Two‐dimensional π‐conjugated metal‐organic framework with high electrical conductivity for electrochemical sensing

Unlocking the future of brain research: MOFs, TMOs, and MOFs/TMOs for electrochemical NTMs detection and analysis

The central nervous system relies heavily on neurotransmitters (NTMs), and NTM imbalances have been linked to a wide range of neurological conditions. Thus, the development of reliable detection techniques is essential for advancing brain studies. This review offers a comprehensive analysis of metal-organic frameworks (MOFs), transition metal oxides (TMOs), and MOFs-derived TMOs (MOFs/TMOs) as materials for electrochemical (EC) sensors targeting the detection of key NTMs, specifically dopamine (DA), epinephrine (EP), and serotonin (SR). The unique properties and diverse families of MOFs and TMOs, along with their nanostructured hybrids, are discussed in the context of EC sensing. The review also addresses the challenges in detecting NTMs and proposes a systematic approach to tackle these obstacles. Despite the vast amount of research on MOFs and TMOs-based EC sensors for DA detection, the review highlights the gaps in the literature for MOFs/TMOs-based EC sensors specifically for EP and SR detection, as well as the limited research on microneedles (MNs)-based EC sensors modified with MOFs, TMOs, and MOFs/TMOs for NTMs detection. This review serves as a foundation to encourage researchers to further explore the potential applications of MOFs, TMOs, and MOFs/TMOs-based EC sensors in the context of neurological disorders and other health conditions related to NTMs imbalances.

Synthesis of Electrical Conductive Metal-Organic Frameworks for Electrochemical Applications

Electrical conductivity is very important property of nanomaterials for using wide range of applications especially energy applications. Metal-organic frameworks (MOFs) are notorious for their low electrical conductivity and less considered for usage in pristine forms. However, the advantages of high surface area, porosity and confined catalytic active sites motivated researchers to improve the conductivity of MOFs. Therefore, 2D electrical conductive MOFs (ECMOF) have been widely synthesized by developing the effective synthetic strategies. In this article, we have summarized the recent trends in developing the 2D ECMOFs, following the summary of potential applications in the various fields with future perspectives.

Metal-Organic Frameworks-Based Nanoplatforms for the Theranostic Applications of Neurological Diseases

Neurological diseases are the foremost cause of disability and the second leading cause of death worldwide. Owing to the special microenvironment of neural tissues and biological characteristics of neural cells, a considerable number of neurological disorders are currently incurable. In the past few years, the development of nanoplatforms based on metal-organic frameworks (MOFs) has broadened opportunities for offering sensitive diagnosis/monitoring and effective therapy of neurology-related diseases. In this article, the obstacles for neurotherapeutics, including delayed diagnosis and misdiagnosis, the existence of blood brain barrier (BBB), off-target treatment, irrepressible inflammatory storm/oxidative stress, and irreversible nerve cell death are summarized. Correspondingly, MOFs-based diagnostic/monitoring strategies such as neuroimaging and biosensors (electrochemistry, fluorometry, colorimetry, electrochemiluminescence, etc.) and MOFs-based therapeutic strategies including higher BBB permeability, targeting specific lesion sites, attenuation of neuroinflammation/oxidative stress as well as regeneration of nerve cells, are extensively highlighted for the management of neurological diseases. Finally, the challenges of the present research from perspective of clinical translation are discussed, hoping to facilitate interdisciplinary studies at the intersections between MOFs-based nanoplatforms and neurotheranostics.

Hierarchical copper-based metal-organic frameworks nanosheet assemblies for electrochemical ascorbic acid sensing

Noninvasive human health monitoring requires the development of efficient electrochemical sensors for the quantitative analysis of infinitesimal biomolecules. In this work, we reported a novel hierarchical nanosheet assemblies (HSA) of copper-based metal-organic frameworks (MOFs) as an electrochemical sensor for ascorbic acid (AA) detection. Copper 1,4-benzenedicarboxylate (CuBDC) HSA was constructed by three steps of in situ growth on stone paper, including hydrolysis, anion exchange, and heteroepitaxy growth. The monodispersed two-dimensional MOFs nanosheet units were aligned in an orderly manner and arranged into three-dimensional hierarchical assemblies. The CuBDC HSA-based AA sensor displayed a high sensitivity of 396.8 μA mM^-1 cm^-2 and a low detection limit of 0.1 μM. Excellent selectivity, stability and reproducibility were also obtained. Benefiting from the advantages of ultrathin nanosheets and nature-inspired hierarchy, this unique architecture facilitated reactant dispersion and maximized the accessible active sites and charge-transport capability and thus had superior catalytic ability for the electro-oxidation of ascorbic acid compared to bulk MOFs. Moreover, the CuBDC HSA sensor performed AA level detection in juice samples with acceptable accuracy and verified the feasibility for sweat AA sensing. This novel MOFs architecture holds great potential as an electrochemical sensor to detect AA for noninvasive human health monitoring in the future.

