Metal-organic Framework Probe Research Articles

Development of a dual-mode Ru-UiO-TPEA MOF probe for highly sensitive and accurate detection of Cu2+ in biological systems

Cu2+ serves as a significant biomarker in various physiological processes. This study presents the development of a novel Ru-UiO-TPEA functionalized metal-organic framework (MOFs) probe for Cu2+ detection, employing both electrochemiluminescence (ECL) and electrochemical (EC) methods. Employing a dual ligand-assisted energy transfer approach, we synthesized Ru-UiO with optimal ECL and EC properties by adjusting the synthesis ratio of biphenyldicarboxylic acid to Ru(dcbpy)32+. This was followed by its conjugation with N-(2-aminoethyl)-N, N′, N′-tris(pyridin-2-ylmethyl) ethane-1,2-diamine (AE-TPEA) to form the highly conjugated Ru-UiO-TPEA probe for Cu2+ detection. As the Cu2+ concentration increased, the probe exhibited a diminished ECL signal and an enhanced differential pulse voltammetry (DPV) signal. The dual-mode detection method enabled cross-validation of the ECL and EC signals, enhancing accuracy and effectively minimizing errors. The ECL and EC methods had detection limits of 0.26 nM (range: 1 nM to 10 μM) and 0.65 nM (range: 2 nM to 80 μM), respectively. Meanwhile, these two methods can effectively detect Cu2+ in rat brain microdialysis fluid. Notably, the measured concentrations correlated well with those determined by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), highlighting its potential in biological and clinical bioelectronic sensing applications.

A non-targeting magnetic metal-organic framework probe for highly specific peptide-mediated precise disease monitoring

Alzheimer's disease (AD) is a universal neurodegenerative disease in older adults with incurable and progressive properties, urging for precise monitoring to perform timely treatment to delay its progression. Herein, we introduced a non-targeting magnetic metal-organic framework probe coupled with high-throughput mass spectrometry, creating a rapid screening strategy for highly specific peptides associated with AD. Notably, an elution-free extraction process was proposed, significantly reducing sample preprocessing time while simultaneously ensuring the efficient detection of captured peptides. Using this elution-free extraction process, high-quality peptide profiles were rapidly extracted from the hundreds of samples from both diseased and healthy individuals. By integrating machine learning algorithms, LC-MS/MS, and Uniprot database searching, we identified three specific serum endogenous peptides (m/z = 4215.41, 2884.77 and 2704.61) closely associated with AD. Remarkably, with the use of any single specific peptide, the AUC (Area Under the Curve) values can reach approximately 0.9 during monitoring AD. Moreover, integrating three specific biomarkers provides a robust basis for machine learning algorithms to build monitoring models, with AUC value up to 1.000. This work represents a substantial advancement in the development of peptide-specific precise monitoring approaches for complex diseases, serving as a catalyst for increased dedication to the molecular detection field.

Copper-pyridine-2,4,6-tricarboxylate metal organic framework nanoparticles based opto-electrochemical sensor for sensitive detection of matrix metalloproteinase‑2

We designed a multiple signal sensing probe based on highly luminescent nanosized Cu-PTC metal-organic framework (MOF). The as synthesized nano-MOF was characterized by various techniques to confirm its morphology, crystallinity and elemental composition. A positively charged matrix metalloproteinase-2 (MMP-2) substrate (a polypeptide) was designed and prepared to interact electrostatically with the negatively charged Cu-PTC MOF probe, resulting in decrease in fluorescence response of the probe. Subsequently, MMP-2 was specifically recognized by the MMP-2 substrate and cleavage of the MMP-2 substrate resulted in “turn-on” fluorescence response from 1 to 175 ng/mL of MMP-2 concentrations with a limit of detection (LOD) of 0.8 ng/mL. In addition, the developed Cu-PTC MOF also exhibited peroxidase-like activity, which was exploited in the electrochemical detection of MMP-2 subjected to the catalysis of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2. The large surface area of the probe and unique catalytic activity toward TMB facilitated fabrication of an excellent sensing platform to detect MMP-2 with a linear range of 0.5–200 ng/mL with a LOD of 0.25 ng/mL. Various potential interfering biomolecules were evaluated and the stability of the constructed biosensor was assessed in optical and electrochemical modes. The reliability of the electrochemical detection mode was further executed by monitoring MMP-2 in biological samples (human serum and cell samples) and good recoveries were recorded.

