Determination of antibiotics in liquids by an amperometric sensor modified with a molecularly imprinted polymer

Determination of 18 veterinary antibiotics in environmental water using high-performance liquid chromatography-q-orbitrap combined with on-line solid-phase extraction

In this paper, an electrochemical sensor for epinephrine (EP), a neurotransmitter was developed by anchoring molecularly imprinted polymeric matrix (MIP) on the surface of gold-coated quartz crystal electrode of electrochemical quartz crystal microbalance (EQCM) using starch nanoparticles (Starch NP) — reduced graphene oxide (RGO) nanocomposite as polymeric format for the first time. Use of EP in therapeutic treatment requires proper dose and route of administration. Proper follow-up of neurological disorders and timely diagnosis of them has been found to depend on EP level. The MIP sensor was developed by electrodeposition of starch NP-RGO composite on EQCM electrode in presence of template EP. As the imprinted sites are located on the surface, high specific surface area enables good accessibility and high binding affinity to template molecule. Differential pulse voltammetry (DPV) and piezoelectrogravimmetry were used for monitoring binding/release, rebinding of template to imprinted cavities. MIP-coated EQCM electrode were characterized by contact angle measurements, AFM images, piezoelectric responses including viscoelasticity of imprinted films, and other voltammetric measurements including direct (DPV) and indirect (using a redox probe) measurements. Selectivity was assessed by imprinting factor (IF) as high as 3.26 (DPV) and 3.88 (EQCM). Sensor was rigorously checked for selectivity in presence of other structurally close analogues, real matrix (blood plasma), reproducibility, repeatability, etc. Under optimized conditions, the EQCM-MIP sensor showed linear dynamic ranges (1–10[Formula: see text][Formula: see text]M). The limit of detection 40 ppb (DPV) and 290 ppb (EQCM) was achieved without any cross reactivity and matrix effect indicating high sensitivity and selectivity for EP. Hence, an eco-friendly MIP-sensor with high sensitivity and good selectivity was fabricated which could be applied in “real” matrices in a facile manner.

Composites of tetracycline (Tc)-imprinted polymethacrylates and quantum dots have been coated on chemically pretreated polyimide substrates (PIs) as fluorescent sensors. In this study, PIs were pretreated by capacitively coupled plasma (CCP) before coating the same composites on them. For the first time, to fabricate sensors by plasma modification of PIs, the CCP conditions, including plasma gas, flow rate, radio frequency generation power, and duration time, the fabrication details, including coating, baking, and stripping steps, and the sample loading process were optimized to perform a linear decrease in fluorescent intensity with Tc concentrations in the range of 5.0–3000 μM (R2 = 0.9995) with a limit of detection of 0.2 μM (S/N = 3, relative standard deviation (RSD) = 2.2%). The selectivity of the stripped PIs was evaluated by the imprinting factors (IFs) for Tc (IF = 7.2), other Tc analogues (IF = 3.4–5.3), and steroids (IF ≈ 1) and by the recoveries of 5.0 μM Tc from bovine serum albumin at 300 μg∙mL−1 (98%, RSD = 3.2%), fetal bovine serum at 1.5 ppt (98%, RSD = 2.8%), and liquid milk (94.5%, RSD = 5.3%). The superiority of the present plasma-treated-based sensor over the previous chemically-treated one in fabrication efficiency and detection effectiveness was clear.

A novel method for the separation of berberine hydrochloride has been developed. Berberine hydrochloride molecularly imprinted polymers were prepared by suspension polymerization in the aqueous phase using berberine hydrochloride as the template, methyl acrylic acid as a functional monomer, and ethylene glycol maleic rosinate acrylate (which contains a phenanthrene ring skeleton) and ethylene glycol dimethacrylate as combinatorial crosslinkers. The imprinted polymers were successfully used as a selective stationary phase in high‐performance liquid chromatography. Separation performance of the chromatographic column was determined from the selectivity (evaluated by separation factor) and sorption selectivity (evaluated by imprinting factor) of the molecularly imprinted and non‐imprinted polymers towards the template. The optimum conditions to maximize separation and imprinting factors were investigated. Acetic acid–methanol solution (0.05% v/v) was selected as the optimum mobile phase, while 0.2 mL min−1 was chosen as the optimized flow rate for selective separation of berberine hydrochloride. The highest imprinting and separation factors obtained were 1.924 and 18.52, respectively. Simultaneously, the chromatographic column backpressure was stable and showed good permeability. The chromatographic column was used to separate effectively template molecules from coptis root extract and other analogues. Such chromatographic columns with high selectivity can be used to selectively separate berberine hydrochloride from other compounds. © 2014 Society of Chemical Industry

