Elucidating doxycycline loading and release performance of imprinted hydrogels with different cross-linker concentrations: a computational and experimental study

Effective non-covalent molecular imprinting on a polymer depends on the extent of non-bonded interactions between the template and other molecules before polymerization. Here, we first determine functional monomers that can yield a doxycycline-imprinted hydrogel based on the hydrogen bond interactions at the prepolymerization step, revealed by molecular dynamics (MD) simulations, molecular docking, and simulated annealing methods. Then, acrylic acid (AA)-based doxycycline (DOX) imprinted (MIP) and non-imprinted (NIP) hydrogels are synthesized in cross-linker ethylene glycol dimethacrylate (EGDMA) ratios of 1.0, 1.5, 2.0, and 3.0 mol%. Here, molecularly imprinted polymer with 3.0 mol% EGDMA has the highest imprinting factor (1.58) and best controlled drug release performance. At this point, full-atom MD simulations of DOX–AA solutions at different EGDMA concentrations reveal that AA and EGDMA compete to interact with DOX. However, at 3.0 mol% EGDMA, AA attains numerous stable hydrogen bond interactions with the drug. This study demonstrates that the concentration of the cross-linker and functional monomer can be adjusted to increase the success of imprinting, where the interplay between these two parameters can be successfully revealed by MD simulations.

Tetracyclines in Food and Feedingstuffs: From Regulation to Analytical Methods, Bacterial Resistance, and Environmental and Health Implications

Antibiotics are widely used as growth promoters in animal husbandry; among them, the tetracyclines are a chemical group of relevance, due to their wide use in agriculture, surpassing in quantities applied almost every other antibiotic family. Seeing the considerable amounts of tetracyclines used worldwide, monitoring of these antibiotics is paramount. Advances must be made in the analysis of antibiotics to assess correct usage and dosage of tetracyclines in food and feedstuffs and possible residues in pertinent environmental samples. The tetracyclines are still considered a clinically relevant group of antibiotics, though dissemination of tolerance and resistance determinants have limited their use. This review focuses on four different aspects: (i) tetracyclines, usage, dosages, and regulatory issues that govern their food-related application, with particular attention to the prohibitions and restrictions that several countries have enforced in recent years by agencies from both the United States and the European Union, (ii) analytical methods for tetracyclines, determination, and residues thereof in feedstuffs and related matrices with an emphasis on the most relevant and novel techniques, including both screening and confirmatory methods, (iii) tetracycline resistance and tetracycline-resistant bacteria in feedstuff, and (iv) environmental and health risks accompanying the use of tetracyclines in animal nutrition. In the last two cases, we discuss the more relevant undesirable effects that tetracyclines exert over bacterial communities and nontarget species including unwanted effects in farmers.

Oxytetracycline recovery from aqueous media using computationally designed molecularly imprinted polymers

Polymers for recovery/removal of the antimicrobial agent oxytetracycline (OTC) from aqueous media were developed with use of computational design and molecular imprinting. 2-Hydroxyethyl methacrylate, 2-acrylamide-2-methylpropane sulfonic acid (AMPS), and mixtures of the two were chosen according to their predicted affinity for OTC and evaluated as functional monomers in molecularly imprinted polymers and nonimprinted polymers. Two levels of AMPS were tested. After bulk polymerization, the polymers were crushed into particles (200-1000 μm). Pressurized liquid extraction was implemented for template removal with a low amount of methanol (less than 20 mL in each extraction) and a few extractions (12-18 for each polymer) in a short period (20 min per extraction). Particle size distribution, microporous structure, and capacity to rebind OTC from aqueous media were evaluated. Adsorption isotherms obtained from OTC solutions (30-110 mg L(-1)) revealed that the polymers prepared with AMPS had the highest affinity for OTC. The uptake capacity depended on the ionic strength as follows: purified water > saline solution (0.9 % NaCl) > seawater (3.5 % NaCl). Polymer particles containing AMPS as a functional monomer showed a remarkable ability to clean water contaminated with OTC. The usefulness of the stationary phase developed for molecularly imprinted solid-phase extraction was also demonstrated. Graphical Abstract Selection of functional monomers by molecular modeling renders polymer networks suitable for removal of pollutants from contaminated aqueous environments, under either dynamic or static conditions.

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.

Molecularly imprinted electrochemical luminescence sensor based on signal amplification for selective determination of trace gibberellin A3

A new molecularly imprinted electrochemical luminescence (MIP-ECL) sensor was developed for Gibberellin A3 (GA3) determination. This sensor is based on competitive binding between the GA3 and the Rhodamine B (RhB)-labeled GA3 (RhB-GA3) to the MIP film. After the competitive binding, the residual RhB-GA3 on the MIP was electro-oxidized to produce RhB oxide, which could greatly amplify the weak electrochemiluminescence (ECL) signal of luminol. The ECL intensity decreased when the RhB-GA3 was replaced by GA3 molecules in the samples. Accordingly, GA3 was determined in the concentration range from 1 × 10(-11) to 3 × 10(-9) mol/L with a detection limit of 3.45 × 10(-12) mol/L. The sensor shows high sensitivity and selectivity, wide response range, good accuracy, and fast response. Beer samples were assayed by using the sensors, and the recoveries ranging from 96.0% to 103.2% were obtained.

To remove or not to remove? The challenge of extracting the template to make the cavities available in Molecularly Imprinted Polymers (MIPs)

Template removal is a critical step in the preparation of most molecularly imprinted polymers (MIPs). The polymer network itself and the affinity of the imprinted cavities for the template make its removal hard. If there are remaining template molecules in the MIPs, less cavities will be available for rebinding, which decreases efficiency. Furthermore, if template bleeding occurs during analytical applications, errors will arise. Despite the relevance to the MIPs performance, template removal has received scarce attention and is currently the least cost-effective step of the MIP development. Attempts to reach complete template removal may involve the use of too drastic conditions in conventional extraction techniques, resulting in the damage or the collapse of the imprinted cavities. Advances in the extraction techniques in the last decade may provide optimized tools. The aim of this review is to analyze the available data on the efficiency of diverse extraction techniques for template removal, paying attention not only to the removal yield but also to MIPs performance. Such an analysis is expected to be useful for opening a way to rational approaches for template removal (minimizing the costs of solvents and time) instead of the current trial-and-error methods.