Non-imprinted Sensor Research Articles

SPR Signal Enhancement With Silver Nanoparticle-Assisted Plasmonic Sensor for Selective Adenosine Detection

In this study, we fabricated adenosine imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-L-cysteine methyl ester-silver nanoparticles (AgNPs)-N-methacryloyl-L-phenylalanine methyl ester) (MIP-Ag) sensor. It is a sensitive, simple, low-cost, and label-free adenosine determination in an aqueous solution without the need for any complicated coupling processes. The sensor without the addition of AgNPs (MIP) was prepared for control experiments to examine the effect of incorporated AgNPs to increase the signal response of surface plasmon resonance. Also, non-imprinted (NIP-Ag) sensor were designed using the same polymerization recipe without adding adenosine to evaluate the imprinting efficiency. The characterization studies of MIP-Ag, NIP-Ag and MIP sensors were carried out by atomic force microscopy and contact angle measurements. It was determined that the MIP-Ag sensor detected the target adenosine molecule 5.10 times more selectively than the competitor guanosine and 3.92 times more than thymidine. Imprinting efficiency was determined by comparing the signal response of MIP-Ag and NIP-Ag sensors. Repeatability studies of the MIP-Ag sensor were statistically analyzed for the 1.0 ppm adenosine, and the percent relative standard deviation of the intraday assays of less than 1.0% showed an insignificant decrease in the detection of adenosine after four adsorption-desorption cycles.

In situ one-step electrochemical preparation of mesoporous molecularly imprinted sensor for efficient determination of indole-3-acetic acid

• An IAA mesoporous molecularly imprinted sensor was consctructed by using in situ electrochemical deposition methods. • The developed sensor showed excellent electrochemical performance due to its micro/nanoporous structure. • The proposed sensor affords favorable sensitivity and selectivity to the detecion of IAA. • The study provied a new avenue for the constrution of high-performance sensors. In this study, a one-step in situ method was developed for the preparation of mesoporous molecularly imprinted sensor for the determination of indole-3-acetic acid. The as-obtained molecularly imprinted films well maintained the mesoporous structure but numerous microporous formed after removal of indole-3-acetic acid. The molecularly imprinted sensors were characterized by various analytical techniques and the data indicated a substantial increase in the electroactive surface area and electrochemical properties of the as-prepared molecularly imprinted sensor thanks to the micro/nanoporous structure. The sensor also showed much better sensitivity and selectivity toward the electrochemical determination of indole-3-acetic acid when compared to both non-imprinted sensor and bare glassy carbon electrode. Under the optimal experimental conditions, the molecularly imprinted sensor displayed a good linear response toward indole-3-acetic acid from 0.080 to 10 μM with a detection limit of 0.050 μM (S/N = 3) and a good selectivity toward common interfering substances. Moreover, the as-prepared molecularly imprinted sensor successfully determined indole-3-acetic acid in real samples composed of soybean sprout and mungbean sprout. In sum, the suggested simple strategy looks promising for the construction of high sensitivity and selectivity electrochemical sensors.

Rapid self-assembly preparation of p-nitrophenol-molecular imprinted photonic crystal sensors

To overcome the long period of three-dimension photonic crystal colloidal array preparation, a rapid self-assembly method is proposed. The effect of microspheres diameter and concentration, heating and nitrogen blowing have been also studied. According to the results, when the microspheres suspension concentration is 0.2 wt% and heating temperature of 70 °C, a highly regular 3D face-centered cubic colloidal crystal array structure self-assembles on the gas-liquid interface within 3 min. Then using this method, a p-nitrophenol-molecular (p-NP) imprinted photonic crystal sensor with high selectivity and sensitivity is prepared. The p-NP imprinted sensor presents twice signal intense than the non-imprinted sensor towards the target, and the structural color changes from blue to green. Meanwhile, the sensor responds in 3 min and can be reversible more than 9 times. This rapid self-assembly method provides a suitable way for large-area colloidal photonic crystal preparation with higher efficiency and good repeatability, which has a high value for practical applications.