Molecularly imprinted poly-o-phenylenediamine with template myoglobin molecules (i.e., polymeric antibodies to myoglobin, molecularly imprinted polymer, MIP) was synthesized via electropolymerization. Electropolymerization, washing, and the interaction of the polymeric antibodies with myoglobin was examined by square wave voltammetry and microgravimetry. The analysis of myoglobin was carried out through direct electrochemical detection of the reduction peak of Fe(3+) of the hemeprotein on screen-printed graphite electrodes modified by the MIP. According to the electrochemical analysis, MIP surfaces demonstrated remarkably higher ability to bind the protein compared to that of surfaces prepared by the same route under the same conditions but in the absence of myoglobin (surfaces of the non-imprinted polymer, NIP). The imprinting factor I max(MIP)/I max(NIP) was found to be 2-4. The equilibrium dissociation constant K d of the interaction of myoglobin with MIP electrodes was evaluated as (2.4 ± 0.5) × 10(-8) M. The lower detection limit of myoglobin by a MIP sensor was determined as 0.5 × 10(-9) M, the range of detectable concentrations being 10(-9)-10(-5) M.

A selective cortisol sensor based on molecularly imprinted poly(glycidylmethacrylate-co ethylene glycol dimethacrylate) (poly(GMA-co-EGDMA)) has been demonstrated for detection of cortisol in human sweat. The non-enzymatic biomimetric flexible sweat sensor was fabricated inexpensively by layer by layer (LbL) assembly. The sensor layers comprised a stretchable polydimethylsiloxane (PDMS) base with carbon nanotubes-cellulose nanocrystals (CNC/CNT) conductive nanoporous nanofilms. The imprinted (MIP) poly(GMA-co-EGDMA) deposited on the CNC/CNT was the cortisol biomimetric receptor. Rapid in analyte response (3min), the cortisol MIP sensor demonstrated excellent performance. The sensor has a limit of detection (LOD) of 2.0ng/mL ± 0.4ng/mL, dynamic range of 10-66ng/mL, and a sensor reproducibility of 2.6% relative standard deviation (RSD). The MIP sensor also had high cortisol specificity and was inherently blind to selected interfering species including glucose, epinephrine, β-estradiol, and methoxyprogestrone. The MIP was four orders of magnitude more sensitive than its non-imprinted (NIP) counterpart. The MIP sensor remains stable over time, responding proportionately to doses of cortisol in human sweat. Graphical abstract.

Simultaneous fluorescence determination of bisphenol A and its halogenated analogs based on a molecularly imprinted paper-based analytical device and a segment detection strategy

The goal of the study is to develop a piezoelectric sensor based on a molecularly imprinted polymer (MIP) for the determination of cefotaxime in liquid media. To obtain an antibiotic-selective sensor, the electrode surface of was modified with a molecularly imprinted polymer. A pre-polymerization mixture was prepared using a copolymer of 1,2,4,5-benzoltetracarboxylic acid and 4,4’-diaminodiphenyloxide, and an aqueous solution of cefotaxime in a ratio of 1:1. Then a two-stage thermoimidization was carried out in a drying cabinet at a temperatures of 80 and 120°C. After that, the sensor was cooled to room temperature and placed in distilled water for 24 h. An imprinting factor (IF = 40.9) and a selectivity coefficient were calculated to assess the ability of a sensor with MIP (cefotaxime) to recognize a template molecule. A low selectivity of a MIP sensor with the cefotaxime imprint to other cephalosporin antibiotics is revealed. The experiments were carried out on an original installation including a piezoelectric sensor, a portable generator, and an MP732 USB-frequency meter connected to a computer. Piezoelectric quartz resonators of AT-cut with silver electrodes with a diameter of 5 mm and a thickness of 0.3 mm with a nominal resonant frequency of 4.00 MHz were used as sensors. The determination of antibiotics in model solutions was carried out by the method of calibration schedule. The range of detectable concentrations (0.1 – 1.0 × 10–4 g/dm3) was experimentally determined. The detection limit of cefotaxime is 1.0 × 10–5 g/dm3. The correctness of the cefotaxime determination of in individual and binary model solutions was verified by the «spike-test». It has been shown that a sensor with MIP-cefotaxime is not sensitive to an extraneous antibiotic. The relative standard deviation does not exceed 10 %.

