GeO4:Mn2+-H5N1 aptamer (ZGO-H5N1 Apt). Upon simultaneous recognition of H5N1 virus, strong persistent luminescent signal changes were produced. Using the unique luminescent characteristics of PLNPs and the high selectivity of imprinted polymers and aptamers, the designed MIP-aptasensor effectively eliminates the autofluorescence background interference of serum samples and realizes the non-autofluorescence detection of H5N1 virus with high sensitivity (a limit of detection of 0.0128 HAU mL-1, 1.16 fM) and selectivity (the imprinting factor for the target H5N1 virus was 6.72). This tool provides a strategy for the design of sensors and their application in complex biological samples.

Sensitive and selective magnetic dispersive microextraction of diazinon from urine samples by molecularly imprinted polymer based on core-shell metal-organic frameworks.

A core-shell magnetic metal-organic framework (Fe3O4 SiO2/ PAEDTC@ MIL- 101 (Fe)) was synthesized as the substrate and then covered with a surface molecularly imprinted polymer (MIP) layer. Next, Fe3O4 SiO2/ PAEDTC@ MIL- 101 (Fe) @ MIP was characterized by XRD, FT-IR, BET, VSM, TEM, and FE-SEM techniques and applied for selective, fast, and sensitive magnetic dispersive solid-phase microextraction (M-DµSPE) of diazinon from urine samples by the GC- FID detection method. The key experimental variables affecting M-DµSPE were studied and optimized by central composite design (CCD). Under optimum conditions (5 mL; sample at pH: 7.0, the mass of solid sorbent; 6 mg, extraction time; 4 min, acetonitrile as an eluent solvent; 1.5 mL, and desorption time; 3 min, and then reconstituted with 100 µL of methanol), the proposed method exhibits high sensitivity with limits of detection and quantification of 0.005 and 0.017 ng mL-1, respectively. Excellent extraction recovery (98.5 %), wide linearity range (0.02-200000 ng mL-1, R2 > 0.992), high enrichment factors (47-53), and satisfactory precision (<6.3 % RSD) were achieved. The MIP- MOF@ M-DµSPE -GC-FID method can be used with high precision and wide linearity to extract and analyze trace levels of diazinon in real urine samples.

Biosensors for Klebsiella pneumoniae with Molecularly Imprinted Polymer (MIP) Technique.

Nosocomial infection is one of the most important problems that occurs in hospitals, as it directly affects susceptible patients or patients with immune deficiency. Klebsiella pneumoniae (K. pneumoniae) is the most common cause of nosocomial infections in hospitals. K. pneumoniae can cause various diseases such as pneumonia, urinary tract infections, septicemias, and soft tissue infections, and it has also become highly resistant to antibiotics. The principal routes for the transmission of K. pneumoniae are via the gastrointestinal tract and the hands of hospital personnel via healthcare workers, patients, hospital equipment, and interventional procedures. These bacteria can spread rapidly in the hospital environment and tend to cause nosocomial outbreaks. In this research, we developed a MIP-based electrochemical biosensor to detect K. pneumoniae. Quantitative detection was performed using an electrochemical technique to measure the changes in electrical signals in different concentrations of K. pneumoniae ranging from 10 to 105 CFU/mL. Our MIP-based K. pneumoniae sensor was found to achieve a high linear response, with an R2 value of 0.9919. A sensitivity test was also performed on bacteria with a similar structure to that of K. pneumoniae. The sensitivity results show that the MIP-based K. pneumoniae biosensor with a gold electrode was the most sensitive, with a 7.51 (% relative current/log concentration) when compared with the MIP sensor applied with Pseudomonas aeruginosa and Enterococcus faecalis, where the sensitivity was 2.634 and 2.226, respectively. Our sensor was also able to achieve a limit of detection (LOD) of 0.012 CFU/mL and limit of quantitation (LOQ) of 1.61 CFU/mL.