Development of molecularly ımprınted polymer based quartz crystal mıcrobalance nanosensor for the determınatıon of tryptophan

ABSTRACT In this study, a quartz crystal microbalance (QCM) nanosensor was prepared to detect tryptophan. QCM nanosensor was prepared through the formation of tryptophan memories on the gold surface of QCM electrode using Methacryloylamidohistidine-Cu(II)-tryptophan ([MAH-Cu(II)]-tryptophan) pre-organised monomer system. The designed pre-organised monomer system was characterised by use of Fourier Transform Infrared (FTIR) and Atomic Force Microscope (AFM) was used to characterise the QCM nanosensors. After the characterisation studies, imprinted and non-imprinted sensors were connected to QCM system to determine the binding of the target molecule, selectivity and the detection of the amount of target molecule in real samples. The results showed that the imprinted QCM nanosensor had high selectivity for tryptophan.

Molecularly imprinted PEDOT on carbon fiber paper electrode for the electrochemical determination of 2,4-dichlorophenol

A highly selective electrochemical sensor has been developed for the determination of the pesticide molecule, 2,4-dichlorophenol (2,4-DCP) using molecularly imprinted conducting polymer. 2,4-dichlorophenol imprinted polymer films were prepared by electropolymerising 3,4-ethylenedioxythiophene (EDOT) on surface of carbon fiber paper electrode (CFP) in presence of 2,4-dichlorophenol. Electrochemical over-oxidation was carried out for the controlled release of 2,4-DCP templates and to generate definite imprinting sites. Surface morphology of the imprinted electrode was analysed by Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry, Fourier Transform Infrared and Raman spectroscopy. In optimized conditions, the voltammetric sensor gave a linear response in the range of 0.21 nM – 300 nM. The significantly low detection limit (0.07 nM) demonstrates the ultra-low sensitivity of the method. The imprinted sensor displayed higher affinity and selectivity towards the target 2,4-DCP over similar structural analogical interference than the non-imprinted sensor. MIP sensor was efficaciously employed for the selective determination of 2,4-DCP in real samples of water.

Development and application of a novel electrochemical sensor based on AuNPS and difunctional monomer-MIPs for the selective determination of Tetrabromobisphenol-S in water samples

Tetrabromobisphenol-S (TBBPS) is a Brominated Flame Retardants (BFRs). TBBPS in trace quantities is lethal and do not only alter the normal performance of the endocrine system but can directly or indirectly provoke hepatoxicity and carcinogenic diseases. Herein, we fabricate a facile electrochemical sensor and investigate its application towards the determination of TBBPS through imprinting technique. TBBPS imprinting was carried out in the presence of methacrylic acid (MAA) and 4-aminothiophenol (4-ATP) functional monomers (DiM) over gold nanoparticles (AuNPs) modified carbon paste electrode (CPE). Transmission electron microscopy (TEM) was used to characterize the imprinted sensor. Performance was thoroughly investigated using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The proposed sensor showed detection behavior towards TBBPS in standard solutions with different concentrations range of 0.1 nM-10 nM and with a detection limit of 0.029 nM. The developed MIP(DiM)@AuNPs/CPE sensor had enhanced recognition capacity compared to MIP electrochemical sensors developed with a mono functional monomer (MIP(MoM)@AuNPs/CPE) and non-imprinted sensors. In addition, the low cost; easier preparation; excellent stability; and good selectivity of MIP(DiM)@AuNPs/CPE electrochemical sensor makes it an attractive alternative to high instrumentation detection techniques.

Pesticide analysis with molecularly imprinted nanofilms using surface plasmon resonance sensor and LC-MS/MS: Comparative study for environmental water samples

