Control of the Coordination Status of the Open Metal Sites in Metal–Organic Frameworks for High Performance Separation of Polar Compounds

Metal–organic frameworks (MOFs) with open metal sites have great potential for enhancing adsorption separation of the molecules with different polarities. However, the elution and separation of polar compounds on such MOFs packed columns using nonpolar solvents is difficult due to too strong interaction between polar compounds and the open metal sites. Here, we report the control of the coordination status of the open metal sites in MOFs by adjusting the content of methanol (MeOH) in the mobile phase for fast and high-resolution separation of polar compounds. To this end, high-performance liquid chromatographic separation of nitroaniline, aminophenol and naphthol isomers, sulfadimidine, and sulfanilamide on the column packed with MIL-101­(Cr) possessing open metal sites was performed. The interaction between the open metal sites of MIL-101­(Cr) and the polar analytes was adjusted by adding an appropriate amount of MeOH to the mobile phase to achieve the effective separation of the polar analytes due to the competition of MeOH with the analytes for the open metal sites. Fourier transform infrared spectra and X-ray photoelectron spectra confirmed the interaction between MeOH and the open metal sites of MIL-101­(Cr). Thermodynamic parameters were measured to evaluate the effect of the content of MeOH in the mobile phase on the separation of polar analytes on MIL-101­(Cr) packed column. This approach provides reproducible and high performance separation of polar compounds on the open metal sites-containing MOFs

Ratiometric Fluorescent Detection of Phosphate in Aqueous Solution Based on Near Infrared Fluorescent Silver Nanoclusters/Metal–Organic Shell Composite

Synthesis of near-infrared (NIR) fluorescent AgNCs with high quantum yield and stability is challenging but important for sensing and bioimaging application. Here, we report the fabrication of AgNCs/metal–organic shell composite via the deposition of metal–organic (zinc–nitrogen) coordination shell around AgNCs for ratiometric detection of phosphate. The composite exhibits NIR emission at 720 nm with 30 nm red-shift in comparison to bare AgNCs and a weak emission at 510 nm from the shell. The absolute quantum yield of NIR fluorescence of the composite is 15%, owing to FRET from the shell to the AgNCs core under the excitation at 430 nm. Besides, the composite is stable due to the protection of the shell. On the basis of the composite, a novel ratiometric fluorescence probe for the detection of phosphate in aqueous solution with good sensitivity and selectivity was developed. The limit of detection (3<i>s</i>) is 0.06 μM, and the relative standard deviation for 10 replicate detections of 10 μM phosphate was 0.6%. The recoveries of spiked phosphate in water, human urine, and serum samples ranged from 94.1% to 103.4%

Self-Assembly of Folate onto Polyethyleneimine-Coated CdS/ZnS Quantum Dots for Targeted Turn-On Fluorescence Imaging of Folate Receptor Overexpressed Cancer Cells

Folate receptor (FR) can be overexpressed by a number of epithelial-derived tumors, but minimally expressed in normal tissues. As folic acid (FA) is a high-affinity ligand to FR, and not produced endogenously, development of FA-conjugated probes for targeted imaging FR overexpressed cancer cells is of significance for assessing cancer therapeutics and for better understanding the expression profile of FR in cancer. Here we report a novel turn-on fluorescence probe for imaging FR overexpressed cancer cells. The probe was easily fabricated via electrostatic self-assembly of FA and polyethyleneimine-coated CdS/ZnS quantum dots (PEI-CdS/ZnS QDs). The primary fluorescence of PEI-CdS/ZnS QDs turned off first upon the electrostatic adsorption of FA onto PEI-CdS/ZnS QDs based on electron transfer to produce negligible fluorescence background. The presence of FR expressed on the surface of cancer cells then made FA desorb from PEI-CdS/ZnS QDs due to specific and high affinity of FA to FR. As a result, the primary fluorescence of PEI-CdS/ZnS QDs adhering to the cells turned on due to the inhibition of electron transfer. The most important merits of the developed probe are its simplicity and the effective avoidance of the false positive results due to the simple electrostatic self-assembly of FA onto the surface of PEI-CdS/ZnS QDs and the involved fluorescence “off-on” mechanism. The probe was demonstrated to be sensitive and selective for targeted imaging of FR overexpressed cancer cells in turn-on mode

Fabrication of Transferrin Functionalized Gold Nanoclusters/Graphene Oxide Nanocomposite for Turn-On Near-Infrared Fluorescent Bioimaging of Cancer Cells and Small Animals

