Nanoscale Metal-Organic Layers Detect Mitochondrial Dysregulation and Chemoresistance via Ratiometric Sensing of Glutathione and pH

Competitive coordination assisted scalable fabrication of FITC‑nickel frameworks anchored nanofiber paper for colorimetric/fluorescent monitoring of shrimp freshness

A novel type of colorimetric/fluorescent nanopaper indicator has been developed from the melt-extruded poly (vinyl alcohol-co-ethylene) nanofibers with surface anchored metal-organic frameworks (MOFs) by an interfacial coordination strategy. Specifically, the fluorescein isothiocyanate molecules could be anchored to the nanofiber surface by nickel ions and co-assembled into a hydrophilic nanocoating via a dynamic water/alcohol solvent evaporation method. Interestingly, this hydrophilic surface enables fast adsorption of moistures and interaction with biological amine vapors, resulting a saffron cake-layer of MOF nanocrystals with ultra-sensitive colorimetric/fluorescent responses based on an alkaline pH/ammonia induced competitive coordination mechanism. Finally, these porous nanofibrous matrix and active nanocoating make the nano-paper an ultra-sensitive optical platform for in-situ monitoring of the shrimp freshness from mins to weeks. Therefore, this composite film shows great potential into advanced paper-based indicators for food quality control and safety in processing industry.

Skin-attachable Tb-MOF ratio fluorescent sensor for real-time detection of human sweat pH

The pH of human sweat is highly related with a variety of diseases, whereas the monitoring of sweat pH still remains challenging for ordinary families. In this study, we developed a novel dual-emission Tb-MOF using DPA as the ligand and further designed and constructed a skin-attachable Tb-MOF ratio fluorescent sensor for real-time detection of human sweat pH. With the increased concentration of H+, the interaction of H+ with carbonyl organic ligand leads to the collapse of the Tb-MOF crystal structure, resulting in the interruption of antenna effect, and correspondingly increasing the emission of the ligand at 380 nm and decreasing the emission of the central ion Tb3+ at 544 nm. This Tb-MOF nanoprobe has a good linear response in the pH range of 4.12-7.05 (R2 = 0.9914) with excellent anti-interference ability. Based on the merits of fast pH response and high sensitivity, the nanoprobe was further used to prepare flexible wearable sensor. The wearable sensor can detect pH in the linear range of 3.50-6.70, which covers the pH range of normal human sweat (4.50-6.50). Subsequently, the storage stability and detection accuracy of the sensors were evaluated. Finally, the sensor has been successfully applied for the detection of pH in actual sweat samples from 21 volunteer and the real-time monitoring of pH variation during movement processing. This skin-attachable Tb-MOF sensor, with the advantages of low cost, visible color change and long shelf-life, is appealing for sweat pH monitoring especially for ordinary families.

Nanoscale Metal-Organic Frameworks as a Photoluminescent Platform for Bioimaging and Biosensing Applications

The tracking of nanomedicines in their concentration and location inside living systems has a pivotal effect on the understanding of the biological processes, early-stage diagnosis, and therapeutic monitoring of diseases. Nanoscale metal-organic frameworks (nano MOFs) possess high surface areas, definite structure, regulated optical properties, rich functionalized sites, and good biocompatibility that allow them to excel in a wide range of biomedical applications. Controllable syntheses and functionalization endow nano MOFs with better properties as imaging agents and sensing units for the diagnosis and treatment of diseases. This minireview summarizes the tunable synthesis strategies of nano MOFs with controllable size, shape, and regulated luminescent performance, and pinpoints their recent advanced applications as optical elements in bioimaging and biosensing. The current limitations and future development directions of nano MOF-contained materials in bioimaging and biosensing applications are also discussed, aiming to expand the biological applications of nano MOF-based nanomedicine and facilitate their production or clinical translation.