SPR sensor chip nanofilms were prepared using a molecular imprinting method. Characterization of nanofilms was achieved by fourier-transform infrared spectroscopy attenuated total reflectance (FTIR-ATR), contact angle, atomic force microscope, and ellipsometer. Kinetic and affinity binding of pesticides were investigated by binding pesticide imprinted and nonimprinted sensor chips to the SPR sensor. Comparative adsorption experiments for SPR sensors were performed to display the selectivity of pesticide imprinted nanofilms. Analysis of the SPR sensors revealed that imprinted nanofilms showed more sensitivity and selectivity than the nonimprinted ones for pesticide determination. Exact masses of molecular and fragmentation ions of pesticides were determined by liquid chromatography ion trap time-of-flight mass spectroscopy (LC/MS-IT-TOF). According to these exact masses and fragmentation ions, an LC–MS/MS method was prepared and validated for qualitative and quantitative analysis of the studied pesticides. The limit of detection values of dimethoate and carbofuran were found to be 16.92 ng L−1 and 20.47 ng L−1 in the LC–MS/MS method and 8.37 ng L−1 and 7.11 ng L−1 in the SPR sensor system, respectively. The accuracy and precision of both methods were determined by comparison of six replicates at three concentrations (50, 250, and 1000 ng L−1), using the same environmental water matrix for each pesticide. SPR sensors showed good accuracy, with recovery percentages between 90 and 95 for both pesticides. The results showed that SPR sensors have higher selectivity and sensitivity, and lower detection limits compared to LC–MS/MS.

Molecularly imprinted polymers for the selective detection of multi-analyte neurotransmitters

This paper reports on the development of electrochemical sensors for the detection of multiple neurotransmitters using molecularly imprinted polymers (MIPs). Pyrrole (PPy) and o-phenylenediamine (o-PD) were used as functional monomers for the MIP sensor development, and the characteristics of those sensors were analyzed. Specifically, we demonstrate a selective detection of dopamine (DA), norepinephrine (NE), and epinephrine (EP) by applying differential pulse voltammetry (DPV) to each uniquely developed MIP-based sensor. Furthermore, the selectivity of the analyte was quantified based on the sensitivity matrix. Our results demonstrate that all MIP sensors possessed higher sensitivity than non-imprinted (NIP) sensors due to the unique molecular receptors. The detection limits of the developed MIP sensors were less than 1.3×10−5M. The uniqueness of the cross-reactivity in the DA-imprinted and EP-imprinted sensors demonstrate the possibility of implementing a multi-analyte sensing platform that can detect multiple neurotransmitters simultaneously from a single sample solution.

An electrochemical nanofilm sensor for determination of 1-hydroxypyrene using molecularly imprinted receptors

Abstract A novel electrochemical nanofilm sensor for 1-hydroxypyrene (1-OHP) was developed based on a molecular imprinted TiO2 gel matrix, which was prepared with Ti(O-n-Bu)4 and 1-OHP using sol–gel technology. Cyclic voltammetry (CV) showed that guest binding on the non-imprinted sensor resulted in nearly the same current changes for all guest molecules, indicating non-specific binding onto the TiO2 gel matrix. In contrast, binding at the molecular imprinted sensor revealed that the selectivity for 1-OHP relative to structurally related guest molecules was estimated to be 1.8–6.7 times greater at 1 × 10−9 M, reflecting its specific adsorption and binding capacity for the template molecule.

A Surface Plasmon Resonance Histamine Sensor Based on an Electropolymerized Molecularly Imprinted Polymer (E-MIP)

In this paper, histamine sensing by surface plasmon resonance (SPR) spectroscopy using an electropolymerized molecularly imprinted polymer (E-MIP) of functionalized polyterthiophene and histamine is reported. The MIP histamine sensor showed good linear relationship (R 2 = 0.995) between the SPR angle shift and the logarithm of histamine concentration, ranging from 15 – 500 μg/mL, with a limit of detection (LOD) of 2.0 μg/mL and a calibration sensitivity of 44.6 m° per log μg/mL histamine. Results also showed higher binding affinity of histamine for the MIP sensor than for the non-imprinted (NIP) sensor indicating excellent specificity. Moreover, the selectivity of the MIP histamine sensor against some of its structural analogues was demonstrated.

Electrochemical sensor based on magnetic molecularly imprinted nanoparticles modified magnetic electrode for determination of Hb

A fast and selective electrochemical sensor for determination of hemoglobin (Hb) was developed based on magnetic molecularly imprinted nanoparticles modified on the magnetic glassy carbon electrode. The nanoparticles Fe3O4@SiO2 with a magnetic core and a molecularly imprinted shell had regular structures and good monodispersity. Hb could be determined directly by electrochemical oxidization with the modified electrode. A magnetic field increased electrochemical response to Hb by two times. Imprinting Hb on the surface of Fe3O4@SiO2 shortened the response time within 7min. Under optimum conditions, the imprinting factor toward the non-imprinted sensor was 2.8, and the separation factor of Hb to horseradish peroxidase was 2.6. The oxidation peak current had a linear relationship with Hb concentration ranged from 0.005mg/ml to 0.1mg/ml with a detection limit (S/N =3) of 0.0010mg/ml. The sensors were successfully applied to analysis of Hb in whole blood samples with recoveries between 95.7% and 105%.