Metal-Organic Framework as a Fluorescent and Colorimetric Dual-Signal Readout Biosensor Platform for the Detection of a Genetic Sequence from the SARS-CoV-2 Genome.

The quest for the development of high-accuracy, point-of-care, and cost-effective testing platforms for SARS-CoV-2 infections is ongoing as current diagnostics rely on either assays based on costly yet accurate nucleic acid amplification tests (NAAT) or less selective and less sensitive but rapid and cost-effective antigen tests. As a potential solution, this work presents a fluorescence-based detection platform using a metal-organic framework (MOF) in an effective assay, demonstrating the potential of MOFs to recognize specific targets of the SARS-CoV-2 genome with high accuracy and rapid process turnaround time. As a highlight of this work, positive detection of SARS-CoV-2 is indicated by a visible color change of the MOF probe with ultrahigh detection selectivities down to single-base mismatch nucleotide sequences, thereby providing an alternative avenue for the development of innovative detection methods for diverse viral genomes.

A luminous strategy for the recognition of toxic antibiotics in water via efficient energy transfer

Fluoroquinolones (FQs) are the class of Antibiotics (ABs) that have been extensively used worldwide for the treatment of diseases caused by bacterial infections. In India, most of these untreated ABs and their unused metabolites present in treated and untreated wastewater end up in agricultural land and water bodies. This can accelerate the problem of antimicrobial resistance in the community. Hence, we aim to develop a cost-effective sensor to detect and monitor the presence of such drugs in water bodies. We have prepared a chemically reduced graphene oxide (rGO) integrated luminescent cerium metal-organic framework (MOF) that specifically targets and recognizes ciprofloxacin (CPFX), norfloxacin (NFX), and ofloxacin (OFX) achieving excellent sensing activity. A remarkable quenching of the fluorescence of MOF composite was observed upon interaction with CPFX, NFX, and OFX with 57.9, 46.3, and 51.6 ppb as limits of detection, respectively, through a Forster resonance energy transfer from the Ce-MOF to the analytes. The applicability of the sensor was also examined with real-time samples collected from the rivers of Chennai city and the MOF probe exhibited an appreciable recovery of results. This is the first study on Ce-MOF-based rGO composite providing a solid rationale for fluorescence detection of FQs with exceptional quenching efficiency and very high sensitivity for monitoring FQs in water bodies even in diluted conditions.

A new resonance Rayleigh scattering method for phenol based on Cr(III) metal–organic framework probe and 4-aminoantipyrine reaction

Stable Cr(III) metal–organic framework (CrMOF) was prepared and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier infrared spectroscopy (FTIR). It was found that in the presence of potassium periodate (KIO4), phenol (PN) reacted with 4-aminoantipyrine (AAP) to form red quinone imine (QI) product, and a resonance Rayleigh scattering energy transfer (RRS-ET) occurred between the acceptor QI and the donor CrMOF. With the increase of PN concentration, RRS-ET increased, and the RRS intensity at 500 nm decreased. Based on this, a new and simple RRS-ET method for the detection of PN was established, with a detection range of 0.01–0.15 mmol/L and a detection limit (DL) of 0.005 mmol/L. The new RRS-ET method was applied to the determination of PN in water. The relative standard deviation (RSD) was 0.94–7.43%, and the recovery was 97–107%.

Construction of boric acid-functionalized metal-organic frameworks for glycopeptide recognition in the serum of cervical cancer patients.

Cervical cancer is one of the most common malignant tumors in women, and it is essential to explore potential biomarkers such as glycopeptides closely related to cancer in physiological samples of cervical cancer patients. Sample pretreatment is required before direct detection using mass spectrometry because there are certain limitations. Meanwhile, it is still highly desired to promote the functionalization and application of metal-organic framework (MOF)-derived materials. Using a post-synthesis modification method, a novel type of boric acid-functionalized MOF probe (designated as UiO-66@PEI@Au@B(OH)2 ) is prepared for recognition of glycopeptides. The results are obtained using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nano-liquid chromarography-tandem mass spectrometry. The UiO-66@PEI@Au@B(OH)2 probe exhibits a low detection limit (0.6fmol μL-1 ), an excellent recovery rate, comparatively good reusability and selectivity (HRP digests:BSA digests =1:500). When UiO-66@PEI@Au@B(OH)2 is used to selectively capture glycopeptides from the serum of a healthy person and a cervical cancer patient, 101 glycopeptides corresponding to 54 glycoproteins and 108 glycopeptides corresponding to 57 glycoproteins are detected, respectively. The successful preparation of UiO-66@PEI@Au@B(OH)2 provides a path for the investigation of the functionalization of MOF-derived materials. The excellent performance of UiO-66@PEI@Au@B(OH)2 not only demonstrates the huge potential of functionalized MOFs in the glycoproteome, but also opens up new phases of the application of MOF-based materials.

