Synthesis of core-shell magnetic molecularly imprinted polymers and detection of sildenafil and vardenafil in herbal dietary supplements

Laser-Induced Graphene Electrodes Modified with a Molecularly Imprinted Polymer for Detection of Tetracycline in Milk and Meat

Tetracycline (TC) is a widely known antibiotic used worldwide to treat animals. Its residues in animal-origin foods cause adverse health effects to consumers. Low-cost and real-time measuring systems of TC in food samples are, therefore, extremely needed. In this work, a three-electrode sensitive and label-free sensor was developed to detect TC residues from milk and meat extract samples, using CO₂ laser-induced graphene (LIG) electrodes modified with gold nanoparticles (AuNPs) and a molecularly imprinted polymer (MIP) used as a synthetic biorecognition element. LIG was patterned on a polyimide (PI) substrate, reaching a minimum sheet resistance (R_sh) of 17.27 ± 1.04 Ω/sq. The o-phenylenediamine (oPD) monomer and TC template were electropolymerized on the surface of the LIG working electrode to form the MIP. Surface morphology and electrochemical techniques were used to characterize the formation of LIG and to confirm each modification step. The sensitivity of the sensor was evaluated by differential pulse voltammetry (DPV), leading to a limit of detection (LOD) of 0.32 nM, 0.85 nM, and 0.80 nM in buffer, milk, and meat extract samples, respectively, with a working range of 5 nM to 500 nM and a linear response range between 10 nM to 300 nM. The sensor showed good LOD (0.32 nM), reproducibility, and stability, and it can be used as an alternative system to detect TC from animal-origin food products.

Metal-Organic Gel-Modulated Synthesis of Hierarchically Porous Molecularly Imprinted Polymers for Efficient Removal of Sildenafil from Water

Molecularly imprinted polymers (MIPs) with high specific recognition capability are promising in environmental remediation. However, traditional MIPs usually show poor specific binding affinity toward templates in pure aqueous medium, thus greatly limiting their practical applications in wastewater treatment. Herein, we proposed a facile and versatile method to synthesize a water-compatible hierarchically porous MIP (HP-MIP), in which a metal-organic gel (MOG) was formed by in situ assembly and acted as a removable structural modulator. Remarkably, the integration of the MOG modulator and template imprinting defects significantly improved the specific template binding affinity of HP-MIP in water. The adsorption behavior of HP-MIP fitted well with the heterogeneous Freundlich isotherm, suggesting that HP-MIP possessed greater site heterogeneity to sildenafil than HP-NIP, which confirmed the efficiency of HP-MIP for the removal of sildenafil from water. This approach provides an important pathway to prepare water-compatible porous MIP for efficient removal of highly toxic organic pollutants from wastewater.

Novel synthesized attapulgite nanoparticles-based hydrophobic monolithic column for in-tube solid-phase microextraction of thiosildenafil, pseudovardenafil, and norneosildenafil in functional foods

In this study, a novel method which involved in-tube solid-phase microextraction (SPME) using an attapulgite (ATP) nanoparticles-based hydrophobic monolithic column was successfully developed. It was coupled with high-performance liquid chromatography-ultraviolet detection for the determination of three phosphodiesterase-5 (PDE-5) inhibitors, including thiosildenafil, pseudovardenafil, and norneosildenafil, in functional foods. The monolithic column was prepared by one-step polymerization, using 3-trimethoxysilylpropyl methacrylate-modified ATP nanoparticles and 1-butyl-3-vinylimidazolium bromide (VBIMBr) as the functional monomers, and ethylene glycol dimethacrylate (EDMA) as the cross-linker. The obtained poly(ATP-VBIMBr-EDMA) monolith was characterized by scanning electron microscopy equipped with energy-dispersive analysis of X-ray, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. The adsorption capacity, up to 2.00 μg/cm calculated by the Langmuir isotherm model, was about six times that of the poly(VBIMBr-EDMA) monolith. Crucial factors affecting the extraction efficiency, including sample solvent, elution solvent, flow rates of sampling loading and elution, sample loading volume, and elution volume, were investigated in details. Under the optimal in-tube SPME conditions, the proposed method showed good reproducibility with run-to-run, column-to-column, and batch-to-batch relative standard deviations less than 7.2%, and low limits of detection of 0.5-0.9 ng/mL in real samples. Thiosildenafil was detected in four types of functional foods with the contents of 1.30-4.78 μg/g. This newly proposed in-tube SPME method based on poly(ATP-VBIMBr-EDMA) monolith may provide a simple, efficient, and promising alternative to daily monitoring of PDE-5 inhibitors in functional foods.

