Dopamine-functionalized cyclodextrins: modification of reduced graphene oxide based electrodes and sensing of folic acid in human serum

Applicability of a green nanocomposite consists of reduced graphene oxide and β-cyclodextrin for electrochemical tracing of methadone in human biofluids validated by international greenness indexes

Background

Detecting methadone (MET) is crucial due to its severe side effects.

Method

Herein, a green nanocomposite based on reduced graphene (rGO) and β-cyclodextrin (β-CD) has been introduced to modify a glassy carbon electrode (GCE) for real-time measurement of MET. This eco-friendly sensing interface has synergistically benefited from both advantages of rGO and β-CD including excellent electron transfer tunneling and surface area enhancement to selectively trap MET based on its shape and size.

Significant findings

The developed sensor electrochemically detected MET at 0.8 V in buffer phosphate with a pH value of 7 under a wide linear concentration range (1 μM-830 μM), including a MET concentration level alarmed based on the consumer opioid tolerance according to the WHO's report. The limit of detection and analytical sensitivity values were calculated to be 333.33 nM and 0.0502 μA μM-1. The acceptable performance of the sensor to detect MET in various real human biofluids including serum, urine, and saliva samples, which is a bonus for the real-time and on-site measurement of MET, may open up a route for noninvasive routine tests in clinical samples. Moreover, the greenness profile of this strategy has been well evaluated by two common international metrics.

Effect of β-cyclodextrin/polydopamine composite modified anode on the performance of microbial fuel cell

The relatively weak microbial adhesion is a bottleneck in improving the power generation performance of microbial fuel cell (MFC). Anode modification is a simple and effective method to solve this problem. A new type of β-cyclodextrin/polydopamine modified carbon felt anode was prepared, and the effects of β-cyclodextrin/polydopamine modified anode on the main performance indexes such as power density and chemical oxygen demand (COD) removal rate of MFC were evaluated. The maximum power density and the output electric energy during the test period of MFC using the modified anode were 102 mW/m² and 84.96 J, which were 364% and 295.3% higher than those of MFC with conventional carbon felt anode, respectively; and the COD removal rate was 124.4% higher than that of MFC with unmodified anode. Modifying the anode with β-cyclodextrin-polyacyclic composite materials is an effective method to improve the overall performance of MFC.

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.

A novel electrochemical paper sensor for low-cost detection of 5-methyltetrahydrofolate in egg yolk

An electrochemical deposition method was used to fabricate a gold nanoflower (AuNF) and carbon nanoparticle (CNP) modified carbon paper (CP) sensor (AuNFs-CNPs/CP) for the low-cost detection of 5-methyltetrahydrofolate (5-mTHF) in egg yolk. AuNF morphology and structures were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), revealing nanoflower sizes in the 50 to 200 nm range. AuNFs formed on the sensor were in the Au⁰. We evaluated 5-mTHF assay performance using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The AuNFs-CNPs/CP sensor detected 5-mTHF concentrations in the ranges from 1 to 5 mg L^-1 and 1-20 μg L^-1, with an excellent limit of detection of 1 μg L^-1 and good selectivity toward 5-mTHF, when compared to other potentially interfering molecules in samples. The AuNFs-CNPs/CP sensor was also used to detect 5-mTHF in folate-rich, and was found to be twice than that of ordinary egg yolk.