Molecular Recognition Receptors Research Articles

Nanoarchitectonics of on–off ratiometric signal amplified electrochemical sensor for chlorpromazine with molecularly imprinted polymer based on Ni-MOF/Fe-MOF-5 hybrid Au nanoparticles

A novel and stable on–off ratiometric electrochemical sensing platform for chlorpromazine (CPZ) detection by combing the selective recognition of molecularly imprinted polymer (MIP) technology and ratiometric quantification strategy. Gold nanoparticles (AuNPs) were first electrodeposited on a bare glassy carbon electrode surface and then modified with a mixture of Ni-MOF/Fe-MOF-5 by drop-coating, and subsequently electropolymerization polythionine (pTHi) as an internal reference to achieve a ratiometric on–off response. The reference signal of pTHi was obtained by the boiling water-bath-assisted in-situ electropolymerization method for the first time. Ni-MOF/Fe-MOF-5 hybrid AuNPs (Ni-MOF/Fe-MOF-5/AuNPs) not only benefited the output signal amplification, but also provided the enlarged surface for immobilization of pThi and MIPs, and served as catalytic active centers to oxidation CPZ. Then, the MIPs membrane was fabricated through in-situ electropolymerization by using CPZ as the template molecule, nicotinamide as a functional monomer. Ratiometric identifying and quantitative sensing model has been proposed based on the combination of MIP membrane as molecular recognition receptor and pTHi used as an internal reference probe, which improves the sensitivity and selectivity of the sensor. Under the optimal conditions, the ratiometric signals of peak current (ICPZ/IpTHi) were linear to CPZ concentration in the range of 0.001–40 μM and 40–900 μM, with the ultralow detection limit of 0.025 μM (S/N = 3). Furthermore, this sensor exhibited high anti-interference ability, reproducibility, satisfactory stability, and outstanding measurement performance in biological samples with favorable recoveries in the range of 98.11–100.81%. Together, the constructed on–off ratiometric MIP sensing platform is a promising tool for the rapid and accurate determination of antipsychotic drugs with high selectivity and stability.

A signal on-off ratiometric electrochemical sensor coupled with a molecular imprinted polymer for selective and stable determination of imidacloprid

This work presents a signal on-off ratiometric electrochemical sensor coupled with a molecular imprinted polymer (MIP) for imidacloprid (IMI) determination. The ratiometric strategy corrects the detection results by setting 6-(Ferrocenyl)hexanethiol (FcHT) as an internal reference. The MIP membrane, as a molecular recognition receptor, has a three-dimensional structure and is complementary in the shape and chemical functionality to the template. The combination of a ratiometric strategy and MIP improves the sensitivity and selectivity of the sensors. The experimental parameters, such as monomer/template ratio, electropolymerization cycle and adsorption time, are optimized to improve the IMI sensing performance of the as-fabricated electrode. Under optimal electrochemical conditions, the proposed sensor is used to detect IMI in laboratory and real samples. In a range as wide as 5 × 10−7−1 × 10−4 mol L−1, a linear relationship is well established, and the value of the correlation coefficient is 0.9984. The limit of detection (LOD, S/N = 3) is well defined as 4.7 × 10−8 mol L−1. The recovery rates range from 97.4% to 103.5% while testing real samples. The fabricated electrode shows superior anti-interference ability for IMI determination in the presence of analogs at a higher level.

Molecular Modeling and Simulation Tools in the Development of Peptide-Based Biosensors for Mycotoxin Detection: Example of Ochratoxin

Mycotoxin contamination of food and feed is now ubiquitous. Exposures to mycotoxin via contact or ingestion can potentially induce adverse health outcomes. Affordable mycotoxin-monitoring systems are highly desired but are limited by (a) the reliance on technically challenging and costly molecular recognition by immuno-capture technologies; and (b) the lack of predictive tools for directing the optimization of alternative molecular recognition modalities. Our group has been exploring the development of ochratoxin detection and monitoring systems using the peptide NFO4 as the molecular recognition receptor in fluorescence, electrochemical and multimodal biosensors. Using ochratoxin as the model mycotoxin, we share our perspective on addressing the technical challenges involved in biosensor fabrication, namely: (a) peptide receptor design; and (b) performance evaluation. Subsequently, the scope and utility of molecular modeling and simulation (MMS) approaches to address the above challenges are described. Informed and enabled by phage display, the subsequent application of MMS approaches can rationally guide subsequent biomolecular engineering of peptide receptors, including bioconjugation and bioimmobilization approaches to be used in the fabrication of peptide biosensors. MMS approaches thus have the potential to reduce biosensor development cost, extend product life cycle, and facilitate multi-analyte detection of mycotoxins, each of which positively contributes to the overall affordability of mycotoxin biosensor monitoring systems.

Tunable Zn2+ and Cu2+ calixarene complexes as polytopic building blocks for guest recognition

Two calix[4]arene receptors containing two or four 3-pyridylmethyl pendants at the lower rim and fixed in the cone conformation have been synthesised. Their complexes with Cu2+ and Zn2+ have been studied via UV–vis absorption spectroscopy in acetonitrile; 1H NMR spectra provide further insights into the binding sites and show that the macrocycles suitably arrange their structure to meet the coordination features of the metal ion. Both ligands form with both Cu2+ and Zn2+ multiple complex species with large stability. The large binding constant values allow to drive the system to the formation of the desired species by appropriately selecting the metal/ligand ratio. The host–guest binding properties of N-methylpyridinium (NMPy) with both the free ligands and their metal complexes have been investigated by 1H NMR spectroscopy in CDCl3/CD3CN (9:1, v/v). The metal ions do not negatively affect the affinity of the calixarenes for NMPy and also allow for the formation of systems with multiple cavities available for guest inclusion, thus paving the way to new heteroditopic receptors for molecular recognition in solution.

Molecular Selective Binding and Nanofabrication of Cucurbituril/Cyclodextrin Pairs

AbstractCucurbiturils (CBs) and cyclodextrins (CDs) are two important classes of macrocyclic molecules, both of which have the capability of forming stable complexes with various molecular or ionic substrates. These capabilities consequently make them attractive as both receptors for molecular recognition and building blocks for the construction of nano‐scaled supramolecular systems. This review mainly deals with representative contributions in comparative studies of selective binding and molecular assembly behaviors of cucurbiturils and cyclodextrins possessing different types of hydrophobic cavities. It also gives a description of the construction of nanometer‐scaled supramolecular architectures through the cooperative assembly employing cucurbiturils and cyclodextrins, as well as their functions. This review will be addressed to students and researchers interested in the supramolecular chemistry of cucurbiturils and cyclodextrins, especially that involving these two classes of macrocyclic receptors in a single system.

A new type of calixarene: octahydroxypyridin.

A new type of calixarene has been synthesised. Like resorcinol and a number of resorcinol derivatives, 2,6-dihydroxypyridine has been proven to form cyclic tetramers in moderate yields with a number of aliphatic and two aromatic aldehydes in acidic media. The problem of the formation of configurational isomers can be reduced by increasing the reaction temperature and time. With electron-rich aromatic aldehydes, 2,6-dihydroxypyridine unexpectedly yields deep-coloured acyclic quinoid systems. The octahydroxypyridine[4]arenes may have a high potential as receptors for molecular recognition and self organisation.