A cellulosic multi-bands fluorescence probe for rapid detection of pH and glutathione

The detection of pH and glutathione (GSH) is positively significant for the cell microenvironment imaging. Here, to assess the pH value and the concentration of GSH efficiently and visually, a cellulose-based multi-bands ratiometric fluorescence probe was designed by assembling MnO2-modified cellulose gold nanoclusters, fluorescein isothiocyanate-grafted cellulose nanocrystals (CNCs) and protoporphyrin IX-modified CNCs. The probe exhibits GSH-responsive, pH-sensitive and GSH/pH-independent fluorescent properties at 440 nm, 520 nm, and 633 nm, respectively. Furthermore, the probe identifies GSH within 4 s by degrading MnO2 into Mn2+ in response to GSH. Ingeniously, the green fluorescence of the probe at 520 nm was decreased with pH, and the red fluorescence at 633 nm remained stable. Therefore, the probe displayed distinguishing fluorescence colors from pink to blue and from green to blue for the synchronous detection of pH and GSH concentration within 4 s. The design strategy provides insights to construct multi-bands fluorescence probes for the rapid detection of multiple target analytes.

A pH-response-based fluorescent probe for detecting the mitophagy process by tracing changes in colocalization coefficients

Mitochondria are not only the center of energy metabolism but also involved in regulating cellular activities. Quality and quantity control of mitochondria is therefore essential. Mitophagy is a lysosome-dependent process to clear dysfunctional mitochondria, and abnormal mitophagy can cause metabolic disorders. Therefore, it is necessary to monitor the mitophagy in living cells on a real-time basis. Herein, we developed a pH-responsive fluorescent probe MP for the detection of the mitophagy process using real-time tracing colocalization coefficients. Probe MP showed good pH responses with high selectivity and sensitivity in spectral testing. Probe MP is of positive charge, which is beneficial for accumulating into mitochondrial in living cells. Cells exhibited pH-dependent fluorescence when they were treated with different pH media. Importantly, the changes in the colocalization coefficient between probe MP and Lyso Tracker® Deep Red from 0.4 to 0.8 were achieved in a real-time manner during the mitophagy stimulated by CCCP, starvation and rapamycin. Therefore, combined with the parameter of the colocalization coefficient, probe MP is a potential molecular tool for the real-time tracing of mitophagy to further explore the details of mitophagy.

Rational design of a near-infrared dual-emission fluorescent probe for ratiometric imaging of glutathione in cells

Sensors for which the output signal is an intensity change for a single-emission peak are easily disturbed by many factors, such as the stability of the instrument, intensity of the excitation light, and biological background. However, for ratiometric fluorescence sensors, the output signal is a change in the intensity ratio of two or more emission peaks. The fluorescence intensity of these emission peaks is similarly affected by external factors; thus, these sensors have the ability to self-correct, which can greatly improve the accuracy and reliability of the detection results. To accurately image glutathione (GSH) in cells, gold nanoclusters (AuNCs) with intrinsic double emission at wavelengths of 606 nm and 794 nm were synthesized from chloroauric acid. With the emission peak at 606 nm as the recognition signal and the emission peak at 794 nm as the reference signal, a near-infrared dual-emission ratio fluorescence sensing platform was constructed to accurately detect changes in the GSH concentration in cells. In vitro and in vivo analyses showed that the ratiometric fluorescent probe specifically detects GSH and enables ultrasensitive imaging, providing a new platform for the accurate detection of active small molecules.

Rationally designed multifunctional nanoparticles as GSH-responsive anticancer drug delivery systems based on host-guest polymers derived from dextran and β-cyclodextrin

Tumor proliferation and metastasis rely on energy provided by mitochondria. The hexokinase inhibitor lonidamine (LND) could suppress the activities in mitochondria, being a potential antitumor drug. However, limited water-solubility of LND may hinder its biomedical applications. Besides, the cancer-killing effect of LND is compromised by the high level of glutathione (GSH) in cancer cells. Therefore, it is urgent to find a proper method to simultaneously deliver LND and deplete GSH as well as monitor GSH level in cancer cells. Herein, a host polymer β-cyclodextrin-polyethylenimine (β-CD-PEI) and a guest polymer dextran-5-dithio-(2-nitrobenzoic acid) (Dextran-SS-TNB) were synthesized and allowed to form LND-loaded GSH-responsive nanoparticles through host-guest inclusion complexation between β-CD and TNB as host and guest molecular moieties, respectively, which functioned as a system for simultaneous delivery of LND and -SS-TNB species into cancer cells. As a result, the delivery system could deplete GSH and elevate reactive oxygen species (ROS) level in cancer cells, further induce LND-based mitochondrial dysfunction and ROS-based immunogenic cell death (ICD), leading to a synergistic and efficient anticancer effect. In addition, -SS-TNB reacted with GSH to release TNB2-, which could be a probe with visible light absorption at 410 nm for monitoring the GSH level in the cells.

