Molecularly Imprinted Electrochemical Sensor Research Articles

A novel molecularly imprinted electrochemical sensor based on quasi-three-dimensional nanomaterials Nb2CTx/AgNWs for specific detection of sulfadiazine.

A novel molecularly imprinted electrochemical sensor (MIECS) was constructed for the specific detection of sulfadiazine (SDZ) in food. Niobium carbide (Nb2CTx) as a typical two-dimensional lamellar nanomaterial has good electrical conductivity and unique structure, which was assembled with one-dimensional silver nanowires (AgNWs) to form quasi-three-dimensional composite nanomaterials (Nb2CTx/AgNWs). As spacer material, AgNWs prevented the aggregation of Nb2CTx and the collapse of Nb2CTx layers. At the same time, a fast electron transport channel was constructed through the synergistic effect between nanomaterialsthe two. The Nb2CTx/AgNWs realized the enhancement of electrical signals. Molecularly imprinted polymers (MIPs) endowed the sensor with selectivity, achieving the specific detection of sulfadiazine. Under the optimal experimental conditions, the method has a wide linear range (1 × 10-8-1 × 10-4 mol L-1) and a low limit of detection (1.30 × 10-9 mol L-1). The sensor was used to detect sulfadiazine in pork, chicken, and feed samples, and the recovery was 82.61-94.87%. The results were in good agreement with the HPLC results, which proved the accuracy and practicability of the method.

Molecularly Imprinted Electrochemical Sensor Constructed by Ferrocene‐Functionalized Carbon Nanotubes for Rapid Recognition and Determination of Tryptophan

AbstractMolecular imprinting is an advanced technology in the fabrication of novel chemical sensors recently applied, enabling rapid responses and highly selective binding to specific molecules, thereby enabling efficient detection of material constituents. In this study, a new molecularly imprinted electrochemical sensor (MIES) utilizing ferrocene‐functionalized carbon‐nanotubes (Fc‐CNTs) was developed for the determination of tryptophan (Trp). The formation of molecularly imprinted polymer (MIP) involves polymerization in dimethyl sulfoxide (DMSO) using Trp, methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as the template molecules, functional monomers, and cross‐linking agents, respectively. Due to the modification of MIPs, the sensor achieves high performance. The sensor demonstrates a linear range from 1 to 45 μM and from 45 to 330 μM, with the limit of detection of 0.44 μM, exceeding that of the majority of sensors reported in the literature. Furthermore, the sensor can effectively detect Trp in real samples, including human serum and amino acid oral liquid. The recovery rate of Trp in human serum samples is 94.2 % to 105.30 %, and in amino acid oral liquid is 94.3 % to 101.68 %. This study provides a promising approach for the effective detection and analysis of tryptophan constituents.

Molecular imprinting electrochemical sensor based on hollow spherical PProDOT-2CH2OH and chitosan-derived carbon materials for highly sensitive detection of chloramphenicol

The misuse of chloramphenicol (CAP) has jeopardized environmental safety. It is critical to create an effective and sensitive CAP detection technique. In this paper, a composite of chitosan (CS)-derived carbon material modified hollow spherical hydroxylated poly(3,4-propylenedioxythiophene) (PProDOT-2CH2OH) was designed, which innovatively used o-phenylenediamine and p-aminobenzoic acid as bi-functional monomers to prepare molecular imprinting polymer (MIP) sensors for highly sensitive analysis and determination of CAP. It was found that the hollow spherical structure of PProDOT-2CH2OH significantly enhanced the rapid electron migration. When combined with the CS-derived carbon material, which has multi-functional sites, it improved the electrical activity and stability of the sensor. It also provided more active centers for the MIP layer to specifically recognize CAP. Therefore, this MIP sensor had a wide linear response (0.0001 ∼ 125 μM), a low limit of detection (LOD, 6.6 pM), excellent selectivity and stability. In addition, studies showed that the sensor has potential practical value. Environmental implicationChloramphenicol (CAP) is one of the most widely used antibiotics with the highest dosage due to its low price and broad-spectrum antimicrobial properties. Due to its incomplete metabolism in living organisms and its difficulty in degrading in the environment, contamination caused by it can pose a threat to public health. In this study, a novel molecularly imprinted sensor (MIP/PC2C1/GCE) was designed to provide a new idea for rapid and precise removal of CAP by adsorption. The detection of CAP in pharmaceutical, water quality, and food fields was realized.

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.

