Oxytetracycline recovery from aqueous media using computationally designed molecularly imprinted polymers

A novel carbonized polymer dots-based molecularly imprinted polymer with superior affinity and selectivity for oxytetracycline removal

Molecularly imprinted polymers (MIPs) synthesized from chain functional monomers are restricted by spatial extension and exhibit relatively poor affinity and selectivity; this results in unsatisfactory applications in complex media. In this study, we prepared unique spherical carbonized polymer dots (CPDs-OH) via the incomplete carbonization of 1-allyl-3-vinylimidazolium bromide and ethylene glycol, and used it as a functional monomer to prepare a newly imprinted polymer (CPDs-OH@MIP) in aqueous media. As a result, the CPDs-OH@MIP exhibited effective recognition of oxytetracycline with an impressive imprinting factor of 6.17, surpassing MIPs prepared with chain functional monomers (1-3). Furthermore, CPDs-OH@MIP exhibited excellent adsorption for oxytetracycline (278.52 mg g-1) and achieved equilibrium in 30 min, with stronger resistance to coexisting cations, anions, and humic acid. Compared to other MIPs and adsorbents, the recognition performance of CPDs-OH@MIP improved 2-4 times; this polymer could remove >92.1% of oxytetracycline in real water samples with at least 10 cycle times. CPDs-OH@MIP prepared using the special spherical monomer forms a denser structure with fewer nonimprinted regions and precisely imprinted sites, remarkably improving the affinity and selectivity of MIPs combined via hydrogen bonds and electrostatic and π-π interactions. Our proposed strategy provides an effective basis for breakthroughs in the practical application of MIPs.

Multifunctional fluorescent Eu-MOF probe for tetracycline antibiotics and dihydrogen phosphate sensing and visualizing latent fingerprints†‡

The contamination of tetracycline antibiotics and dihydrogen phosphate (H₂PO₄⁻) in food and the environment is one of the major concerns for human health. Herein, a water-stable carboxyl-functionalized europium metal–organic framework (Eu-MOF) was prepared and demonstrated, for the first time, as a dual-responsive fluorescent sensor of tetracycline antibiotics (oxytetracycline (OTC), tetracycline (TC), and doxycycline (DOX)) and H₂PO₄⁻via fluorescent turn-on and turn-off, respectively. Eu-MOF presents a sensitive and selective detection of OTC with a rapid response time (1 min) and good anti-interference ability. The limits of detection (LODs) of 78 nm, 225 nm, and 201 nM were achieved for OTC, TC, and DOX, respectively. Coordination and hydrogen bonding led to energy and electron transfer from the TC to the MOF, contributing to the fluorescent enhancement mechanism. Moreover, Eu-MOF can effectively detect H₂PO₄⁻via fluorescence turn-off with a LOD of 0.70 μM. The interactions between H₂PO₄⁻ and MOF interrupt the energy transfer from ligand to MOF, leading to fluorescence quenching. In addition, Eu-MOF was successfully applied to determine OTC and H₂PO₄⁻ in real samples, obtaining satisfactory recoveries and RSDs. More fascinating, Eu-MOF could be utilized to develop latent fingerprints on various surfaces, providing well-defined fluorescent fingerprint details in which the sweat pores can be seen with the naked eye.

Water-stable Eu-MOF as a fluorescent probe for detecting tetracycline antibiotics and dihydrogen phosphate in real samples and visualization of latent fingerprints.

Efficient removal of pefloxacin from aqueous solution by acid-alkali modified sludge-based biochar: adsorption kinetics, isotherm, thermodynamics, and mechanism

In this paper, one kind of acid-alkali modified sludge-based biochar (ASBC) was synthesized, characterized, and employed as adsorbent for the removal of pefloxacin. The characterization results showed that the specific surface area (SSA) of ASBC (53.381 m²/g) was significantly higher than that of SBC (24.411 m²/g). ASBC had a rougher surface, larger particle distribution, lower zero point charge, and richer functional groups (e.g., C-O and O-H) than SBC. The adsorption capacity of ASBC was 1.82 times than that of SBC. After 8 adsorption cycles in reuse experiment, the adsorption capacity of ASBC for pefloxacin still reached 144.08 mg/L, indicating that ASBC has good reusability. Static experiments showed that the optimal pH value was 6.0 in the adsorption of pefloxacin on SBC and ASBC. The result of adsorption kinetics indicated that the pseudo-second-order model could describe well the adsorption process. The Freundlich model was better than the Langmuir model to describe the adsorption of pefloxacin by ASBC, indicating that the adsorption process was mainly multilayer adsorption. Thermodynamic result showed that the adsorption of pefloxacin by ASBC was spontaneous and endothermic. The removal mechanism of pefloxacin by ASBC is mainly the substitution reaction and π-π EDA interaction. In summary, acid-alkali modified biochar is an effective adsorbent for pefloxacin in aqueous solution, and has great application prospects.