Molecularly imprinted electrochemical sensor prepared on a screen printed carbon electrode for naloxone detection

Naloxone (NLX) is a pharmaceutical used as opioid antagonist. A molecular imprinted polymer electrochemical sensor for simple and rapid detection of NLX was prepared through the modification of commercial available screen printed carbon electrode (SPCE). The SPCE was modified with multi-walled carbon nanotubes (MWCNT) by drop coating to increase the signal response and improve the sensitivity. The MIP preparation was carried out via in situ electropolymerization using 4-aminobenzoic acid (4-ABA) as functional monomer. The morphology of the obtained sensor was characterized by scanning electron microscopy (SEM). Several parameters controlling the preparation and performance of the MIP sensor were studied and optimized. The electrochemical behavior of NLX at MIP and control non-imprinted (NIP) sensor was evaluated by differential pulse voltammetry (DPV), demonstrating a better MIP response and the success of the imprinting. The proposed MIP/MWCNT/SPCE sensor showed a linear relationship between peak current intensity and NLX concentration in the range between 0.25 and 10.0μM, with limits of detection (LOD) and quantification (LOQ) of 0.20μM and 0.67μM respectively. The repeatability and reproducibility were also tested with relative standard deviations (RSD) of 4.6 and 9.6% respectively. Moreover, the applicability of the method was successfully confirmed with detection of NLX in biological samples (urine and human serum). The sensor is promising to be used for screening NLX in point-of-care people with opioid overdose.

Ag/N-doped reduced graphene oxide incorporated with molecularly imprinted polymer: An advanced electrochemical sensing platform for salbutamol determination

In this work, the metallic silver and non-metallic nitrogen co-doped reduced graphene oxide (Ag-N-RGO) was first synthesized by a simple and cost-effective strategy, and then a molecularly imprinted polymer (MIP) was formed in situ at the surface of the prepared composite via electropolymerization of o-phenylenediamine in the presence of salbutamol as the template molecule. The electrochemical characterizations demonstrate that the bifunctional graphene-based composite shows improved catalytic performance than that of pristine graphene doped with one-component or none. The MIP sensor based on Ag-N-RGO owns high porous surface structure, resulting in the increased current response and enhanced recognition capacity than that of non-imprinted sensor. The outstanding performance of the developed sensor derives from the combined advantages of Ag-N-RGO with effective catalytic property and MIP with excellent selectivity. Under the optimal conditions, the electrochemical response of the developed sensor is linearly proportional to the concentration of salbutamol in the range of 0.03–20.00µmolL−1 with a low detection limit of 7 nmol L−1. The designed sensor has exhibited the multiple advantages such as low cost, simple manufacture, convenient use, excellent selectivity and good reproducibility. Finally, the proposed method has been extended for the determinations of salbutamol in human urine and pork samples, and the satisfactory recoveries between 98.9–105.3% are achieved.

Protein imprinted materials designed with charged binding sites on screen-printed electrode for microseminoprotein-beta determination in biological samples

In the past few years a large effort is being made aiming at the development of fast and reliable tests for cancer biomarkers. Protein imprinted sensors can be a fast and reliable strategy to develop tailor made sensors for a large number of relevant molecules.This work aims to produce, optimize and use in biological samples a biosensor for microseminoprotein-beta (MSMB).Caffeic acid (CAF) electropolimerization was performed in the presence of microseminoprotein-beta (MSMB) creating target protein specific cavities on the surface of a screen-printed carbon. Dopamine was introduced as charged monomer labelling the binding site and was allowed to self-organize around the protein. The subsequent electropolimerization was made by applying a constant potential of +2.0V, for 30s, on a carbon screen-printed electrode, immersed in a solution of protein and CAF prepared in phosphate buffer.The sensor with charged monomers showed a more sensitive response, with an average slope of −7.59μA/decade, linear concentration range of 0.5–100ng/mL and a detection limit of 0.12ng/mL. The corresponding non-imprinted sensor displayed an inconsistent response over the range of the calibration curve. The biosensor was successfully applied to the analysis of MSMB in serum and urine samples.