Fluorescence Resonance Energy Transfer (FRET)-Based Sensor for Detection of Foodborne Pathogenic Bacteria: A Review

Sensitive and rapid determination of foodborne pathogenic bacteria is of practical importance for the control and prevention of foodborne illnesses. Nowadays, with the prosperous development of fluorescence assays, fluorescence resonance energy transfer (FRET)-derived diagnostic strategies are extensively employed in quantitative analysis of different pathogenic bacteria in food-related matrices, which displays a rapid, simple, stable, reliable, cost-effective, selective, sensitive, and real-time way. Considering the extensive efforts that have been made in this field so far, we here discuss the up-to-date developments of FRET-based diagnostic approaches for the determination of key foodborne pathogens like Staphylococcus aureus, Escherichia coli, Vibrio parahaemolyticus, Salmonella spp., Campylobacter spp., and Bacillus cereus in complex food-related matrices. Moreover, the principle of this technology, the choosing standards of acceptor-donor pairs, and the fluorescence properties are also profiled. Finally, the current prospects and challenges in this field are also put forward.

A dual-mode ratiometric aptasensor for accurate detection of pathogenic bacteria based on recycling of DNAzyme activation

Pathogenic bacteria have a significant impact on food safety. Herein, an innovative dual-mode ratiometric aptasensor was constructed for ultrasensitive and accurate detection of Staphylococcus aureus (S. aureus) based on recycling of DNAzyme activation on gold nanoparticles-functionalized MXene nanomaterials (MXene@Au NPs). Electrochemiluminescent (ECL) emitter-labeled probe DNA (probe 2-Ru) containing the blocked DNAzyme was partly hybridized with aptamer and then captured by electrochemical (EC) indicator-labeled probe DNA (probe 1-MB) on electrode surface. When S. aureus presented, the conformation vibration of probe 2-Ru activated the blocked DNAzymes, leading to recycling cleavage of probe 1-MB and ECL tag close to electrode surface. Based on the reverse change tendencies of ECL and EC signals, aptasensor achieved S. aureus quantification from 5 to 10⁸ CFU/mL. Moreover, the self-calibration characteristic of the aptasensor with dual-mode ratiometric readout ensured the reliable measurement of S. aureus in real samples. This work showed useful insight into sensing foodborne pathogenic bacteria.

A novel near-infrared fluorescent probe with hemicyanine scaffold for sensitive mitochondrial pH detection and mitophagy study

Mitochondria, as an energy-producing powerhouse in live cells, is considered to be directly linked to cellular health. However, dysfunctional mitochondria and abnormal mitochondria pH would possibly activate mitophagy, cell apoptosis and intercellular acidification process. In this work, we synthesized a novel near infrared fluorescent probe (FNIR-pH) for measurement of mitochondrial pH based on the hemicyanine skeleton as a fluorophore. The FNIR-pH probe functioned as a mitochondrial pH substrate and exhibited quick and sensitive turn-on fluorescence responses to mitochondrial pH in basic solution due to the deprotonation of hydroxy group in the structure. From pH 3.0 to 10.0, the FNIR-pH exhibited almost 100-fold increase in fluorescence intensity at 766 nm wavelength. The FNIR-pH also displayed superior selectivity to various metal ions, excellent photostability, and low cytotoxicity, which facilitated further biological application. Owing to the proper pKa value of 7.2, the FNIR-pH paved the way for real-time monitoring of mitochondria pH changes in live cells and sensitive sensing of mitophagy. Moreover, the FNIR-pH probe was also implemented for fluorescent imaging of tumor-bearing mice to validate its potential application for in vivo imaging of bioanalytes and biomarkers.