Core-Shell Molecularly Imprinted Polymer Nanocomposites for Biomedical and Environmental Applications

Core-shell polymers represent a class of composite particles comprising of minimum two dissimilar constituents, one at the center known as a core which is occupied by the other called shell. Core-shell molecularly imprinting polymers (CSMIPs) are composites prepared via printing a template molecule (analyte) in the coreshell assembly followed by their elimination to provide the everlasting cavities specific to the template molecules. Various other types of CSMIPs with a partial shell, hollow-core and empty-shell are also prepared. Numerous methods have been reported for synthesizing the CSMIPs. CSMIPs composites could develop the ability to identify template molecules, increase the relative adsorption selectivity and offer higher adsorption capacity. Keen features are measured that permits these polymers to be utilized in numerous applications. It has been developed as a modern technique with the probability for an extensive range of uses in selective adsorption, biomedical fields, food processing, environmental applications, in utilizing the plant's extracts for further applications, and sensors. This review covers the approaches of developing the CSMIPs synthetic schemes, and their application with special emphasis on uses in the biomedical field, food care subjects, plant extracts analysis and in environmental studies.

Novel synthesis of nanocomposite for the extraction of Sildenafil Citrate (Viagra) from water and urine samples: Process screening and optimization

A sensitive analytical method is investigated to concentrate and determine trace level of Sildenafil Citrate (SLC) present in water and urine samples. The method is based on a sample treatment using dispersive solid-phase micro-extraction (DSPME) with laboratory-made Mn@ CuS/ZnS nanocomposite loaded on activated carbon (Mn@ CuS/ZnS-NCs-AC) as a sorbent for the target analyte. The efficiency was enhanced by ultrasound-assisted (UA) with dispersive nanocomposite solid-phase micro-extraction (UA-DNSPME). Four significant variables affecting SLC recovery like; pH, eluent volume, sonication time and adsorbent mass were selected by the Plackett-Burman design (PBD) experiments. These selected factors were optimized by the central composite design (CCD) to maximize extraction of SLC. The results exhibited that the optimum conditions for maximizing extraction of SLC were 6.0 pH, 300μL eluent (acetonitrile) volume, 10mg of adsorbent and 6min sonication time. Under optimized conditions, virtuous linearity of SLC was ranged from 30 to 4000ngmL^-1 with R² of 0.99. The limit of detection (LOD) was 2.50ngmL^-1 and the recoveries at two spiked levels were ranged from 97.37 to 103.21% with the relative standard deviation (RSD) less than 4.50% (n=15). The enhancement factor (EF) was 81.91. The results show that the combination UAE with DNSPME is a suitable method for the determination of SLC in water and urine samples.

Determination of synthetic phosphodiesterase-5 inhibitors by LC-MS2 in waters and human urine submitted to dispersive liquid-liquid microextraction

High-performance liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS²) with a triple quadrupole is proposed for determining the synthetic phosphodiesterase-5 inhibitors, sildenafil, tadalafil and vardenafil, and the active metabolite N-desmethyl sildenafil. The method was successfully applied to the analysis of waters of different origins and human urine samples. Dispersive liquid-liquid microextraction (DLLME) was applied in the classical way for water analysis, whereas a previous extraction into an organic solvent was necessary for urine samples, the acetonitrile extract being used as dispersant solvent in the DLLME step. The analytes were determined by LC-ESI-MS² in the multiple reaction monitoring mode. Detection limits were in the 5-50 and 15-250ngL^-1 ranges for water and urine samples, respectively. The repeatability was calculated using the relative standard deviation, obtaining values of between 3.6% and 10.1%. The enrichment factors were between 75 and 81. Accuracy of the procedure was calculated through recovery assays and average recoveries ± SD (n = 48) of 93.6 ± 3.5 and 91.1 ± 3.5 were obtained for water and urine samples, respectively. None of the samples analyzed contained the target compounds, at least above the corresponding detection limits.

Molecular imprinting: perspectives and applications

This critical review presents a survey of recent developments in technologies and strategies for the preparation of MIPs, followed by the application of MIPs in sample pretreatment, chromatographic separation and chemical sensing.

Recognition and selective adsorption of pesticides by superparamagnetic molecularly imprinted polymer nanospheres

Selective adsorption of pesticides phosalone, diazinon, and chlorpyrifos from aqueous solution by superparamagnetic molecularly imprinted polymer nanosphere.