A molecularly imprinted antibiotic receptor on magnetic nanotubes for the detection and removal of environmental oxytetracycline

The detection and elimination of antibiotic contaminants, such as oxytetracycline (OTC), a broad-spectrum tetracycline antibiotic, would be of help in efficient environmental monitoring, agriculture and food safety tests. Nevertheless, currently available methodologies, which mostly rely on the chromatographic separation of OTC, suffer from low sensitivity and complicated processes. Thus, we report here on the design and synthesis of a fluorescent sensor based on molecularly imprinted magnetic halloysite nanotubes (referred to as MHNTs@FMIPs) for the effective detection and purification of OTC in actual environmental samples. The fluorescence of the MHNTs@FMIPs was quenched obviously upon loading with OTC, covering a linear concentration range of 10-300 nM with a limit of detection (LOD) as low as 8.1 nM. The imprinting factor is 4.47, indicating an excellent specificity. Furthermore, the MHNTs@FMIPs can be applied to the quantitative detection of OTC (5 cycles of 300 nM) in aquaculture wastewater and Yangtze River water, demonstrating their immense application potential.

The Use of Computational Methods for the Development of Molecularly Imprinted Polymers

Recent years have witnessed a dramatic increase in the use of theoretical and computational approaches in the study and development of molecular imprinting systems. These tools are being used to either improve understanding of the mechanisms underlying the function of molecular imprinting systems or for the design of new systems. Here, we present an overview of the literature describing the application of theoretical and computational techniques to the different stages of the molecular imprinting process (pre-polymerization mixture, polymerization process and ligand-molecularly imprinted polymer rebinding), along with an analysis of trends within and the current status of this aspect of the molecular imprinting field.

Review on molecular imprinting technology and its application in pre-treatment and detection of marine organic pollutants

Molecular imprinting technology (MIT) has been considered as an attractive method to produce artificial receptors with the memory of size, shape and functional groups of the templates and has become an emerging technique with the potential in various fields due to recognitive specificity, high efficient selectivity and mechanical stability, which can effectively remove background interference and is suitable for the pre-treatment and analysis of trace level substances in complex matrix samples. Nearly 100 papers about the application of MIT in the detection of marine pollutants were found through Science Citation Index Expanded (SCIE). On this basis, combined with the application of MIT in other fields, the pre-treatment process of marine environmental samples was summarized and the potential of four types of different molecularly imprinted materials in the pre-treatment and detection of marine organic pollutants (including antibiotics, triazines, organic dyes, hormones and shellfish toxins) samples was evaluated, which provides the innovative configurations and progressive applications for the analysis of marine samples, and also highlights future trends and perspectives in the emerging research field.

Functionalizing non-smectic clay via methoxy-modification for enhanced removal and recovery of oxytetracycline from aqueous media

Kaolinite and methoxy-modified kaolinite were used as novel adsorbents for oxytetracycline (OTC) removal and recovery from aqueous media. Batch adsorption experiments were performed to study the effect of pH, ionic strengths, initial concentration, and contact time on OTC adsorption. The adsorbents were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after adsorption. Adsorption of OTC reached its maximum when solution pH increased up to 6 for 0.001 M ionic strength, above which adsorption decreased further when solution pH increased. Freundlich and Langmuir's models best fit the equilibrium data with a strong dependency on OTC adsorption capacity giving its maximum at 36 mg g^-1. Binding is postulated for OTC adsorption on pristine kaolinite as a special case of Hill model with independent binding interaction of OTC adsorption onto the clay that affects the adjacent sites on the pristine kaolinite, in contrast with the adsorption of OTC on methoxy-modified kaolinite. Nitrogen peaks of the XPS spectra indicated changes in the oxidation states of C-N bonds in the N1s peaks by forming tertiary amide C-N and methoxy O-CH₃ bonds which corroborated with the results from FTIR spectra. Removal efficiencies and spectroscopic results indicate that performance on methoxy-modified kaolinite is a promising modification on the clay for recovering antibiotics from wastewater.

An Update on Molecularly Imprinted Polymer Design through a Computational Approach to Produce Molecular Recognition Material with Enhanced Analytical Performance

Molecularly imprinted polymer (MIP) computational design is expected to become a routine technique prior to synthesis to produce polymers with high affinity and selectivity towards target molecules. Furthermore, using these simulations reduces the cost of optimizing polymerization composition. There are several computational methods used in MIP fabrication and each requires a comprehensive study in order to select a process with results that are most similar to properties exhibited by polymers synthesized through laboratory experiments. Until now, no review has linked computational strategies with experimental results, which are needed to determine the method that is most appropriate for use in designing MIP with high molecular recognition. This review will present an update of the computational approaches started from 2016 until now on quantum mechanics, molecular mechanics and molecular dynamics that have been widely used. It will also discuss the linear correlation between computational results and the polymer performance tests through laboratory experiments to examine to what extent these methods can be relied upon to obtain polymers with high molecular recognition. Based on the literature search, density functional theory (DFT) with various hybrid functions and basis sets is most often used as a theoretical method to provide a shorter MIP manufacturing process as well as good analytical performance as recognition material.