Synthesis and characterization of a novel molecularly imprinted polymer for the controlled release of rivastigmine tartrate.

To develop novel imprinted poly (methacrylic acid) nanoparticles for the controlled release of Rivastigmine Tartrate (RVS), the amalgamation of molecular imprinting techniques and polymerization of precipitates were applied in this work. By permuting different concentrations of pentaerythritol triacrylate (PETA) or trimethylolpropane triacrylate (TMPTA) as cross-linkers, ten different samples were synthesized, and their abilities assessed for RVS absorption. Among them, uniform mono-disperse nanoparticles were synthesized in an RVS/PMAA/PETA mole ratio of 1:6:12, named molecularly imprinted polymers 2 (MIP2), which showed the highest RVS absorption. Analytical procedures involving the Fourier transform infrared (FT-IR), Thermogeometric analysis (TGA), Field emission scanning electron microscopy (FE-SEM), Dynamic light scattering (DLS), and absorption/desorption porosimetry (BET) measurements were applied to characterize the morphology and physicochemical properties of the MIP2. In addition, the cytotoxicity of the MIP2 sample was measured by MTT assay on an L929 cell line. Studies pertaining to the in-vitro release of RVS from MIP2 samples showed that the prepared sample had a controlled and sustained release compared, which differed from the results obtained from the non-imprinted polymer (NIP) with the same formulization. Results obtained further reinforced the feasibility of prepared MIPs as a prime candidature for RVS drug delivery to alleviate Alzheimer's and other diseases.

Ag(I) Pyridine-Amidoxime Complex as the Catalysis Activity Domain for the Rapid Hydrolysis of Organothiophosphate-Based Nerve Agents: Mechanistic Evaluation and Application.

Two novel Ag(I) complexes containing synergistic pyridine and amidoxime ligands (Ag-DPAAO and Ag-PAAO) were first designed as complex monomers. Taking advantage of the molecular imprinting technique and solvothermal method, molecular imprinted porous cross-linked polymers (MIPCPs) were developed as a robust platform for the first time to incorporate Ag-PAAO into a polymer material as a recyclable catalyst. Advantageously, the observed pseudo first-order rate constant (kobs) of MIPCP-Ag-PAAO-20% for ethyl-parathion (EP) hydrolysis is about 1.2 × 104-fold higher than that of self-hydrolysis (30 °C, pH = 9). Furthermore, the reaction mechanism of the MIPCP-containing Ag-PAAO-catalyzed organothiophosphate was analyzed in detail using density functional theory and experimental spectra, indicating that the amidoxime can display dual roles for both the key coordination with the silver ion and nucleophilic attack to weaken the P-OAr bond in the catalytic active site.

Magnetic molecularly imprinted polymer nanoparticles for the extraction and clean-up of thiamethoxam and thiacloprid in light and dark honey.

In this work, new selective and sensitive dual-template molecularly imprinted polymer nanoparticles (MIPs) were synthesized and characterized. Sorbent MIPs were investigated for simultaneous extraction and clean-up of thiamethoxam and thiacloprid from light and dark honey samples. In this study, ultra-high-performance liquid chromatography-tandem mass spectrometry triple-quadrupole (UHPLC-MS/MS) (QQQ) was used to detect and quantify the pesticides. The kinetic model with adsorption kinetics of sorbent was investigated. The optimal adsorption conditions were 80 mg of polymer MIPs, a 30-min extraction time, and a pH of 7. The detection limit (LOD) and the quantification limit (LOQ) varied from 0.045 to 0.070 µg kg-1 and from 0.07 to 0.10 µg kg-1, respectively. The intra-day and inter-day precision (RSD, %) ranged from 1.3 to 2.0% and from 8.2 to 12.0%, respectively. The recovery of thiamethoxam and thiacloprid ranged from 96.8 to 106.5% and 95.3 to 104.4%, respectively, in light and dark honey samples.