Ratiometric electrochemical OR gate assay for NSCLC-derived exosomes

Non-small cell lung cancer (NSCLC) is the most common pathological type of LC and ranks as the leading cause of cancer deaths. Circulating exosomes have emerged as a valuable biomarker for the diagnosis of NSCLC, while the performance of current electrochemical assays for exosome detection is constrained by unsatisfactory sensitivity and specificity. Here we integrated a ratiometric biosensor with an OR logic gate to form an assay for surface protein profiling of exosomes from clinical serum samples. By using the specific aptamers for recognition of clinically validated biomarkers (EpCAM and CEA), the assay enabled ultrasensitive detection of trace levels of NSCLC-derived exosomes in complex serum samples (15.1 particles μL^-1 within a linear range of 10²-10⁸ particles μL^-1). The assay outperformed the analysis of six serum biomarkers for the accurate diagnosis, staging, and prognosis of NSCLC, displaying a diagnostic sensitivity of 93.3% even at an early stage (Stage I). The assay provides an advanced tool for exosome quantification and facilitates exosome-based liquid biopsies for cancer management in clinics.

Nanotechnology-integrated ferroptosis inducers: a sharp sword against tumor drug resistance

Presently, the biggest hurdle to cancer therapy is the inevitable emergence of drug resistance. Since conventional therapeutic schedules fall short of the expectations in curbing drug resistance, the development of novel drug resistance management strategies is critical. Extensive research over the last decade has revealed that the process of ferroptosis is correlated with cancer resistance; moreover, it has been demonstrated that ferroptosis inducers reverse drug resistance. To elucidate the development and promote the clinical transformation of ferroptosis strategies in cancer therapy, we first analyzed the roles of key ferroptosis-regulating molecules in the progression of drug resistance in-depth and then reviewed the design of ferroptosis-inducing strategies based on nanotechnology for overcoming drug resistance, including glutathione depletion, reactive oxygen species generation, iron donation, lipid peroxidation aggregation, and multiple-drug resistance-associated tumor cell destruction. Finally, the prospects and challenges of regulating ferroptosis as a therapeutic strategy for reversing cancer therapy resistance were evaluated. This review aimed to provide a comprehensive understanding for researchers to develop ferroptosis-inducing nanoplatforms that can overcome drug resistance.

Nontraditional Redox Active Aliphatic Luminescent Polymer for Ratiometric pH Sensing and Sensing-Removal-Reduction of Cu(II): Strategic Optimization of Composition

Here, redox active aliphatic luminescent polymers (ALPs) are synthesized via polymerization of N,N-dimethyl-2-propenamide (DMPA) and 2-methyl-2-propenoic acid (MPA). The structures and properties of the optimum ALP3, ALP3-aggregate and Cu(I)-ALP3, ratiometric pH sensing, redox activity, aggregation enhanced emission (AEE), Stokes shift, and oxygen-donor selective coordination-reduction of Cu(II) to Cu(I) are explored via spectroscopic, microscopic, density functional theory-reduced density gradient (DFT-RDG), fluorescence quenching, adsorption isotherm-thermodynamics, and electrochemical methods. The intense blue and green fluorescence of ALP3 emerges at pH = 7.0 and 9.0, respectively, due to alteration of fluorophores from -C(═O)N(CH₃ )₂ / -C(═O)OH to -C(O^- )═N⁺ (CH₃ )₂ / -C(═O)O^- , inferred from binding energies at 401.32 eV (-C(O^- )═N⁺ (CH₃ )₂ ) and 533.08 eV (-C(═O)O^- ), significant red shifting in absorption and emission spectra, and peak at 2154 cm^-1 . The n-π* communications in ALP3-aggregate, hydrogen bondings within 2.34-2.93 Å (intramolecular) in ALP3 and within 1.66-2.89 Å (intermolecular) in ALP3-aggregate, respectively, contribute significantly in fluorescence, confirmed from NMR titration, ratiometric pH sensing, AEE, excitation dependent emission, and Stokes shift and DFT-RDG analyses. For ALP3, Stokes shift, excellent limit of detection, adsorption capacity, and redox potentials are 13561 cm^-1 /1.68 eV, 0.137 ppb, 122.93 mg g^-1 , and 0.33/-1.04 V at pH 7.0, respectively.

Two-dimensional metal-organic frameworks: from synthesis to bioapplications

As a typical class of crystalline porous materials, metal-organic framework possesses unique features including versatile functionality, structural and compositional tunability. After being reduced to two-dimension, ultrathin metal-organic framework layers possess more external excellent properties favoring various technological applications. In this review article, the unique structural properties of the ultrathin metal-organic framework nanosheets benefiting from the planar topography were highlighted, involving light transmittance, and electrical conductivity. Moreover, the design strategy and versatile fabrication methodology were summarized covering discussions on their applicability and accessibility, especially for porphyritic metal-organic framework nanosheet. The current achievements in the bioapplications of two-dimensional metal-organic frameworks were presented comprising biocatalysis, biosensor, and theranostic, with an emphasis on reactive oxygen species-based nanomedicine for oncology treatment. Furthermore, current challenges confronting the utilization of two-dimensional metal-organic frameworks and future opportunities in emerging research frontiers were presented.