Imprinted Contact Lenses for Ocular Administration of Antiviral Drugs

A variety of ocular diseases are caused by viruses, and most treatments rely on the use of systemic formulations and eye drops. The efficient ocular barriers that oppose antiviral drug penetration have prompted the development of improved topical delivery platforms. The aim was to design hydrogel contact lenses endowed with an affinity for acyclovir (ACV) and its prodrug valacyclovir (VACV), first-choice drugs against herpes simplex virus (HSV) ocular keratitis, and that can sustain the release of therapeutic doses during daily wearing. Functional monomers suitable for interaction with these drugs were screened using computational modeling. Imprinted and non-imprinted hydrogels were prepared with various contents in the functional monomer methacrylic acid (MAA) and characterized in terms of swelling, transmittance, mechanical properties, and ocular compatibility (hen’s egg test on chorioallantoic membrane (HET-CAM) assay). The values were in the range typical of soft contact lenses. Compared to ACV, the capability to load VACV was remarkably higher due to stronger electrostatic interactions with MAA. The advantages of the imprinting technology were evidenced for VACV. Stability of VACV loading solution/hydrogels under steam heat sterilization and subsequent drug release was investigated. Permeability studies through bovine and porcine cornea and sclera of the drug released from the hydrogels revealed that VACV accumulates in the cornea and can easily cross the sclera, which may facilitate the treatment of both anterior and posterior eye segments diseases.

Specific adsorption of tetracycline from milk by using biocompatible magnetic molecular imprinting material and evaluation by ECD

Biocompatible magnetic molecularly imprinted polymers (BMMIPs) were prepared with Zein for the first time, and were used to enrich tetracycline compounds selectively. Innovative combination of BMMIPs and electrochemistry to obtain lower detection line to satisfy industrial detection demands. Using Zein as the crosslinking agent, the polymers were synthesized on the surface of Fe₃O₄ particles. The scanning electron microscope, transmission electron microscope and X-ray diffraction technologies were used to characterize BMMIPs. Through optimization, BMMIPs attained large adsorption capacity (236.40 mg/g) with fast kinetics (40 min) and followed the Langmuir isotherm and pseudo-second-order kinetic models. BMMIPs had good recognition ability, the selective factors of oxytetracycline, chlortetracycline, doxycycline were 4.78, 4.23, and 3.39, respectively. Excellent linearity was attained in the range of 0.025-500 μg/mL, with low detection limits and low quantitation limits of 0.025 and 0.083 μg/mL. According to our exploring, BMMIPs was ideal materials for enrichment of tetracycline in complex biological samples.

Retention and molecular-recognition mechanisms of molecularly imprinted polymers for promazine derivatives

Monodisperse molecularly imprinted polymers (MIPs) for promazine derivatives [promazine (PZ), methylpromazine (MPZ), chlorpromazine (CPZ) and bromopromazine (BPZ)], MIP_PZ, MIP_MPZ, MIP_CPZ and MIP_BPZ, were prepared using methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate as a crosslinker by multi-step swelling and polymerization. The retention and molecular-recognition properties of the obtained MIPs were evaluated using LC in hydrophilic interaction chromatography (HILIC) and reversed-phase modes. In computational approaches, intermolecular interaction modes and energies between PZ derivatives and MAAs were evaluated at the HF/6-311G(d,p) level. The interaction energies of PZ, MPZ, CPZ and BPZ with 4 equivalents of MAAs were calculated. The results indicated that the interaction of the aliphatic amine moiety of a PZ derivative with MAA gave almost similar interaction energies at the HF/6-311G(d,p) level, and that the interaction of the sulfur atom of a phenothiazine scaffold with MAA was also the case. The third interaction of the aromatic amine of a PZ derivative with MAA was in the order of MPZ > PZ > CPZ > BPZ presumably due to the change of basicity by the electron-donating or electron-withdrawing effect of a subsituent. Furthermore, the fourth attractive modes of CPZ and BPZ were suggested to be the interaction of their halogen atoms with MAA through both halogen bonding and hydrogen bonding, while PZ and MPZ were suggested to have the weak C-H ⋅⋅⋅ π interaction with MAA. In HILIC mode, the interaction energies at the HF method had good correlation with the retention factor of a PZ derivative on each MIP, indicating that in addition to the shape recognition, the attractive electrostatic interactions would be more responsible for its retention rather than the dispersion energies. Furthermore, in addition to the shape recognition, ionic and hydrophobic interactions, and halogen bonding and hydrogen bonding (the last interaction seems to be weak) seem to work for the retention and molecular-recognition of PZ derivatives on the MIPs in reversed-phase mode.