A base-stable metal-organic framework for sensitive and non-enzymatic electrochemical detection of hydrogen peroxide

Facile synthesis of a zeolitic imidazolate framework-8 with reduced graphene oxide hybrid material as an efficient electrocatalyst for nonenzymatic H2O2 sensing

A zeolitic imidazolate framework-8 (ZIF-8)/reduced graphene oxide (rGO) nanocomposite was formed by using an efficient synthetic method. The morphology and structure of the ZIF-8/rGO nanocomposite were characterized by scanning electron spectroscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) mapping. The ZIF-8/rGO nanocomposites were immobilized on a carbon paste electrode (CPE) to construct a high-performance nonenzymatic electrochemical H2O2 sensor. A cyclic voltammetry (CV) study showed that the ZIF-8/rGO nanocomposites displayed better electrocatalytic activity toward H2O2 reduction compared to that of ZIF-8. An amperometric study indicated that the H2O2 sensor displayed high performance, which offered a low detection limit (0.05 μM) (S/N = 3), a high sensitivity (4.01 μA mM-1 cm-2), and a wide linear range (from 1.0 to 625 μM). An electrochemical reaction mechanism was proposed for H2O2 reduction on the ZIF-8/rGO/CPE. Importantly, the as-fabricated H2O2 sensor exhibited good reproducibility and excellent selectivity. Furthermore, the constructed high-performance sensor was utilized to monitor the H2O2 levels in real samples, and satisfactory results were obtained. These results demonstrated that the ZIF-8/rGO nanocomposite can be used as a good electrochemical sensor material in practical applications.

Synthesis, Characterization, and Biomedical Applications of an Alkylated Quercetin-Gadolinium Complex

Flavonoids and their derivatives have been extensively studied for their pharmaceutical applications due to their antioxidant and anti-inflammatory properties. The coordination complexes of several flavonoids have demonstrated DNA binding ability that can confer anticancer properties. The structure of the flavonoid has a pronounced influence on its pharmacological properties. Herein we report the synthesis and characterization of alkylated quercetin and its complex with gadolinium. The structure of the complex was confirmed using spectroscopic techniques. The ability of the gadolinium-alkylated quercetin complex to serve as a magnetic contrast agent was compared with gadolinium-quercetin complex. The quercetin-gadolinium complex was found to exhibit better contrast property with a relaxivity of 0.2952 μg mL^-1 s^-1 when compared to the gadolinium complex of alkylated quercetin. This difference primarily arises due to the greater hydrophobicity of the alkylated quercetin complex that restricts access of water. However, the alkylated quercetin was found to exhibit better enzyme mimic activity as the metal ion served as a redox center that enabled quantification of hydrogen peroxide in the concentration range 50-450 μM within 5 s with a sensitivity of 64 nA/μM and limit of detection of 7.3 μM. The better sensing performance of the alkylated quercetin-gadolinium complex, reported here for the first time, when compared to quercetin-gadolinium complex can be attributed to the enhanced electroactive area on the working electrode.

Enzymeless electrochemical determination of hydrogen peroxide at a heteropolyanion-based composite film electrode

For the first time, a sensitive and efficient composite film of [PB/WV–Pt@Pd]₆was constructed for H₂O₂detection.

Simple, low-cost, sensitive and label-free aptasensor for the detection of cardiac troponin I based on a gold nanoparticles modified titanium foil

This research demonstrated the electrochemical modification of low-cost titanium (Ti) metal substrate with gold nanoparticles (AuNPs) for the aptamer-based detection of cardiac troponin I (cTnI). AuNPs were deposited onto Ti sheets by the potential-step deposition method with high density and homogeneity as well as good crystallinity. It was then applied as a transducer to immobilize a thiol-functionalized DNA aptamer via the self-assembled monolayer mechanism for the specific binding of cTnI. This was verified through electrochemical and morphological analyses. The aptasensor could detect cTnI in a linear range of 1-1100 pM with a detection limit of ca. 0.18 pM. The aptasensor showed high sensitivity and specificity to cTnI over other interfering compounds with good recoveries in the diluted human serum samples.

Metal-Organic Frameworks for the Development of Biosensors: A Current Overview

This review focuses on the fabrication of biosensors using metal-organic frameworks (MOFs) as recognition and/or transducer elements. A brief introduction discussing the importance of the development of new biosensor schemes is presented, describing these coordination polymers, their properties, applications, and the main advantages and drawbacks for the final goal. The increasing number of publications regarding the characteristics of these materials and the new micro- and nanofabrication techniques allowing the preparation of more accurate, robust, and sensitive biosensors are also discussed. This work aims to offer a new perspective from the point of view of materials science compared to other reviews focusing on the transduction mechanism or the nature of the analyte. A few examples are discussed depending on the starting materials, the integration of the MOF as a part of the biosensor and, in a deep detail, the fabrication procedure.