Adsorption behavior of a computer-aid designed magnetic molecularly imprinted polymer via response surface methodology

A combined computer simulation and experimental study of magnetic a molecularly imprinted polymer was put forward and verified.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Magnetic Molecularly Imprinted Polymers Based on Poly[2,2’-(p-oxidiphenylene)-5,5’-bibenzimidazole] (OPBI) for Selective Detection of Nonylphenol in Water Samples

Magnetic molecularly imprinted polymers (MMIPs) based on poly [2,2’-(p-oxidiphenylene)-5,5’-bibenzimidazole] (OPBI) composites were synthesized for the selective adsorption and detection of nonylphenol (NP) from water samples. During polymerization, Fe3O4@C was used as supporter and magnetic substance and OPBI not only was used as crosslinking agent but also functional monomer. Morphology of Fe3O4@C and MMIPs were investigated by scanning electron microscopy (SEM). The kinetics of adsorption followed the pseudo-first-order model. Selectivity of MMIPs was further demonstrated through HPLC analysis of the water samples, in which bisphenol A (BPA), phenol, 4-nitrophenol (4-NP) and tetrabromobisphenol (TBBPA) were dissolved respectively. The result showed that MMIPs had more effectively recognition capability of NP than other contrasts.

Application of functionalized magnetic nanoparticles in sample preparation

Functionalized magnetic nanoparticles have attracted much attention in sample preparation because of their excellent performance compared with traditional sample-preparation sorbents. In this review, we describe the application of magnetic nanoparticles functionalized with silica, octadecylsilane, carbon-based material, surfactants, and polymers as adsorbents for separation and preconcentration of analytes from a variety of matrices. Magnetic solid-phase extraction (MSPE) techniques, mainly reported in the last five years, are presented and discussed.

High throughput detection of human neutrophil peptides from serum, saliva, and tear by anthrax lethal factor-modified nanoparticles

Human α defensins human neutrophil peptide 1-3 (HNP 1-3) are potential prognostic cancer biomarkers. Metalloprotein anthrax lethal factor (ALF) binds to HNP 1-3 in a Zn2+-dependent manner. We conjugated ALF to the surface of magnetic nanoparticles (MNP) to magnetically isolate the HNPs, and used Zn2+ to control the capture and release HNPs.

Detection and validated quantification of the phosphodiesterase type 5 inhibitors sildenafil, vardenafil, tadalafil, and 2 of their metabolites in human blood plasma by LC-MS/MS--application to forensic and therapeutic drug monitoring cases

INTRODUCTION

Phosphodiesterase type 5 inhibitors such as sildenafil, vardenafil, and tadalafil are a class of drugs used primarily in the treatment of erectile dysfunction. Sildenafil and tadalafil are also approved for the treatment of pulmonary hypertension. The aim of this study was to develop and validate a procedure for the detection and quantification of these 3 drugs and some of their metabolites in human blood plasma.

METHODS

After liquid-liquid extraction of 0.5 mL of blood plasma using diethyl ether-ethyl acetate (1:1), the analytes sildenafil, norsildenafil, vardenafil, norvardenafil, and tadalafil were separated using a Shimadzu Prominence High-Performance Liquid Chromatography System (C18 separation column, gradient elution, and a total flow of 0.5 mL/min). They were detected using an AB Sciex 3200 Q-Trap LC-MS-MS System (electrospray ionization and multiple reaction monitoring mode). The method was fully validated according to international guidelines.

RESULTS

The assay was found to be selective for the tested compounds. It was linear from 5 to 1000 ng/mL for sildenafil, from 2 to 700 ng/mL for norsildenafil, from 0.5 to 350 ng/mL for vardenafil, from 0.5 to 200 ng/mL for norvardenafil, and from 5 to 1000 ng/mL for tadalafil. The recoveries were generally more than 50%. Matrix effects were not observed. Accuracy, repeatability, and intermediate precision were within the required limits (<15% or <20% near the limit of quantification). No instability was observed after repeated freezing and thawing or in processed samples.

CONCLUSIONS

A liquid chromatography-tandem mass spectrometry assay for the determination of sildenafil, norsildenafil, vardenafil, norvardenafil, and tadalafil in human blood plasma was developed and validated. It has proven to be selective, linear, accurate, and precise for all studied drugs. The method has also proven to be applicable for forensic cases and for therapeutic drug monitoring.

Synthesis of multi-core-shell magnetic molecularly imprinted microspheres for rapid recognition of dicofol in tea

Magnetic multi-core-shell molecularly imprinted microspheres (Fe3O4@MIMs) based on multi-Fe3O4 nanoparticles as core structures and dummy imprinted materials as shell structures have been synthesized by a surface-imprinted technique using dichlorodiphenyltrichloroethane as the dummy template and were successfully used as a specific adsorbent for rapid isolation of trace levels of dicofol from teas. The resulting Fe3O4@MIMs were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, and thermogravimetric analysis. In comparison to the imprinted polymers prepared by the traditional polymerizations, the obtained Fe3O4@MIMs showed regularly spherical shape, porous morphologies, high saturation magnetization [56.8 electromagnetic units (emu)/g], and rapid response time (15 s). The as-synthesized Fe3O4@MIMs, which incorporated the excellent molecular recognition and magnetic separation properties, were successfully used as special adsorbents for rapid isolation and extraction of trace levels of dicofol and its analogues from a complicated tea matrix.