Layer-by-layer assembled multilayer films of exfoliated layered double hydroxide and carboxymethyl-β-cyclodextrin for selective capacitive sensing of acephatemet

da Silva Alves D, Okeke C, Breslin CB. Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.

Antimicrobial coatings on polyethylene terephthalate based on curcumin/cyclodextrin complex embedded in a multilayer polyelectrolyte architecture

Bacterial contamination is a growing concern worldwide. The aim of this work was to develop an antimicrobial coating based on curcumin-cyclodextrin inclusion complex and using polyethylene terephthalate (PET) film as a support matrix. After a pre-treatment aimed to provide sufficient electric charge to the PET surface, it was electrostatically coated with repeated multilayers comprising alternately deposited positively-charged poly-l-lysine (PLL) and negatively-charged poly-l-glutamic acid (PLGA) and carboxymethyl-β-cyclodextrin (CMBCD). The coatings had an architecture (PLL-PLGA)₆-(PLL-PLGA-PLL-CMBCD)_n, with the number of repeated multilayers n varying from 5 to 20. The CMBCD molecules were either covalently cross-linked using carbodiimide crosslinker chemistry or left unbound. The surface morphology, structure and elemental composition of the coatings were analysed by scanning electron microscopy and energy dispersive x-ray spectroscopy. To impart antimicrobial properties to the coatings they were loaded with a natural phenolic compound curcumin forming inclusion complexes with β-cyclodextrin. The non-cross-linked coatings showed bactericidal activity towards Escherichia coli in the dark, and this activity was further enhanced upon illumination with white light. Curcumin was released from the non-cross-linked coatings into an aqueous medium in the form of cyclodextrin inclusion complex. After the cross-linking, the coating lost its dark antimicrobial activity but retained the photodynamic properties. Stabilized cross-linked curcumin-loaded coatings can serve a basis for developing photoactivated antimicrobial surfaces controlling bacterial contamination and spread.

Simultaneous determination of two flavonoids based on disulfide linked β-cyclodextrin dimer and Pd cluster functionalized graphene-modified electrode

Illustration of the SS-β-CD–Pd@RGO nanohybrids simultaneously sensing baicalin and luteolin by an electrochemical strategy.

Characterization of Strong and Crystalline Polyvinyl Alcohol/Montmorillonite Films Prepared by Layer-by-Layer Deposition Method

The preparation of a high-strength and highly crystalline nanocomposite with a layered structure by the use of layer-by-layer deposition (LbL) method from polyvinyl alcohol (PVOH) and montmorillonite (MMT) platelets is reported. The crystallinity and interactions between the components were studied by the use of Fourier transform infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The nanocomposite film structure was investigated by the use of scanning electron microscope (SEM) and atomic force microscopy (AFM). The stiffness of the LbL PVOH/MMT film was significantly higher compared to pure PVOH and conventional PVOH/MMT nanocomposite. The structural and thermal studies on thin PVOH/MMT films indicated the enhanced crystallinity of the polymer.