Transferrin (Tf)-functionalized gold nanoclusters (Tf-AuNCs)/graphene oxide (GO) nanocomposite (Tf-AuNCs/GO) was fabricated as a turn-on near-infrared (NIR) fluorescent probe for bioimaging cancer cells and small animals. A one-step approach was developed to prepare Tf-AuNCs via a biomineralization process with Tf as the template. Tf acted not only as a stabilizer and a reducer but also as a functional ligand for targeting the transferrin receptor (TfR). The prepared Tf-AuNCs gave intense NIR fluorescence that can avoid interference from biological media such as tissue autofluorescence and scattering light. The assembly of Tf-AuNCs and GO gave the Tf-AuNCs/GO nanocomposite, a turn-on NIR fluorescent probe with negligible background fluorescence due to the super fluorescence quenching property of GO. The NIR fluorescence of the Tf-AuNCs/GO nanocomposite was effectively restored in the presence of TfR, due to the specific interaction between Tf and TfR and the competition of TfR with the GO for the Tf in Tf-AuNCs/GO composite. The developed turn-on NIR fluorescence probe offered excellent water solubility, stability, and biocompatibility, and exhibited high specificity to TfR with negligible cytotoxicity. The probe was successfully applied for turn-on fluorescent bioimaging of cancer cells and small animals

Zeolitic Imidazolate Framework‑8 for Fast Adsorption and Removal of Benzotriazoles from Aqueous Solution

1<i>H</i>-benzotriazole (BTri) and 5-tolyltriazole (5-TTri) are emerging pollutants; the development of novel materials for their efficient adsorption and removal is thus of great significance in environmental sciences. Here, we report the application of zeolitic imidazolate framework-8 (ZIF-8) as a novel adsorbent for fast removal of BTri and 5-TTri in aqueous solution in view of adsorption isotherms, kinetics and thermodynamics, desorption, and adsorbent regeneration. The adsorption of BTri and 5-TTri on ZIF-8 was very fast, and most of BTri and 5-TTri were adsorbed in the first 2 min. The adsorption for BTri and 5-TTri follows a pseudo-second-order kinetics and fits the Langmuir adsorption model with the adsorption capacity of 298.5 and 396.8 mg g^–1 for BTri and 5-TTri at 30 °C, respectively. The adsorption was a spontaneous and endothermic process controlled by positive entropy change. No remarkable effects of pH, ionic strength, and dissolved organic matter on the adsorption of BTri and 5-TTri on ZIF-8 were observed. The used ZIF-8 could be regenerated effectively and recycled at least three times without significant loss of adsorption capacity. In addition, ZIF-8 provided much larger adsorption capacity and faster adsorption kinetics than activated carbon and ZIF-7. The hydrophobic and π–π interaction between the aromatic rings of the BTri and 5-TTri and the aromatic imizole rings of the ZIF-8, and the coordination of the nitrogen atoms in BTri and 5-TTri molecules to the Zn²⁺ ions in the ZIF-8 framework was responsible for the efficient adsorption. The fast adsorption kinetics, large adsorption capacity, excellent reusability as well as the pH, ionic strength, and dissolved organic matter insensitive adsorption create potential for ZIF-8 to be effective at removing benzotriazoles from aqueous solution

Liposome-Coated Persistent Luminescence Nanoparticles as Luminescence Trackable Drug Carrier for Chemotherapy

Near-infrared persistent luminescence nanoparticles (NIR-PLNPs) are promising imaging agents due to deep tissue penetration, high signal-to-noise ratio, and repeatedly charging ability. Here, we report liposome-coated NIR-PLNPs (Lipo-PLNPs) as a novel persistent luminescence imaging guided drug carrier for chemotherapy. The Lipo-PLNP nanocomposite shows the advantages of superior persistent luminescence and high drug loading efficiency and enables autofluorescence-free and long-term tracking of drug delivery carriers with remarkable therapeutic effect

Biomimetic Persistent Luminescent Nanoplatform for Autofluorescence-Free Metastasis Tracking and Chemophotodynamic Therapy