Aflatoxin B1 Detection Using a Highly-Sensitive Molecularly-Imprinted Electrochemical Sensor Based on an Electropolymerized Metal Organic Framework.

A sensitive electrochemical molecularly-imprinted sensor was developed for the detection of aflatoxin B1 (AFB1), by electropolymerization of p-aminothiophenol-functionalized gold nanoparticles in the presence of AFB1 as a template molecule. The extraction of the template leads to the formation of cavities that are able to specifically recognize and bind AFB1 through π-π interactions between AFB1 molecules and aniline moities. The performance of the developed sensor for the detection of AFB1 was investigated by linear sweep voltammetry using a hexacyanoferrate/hexacyanoferrite solution as a redox probe, the electron transfer rate increasing when the concentration of AFB1 increases, due to a p-doping effect. The molecularly-imprinted sensor exhibits a broad linear range, between 3.2 fM and 3.2 µM, and a quantification limit of 3 fM. Compared to the non-imprinted sensor, the imprinting factor was found to be 10. Selectivity studies were also performed towards the binding of other aflatoxins and ochratoxin A, proving good selectivity.

Biomimetic potentiometric sensor for chlorogenic acid based on electrosynthesized polypyrrole

A sensor was fabricated by modifying pencil graphite electrodes with molecularly imprinted polypyrrole (MIPpy) synthesized by electropolymerization of pyrrole monomer at constant potential in the presence of chlorogenic acid (CGA). A comparison between the non-imprinted modified pencil graphite electrode and the molecularly imprinted pencil graphite electrode is reported. Several important parameters controlling the performance of the polypyrrole and the method efficiencies were investigated and optimized. Surface morphology of imprinted and non-imprinted sensor was characterized by scanning electron microscope (SEM) and atomic force microscope (AFM). The molecularly imprinted layer exhibited selectivity and sensitivity toward CGA. Under optimized conditions, the calibration curve demonstrated linearity over a concentration range of 1×10−2mol/L to 1×10−6mol/L with a correlation coefficient (R2) of 0.993 and has life span of more than 3 months without any considerable change in the measured response. The sensor exhibited a sensitivity of −54.7mV per decade. As an application, this potentiometric sensor has been successfully applied to the determination of CGA content in four different coffee samples and compared with HPLC results.

Electrochemical Molecular Imprinted Sensors Based on Electrospun Nanofiber and Determination of Ascorbic Acid.

In this study, electrochemical molecularly imprinted sensors were fabricated and used for the determination of ascorbic acid (AA). Nanofiber membranes of cellulose acetate (CA)/multi-walled carbon nanotubes (MWCNTs)/polyvinylpyrrolidone (PVP) (CA/MWCNTs/PVP) were prepared by electrospinning technique. After being transferred to a glass carbon electrode (GC), the nanofiber interface was further polymerized with pyrrole through electrochemical cyclic voltammetry (CV) technique. Meanwhile, target molecules (such as AA) were embedded into the polypyrrole through the hydrogen bond. The effects of monomer concentration (pyrrole), the number of scan cycles and scan rates of polymerization were optimized. Differential pulse voltammetry (DPV) tests indicated that the oxidation current of AA (the selected target) were higher than that of the structural analogues, which illustrated the selective recognition of AA by molecularly imprinted sensors. Simultaneously, the molecularly imprinted sensors had larger oxidation current of AA than non-imprinted sensors in the processes of rebinding. The electrochemical measurements showed that the molecularly imprinted sensors demonstrated good identification behavior for the detection of AA with a linear range of 10.0 - 1000 μM, a low detection limit down to 3 μM (S/N = 3), and a recovery rate range from 94.0 to 108.8%. Therefore, the electrochemical molecularly imprinted sensors can be used for the recognition and detection of AA without any time-consuming elution. The method presented here demonstrates the great potential for electrospun nanofibers and MWCNTs to construct electrochemical sensors.