Quantification of Enterohemorrhagic Escherichia coli via Optical Nanoantenna and Temperature-responsive Artificial Antibodies.

Enterohemorrhagic Escherichia coli are a dangerous bacterium known to be harmful to the human body, with some infections even resulting in death. Given this danger, food factories are required to perform a quick bacterial test to confirm the absence of this pathogen prior to shipping. We have developed a novel molecular imprinting polymer (MIP) particle that has encapsulated gold nanoparticles (AuNPs) and which can function as both a receptor and an optical signal transmitter in biological systems. This MIP particle is artificially synthesized and can be engineered to specifically recognize and capture antigens on the bacterial cell membrane. In addition, MIP particles containing AuNPs generate strong scattered light signals, and binding of the MIP particles improves the optical intensity of the target bacterial cells. This enables clear visualization under a dark-field microscope and quantification of the target bacteria using the scattering light intensity. Here we describe the successful quantification of Escherichia coli O157 cells in real meat samples using this technology in conjunction with a simple labelling step.

Fabrication of an electrochemical biodevice for ractopamine detection under a strategy of a double recognition of the aptamer/molecular imprinting polymer.

The importance of RAC tracking in human biofluids has boosted many demands for designing an ultrasensitive tool to determine the trace value of the RAC from clinical, judicial, and forensic centers. In this study, an electrochemical biodevice has developed for the highly selective detection of this illegal feed additive under a double recognition strategy of the aptamer (Apt) and molecular imprinting polymer (MIP) on a glassy carbon electrode (GCE). The sensing relies on this fact that both the MIP and Apt act synergistically to trap the RAC molecules. The sensing surface fabrication steps have been monitored by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV(. The charge transfer resistance (Rct) value of the redox probe as a representative of the biodevice response has increased linearly with the RAC concentration increasing in a dynamic range of 1 fM to 1.90 µM. The detection limit (LOD) value has been estimated to be 330 aM, lower than all of the reported methods in the RAC sensing. Furthermore, the practical feasibility of biodevice has been evaluated in some human blood serum and urine samples. This strategy offers some useful advantages in reliable detection of the RAC, which may help in the routine analysis, as mandated by regulatory agencies.

Enhancement anti-interference ability of photoelectrochemical sensor via differential molecularly imprinting technique demonstrated by dopamine determination.

Molecularly imprinting polymers (MIPs), as artificial antibodies with high recognition selectivity to template molecules, are widely used in various biosensors. To improve further the selectivity of MIPs-based photoelectrochemical (PEC) biosensors, we report a differential strategy using non-imprinted polymers (NIPs) as the reference. In a proof-to-concept example for the determination of dopamine (DA), MIPs and NIPs membranes were fabricated by electrochemical polymerization of polypyrrole membranes on the surface of graphene quantum dots (GQDs)/TiO2 nanotubes (NTs). The photocurrent difference between the two PEC cells, MIPs@GQDs/TiO2 NTs-Pt and NIPs@GQDs/TiO2 NTs-Pt, was measured as the signal. As the non-specific adsorption of non-template molecules on the outside surface of MIPs and NIPs membranes is similar, the anti-interference ability for the determination of DA is much improved by using differential strategy. In the normal and differential PEC measurement models, 10.0 µM ascorbic acid is equivalent to 3.12 and 0.40 µM DA, respectively. Further, the smaller specific surface area in NIPs membrane was compensated by using a weight factor to correct the residual interference in a modified differential model. By using 10.0 µM ascorbic acid as the balance point, the presence of 10.0 µM H2O2, glutathione, uric acid or glucose is equivalent only to 0.090, 0.061,0.11 or 0.041 µM of DA, respectively, which are about 3-7% of their interference levels in the normal photocurrent model. The differential PEC method was applied in the determination of DA in serum samples in the linear range of 0.05-12.5 µM, with the detection limit of 0.018 µM.

Electrochemical fabrication of reduced MoS2-based portable molecular imprinting nanoprobe for selective SERS determination of theophylline.