Semiconducting CuxNi3-x(hexahydroxytriphenylene)2 framework for electrochemical aptasensing of C6 glioma cells and epidermal growth factor receptor

A 2D CuNi metal-organic framework (MOF) named CuxNi3-x(HHTP)2 was synthesized with 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) as the linker and was used as a sensitive scaffold to adsorb aptamer strands for the electrochemical detection of living C6 glioma cells and one of their biomarkers, epidermal growth factor receptor (EGFR). Different from conventional MOFs, the CuxNi3-x(HHTP)2 MOF comprises long-range delocalized electrons, a graphene-analog nanostructure, multiple metal states (Cu0/Cu+/Cu2+ and Ni2+/Ni3+), and abundant oxygen vacancies. With these features, the CuxNi3-x(HHTP)2 MOF anchored a large amount of C6 cell-targeted aptamer strands via coordination among metal centers, oligonucleotides, π-π stacking, and van der Waals force. The CuxNi3-x(HHTP)2-based cytosensor showed a low limit of detection (LOD) of 21 cells mL-1 toward C6 glioma cells within a wide range from 50 cells mL-1 to 1 × 105 cells mL-1. Moreover, the proposed aptasensor displayed high selectivity, good stability, acceptable reproducibility, and a low LOD of 0.72 fg mL-1 for detecting EGFR with the concentration ranging from 1 fg mL-1 to 1 ng mL-1. The aptasensor based on the CuxNi3-x(HHTP)2 MOF exhibited superior sensing performance over those based on its monometallic analogues such as Cu3(HHTP)2 MOF and Ni3(HHTP)2 MOF. Hence, this sensing strategy based on a bimetallic semiconducting MOF shows great potential for cancer diagnosis.

Two-dimensional conjugated metal–organic frameworks (2D c-MOFs): chemistry and function for MOFtronics

Two-dimensional conjugated MOFs are emerging for multifunctional electronic devices that brings us “MOFtronics”, such as (opto)electronics, spintronics, energy devices.

Employing Conductive Metal-Organic Frameworks for Voltammetric Detection of Neurochemicals

This paper describes the first implementation of an array of two-dimensional (2D) layered conductive metal-organic frameworks (MOFs) as drop-casted film electrodes that facilitate voltammetric detection of redox active neurochemicals in a multianalyte solution. The device configuration comprises a glassy carbon electrode modified with a film of conductive MOF (M₃HXTP₂; M = Ni, Cu; and X = NH, 2,3,6,7,10,11-hexaiminotriphenylene (HITP) or O, 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP)). The utility of 2D MOFs in voltammetric sensing is measured by the detection of ascorbic acid (AA), dopamine (DA), uric acid (UA), and serotonin (5-HT) in 0.1 M PBS (pH = 7.4). In particular, Ni₃HHTP₂ MOFs demonstrated nanomolar detection limits of 63 ± 11 nM for DA and 40 ± 17 nM for 5-HT through a wide concentration range (40 nM-200 μM). The applicability in biologically relevant detection was further demonstrated in simulated urine using Ni₃HHTP₂ MOFs for the detection of 5-HT with a nanomolar detection limit of 63 ± 11 nM for 5-HT through a wide concentration range (63 nM-200 μM) in the presence of a constant background of DA. The implementation of conductive MOFs in voltammetric detection holds promise for further development of highly modular, sensitive, selective, and stable electroanalytical devices.

Two-Dimensional Conductive Metal-Organic Frameworks Based on Truxene

Two dimensional conductive metal-organic frameworks (2D cMOFs) have been widely applied as electrocatalysts, electronic devices, and sensors. In addition, their intrinsic electronic properties could be efficiently tuned via varying the conjugated linkers. Herein, we report a novel 2D cMOF based on complexation of 2,3,7,8,12,13-hexahydroxyl truxene and copper ions via the energy economical interfacial reaction. This 2D cMOF was obtained as a brilliant black powder and showed a bulk electrical conductivity of 3.5 × 10^-3 S cm^-1 at 30 °C. Additionally, the cMOF-modified glassy carbon electrode could act as an electrochemical sensor for sensing paraquat with a limit of detection at 4.1 × 10^-8 M (S/N = 3). The accession of truxene-Cu to the cMOF family would shed new light on the impact of the organic conjugated linker and broaden the scope of cMOFs' applications.