Citric acid cross-linked β-cyclodextrins: A review of preparation and environmental/biomedical application

The β-cyclodextrins (β-CD) are biocompatible macrocyclic candidates for the preparation of various composites with enhanced functions. While nontoxic and biodegradable citric acid (CA) is the favorite crosslinking agent for fabricating hierarchical advanced structures. The carboxyl and hydroxyl groups on CA can serve as "structural bridges" and enhance the solubility of β-CD. Leading to the construction of CA cross-linked β-CD with marvelous complicated structures and targeted functions. Here, we directly categorized the grafted composite materials into two main types such as organic and inorganic materials. Particularly, some representative composite materials are listed and analyzed in detail according to their preparation, advantages of unique characteristics, as well as the possible applications in environmental and biomedical fields such as adsorption of pollutants, sensors, and biomedical applications.

Cyclodextrin Host-Guest Recognition in Glucose-Monitoring Sensors

Diabetes mellitus is a prevalent chronic health condition that has caused millions of deaths worldwide. Monitoring blood glucose levels is crucial in diabetes management, aiding in clinical decision making and reducing the incidence of hypoglycemic episodes, thereby decreasing morbidity and mortality rates. Despite advancements in glucose monitoring (GM), the development of noninvasive, rapid, accurate, sensitive, selective, and stable systems for continuous monitoring remains a challenge. Addressing these challenges is critical to improving the clinical utility of GM technologies in diabetes management. In this concept, cyclodextrins (CDs) can be instrumental in the development of GM systems due to their high supramolecular recognition capabilities based on the host-guest interaction. The introduction of CDs into GM systems not only impacts the sensitivity, selectivity, and detection limit of the monitoring process but also improves biocompatibility and stability. These findings motivated the current review to provide a comprehensive summary of CD-based blood glucose sensors and their chemistry of glucose detection, efficiency, and accuracy. We categorize CD-based sensors into four groups based on their modification strategies, including CD-modified boronic acid, CD-modified mediators, CD-modified nanoparticles, and CD-modified functionalized polymers. These findings shed light on the potential of CD-based sensors as a promising tool for continuous GM in diabetes mellitus management.

A novel cationic graphene modified cyclodextrin adsorbent with enhanced removal performance of organic micropollutants and high antibacterial activity

The coexistence of pathogenic microorganisms and refractory organic chemicals in water nurtures certain biological and chemical risks to human beings and the water environment as a whole. For an environmentally friendly utilization of water cleaning and recycling technologies, a bifunctional cationic cyclodextrin material (GD-DTAC) with adsorption and bactericidal function was designed. By a simple crosslinking method, GD-DTAC was prepared with graphene supported citric acid-β-cyclodextrin polymer (GD) and dimethyldodecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DTAC). Following the introduction of rich quaternary ammonium groups by DTAC, GD-DTAC realized a double regulation of surface positive charge and wettability. The maximum adsorption capacities of Roxarsone (ROX), Methyl Orange (MO) and Bisphenol A (BPA) were 153.59 mg/g, 445.60 mg/g and 237.90 mg/g, respectively. Antibacterial activity tests showed the efficiency of DTAC not only for enhanced adhesion resistance, but it also realized the sterilization function. This work displays the potential of the prepared bifunctional materials for the removal of pollutants from wastewater as well as the suppression of micro-pollutants. The successful preparation of GD-DTAC provided a basis for the bifunctional material, which showed a great potential in adsorption and antibiosis.

Application of nanomaterials decorated with cyclodextrins as sensing elements for environment analysis