Electrochemical sensor for the detection of estradiol based on electropolymerized molecularly imprinted polythioaniline film with signal amplification using gold nanoparticles

A sensitive electrochemical molecularly imprinted sensor was developed for the detection of estradiol, by electropolymerization of p-aminothiophenol functionalized gold nanoparticles in the presence of estradiol as template molecule. The extraction of the template leads to the formation of cavities that are able to recognize and bind estradiol with high affinity. The performance of the developed sensor for the detection of estradiol was investigated by linear sweep voltammetry using a hexacyanoferrate/hexacyanoferrite solution as redox probe. The molecularly imprinted sensor exhibits a broad linear range, between 3.6 fM and 3.6 nM and a limit of quantification of 1.09 fM. Compared to the non-imprinted sensor, the imprinted sensor exhibits high affinity for the binding of estradiol. Moreover, selectivity studies, performed towards binding of testosterone, a hormone with similar chemical structure, proved high sensor selectivity. Furthermore, the molecularly imprinted sensor was applied for the analysis of spiked river samples with good recoveries.

Molecularly imprinted electrochemical sensor based on nickel nanoparticle-modified electrodes for phenobarbital determination

Uniform nickel nanoparticles were applied to improve the sensitivity of sensors for phenobarbital (PB) determination. A Ni nanoparticle-modified imprinted electrochemical sensor was developed by thermal polymerization with the use of methacrylic acid as the functional monomer and ethylene glycol maleic rosinate acrylate as the crosslinking agent. The chemical structures and morphologies of the imprinted films were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The success of the fabrication of Ni nanoparticles, as well as the Ni nanoparticle-modified imprinted electrochemical sensor, was confirmed by the analytical results. The electrochemical properties of the modified molecularly imprinted and non-imprinted polymer sensors were investigated by cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. Results showed that the electrochemical properties of the molecularly imprinted sensor were remarkably different from those of the non-imprinted sensor. Linear responses of the imprinted sensor to PB were observed for concentrations ranging from 1.4×10−7mol L−1 to 1.3×10−4molL−1 (r2=0.9976), with a detection limit of 8.2×10−9mol L−1 (S/N=3). The imprinted electrochemical sensor was used to determine PB in actual fish samples, in which average recoveries between 95.60% and 104.67% were achieved. The developed Ni nanoparticle-modified electrochemical sensor exhibited high sensitivity, high selectivity, and good recovery.

Novel Prostate Specific Antigen plastic antibody designed with charged binding sites for an improved protein binding and its application in a biosensor of potentiometric transduction

This work shows that the synthesis of protein plastic antibodies tailored with selected charged monomers around the binding site enhances protein binding. These charged receptor sites are placed over a neutral polymeric matrix, thus inducing a suitable orientation the protein reception to its site. This is confirmed by preparing control materials with neutral monomers and also with non-imprinted template. This concept has been applied here to Prostate Specific Antigen (PSA), the protein of choice for screening prostate cancer throughout the population, with serum levels >10ng/mL pointing out a high probability of associated cancer.Protein Imprinted Materials with charged binding sites (C/PIM) have been produced by surface imprinting over graphene layers to which the protein was first covalently attached. Vinylbenzyl(trimethylammonium chloride) and vinyl benzoate were introduced as charged monomers labelling the binding site and were allowed to self-organize around the protein. The subsequent polymerization was made by radical polymerization of vinylbenzene. Neutral PIM (N/PIM) prepared without oriented charges and non imprinted materials (NIM) obtained without template were used as controls.These materials were used to develop simple and inexpensive potentiometric sensor for PSA. They were included as ionophores in plasticized PVC membranes, and tested over electrodes of solid or liquid conductive contacts, made of conductive carbon over a syringe or of inner reference solution over micropipette tips. The electrodes with charged monomers showed a more stable and sensitive response, with an average slope of -44.2mV/decade and a detection limit of 5.8×10−11mol/L (2ng/mL). The corresponding non-imprinted sensors showed lower sensitivity, with average slopes of -24.8mV/decade. The best sensors were successfully applied to the analysis of serum, with recoveries ranging from 96.9 to 106.1% and relative errors of 6.8%.