Human serum albumin-imprinted polymers with high capacity and selectivity for abundant protein depletion

Nowadays, most Belgian patients with type 1 diabetes use flash glucose monitoring (FreeStyle Libre [FSL]; Abbott Diabetes Care, Alameda, California) to check their glucose values, but some patients find the sensor on the upper arm too visible. The aim of the present study was to compare the accuracy and precision of FSL sensors when placed on different sites. A total of 23 adults with type 1 diabetes used three FSL sensors simultaneously for 14 days on the upper arm, abdomen and upper thigh. FSL measurements were compared with capillary blood glucose (BG) measurements obtained with a built-in FSL BG meter. The aggregated mean absolute relative difference was 11.8 ± 12.0%, 18.5 ± 18.4% and 12.3 ± 13.8% for the arm, abdomen (P = .002 vs arm) and thigh (P = .5 vs arm), respectively. Results of Clarke error grid analysis for the arm and thigh were similar (zone A: 84.9% vs 84.5%; P = .6), while less accuracy was seen for the abdomen (zone A: 69.4%; P = .01). Apart from the first day, the accuracy of FSL sensors on the arm and thigh was more stable across the 14-day wear duration than accuracy of sensors on the abdomen, which deteriorated mainly during week 2 (P < .0005). The aggregated precision absolute relative difference was markedly lower for the arm/thigh (10.9 ± 11.9%) compared with the arm/abdomen (20.9 ± 22.8%; P = .002). Our results indicate that the accuracy and precision of FSL sensors placed on the upper thigh are similar to the upper arm, whereas the abdomen performed unacceptably poorly.

In this study, molecularly imprinted nanohybrids with "necklace-like" nanostructures were developed based on self-assembled polymeric nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) by employing melamine as template molecules. An amphiphilic copolymer poly(acrylic acid- co-(7-(4-vinylbenzyloxy)-4-methyl coumarin)- co-ethylhexyl acrylate) (poly(AA- co-VMc- co-EHA), PAVE) containing photosensitive coumarin units was synthesized first. Then, the PAVE copolymers were co-assembled with MWCNTs in the presence of template molecules, generating photosensitive molecularly imprinted nanohybrids (MIP-MWCNTs) with necklace-like structures. Subsequently, the MIP-MWCNTs nanohybrids were used to modify electrode surface followed by photo-polymerization of the coumarin units in the nanohybrids, leading to a network architectured complex film. After extracting melamine molecules by electrolysis, a melamine MIP sensor was successfully developed. The as-prepared sensor exhibited a significantly wide linear range (1.0 × 10-12-1.0 × 10-6 mol L-1) and a low detection limit (5.6 × 10-13 mol L-1) for melamine detection. High selectivity of the sensor toward melamine was well demonstrated with respect to other melamine analogues and interferents. Furthermore, the MIP sensor showed high stability and reproducibility. The excellent performance of the MIP sensor can be attributed to the unique nanostructure of the complex film provided by these necklace-like nanohybrids. On the one hand, the nanosized polymeric MIP nanoparticles along the MWCNTs increase the effective electrode surface area and thus offer a high melamine-binding capacity. On the other hand, the MWCNTs in MIP-MWCNTs nanohybrids serve as "electronic bridges" to accelerate the electron transfer among the complex MIP film. More importantly, the MIP sensor was practically used to monitor melamine in milk samples, demonstrating a promising feature for applications in the analysis of food like milk and other food products including milk powder, infant formula, and animal feed. Considering the ease of polymeric nanoparticles functionalization, the necklace-like nanohybrids would be extended to wider applications in many other sensors and devices.