Environmental pollution has brought adverse socio-economic consequences. Organic pollutants and heavy metals are the main culprits of environmental pollution. It is of great importance to develop novel, simple, rapid, sensitive, and low-cost detection approaches for sensing trace pollutants in environmental samples. A lot of detection strategies which are based on varieties of nanomaterials have been developed for environmental analysis in past decades. In this review, we retrospect a variety of nanomaterials decorated with cyclodextrins (CDs), including carbon nanomaterials decorated with CDs, noble metal nanomaterials decorated with CDs and other nanomaterials decorated with CDs, and their application in environmental analysis. CDs is a type of ideal modifying molecules which could recognize targets, improve the solubility and dispersibility of corresponding functionalized materials, and enhance the detecting performance of designed sensors. CDs have been widely immobilized to carbon nanomaterials, noble metal nanomaterials, phosphorene (BP) nanocomposites, metal organic framework (MOF), and magnetic nanomaterials, and these nanocomposites have been utilized as the sensing elements for different target analytes. Immobilizing CDs on different nanomaterials could extremely expand the development of new sensing systems for environmental analysis based on these materials, greatly broaden the species of sensing targets, and apparently improve their sensing performance. Herein, the nanomaterials decorated with CDs, as sensing elements for environmental analysis, were reviewed including the types of nanomaterials decorated with CDs and their applications in various sensing strategies for environmental analysis. Finally, the perspectives of the nanomaterials decorated with CDs used as sensing elements were also discussed.

β-Cyclodextrin functionalized 3D reduced graphene oxide composite-based electrochemical sensor for the sensitive detection of dopamine

A three-dimensional reduced graphene oxide nanomaterial with β-cyclodextrin modified glassy carbon electrode (3D-rGO/β-CD/GCE) was constructed and used to detect the electrochemical behavior of dopamine (DA). The nanocomposite materials were characterized by scanning electron microscopy (SEM), infrared spectrometry (FT-IR), Raman spectrogram and thermogravimetric analysis (TGA), which showed that β-CD was well modified on 3D graphene with a porous structure. The electrochemical properties of different modified electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), proving the highest electron transfer rate of the 3D-rGO/β-CD modified electrode. The experimental conditions such as scan rate, pH, enrichment time and layer thickness were optimized. Under the best experimental conditions, DA was detected by differential pulse voltammetry (DPV) by 3D-rGO/β-CD/GCE with excellent electrocatalytic ability and satisfactory recognition ability, resulting in a wide linear range of 0.5-100 μM and a low detection limit (LOD) of 0.013 μM. The modified electrode based on 3D-rGO/β-CD nanocomposites is promising in the field of electrochemical sensors due to its high sensitivity and other excellent properties.

Peroxidase-like activity of magnetic poly(glycidyl methacrylate-co-ethylene dimethacrylate) particles

Poly(glycidyl methacrylate) (PGMA) is prone to modifications with different functional groups, magnetic fluids or direct coupling with biological molecules. The purpose of this research was to synthesize new magnetically responsive particles with peroxidase-like activity. Poly(glycidyl methacrylate-co-ethylene dimethacrylate) [P(GMA-EDMA)] particles containing carboxyl groups were obtained by emulsifier-free emulsion polymerization and hydrolysis and oxidation of PGMA with KMnO4, resulting in poly(carboxymethyl methacrylate-co-ethylene dimethacrylate) [P(CMMA-EDMA)] particles. Thionine (Th) was also attached to the particles [(P(CMMA-EDMA)-Th] via EDC/NHS chemistry to observe its effect on electron transfer during the oxidation reaction. Finally, the particles were coated with a nitric acid-stabilized ferrofluid in methanol. The resulting magnetic particles were characterized by several methods, including scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. The effect of EDMA on the P(CMMA-EDMA) particle size and size distribution was investigated; the particle size changed from 300 to 340 nm, and the particles were monodispersed with a saturation magnetization of 11 Am2/kg. Finally, the effects of temperature and pH on the peroxidase-like activity of the magnetic P(CMMA-EDMA) and P(CMMA-EDMA)-Th particles were investigated. The particles, which exhibited a high activity at pH 4-6 and at ∼37 °C, represent a highly sensitive sensor component potentially useful in enzyme-based immunoassays.