An ionic liquid-modified PEDOT/Ti3C2TX based molecularly imprinted electrochemical sensor for pico-molar sensitive detection of L-Tryptophan in milk

L-Tryptophan (L-Trp) is essential for the human body and can only be obtained externally. It is important to develop a method to efficiently detect L-Trp in food. In this work, ionic liquid (IL) modified poly(3,4-ethylendioxythiophene)/ Titanium carbide (PEDOT/Ti3C2TX) was used as a substrate material to improve detection sensitivity. Molecular imprinted polymers (MIP) film for specific recognition of L-Trp was fabricated on the surface of modified electrodes using electrochemical polymerization. The monitoring results showed that the molecularly imprinted electrochemical sensors (MIECS) exhibited good linearity ranges (10−6 - 0.1 μM and 0.1–100 μM) with a low detection limit (LOD) of 2.09 × 10−7 μM. In addition, the MIECS exhibited remarkable stability, reproducibility, and immunity to interference. A good recovery (93.54–99.59%) was demonstrated in the detection of milk. The sensor was expected to be developed as a highly selective and sensitive portable assay, and applied to the detection of L-Trp in food.

Molecularly imprinted electrochemical sensor based on metal-covalent organic framework for specifically recognizing norfloxacin from unpretreated milk.

Here, a molecularly imprinted electrochemical sensor (MIECS) was designed and fabricated for specifically monitoring norfloxacin (NFX), an entirely synthetic antibiotic. In which, Cu2+ dopped covalent organic framework (COF) was used to connect NFX imprinting layer and glassy carbon electrode through covalence. Under optimized conditions, the linear range is as wide as 5 orders of magnitude, and the detection limit is 5.94×10-3 μM (estimated based on S/N=3). Average recoveries are among 92.4%-99.0% with relative standard deviations≤4.05% (n=3) in (spiked) whole, low-fat, and skimmed milk, validated by independent HPLC assays. The excellent performance can be ascribed to the significant recognition and enriching ability of the imprinting layer, improved conductivity of Cu2+ dopped covalent organic framework, and high stability of covalence between layers. We hope the work will act as a model of MIECSs for rapidly and selectively detecting trace drug residue in complex real samples.

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%.

A multi-walled carbon nanotubes-based molecular imprinting electrochemical sensor for the detection of Aspartame in sports beverage

A multi-walled carbon nanotubes-based molecular imprinting electrochemical sensor for the detection of Aspartame in sports beverage

Fabrication of a molecular imprinting electrochemical sensor for detecting acid phosphatase in black bean sprouts

Fabrication of a molecular imprinting electrochemical sensor for detecting acid phosphatase in black bean sprouts

Ultra-sensitive detection of ciprofloxacin hydrochloride in milk by molecularly imprinted electrochemical sensor based on S-CoFe-MOFs/AuNPs

Ciprofloxacin hydrochloride is widely used to treat animal diseases. However, its chronic abuse has caused serve accumulation in animal-derived foods, which has seriously damaged human health. Thus, in this study, a novel molecularly imprinted electrochemical sensor (MIES) was designed for selective and ultra-sensitive detection of ciprofloxacin hydrochloride (CPFX) in milk. The sensor was based on the molecularly imprinted polymers (MIPs) synthesized with poly-pyrrole (PPy) as the functional monomer, AuNPs and S-CoFe-MOFs (CoFe-Metal organic frameworks coated with chitosan) as the supporting materials, and CPFX as the template molecule. The electrochemical behavior of MIPs/S-CoFe-MOFs/AuNPs/GCE was studied by several electrochemical methods, which showed a wider detection linear range (0.05 ~ 500 ng·mL-1) and lower detection limit (0.0033 ng·mL-1) than those in previous reports. The optimization of experiments confirmed the good selectivity and stability of the sensors----- with the milk sample recovery of 89.04% ~ 110.26%, and the relative standard deviations (RSD) of less than 5.5%, which was close to HPLC. In conclusion, the sensor we constructed has a high selectivity and stability potential in detecting CPFX in milk.