The molecularly imprinted polymers are artificial polymers that, during the synthesis, create specific sites for a definite purpose. These polymers due to their characteristics such as stability, easy of synthesis, reproducibility, reusability, high accuracy, and selectivity have many applications. However, the variety of the functional monomers, templates, solvents, and synthesis conditions like pH, temperature, the rate of stirring, and time, limit the selectivity of imprinting. The Practical optimization of the synthetic conditions has many drawbacks, including chemical compound usage, equipment requirements, and time costs. The use of machine learning (ML) for the prediction of the imprinting factor (IF), which indicates the quality of imprinting is a very interesting idea to overcome these problems. The ML has many advantages, for example a lack of human error, high accuracy, high repeatability, and prediction of a large amount of data in the minimum time. In this research, ML was used to predict the IF using non-linear regression algorithms, including classification and regression tree, support vector regression, and k-nearest neighbors, and ensemble algorithms, like gradient boosting (GB), random forest, and extra trees. The data sets were obtained practically in the laboratory, and inputs, included pH, the type of the template, the type of the monomer, solvent, the distribution coefficient of the MIP (KMIP), and the distribution coefficient of the non-imprinted polymer (KNIP). The mutual information feature selection method was used to select the important features affecting the IF. The results showed that the GB algorithm had the best performance in predicting the IF, and using this algorithm, the maximum R2 value (R2 = 0.871), and the minimum mean absolute error (MAE = − 0.982), and mean square error were obtained (MSE = − 2.303).

Detection of several quinolone antibiotic residues in water based on Ag-TiO2 SERS strategy

The concentration of antibiotic residues in water and animal-derived foods is low and the matrix is complex, and effective extraction of antibiotic residues in them is a key factor for accurate quantification. It is important to establish a rapid and effective method for the analytical determination of antibiotics in water and foods. In this study, a type of novel magnetic COF (Fe3O4@SiO2@PDE-TAPB-COF) was synthesized and characterized. Moreover, Fe3O4@SiO2@PDE-TAPB-COF combined with ultra-high performance liquid chromatography-tandem mass spectrometry was used to determine the 11 sulfonamide antibiotics (SAs) in water and food. The parameters including pH, adsorption amount, adsorption time, type of elution solvent and elution time were optimized. Under the optimal conditions, the standard curves of 11 SAs showed good linearity (R 2 > 0.999) in their respective concentration ranges and had lower detection and quantification limits. The spiked recoveries of the developed MSPE-UPLC-MS/MS method for the 11 SAs in water and foods were 74.3-107.2% and 75.1-102.5%, respectively. And the relative standard deviations (RSDs) were less than 9.56% (n = 7). The results indicated that the method can be used for the determination of SAs in foods and water with low detection limits and high sensitivity.

The influence of various silica gel supports with different shapes and sizes on the recognition properties of surface molecular imprinted polymers (MIPs) was investigated. MIPs for selective recognition and adsorption of gossypol were synthesized via the sol–gel process with a surface imprinting technique on silica gel substrates. 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were chosen as the functional monomer and the cross-linker. The morphology and structure of the gossypol-MIPs were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and a standard Brunauer–Emett–Teller (BET) analysis. Results indicated that the surface imprinted polymer layer facilitated the removal and rebinding of the template, and thus, achieved fast binding kinetics. Compared with the MIPs prepared on irregularly shaped silica with a broad particle size distribution, the MIPs using regularly-shaped silica of uniform size showed higher imprinting factor (IF), and the MIP made with a relatively larger sized (60 μm) spherical silica, demonstrated higher adsorption capacity compared to the MIPs made with smaller sized, spherical silica. The MIP prepared with 60 μm spherically shaped silica, featured a fast adsorption kinetic of 10 min, and a saturated adsorption capacity of 204 mg·g−1. The gossypol-MIP had higher selectivity (IF = 2.20) for gossypol over its structurally-similar analogs ellagic acid (IF = 1.13) and quercetin (IF = 1.20). The adsorption data of the MIP correlated well with the pseudo-second-order kinetic model and the Freundlich isotherm model, which implied that chemical adsorption dominated, and that multilayer adsorption occurred. Furthermore, the MIP exhibited an excellent regeneration performance, and the adsorption capacity of the MIP for gossypol only decreased by 6% after six reused cycles, indicating good application potential for selective adsorption of gossypol.