A Fluorescent Metal-Organic Framework for Food Real-Time Visual Monitoring.

Due to increasing food-safety issues, exploiting efficient approaches for food quality assessment and instrumentation has attracted concerns worldwide. Herein, a smart evaluation system based on a fluorescent metal-organic framework (MOF) is developed for real-time visual monitoring of food freshness. Via post-synthetic modification, a ratiometric fluorescent MOF probe is constructed by covalently coupling fluorescein 5-isothiocyanate (5-FITC) with NH2 -rich lanthanide MOF. The probes exhibit a dual-emissive-responsive to biogenic amine, resulting in an increase in FITC emission along with a decrease in Eu3+ emission accompanied by a clear distinguishable color transition from orange red to green. After doping the probes on a flexible substrate, the obtained MOF composite film can be integrated with a smartphone-based portable platform easily. It is proved that this smart evaluation system can be used for on-site inspection of the freshness of raw fish samples. This work develops a fluorescent MOF-based smart evaluation system as a novel platform for application in food monitoring, which not only has enormous economic value but also holds great public health significance.

Lysosome targeting metal-organic framework probe LysFP@ZIF-8 for highly sensitive quantification of carboxylesterase 1 and organophosphates in living cells

Herein, a lysosomal targeting LysFP@ZIF-8 metal-organic framework (MOF) was fabricated using fluorescent protein chromophore-based probe (LysFP) for selectively detection of carboxylesterase 1 (CES1) in living cells. Unlike the regular small molecule fluorescent probes, LysFP@ZIF-8 showed wide range pH tolerabiligy, high selectivity and sensitivity to CES1 in bio-samples, and was successfully applied to achieve the visual monitoring of CES1 activity in living cells. Low detection limit and high fluorescence quantum yield was calculated as 79 ng/mL and 0.76 for LysFP@ZIF-8, respectively. Furthermore, LysFP@ZIF-8 can also serve as a fluorescence indicator of organophosphates pesticide exposure in the way of hydrolyzing the carboxylic acid ester group in LysFP. This type of probe can inspire the development of fluorescent tools for further explore many pathological processes.

A highly fluorescent post-modified metal organic framework probe for selective, reversible and rapid carbon dioxide detection

The monitoring of the arterial and exhaled CO2 is of great importance. Despite of many reports on metal organic frameworks (MOFs) in adsorbing and separating CO2, the application of fluorescent MOFs probes for CO2 detection was rarely reported. A new fluorescent MOF probe UIO-66-ONa for CO2 detection was developed via post-synthesis of UIO-66-NH2 through a Schiff base reaction with salicylaldehyde and further treatment with sodium hydroxide. This probe exhibited a remarkable fluorescence color change from green to blue and showed excellent sensitivity and selectivity for CO2 sensing in solution. The detection limit was as low as 3.5 × 10−7 M. The excellent sensing performance of UIO-66-ONa was ascribed to the efficient reaction between sodium phenolic group and CO2, which led to the transformation of UIO-66-ONa to UIO-66-OH as evidenced by the emission spectra. This post-synthetic modification idea provided a new strategy for designing fluorescent MOFs probes for CO2 detection.

A highly fluorescent metal organic framework probe for 2,4,6-trinitrophenol detection via post-synthetic modification of UIO-66-NH2

Metal organic frameworks (MOFs) have been hotly concerned due to their unique structure and properties. A new highly fluorescent MOF was developed via post-synthesis of UIO-66-NH2 through an efficient click reaction with 1-ethynylpyrene for the 2,4,6-trinitrophenol (PA) detection which named UIO-66-Py. It exhibited a significantly enhanced fluorescence intensity than UIO-66-NH2 and showed excellent selectivity and sensitivity for sensing PA in solution via the fluorescence quenching mechanism. The UIO-66-Py showed an 85% fluorescence quenching efficiency with 0.203 mM PA and the detection limit was 4.5 × 10−7 M. The excellent selectivity of the probe was ascribed to the hydrogen bond interaction between UIO-66-Py and PA as evidenced by FT-IR. The hydrogen bond interaction promoted the photo-induced electron transfer (PET) between UIO-66-Py and PA which leading to the better selectivity of UIO-66-Py for PA detection over TNT. This post-synthetic modification idea provided a strategy for the development of MOFs with multifunctional sensing.