Fabrication of molecular imprinting electrochemical sensor for determination of 2-O-(β-d-glucopyranosyl) ascorbic acid

2-O-(β-D-glucopyranosyl (AA2βG) is a natural component unique to Lycium barbarum (goji berry). The detection of its content can identify the quality of Goji berry extract and provide a new quality standard for Goji berry extract. Currently, there is only one report of electrochemical detection of AA2βG. Further improvement of electrochemical detection of AA2βG is necessary. Molecular imprinting polymer (MIP) is predetermined, identifiable and practical. The MIP-based electrochemical sensor has the advantages of high selectivity, fast response and easy operation. In this study, AuNPs and graphene composite was synthesized and modified the glassy carbon electrode, and 4-aminothiophenol (4-ATP) was self-assembled onto the AuNPs/GCE electrode surface by Au-S bonding, and then graphene was modified onto the electrode surface. 4-ATP and AA2βG were selected as the functional monomer and template molecule, respectively. Under optimal conditions, the sensor can achieve linear detection in the range of 100 nM to 10 μM and 10 μM to 100 μM, respectively. The detection limit can reach 27 nM.

A Molecularly Imprinted Polypyrrole/GO@Fe3O4 Nanocomposite Modified Impedimetric Sensor for the Routine Monitoring of Lysozyme

Lysozyme (LYS) applications encompass anti-bacterial activity, analgesic, and anti-inflammatory effects. In this work, a porous framework that was based on the polymerization of pyrrole (PPy) in the presence of multi-functional graphene oxide/iron oxide composite (GO@Fe3O4) has been developed. Oxygen-containing and amine groups that were present in the nanocomposite were availed to assembly LYS as the molecularly imprinted polymer (MIP) template. The synthesized material (MIPPy/GO@Fe3O4) was electrodeposited on top of a gold microelectrode array. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to confirm the adequate preparation of GO@Fe3O4, and the characterization of the resulting molecularly imprinted electrochemical sensor (MIECS) was carried out by electrochemical impedance spectrometry (EIS), FT-IR analysis, and scanning electron microscopy (SEM). The impedimetric responses were analyzed mathematically by fitting to a Q(Q(RW)) equivalent circuit and quantitative determination of LYS was obtained in a linear range from 1 pg/mL to 0.1 µg/mL, presenting good precision (RSD ≈ 10%, n = 5) and low limit of detection (LOD = 0.009 pg/mL). The fabrication of this device is relatively simple, scalable, rapid, and economical, and the sensor can be used up to nine times without disintegration. The MIECS was successfully applied to the determination of LYS in fresh chicken egg white sample and in a commercial drug, resulting in a straightforward platform for the routine monitoring of LYS.

A Label-Free Molecularly Imprinted Electrochemical Sensor Based on MXene Nanosheets Modified by Gold Nanoparticles for Sensitive and Selective Detection of Homocysteine

A label-free molecularly imprinted electrochemical sensor (MIECS) based on electropolymerized molecularly imprinted polymer (MIP) was developed for the determination of homocysteine (Hcy) in serum for the first time. MXene@AuNPs with layered structure was synthesized on the electrode by modifying MXene with gold nanoparticles (AuNPs). MIP based on dopamine hydrochloride (DA) were electropolymerized onto the surface of MXene@AuNPs modified electrode by molecular docking and quantum chemical calculations for specific recognition of Hcy. MXene@AuNPs as a carrier for immobilizing MIP steadily enhances the conductivity of the electrode (about 4.2-fold) and plays a crucial part in improving the detection sensitivity of MIECS. The results showed that the current response linearly decreased with the increasing concentration of Hcy in the detection range from 1 × 10−13 to 1 × 10−5 mol l−1, the limit of detection (LOD) and limit of quantification (LOQ) of 11.81 fmol l−1 and 39.49 fmol l−1, respectively. With favorable selectivity, stability, reproducibility and ruggedness, the developed MIECS was applied to the determination of Hcy in human serum samples with recoveries of 87.83%–92.58%. The proposed strategy has potential application for disease surveillance.

An advanced molecularly imprinted electrochemical sensor based bifunctional monomers for highly sensitive detection of nitrofurazone

The combination of molecularly imprinted technology and electrochemical sensor can prepare stable and excellent anti-interference molecularly imprinted electrochemical sensor (MIECS), realizing the highly specific recognition of nitrofurazone (NFZ). Bifunctional monomers and zeolitic imidazolate frameworks (ZIF) modified carboxylic multi-walled carbon nanotubes (c-MWCNTs) nanocompostites were used to solve the problems of low conductivity and limited number of imprinted holes in molecularly imprinted polymer (MIP) membrane. The porous nanocomposite can efficiently improve the conductivity and increase the surface of electrode, providing abundant molecularly imprinted holes and enabling a wide detection range. Nicotinamide (NA) and 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) acted as bifunctional monomers and NFZ as template molecules, which were electropolymerized to MIP on the modified electrode. In the optimal experimental environment, the electrochemical response of MIECS to NFZ was linear in a certain concentration range. The linear range was from 10–13 M to 10–6 M, and the detection limit was 6.7 ×10–14 M. The MIECS showed excellent anti-interference performance, which was attributed to the unique holes generated by the polymerization of bifunctional monomers. MIECS also owned good stability and reproducibility and has been successfully applied to the detection of actual urine and water samples.

