Research Progress of UiO-66-Based Electrochemical Biosensors

A dual recognition-based strategy employing Ni-modified metal-organic framework for in situ screening of SIRT1 inhibitors from Chinese herbs

Sirtuin1 (SIRT1), an NAD+-dependent histone deacetylase, plays a crucial role in regulating molecular signaling pathways. Recently, inhibition of SIRT1 rather than its activation shows the therapeutic potential for central nervous system disorder, however, the discovered SIRT1 inhibitors remains limited. In this work, a dual recognition-based strategy was developed to screen SIRT1 inhibitors from natural resources in situ. This approach utilized a Ni-modified metal-organic framework (Ni@Tyr@UiO-66-NH2) along with cell lysate containing an engineered His-tagged SIRT1 protein, eliminating the need for purified proteins, pure compounds, and protein immobilization. The high-performance Ni@Tyr@UiO-66-NH2 was synthesized by modifying the surface of UiO-66-NH2 with Ni2+ ions to specifically capture His-tagged SIRT1 while persevering its enzyme activity. By employing dual recognition, in which Ni@Tyr@UiO-66-NH2 recognized SIRT1 and SIRT1 recognized its ligands, the process of identifying SIRT1 inhibitors from complex matrix was vastly streamlined. The developed method allowed the efficient discovery of 16 natural SIRT1 inhibitors from Chinese herbs. Among them, 6 compounds were fully characterized, and suffruticosol A was found to have an excellent IC50 value of 0.95 ± 0.12 μM. Overall, an innovative dual recognition-based strategy was proposed to efficiently identify SIRT1 inhibitors in this study, offering scientific clues for the development of drugs targeting CNS disorders.

Downsizing and soft X-ray tomography for cellular uptake of interpenetrated metal-organic frameworks

Metal-organic frameworks (MOFs) are porous materials with potential in biomedical applications such as sensing, drug delivery, and radiosensitization. However, how to tune the properties of the MOFs for such applications remains challenging. Herein, we synthesized two MOFs, Zr-PEB and Hf-PEB. Zr-PEB can be classified as porous interpenetrated zirconium frameworks (PIZOFs) and Hf-PEB is its analogue. We controlled their sizes while maintaining their crystal structure by employing a coordination modulation strategy. They were designed to serve as sensitizer for X-ray therapy and as potential drug carriers. Comprehensive characterizations of the MOFs' properties have been conducted, and the in vitro biological impacts have been studied. Since viability assay showed that Hf-PEB was more biocompatible compared to Zr-PEB, the cellular uptake of Hf-PEB by cells was evaluated using both fluorescence microscopy and soft X-ray tomography (SXT), and the three-dimensional structure of Hf-PEB in cells was observed. The results revealed the potential of Zr-PEB and Hf-PEB as nanomaterials for biomedical applications and demonstrated that SXT is an effective tool to assist the development of such materials.

Sensitive determination of 4,6-dinitro-o-cresol based on a glassy carbon electrode modified with Zr-UiO-66 metal-organic framework entrapped FMWCNTs

A DNOC electrochemical sensor has been developed by using a composite of Zr-UiO-66 and FMWCNTs on a glassy carbon electrode (GCE) and using the differential pulse voltammetry technique. The synthesized materials were physico-chemically characterized by BET, PXRD, FTIR, TGA, EDX, and FESEM. Cyclic voltammetry showed that DNOC has three oxidation peaks at 0.03 V (RSD: 0.23%), 0.42 V (RSD: 0.21%), and 1.32 V (RSD: 0.32%) and three reduction peaks at - 0.20 V (RSD: 0.15%), - 0.82 V (RSD: 0.26%), and - 1.14 V (RSD: 0.19%) which follow a diffusion-controlled mechanism. Different parameters were optimized using differential pulse voltammetry and good linear ranges were found for the simultaneous detection of the three reduction peaks. For a specific concentration range of 0.1-50 μM, a limit of detection of 0.119 μM based on 3Sb/m was obtained. The interfering effects of five non-phenolic pesticides and five heavy metals were evaluated to highlight the selectivity of the developed sensor. It is the first report of an electrochemical DNOC sensor in which all three oxidation peaks are prominently visible. Ethion and chloropyriphos were found to inhibit the redox process of DNOC on the developed sensor platform Zr-UiO-66/FMWCNT/GCE. The sensor was successfully applied to DNOC determination in spiked potato samples and the results showed a standard deviation of less than 3%. The proposed method is expected to provide a novel platform for the quantitative determination of DNOC pesticides in vegetables.