A new portable molecular imprinting polymer (MIP)-SERS nanoprobe is fabricated by a convenient electrochemical method. Single-layered MoS2 is electrochemically reduced on a screen-printed electrode as the scaffold. Functional monomers o-phenylenediamine (oPD), template theophylline (THP), and SERS-active Au nanoparticles (AuNPs) are then one-step electropolymerized on the scaffold. The morphology of the nanoprobe is found to be a three-dimensional and porous structure. The abundant AuNPs with the size of 45~50 nm are trapped within the growing MIP instead of being confined to the surface. The thickness of MIP film is calculated to 25.1 nm. The nanoprobe displays a strong SERS effect for THP using 532 nm as excitation wavelength with a detection limit (LOD) of 0.01 nM. The SERS peak intensity at 1487 cm-1 increases linearly with the concentration of THP in the range 0.1 nM to 0.1 mM. After the template is removed, the imprint-removed nanoprobe is generated for selective binding of THP. The re-binding kinetics study implies the portable MIP-SERS nanoprobe can reach the adsorption equilibrium within 8 min. This nanoprobe exhibits low SERS interference for structural analogues theobromine (THB) and caffeine (CAF). The nanoprobe was employed to THP determination in tea drink samples, with recoveries ranging from 99.0 to 102.0% and relative standard deviations of < 5.0%. Graphical abstractSchematic representation of a portable molecular imprinting SERS nanoprobe used for selective and sensitive theophylline recognition. The nanoprobe is fabricated by one-step electropolymerized o-phenylenediamine (oPD), theophylline, and electroreduced Au nanoparticles (AuNPs) on reduced MoS2 (rMoS2) modified screen-printed electrode (SPE).

Enzyme induced molecularly imprinted polymer on SERS substrate for ultrasensitive detection of patulin.

We designed a new type of MIP-SERS substrate for specific and label-free detection of patulin (PAT), by combining molecular imprinting polymer (MIP) selectivity and SERS technology sensitivity. Initially, the solid substrate of PDMS/AAO was prepared using poly dimethylsiloxane (PDMS) concreted anodized aluminum oxide (AAO) template. Then moderate Au was sputtered on the surface of PDMS/AAO to obtain Au/PDMS/AAO SERS substrate. Based on the HRP enzyme initiated in situ polymerization on the Au/PDMS/AAO, the MIP-SERS substrate was successfully synthesized with selective polymer and high tense of SERS "hot spots". The new MIP-SERS substrate showed strong SERS enhancement effect and good selectivity for PAT. Besides, the results showed that the method owned a linear range from 5 × 10-10 to 10-6 M with the limit of detection (LOD) of 8.5 × 10-11 M (S/N = 3) for PAT. The proposed method also exhibited acceptable reproducibility (relative standard deviation, RSD = 4.7%)，good stability (Raman intensity is above 80% after two weeks) and recoveries from 96.43% to 112.83% with the average RSD of 6.3%. The substrate is easy to use without complex sample pretreatment, which makes it a potential candidate as a rapid and sensitive detection method in food samples.

Epitope Molecularly Imprinted Polymer Nanoparticles for Chemo-/Photodynamic Synergistic Cancer Therapy Guided by Targeted Fluorescence Imaging.