Design of a calix[4]arene-functionalized metal-organic framework probe for highly sensitive and selective monitor of hippuric acid for indexing toluene exposure

In the present work, a novel metal-organic framework (MOF) fluorescent probe was prepared by post-synthetic modification of MIL-53-NH2(Al) with carboxylatocalix[4]arene (CC[4]A). The introduced CC[4]A could not only enhance the fluorescence performance and the recognition ability of the probe, but also sustain the high stability under UV light and moisture conditions. A method based on the as-synthesized CC[4]A@MIL-53-NH2(Al) probe was established for sensing hippuric acid. The detection limit was determined to be as low as 3.7 μg mL−1. Over the concentration range of 0.005–3 mg mL−1, the calibration curve was obtained with a satisfactory linearity (R2 = 0.993). The method was successfully used for rapid and highly selective direct monitor of hippuric acid in human urine. The sensor had great potential to be used as a simple diagnostic tool for hippuric acid in human urine which is regarded as a biological index of toluene exposure.

Multifunctional Metal–Organic Framework Nanoprobe for Cathepsin B-Activated Cancer Cell Imaging and Chemo-Photodynamic Therapy

Integration of a photodynamic therapy platform with a drug-delivery system in a porous structure is an urgent challenge for enhanced anticancer therapy. Here, an amino-functionalized metal-organic framework (MOF), which is useful as efficient delivery vehicle for drugs and provides the -NH2 group for postsynthetic modification, is chosen and well-designed for cell imaging and chemo-photodynamic therapy. The multifunctional MOF nanoprobe was first assembled with camptothecine drug via noncovalent encapsulation and then bound with folic acid as the targeted element and chlorine e6 (Ce6)-labeled CaB substrate peptide as the recognition moiety and signal switch. The designed MOF probe can realize cathepsin B-activated cancer cell imaging and chemo-photodynamic dual-therapy combining Ce6 as the photosensitizer and the camptothecine drug. Compared with the individual treatment, the dual-functional nanoprobe presents an enhanced treatment efficiency in terms of the time of chemotherapy, laser power, and irradiation time of the photodynamic therapy, which has been confirmed in cancer cells and in vivo assays. This work presents a significant example of the MOF nanoprobe as an intracellular switch and shows great potential in cancer cell targeted imaging and multiple therapies.

The sensitive detection of formaldehyde in aqueous media using zirconium-based metal organic frameworks

The amino derivative of the UiO-66 metal organic framework (MOF) was investigated for potential use as a sensing probe for formaldehyde (FA) in an aqueous medium. The sensitivity and specificity of this MOF probe were virtually unaffected by the presence of other tested reference aldehydes, e.g., propionaldehyde (PA), butyraldehyde (BA), and valeraldehyde (VA). The maximum incubation time for the interaction of the MOF probe against 100ppm of FA standard was estimated at 2min. The linear detection of FA molecules using the proposed probe was performed in the range of 10–100ppm with a limit of detection (LOD) at 4ppm. The stability of the MOF for FA detection was estimated through a series of adsorption-desorption cycles. DFT calculations showed that the selective sensing/capture of FA corresponded to the formation of a stable, non-covalent bond between FA and the C6H3NH2 unit of the MOF. This interaction decreased the HOMO/LUMO gap of FA by approximately 0.8eV, a trend that was not evident for all other aldehydes. The results of FTIR, TGA, and XPS analysis confirmed a small but visible change in the chemical environment of the NH and CH bonds of UiO-66-NH2 upon their interactions with FA molecules. Therefore, the proposed MOF probe appears suitable for sensing FA in an aqueous medium.

Postsynthetic modification of metal–organic framework for hydrogen sulfide detection

Hydrogen sulfide (H2S) has recently been identified as the third biological gaseous messenger (gasotransmitter) that is involved in regulating many important physiological processes. The detection of H2S is thus essential for its roles but remain challenging in living systems. We report herein a novel turn-on fluorescent probe for H2S detection based on azide functionalized metal-organic framework (MOF). The MOF probe displayed high sensitivity (detection limit, 28.3μM), excellent selectivity, and fast response (<2min) toward H2S over other biologically relevant species. We envisage that this MOF probe can be employed as a useful tool to further elucidate the biological roles of H2S.