Post-exfoliation functionalisation of metal-organic framework nanosheets via click chemistry

The liquid exfoliation of layered metal-organic frameworks (MOFs) to form nanosheets (MONs) exposes buried functional groups making them useful in a range of sensing and catalytic applications. Here we show how high yielding click reactions can be used post-exfoliation to systematically modify the surface chemistry of MONs allowing for tuning of their surface properties and their use in new applications. A layered amino-functionalised framework is converted through conventional post-synthetic functionalisation of the bulk MOF to form azide functionalised frameworks of up to >99% yield. Ultrasonic liquid exfoliation is then used to form few-layer nanosheets, which are further functionalised through post exfoliation functionalisation using Cu(I)-catalysed azide-alkyne cycloaddition reactions. Here we demonstrate the advantages of post-exfoliation functionalisation in enabling: (1) a range of functional groups to be incorporated in high yields; (2) tuning of nanosheet surface properties without the need for extensive recharacterisation; (3) the addition of fluorescent functional groups to enable their use in the sensing of hazardous nitrobenzene. We anticipate that the versatility of different functional groups that can be introduced through high yielding click reactions will lead to advances in the use of MONs and other 2D materials for a variety of applications.

DNA-Damage-Response-Targeting Mitochondria-Activated Multifunctional Prodrug Strategy for Self-Defensive Tumor Therapy

We report a novel multifunctional construct, M1, designed explicitly to target the DNA damage response in cancer cells. M1 contains both a floxuridine (FUDR) and protein phosphatase 2A (PP2A) inhibitor combined with a GSH-sensitive linker. Further conjugation of the triphenylphosphonium moiety allows M1 to undergo specific activation in the mitochondria, where mitochondria-mediated apoptosis is observed. Moreover, M1 has enormous effects on genomic DNA ascribed to FUDR's primary function of impeding DNA/RNA synthesis combined with diminishing PP2A-activated DNA repair pathways. Importantly, mechanistic studies highlight the PP2A obtrusion in FUDR/5-fluorouracil (5-FU) therapy and underscore the importance of its inhibition to harbor therapeutic potential. HCT116 cell xenograft-bearing mice that have a low response rate to 5-FU show a prominent effect with M1, emphasizing the importance of DNA damage response targeting strategies using tumor-specific microenvironment-activatable systems.

Multi-Emission from Single Metal-Organic Frameworks under Single Excitation

Multi-emission materials have come to prominent attention ascribed to their extended applications other than single-emission ones. General and robust design strategies of a single matrix with multi-emission under single excitation are urgently required. Metal-organic frameworks (MOFs) are porous materials prepared with organic ligands and metal nodes. The variety of metal nodes and ligands makes MOFs with great superiority as multi-emission matrices. Guest species encapsulated into the channels or pores of MOFs are the additional emission sites for multi-emission. In this review, multi-emission MOFs according to the different excitation sites are summarized and classified. The emission mechanisms are discussed, such as antenna effect, excited-state intramolecular proton transfer (ESIPT) and tautomerism for dual-emission. The factors that affect the emissions are revealed, including ligand-metal energy transfer and host-guest interaction, etc. Multi-emission MOFs could be predictably designed and prepared, once the emissive factors are controlled rationally in combination with the different multi-emission mechanisms. Correspondingly, new and practical applications are realized, including but not limited to ratiometric/multi-target sensing and bioimaging, white light-emitting diodes, and anti-counterfeiting. The design strategies of multi-emission MOFs and their extensive applications are reviewed. The results will shed light on other multi-emission systems to develop the structure-derived functionality and applications.