Carbon dioxide adsorption to UiO-66: theoretical analysis of binding energy and NMR properties

UiO-66 is one of the most valuable metal-organic frameworks because of its excellent adsorption capability for gas molecules and its high stability towards water. Herein we investigated adsorption of carbon dioxide (CO2), acetone, and methanol to infinite UiO-66 using DFT calculations on an infinite system under periodic-boundary conditions and post-Hartree-Fock (SCS-MP2 and MP2.5) calculations on cluster models. Three to four molecules are adsorbed at each of four μ-OH groups bridging three Zr atoms in one unit cell (named Site I). Six molecules are adsorbed around three pillar ligands, where the molecule is loosely surrounded by three terephthalate ligands (named Site II). Also, six molecules are adsorbed around the pillar ligand in a different manner from that at Site II, where the molecule is surrounded by three terephthalate ligands (named Site III). Totally fifteen to sixteen CO2 molecules are adsorbed into one unit cell of UiO-66. The binding energy (BE) decreases in the order Site I > Site III > Site II for all three molecules studied here and in the order acetone > methanol ≫ CO2 in the three adsorption sites. At the site I, the protonic H atom of the μ-OH group interacts strongly with the negatively charged O atom of CO2, acetone and methanol, which is the origin of the largest BE value at this site. Although the DFT calculations present these decreasing orders of BE values correctly, the correction by post-Hartree-Fock calculations is not negligibly small and must be added for obtaining better BE values. We explored NMR spectra of UiO-66 with adsorbed CO2 molecules and found that the isotropic shielding constants of the 1H atom significantly differ among no CO2, one CO2 (at Sites I, II, or III), and fifteen CO2 adsorption cases (Sites I to III) but the isotropic 17O and 13C shielding constants change moderately by adsorption of fifteen CO2 molecules. Thus, 1H NMR measurement is a useful experiment for investigating CO2 adsorption.

A UiO-66-NH2 MOF/PAMAM Dendrimer Nanocomposite for Electrochemical Detection of Tramadol in the Presence of Acetaminophen in Pharmaceutical Formulations

In this work, we prepared a novel electrochemical sensor for the detection of tramadol based on a UiO-66-NH₂ metal-organic framework (UiO-66-NH₂ MOF)/third-generation poly(amidoamine) dendrimer (G3-PAMAM dendrimer) nanocomposite drop-cast onto a glassy carbon electrode (GCE) surface. After the synthesis of the nanocomposite, the functionalization of the UiO-66-NH₂ MOF by G3-PAMAM was confirmed by various techniques including X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field emission-scanning electron microscopy (FE-SEM), and Fourier transform infrared (FT-IR) spectroscopy. The UiO-66-NH₂ MOF/PAMAM-modified GCE exhibited commendable electrocatalytic performance toward the tramadol oxidation owing to the integration of the UiO-66-NH₂ MOF with the PAMAM dendrimer. According to differential pulse voltammetry (DPV), it was possible to detect tramadol under optimized circumstances in a broad concentration range (0.5 μM-500.0 μM) and a narrow limit of detection (0.2 μM). In addition, the stability, repeatability, and reproducibility of the presented UiO-66-NH₂ MOF/PAMAM/GCE sensor were also studied. The sensor also possessed an acceptable catalytic behavior for the tramadol determination in the co-existence of acetaminophen, with the separated oxidation potential of ΔE = 410 mV. Finally, the UiO-66-NH₂ MOF/PAMAM-modified GCE exhibited satisfactory practical ability in pharmaceutical formulations (tramadol tablets and acetaminophen tablets).

UiO-66-Derived PBA Composite as Multifunctional Electrochemical Non-Enzymatic Sensor Realizing High-Performance Detection of Hydrogen Peroxide and Glucose

In this work, a highly efficient multifunctional non-enzymatic electrochemical sensor is successfully fabricated based on a facile two-step synthetic strategy. It resolves two important challenges of poor stability and low reproducibility compared to conventional electrochemical enzyme-based sensors. Herein, a metal-organic framework (UiO-66) is selected as a sacrificial template to construct the corresponding Prussian blue analogue (PBA) target to improve its stability and conductivity, namely, PBA/UiO-66/NF. Target PBA/UiO-66/NF exhibits excellent electrochemical sensing performance as hydrogen peroxide (H₂O₂) and glucose sensors with ultrahigh sensitivity of up to 1903 μA mM^-1 cm^-2 for H₂O₂ and 22,800 μA mM^-1 cm^-2 for glucose, as well as a very low detection limit of 0.02 μM (S/N = 3) for H₂O₂ and 0.28 μM for glucose. Especially, extremely high stability can be observed, which will be beneficial for practical application.

A porous Ti-based metal-organic framework for CO2 photoreduction and imidazole-dependent anhydrous proton conduction

The anhydrous proton conductivity of Im@IEF-11 resulting from the integration of imidazole and porous IEF-11 has been investigated, and the highest proton conductive value can reach up to 7.64 × 10^-2 S cm^-1. Furthermore, IEF-11 is also developed to reduce CO₂ due to its reasonable structure and suitable energy band, and its CO formation rate is 31.86 μmol g^-1 h^-1.

Capacitive Desalination and Disinfection of Water Using UiO-66 Metal-Organic Framework/Bamboo Carbon with Chitosan

The zirconium-based metal-organic framework (MOF) (UiO-66)/bamboo carbon (BC) composite with chitosan was prepared using hydrothermal and impregnation methods and used for capacitive desalination (CDI) and disinfection of water. The results showed that these composites had fast ion exchange and charge transfer properties. During the CDI process, these composites' electrodes exhibited good cycle stability, electrosorption capacity (4.25 mg/g) and excellent bactericidal effect. These carbon-based composites electrodes' bactericidal rate for Escherichia coli could reach 99.99% within 20 minutes; therefore, they had good performance and were a good choice for high-performance deionization applications.