Melamine-imprinted electrochemical sensor of graphene/ionic liquid composites and its use for the detection of melamine in dairy products

• Melamine-imprinted electrochemical sensor • Molecularly imprinted polymer • Dairy products supervision • Graphene/ionic liquid compound modification By exchanging the conventional role of functional monomer and template molecules, we develop a new molecularly imprinted nanospheres with grape grain structures based on multi-hydrogen bonding interactions between melamine and 6-aminouracil. Molecular imprinting-electrochemical sensor was established with the assistance of graphene and ionic liquids. The content of melamine in dairy products was detected by the molecular imprinting-electrochemical sensor. The detection limit was determined to be as low as 1.57 × 10 −3 mg kg -1 .

Covalent molecularly imprinted electrochemical sensor modulated by borate ester bonds for hygromycin B detection based on the synergistic signal amplification of Cu-MOF and MXene

A molecularly imprinted electrochemical sensor (MIES) modified with Cu-MOF and Ti3C2Tx was successfully prepared for the detection of hygromycin B in food. According to the pH sensitive property of reversible borate ester bonds, a molecularly imprinted polymers (MIP) were constructed on the modified gold electrode (GE) surface by electropolymerization to realize the controllable elution and adsorption of template molecules. Cu-MOF with large specific surface area and Ti3C2Tx with excellent electrical conductivity cooperate to improve the overall analytical performance of MIES. The morphology and electrochemical performance of the sensor were evaluated. Under the optimal experimental conditions, the method showed superior selectivity to hygromycin B with a linear range of 5 × 10−9–5 × 10−6 M and a detection limit of 1.92 × 10−9 M (S/N = 3). The detection results of this method are in good agreement with HPLC-MS/MS, which proves that the method has reliable practicability and accuracy.

A molecularly imprinted electrochemical sensor based on cationic intercalated two-dimensional titanium carbide nanosheets for sensitive and selective detection of triclosan in food samples

An advanced molecularly imprinted electrochemical sensor (MIECS) based on two-dimensional materials MXene was developed for determination of triclosan (TCS) in food samples for the first time. Two-dimensional titanium carbide (Ti3C2Tx) were introduced to improve electrochemical response of the MIECS. K+ ions were spontaneously inserted into Ti3C2Tx nanosheets to form K+-Ti3C2Tx by soaking in alkali solution, thus improving the sensitivity of the sensor. Molecularly imprinted polymers (MIP) were prepared by electropolymerization of para aminobenzoic acid (p-ABA), which can specifically recognize TCS. Under optimal conditions, the linear relationship between the current intensity and TCS concentration was obtained from 10 nmol L−1 to 50 μmol L−1 with a low detection limit of 1.18 nmol L−1. The proposed MIECS showed good repeatability for detecting TCS at a concentration of 500 nmol L−1 solution by preparing five parallel modified electrodes, with a relative standard deviation (RSD) of 3.42%. At the spiked concentration levels of 0.05, 0.1, 0.5 mg L−1/mg kg−1, the recoveries range of TCS in peach juice, onions and fish samples were 86.38%–95.52%. The proposed MIECS combining the advantages of Ti3C2Tx and MIP exhibited good sensitivity and selectivity, providing strategy of utilizing MXenes in the construction of electrochemical sensing platform and holding great promise in the field of food safety.

A molecularly imprinted electrochemical sensors based on bamboo-like carbon nanotubes loaded with nickel nanoclusters for highly selective detection of cortisol

Nitrogen doped bamboo-liked carbon nanotubes loaded with nickel nanoclusters were prepared by single-pot pyrolysis method. On this basis, a molecularly imprinted electrochemical sensor (MIECS) with the specific recognition sites of cortisol was studied. Using o-phenylenediamine as functional monomer and cortisone as template, molecularly imprinted polymer films were prepared by simple and controllable electropolymerization. After a series of optimized conditions, the MIECS shows a wide linear range of 10−14 M to 10−9 M for cortisol with a low detection limit at 2.37 × 10−15 M. Moreover, this sensing platform has been applied to the detection of cortisol in saliva samples and satisfactory results has been obtained.