Fabrication of Two-Dimensional Metal-Organic Framework Nanosheets through Crystal Dissolution-Growth Kinetics

Controlling the morphology of the metal-organic framework (MOF) for nanosheets is beneficial for understanding their crystal growth kinetics and useful for extending these MOF nanosheets to advanced applications, in particular for gas separation and device integration. However, synthesizing MOF nanosheets with uniform thickness or desirable size still remains challenging. Herein, we provide a crystal dissolution-growth strategy for fabricating dispersible porphyrin MOF nanosheets with lateral dimensions and nanometer thickness. A morphological transition (bulk crystals-nanosheets-bulk crystals) in Zn-TCPP was observed when controlling the crystal growth kinetics by adjusting the reaction parameters (temperature and acidity). These findings encouraged the synthesis of other types of nanosheets (Cu-TCPP, Zn-TCPP (Pd), and Cu-BDC nanosheets). Zn-TCPP (Pd) nanosheets were applied in field-effect transistors and exhibited photoresponse characteristics. This work demonstrates a new strategy for obtaining MOF nanosheets and casts a new light upon fabricating two-dimensional inorganic-organic hybrid materials with controlled thickness.

A ratiometric pH probe for acidification tracking in dysfunctional mitochondria and tumour tissue in vivo

With an ideal pKa (7.4) for mitochondrial pH monitoring, CouDa could immobilize in mitochondria independent of MMP. Acidification tracking was realized in dysfunctional mitochondria and tumour tissue.

ZIF-8 with cationic defects toward efficient 125I2 uptake for in vitro radiotherapy of colon cancer

Introducing 2,3-dimethyl-1H-imidazol-3-ium iodide (Dmim) as a monodentate ligand during the preparation of ZIF-8 yields ZIF-8+(50) and ZIF-8+(38) with cationic ‘missing linker’ defects. ZIF-8+(38) adsorbs 125I2 and the resulting radioactive host-guest...

One-Step Electrochemical Growth of 2D/3D Zn(II)-MOF Hybrid Nanocomposites on an Electrode and Utilization of a PtNPs@2D MOF Nanocatalyst for Electrochemical Immunoassay

To date, two-dimensional (2D) and three-dimensional (3D) metal organic frameworks (MOFs) have been promising materials for applications in electrocatalysis, separation, and sensing. However, the exploration of a simple method for simultaneous fabrication of 2D/3D MOFs on a surface remains challenging. Herein, a one-step and in situ electrosynthesis strategy for fabrication of 2D Hemin-bridged MOF sheets (Hemin-MOFs) or 2D/3D Zn(II)-MOF hybrid nanocomposites on an electrode is reported. It exhibits varied morphologies at different electrodeposition times and attains a 2D/3D complex morphology by adding 1,3,5-benzenetricarboxylic acid (H₃BTC) as an organic ligand. The morphology and size of 2D Hemin-MOFs are important factors that influence their performance. Since Pt nanoparticles (PtNPs) are grown on 2D Hemin-MOF sheets, this composite can serve as the peroxidase mimics and PtNPs can act as an anchor to capture the antibody. Therefore, this hybrid nanosheet-modified electrode is used as an electrochemical sensing platform for ultrasensitive pig immunoglobulin G (IgG) and the surface-protective antigen (Spa) protein of Erysipelothrix rhusiopathiae immunodetection. Moreover, this work provides a new avenue for the electrochemical synthesis of 2D/3D MOF hybrid nanocomposites with a high surface area and biomimetic catalysts.

In Vitro Anticancer Activity of Nanoformulated Mono- and Di-nuclear Pt Compounds

Nanoformulations of mononuclear Pt complexes cis-PtCl₂ (PPh₃ )₂ (1), [Pt(PPh₃ )₂ (L-Cys)] ⋅ H₂ O (3, L-Cys=L-cysteinate), trans-PtCl₂ (PPh₂ PhNMe₂ )₂ (4; PPh₂ PhNMe₂ =4-(dimethylamine)triphenylphosphine), trans-PtI₂ (PPh₂ PhNMe₂ )₂ (5) and dinuclear Pt cluster Pt₂ (μ-S)₂ (PPh₃ )₄ (2) have comparable cytotoxicity to cisplatin against murine melanoma cell line B16F10. Masking of these discrete molecular entities within the hydrophobic core of Pluronic® F-127 significantly boosted their solubility and stability, ensuring efficient cellular uptake, giving in vitro IC₅₀ values in the range of 0.87-11.23 μM. These results highlight the potential therapeutic value of Pt complexes featuring stable Pt-P bonds in nanocomposite formulations with biocompatible amphiphilic polymers.

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.