It is a still tough task to precisely target cancer cells and efficiently improve the therapeutic efficacy of various therapies at the same time. Here, dual-template imprinting polymer nanoparticles (MIPs) with a core-shell structure were prepared, in which fluorescent silica nanoparticles (FSiO2) were the core and the imprinted polymer layers were the outermost shell. The imprinted layer was designed and constructed via free-radical precipitation approach on the surface of FSiO2, which simultaneously encapsulated gadolinium-doped silicon quantum dots and photosensitizers (Ce6). During the polymerization process, two template molecules were introduced into the mixtures, one was the epitope of CD59 protein (YNCPNPTADCK), which was overexpressed on the surface of a great deal of the solid cancers, and the other was antitumor agent doxorubicin (DOX) to be used for chemotherapy. Furthermore, the embedded Ce6 could generate toxic 1O2 under 655 nm laser irradiation to kill cancer cells, combining with the loaded-DOX to obtain a synergistic cancer therapy. Moreover, owing to the introduction of gadolinium-doped silicon quantum dots, Ce6, and DOX, the MIPs were endowed with targeted fluorescence imaging (FI) and MR imaging (MRI). In vitro and in vivo experiments had been conducted to demonstrate the excellent targeting ability and desirable treatment effect with negligible toxicity to healthy tissues and organs. As a consequence, the designed MIPs can promote the development of targeted recognition against biomarkers and precise treatment guided with cell imaging tools.

An enzyme-free sensing platform based on molecularly imprinted polymer/MWCNT composite for sub-micromolar-level determination of pyruvic acid as a cancer biomarker.

Pyruvic acid (PA) has been demonstrated to be an important cancer biomarker. Herein, carbon/carbon nanotube paste electrode was modified with the newly synthesized PA-imprinted polymer (MIP) and used as an enzyme-free sensor for PA assay. Methacrylic acid and ethylene glycol dimethacrylate were copolymerized in the presence of PA to prepare PA-IP. The MIP was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. To analyze PA by the MIP/CNT-CP electrode, the electrode was incubated in the PA solution for a constant time and then, the anodic differential pulse voltammetry signal was recorded. Both extraction and electrochemical determination solutions were the same, making the procedure simple and fast. Presence of the CNT in the MIP electrode led to a great enhancement in the PA signal. The MIP material not only pre-concentrated PA at the electrode surface but also increased the electron-exchange rate. This was confirmed by electrochemical impedance spectroscopy. The effects of electrode composition, extraction condition, and voltammetry parameters on the sensing efficiency were optimized. Dynamic linear range, detection limit, and RSD of the sensor were estimated to be 0.1-200 µM, 0.048 µM (S/N), and 3.6% (n = 3), respectively. The utility of the method was confirmed by appropriate analysis results obtained for the determination of PA in the plasma and urine samples. Graphical Abstract.

Impedimetric ultrasensitive detection of chloramphenicol based on aptamer MIP using a glassy carbon electrode modified by 3-ampy-RGO and silver nanoparticle.

In this research work, a biosensor with a dual recognition system was fabricated and founded on a combination of aptasensing and the molecular imprinting union of the chloramphenicol (CAP) selective detection. CAP, is an antibiotic, was applied in veterinary and human in order to treat gram-positive and gram-negative infections. It is worth mentioning that CAP residue brings about earnest side effects on human health. According to this, in this sensing system, 3-aminomethyl pyridine functionalized graphene oxide (GO) (3-ampy-RGO) has been coated on the surface of GCE. Afterwards, the silver nanoparticle (AgNPs) was coated on the 3-ampy-RGO/GCE and, then, the CAP complex-amino-aptamer (NH2-Apt[CAP]) was attached to the AgNP/3-ampy-RGO/GCE using a kind of bonding formation of Ag-N. In this sense, it is worth noting that the resorcinol electropolymerization around the complex of aptamer/CAP would confine the complex and, then, retain the aptamer. Following the CAP removal, the MIP cavity, as it was supposed, synergistically acted with that of the embedded aptamer in order to construct a nanohybrid receptor. Interestingly, the double exact property of the molecular imprinting polymers and aptamers led to the superb sensing properties. In the mentioned system it was illustrated that the linear range was from 1.0 pM to 1.0 nM with the detection limit of 0.3 pM; consequently, as observed, it was better than or as good as other similar assays. Moreover, the mentioned system whose activity was observed in the various interferences presence showed great selectivity in detected the CAP. Finally, the designed sensor exhibited outstanding results when applied to detect CAP in milk samples.