Carbofuran-imprinted sensor based on a modified electrode and prepared via combined multiple technologies: Preparation process, performance evaluation, and application

Carbofuran (CBF) is a highly toxic pesticide that has been classified as hazardous to humans; however, it is still used in agriculture because of its high efficiency and low cost. Therefore, the detection of CBF is critical for consumer health and environmental quality issues. In this study, a nanomaterial-modified molecularly imprinted electrochemical sensor (MIECS) for CBF detection was prepared based on self-assembly and electropolymerization. The sensor was analyzed via electrochemical methods, computer simulation, and ultraviolet spectroscopy. Carbofuran was used as the template molecule and 4-hydroxythiophenol (4-HTP) as the functional monomer. Reduced graphene oxide (RGO) and Au-nanoparticles (AuNps) were used to modify a working electrode layer by layer. First, 4-HTP was self-assembled on the surface of the Au-nanoparticle modified layer using Au-S bonds. Then 4-HTP was self-assembled around the CBF using hydrogen bonding. Finally, the CBF molecularly imprinted polymer membrane was prepared by electropolymerization, and the template molecules were eluted using ethanol (75 vol%) and 0.4 mol/L NaOH solution (25 vol%). Through the use of the template molecules, the molecularly imprinted electrochemistry sensor for CBF detection was successfully constructed. In the experiment, Gaussian 09 at the density functional theory level of M06-2X/6-31 g(d) was used to screen the functional monomers and optimize the configurations of the template molecule and functional monomer complex, and the action forms and mechanism of the template and monomer were analyzed using a simulation with Gaussian 09. The imprinted effect and selection performance of the sensor were studied using cyclic voltammetry (CV) and square-wave voltammetry (SWV). The imprinted sensor was applied for the rapid detection of CBF in foods. The results showed that the template molecule and functional monomer interacted through hydrogen bonding, and this formed a CBF-4(4-HTP) complex. The sensor showed a good performance. It specifically recognized the template molecule and its structural analogs. The linear response range of the CBF was 1.0 × 10−9–1.0 × 10−5 mol/L, with a good linear relationship (R2 = 0.9994). The detection limit was 3.3 × 10−10 mol/L. The recoveries were between 95.20% and 105.45%, and the relative standard deviations were 0.48%–2.40%. The sensor has the advantages of low cost, good selectivity and stability, high sensitivity, and accurate and rapid detection. It is suitable for the sensitive and rapid detection of carbofuran residues in foods.

Electrochemical sensor based on corncob biochar layer supported chitosan-MIPs for determination of dibutyl phthalate (DBP)

The new corncob biochar layer supported chitosan-based molecular imprinting electrochemical sensor was successfully prepared. Compared with the bare electrode, the new sensor had a good imprinted effect. • A MIP-DBP-CTS/F-CC 3 /GCE novel senor was prepared by molecular imprinting. • The sensor combined the advantages of F-CC 3 and MIP achieved high sensitivity and selective detection of DBP. • The sensor for DBP exhibits a low detection limit of 2.6 nM. • The designed sensor was successfully applied to DBP detection in rice wine purchased in the market. A highly selective and sensitive electrochemical sensor (MIP-DBP-CTS/F-CC 3 /GCE) for dibutyl phthalate (DBP) detection was prepared. Firstly the functional corncob biochar (F-CC 3 ) was cast on a glassy carbon electrode (GCE) to form F-CC 3 film. Then, the pretreated GCEs were further modified by molecularly imprinted polymers synthesized with CTS as functional monomer, DBP as the template molecule, glutaraldehyde as the crosslinking agent. The MIP-DBP-CTS/F-CC 3 /GCE sensor was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results showed that the utilization of conductive F-CC 3 as interlayer spacers efficiently inhibited the aggregation of CTS and formed a well-defined porous structure, as a result of increasing the effective surface area, an enhancement of the electrical conductivity was observed. This sensor takes advantages of molecularly imprinted technique and F-CC 3 biomass materials to achieve high selectivity and high sensitivity for the determination of DBP. The as-prepared molecular imprinting sensor, under the optimized conditions, presented a good linear relationship ( R 2 = 0.9929) between the response current Δ I and the DBP concentration ranging of 0 ~ 1.8 μM with a limit of detection (LOD) of 0.0026 μM. Besides, this newly developed sensor was utilized for the detection of DBP in rice wine purchased in the market with satisfactory results.