Optimization and Characterization of Wheat Bran Modified by Citric Acid Using a Dry Reaction Method for Enhancement of Methylene Blue Adsorption

Wheat bran is modified thermochemically through reaction with citric acid, as carboxyl groups bearing agent, according to a dry condition method at the elevated temperature. In this study, the main objectives are optimization the factors affecting on the pendant carboxylic acid groups of wheat bran–citrate, including concentration of citric acid solution (0–1.8 M), volume of citric acid solution (5.4–16.2 g), curing temperature (0–170 °C), curing time (0–90 min.), mixing method (solution mixing vs kneading) of reactants, and the catalyst effect (0–5, sodium phosphate dibasic dodecahydrate/citric acid molar ratio). The amount of pendant carboxylic acid groups is determined by simple acid-base titration. The obtained methylene blue adsorption data is well matched with the amount of pendant carboxylic acid groups in wheat bran–citrate and this amount increase with an increase in pendant carboxylic acid groups.

Surface modification of graphene oxide with stimuli-responsive polymer brush containing β-cyclodextrin as a pendant group: Preparation, characterization, and evaluation as controlled drug delivery agent

In this work, stimuli-responsive graphene oxide/polymer brush nanocomposites (GPBNs) prepared through the polymerization of acrylic acid (AA), N-isopropylacrylamide (NIPAM) and acrylated β-cyclodextrin (Ac-β-CD) from the graphene oxide (GO) surface. The attachment of polymers on the GO surface was approved using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV-vis spectroscopy (UV-vis) and thermogravimetric (TGA) analysis. Scanning electron microscopy (SEM) was used to observe the morphological change on the GO surface after polymer grafting. Transition electron microscopy (TEM) showed that polymeric brushes were decorated on the GO surface. The growth of polymer brushes on the GO was further confirmed using atomic force microscopy (AFM). Both hydrophilic (doxorubicin, DOX) and hydrophobic (Methotrexate MTX) drugs were co-loaded in the prepared graphene Oxide/Polyacrylated β-cyclodextrin/polyacrylic acid/poly N-isopropylacrylamide brush nanocomposite (GCANBN). Drug releases from GCANBN were studied using UV-vis. MTT assay was used for the evaluation of in-vitro cytotoxicity of GCANBN. The prepared system showed its efficacy as a nanocarrier for both types of drugs.

Influence from the types of surface functional groups of RGO on the performances of thermal interface materials

RGO nanosheets-modified epoxy resin (ER) is a major research interest because of the high thermal performance of the resulting thermal interface materials (TIMs).

Supramolecule-Inspired Fabrication of Carbon Nanoparticles In Situ Anchored Graphene Nanosheets Material for High-Performance Supercapacitors

The remarkable electrochemical performance of graphene-based materials has drawn a tremendous amount of attention for their application in supercapacitors. Inspired by supramolecular chemistry, the supramolecular hydrogel is prepared by linking β-cyclodextrin to graphene oxide (GO). The carbon nanoparticles-anchored graphene nanosheets are then assembled after the hydrothermal reduction and carbonization of the supramolecular hydrogels; here, the β-cyclodextrin is carbonized to carbon nanoparticles that are uniformly anchored on the graphene nanosheets. Transmission electron microscopy reveals that carbon nanoparticles with several nanometers are uniformly anchored on both sides of graphene nanosheets, and X-ray diffraction spectra demonstrate that the interlayer spacing of graphene is enlarged due to the anchored nanoparticles among the graphene nanosheets. The as-prepared carbon nanoparticles-anchored graphene nanosheets material (C/r-GO-1:3) possesses a high specific capacitance (310.8 F g^-1, 0.5 A g^-1), superior rate capability (242.5 F g^-1, 10 A g^-1), and excellent cycle stability (almost 100% after 10 000 cycles, at the scan rate of 50 mV s^-1). The outstanding electrochemical performance of the resulting C/r-GO-1:3 is mainly attributed to (i) the presence of the carbon nanoparticles, (ii) the enlarged interlayer spacing of the graphene sheets, and (iii) the accelerated ion transport rates toward the interior of the electrode material. The supramolecule-inspired approach for the synthesis of high-performance carbon nanoparticles-modified graphene sheets material is promising for future application in graphene-based energy storage devices.

Water-soluble cationic poly(β-cyclodextrin-co-guanidine) as a controlled vitamin B2delivery carrier

Vitamin B₂(VB₂) is effectively incorporated into novel water-soluble cationic β-cyclodextrin (β-CD) polymers in order to improve its physiochemical properties.