Synthesis of magnetic halloysite nanotube-based molecularly imprinted polymers for sensitive spectrophotometric detection of metoclopramide in urine samples

Chitosan-based hydrogel beads with molecularly imprinted receptors on halloysite nanotubes for tetracycline separation in water and soil

Tetracycline (TC), a commonly utilized broad-spectrum antibiotic, is frequently detected in water and soil, posing a significant risk to the natural environment and human health. In the present study, the composite hydrogel beads based on chitosan (CS) and halloysite-supported molecularly imprinted polymers, synthesized by two procedures with significantly different solvent volumes (Hal@MIPa(b)), were obtained and used to adsorb the antibiotic. The presence of Hal improved the thermal stability of the hydrogel beads. The system with a thinner polymer layer (CS_Hal@MIPb), containing polymers produced under conditions of significantly higher reagent dilution, was more resistant to higher temperatures than CS_Hal@MIPa. The adsorptive properties were compared with pure CS beads, those containing incorporated Hal, and free polymers obtained by different protocols (MIPa(b)). In the optimized pH 5.0, the maximum adsorption capacities were 175.24 and 178.05 mg g-1 for CS_Hal@MIPa and CS_Hal@MIPb, respectively. The values were slightly lower compared to the systems with free polymers, but the materials achieved equilibrium more rapidly (12 h). The adsorption process was spontaneous and exothermic. Freundlich isotherm and pseudo-second-order kinetic models most accurately described the experimental data. The hydrogel beads retained high selectivity in the presence of other antibiotics, and their high efficiency in the TC removal from real water samples was maintained. Their addition to soil enhanced adsorption capacities, surpassing that of chitosan-based beads containing free polymers. Significantly, the quantity of TC desorption diminished due to the halloysite's presence, which limited its penetration into groundwater. The primary mechanism of tetracycline adsorption on the hydrogel beads studied is pore filling, but other interactions (hydrogen bonding, π-π stacking, electrostatic attraction) are also involved.

Mycotoxins detection: view in the lens of molecularly imprinted polymer and nanoparticles

Molecularly imprinted polymers (MIPs) are tailor-made functional composites which selectively recognize and bind the target molecule of interest. MIP composites are products of the massively cross-linked polymer matrices, generated via polymerization, with bio-inspired recognition cavities that are morphologically similar in size, shape and spatial patterns to the target conformation. These features have enabled researchers to expand the field of molecular recognition, more specifically for target with peculiar requirements. Nevertheless, MIPs alone are characterized with weak sensitivity. Besides, nanoparticles (NPs) are remarkably sensitive but also suffer from poor selectivity. Intriguingly, the combination of the two results in a highly sensitive and selective MIP composite. For instance, the conjugation of different functional NPs with MIPs can generate new flexible target capture tools, either a dynamic sensor or a novel drug delivery system. In this regard, although the technology is considered an established and feasible approach, it is still perceived as a burgeoning technology for various fields, which makes it unceasingly worthy reviewing. Therefore, in this review, we attempt to give an update on various custom-made biosensors based on MIPs in combination with various NPs for the detection of mycotoxins, the toxic secondary metabolites of fungi. We first summarize the classification, prevalence, and toxicological characteristics of common mycotoxins. Next, we provide an overview of MIP composites and their characterization, and then segment the role of NPs with respect to common types of MIP-based sensors. At last, conclusions and outlook are discussed.

Molecularly imprinted polymers in toxicology: a literature survey for the last 5 years

The science of toxicology dates back almost to the beginning of human history. Toxic chemicals, which are encountered in different forms, are always among the chemicals that should be investigated in criminal field, environmental application, pharmaceutic, and even industry, where many researches have been carried out studies for years. Almost all of not only drugs but also industrial dyes have toxic side and direct effects. Environmental micropollutants accumulate in the tissues of all living things, especially plants, and show short- or long-term toxic symptoms. Chemicals in forensic science can be known by detecting the effect they cause to the body with the similar mechanism. It is clear that the best tracking tool among analysis methods is molecularly printed polymer-based analytical setups. Different polymeric combinations of molecularly imprinted polymers allow further study on detection or extraction using chromatographic and spectroscopic instruments. In particular, methods used in forensic medicine can detect trace amounts of poison or biological residues on the scene. Molecularly imprinted polymers are still in their infancy and have many variables that need to be developed. In this review, we summarized how molecular imprinted polymers and toxicology intersect and what has been done about molecular imprinted polymers in toxicology by looking at the studies conducted in the last 5 years.

Determination of bongkrekic acid and isobongkrekic acid in rice noodles by HPLC-Orbitrap HRMS technology using magnetic halloysite nanotubes

The existing extraction and detection methods of bongkrekic acid (BKA) and isobongkrekic acid (IBKA) are complex, time-consuming and solvent-consuming. In this work, a simple and fast pre-concentration procedure based on Fe₃O₄/HNTs was developed for the determination of BKA and IBKA in rice noodles using HPLC-Orbitrap HRMS. The structure and morphology of Fe₃O₄/HNTs was characterized by means of XRD, SEM, FT-IR and VSM. Parameters affecting the extraction efficiency including adsorbent amount, pH, extraction time, type and volume of eluent were investigated by employing the response surface method. Results indicated that the proposed method had favorable linearity in the concentration range of 2-200 μg/L with a correlation coefficient >0.998. Method LOD and LOQ were 0.3 μg/kg and 1.0 μg/kg, respectively. Finally, the method was successfully applied to determine BKA and IBKA in rice noodle samples from southern China with recoveries ranging from 79.8% to 102.6% and relative standard deviation (RSD) of 4.2%-7.1%.