Metastasis is the main cause of death in people with cancer. Early diagnosis and targeted therapy for metastasis is crucial for the survival of the cancer patients. However, metastasis is hard to trace for its small size, dispersed distribution and unvascularized anatomy. Here we report a biomimetic persistent luminescent nanoplatform for noninvasive high-sensitive diagnosis and 808 nm laser controlled photodynamics assisted chemotherapy of metastasis. The nanoplatform is composed of a photosensitizer functionalized persistent luminescent nanoparticle core, a doxorubicin loaded hollow silica interlayer and a cancer cell membrane shell for effective metastasis theranostic. The cancer cell membrane shell prevents drug leakage and endows the nanoplatform with targeting ability to metastasis. The reactivatable persistent luminescence of persistent luminescent nanoparticles not only enables long-term in vivo metastasis tracking, but also provides internal light source for singlet oxygen generation to kill cancer cells and further break the membrane shell for drug release. This work provides a promising strategy to develop persistent luminescence imaging guided theranostic nanoplatforms for early metastasis

Fluorescent Metal–Organic Framework MIL-53(Al) for Highly Selective and Sensitive Detection of Fe³⁺ in Aqueous Solution

Fluorescent metal–organic frameworks (MOFs) have received great attention in sensing application. Here, we report the exploration of fluorescent MIL-53­(Al) for highly selective and sensitive detection of Fe³⁺ in aqueous solution. The cation exchange between Fe³⁺ and the framework metal ion Al³⁺ in MIL-53­(Al) led to the quenching of the fluorescence of MIL-53­(Al) due to the transformation of strong-fluorescent MIL-53­(Al) to weak-fluorescent MIL-53­(Fe), allowing highly selective and sensitive detection of Fe³⁺ in aqueous solution with a linear range of 3–200 μM and a detection limit of 0.9 μM. No interferences from 0.8 M Na⁺; 0.35 M K⁺; 11 mM Cu²⁺; 10 mM Ni²⁺; 6 mM Ca²⁺, Pb²⁺, and Al³⁺; 5.5 mM Mn²⁺; 5 mM Co²⁺ and Cr³⁺; 4 mM Hg²⁺, Cd²⁺, Zn²⁺, and Mg²⁺; 3 mM Fe²⁺; 0.8 M Cl^–; 60 mM NO₂^– and NO₃^–; 10 mM HPO₄^2–, H₂PO₄^–, SO₃^2–, SO₄^2–, and HCOO^–; 8 mM CO₃^2–, HCO₃^–, and C₂O₄^2–; and 5 mM CH₃COO^– were found for the detection of 150 μM Fe³⁺. The possible mechanism for the quenching effect of Fe³⁺ on the fluorescence of MIL-53­(Al) was elucidated by inductively coupled plasma-mass spectrometry, X-ray diffraction spectrometry, and Fourier transform infrared spectrometry. The specific cation exchange behavior between Fe³⁺ and the framework Al³⁺ along with the excellent stability of MIL-53­(Al) allows highly selective and sensitive detection of Fe³⁺ in aqueous solution. The developed method was applied to the determination of Fe³⁺ in human urine samples with the quantitative spike recoveries from 98.2% to 106.2%

Intracellular Messenger RNA Triggered Catalytic Hairpin Assembly for Fluorescence Imaging Guided Photothermal Therapy

We show a theranostic nanoplatform for messenger RNA (mRNA) triggered enhanced fluorescence imaging guided therapy. Catalytic hairpin assembly (CHA) and gold nanorods (AuNRs) are employed to fabricate the theranostic nanoplatform. Two hairpin DNAs and Cy5 labeled duplex DNA are integrated into the CHA for mRNA triggered fluorescence signal amplification via hybridization and displacement with mRNA. The AuNRs act both as the fluorescence quencher and the photothermal therapy (PTT) agent. The nanoplatform not only enables sensitive and specific imaging of target mRNA in living cells and good differentiating of the survivin mRNA expression levels in different cell lines but also offers excellent photothermal conversion efficiency for PTT. The developed nanoplatform has great potential for sensitive and specific intracellular mRNA imaging guided PTT

Room-Temperature Phosphorescent Discrimination of Catechol from Resorcinol and Hydroquinone Based on Sodium Tripolyphosphate Capped Mn-Doped ZnS Quantum Dots

A room-temperature phosphorescence (RTP) strategy was developed for direct, additive-free discrimination of catechol from resorcinol and hydroquinone based on sodium tripolyphosphate capped Mn-doped ZnS quantum dots (STPP-Mn-ZnS QDs). The RTP response of STPP-Mn-ZnS QDs to the three isomers was pH-dependent, and the greatest difference in the RTP response to the isomers was observed at pH 8.0: catechol enhanced the RTP intensity of the QDs, while resorcinol and hydroquinone had little effect on the RTP intensity of the QDs. The enhanced RTP intensity of 1 μM catechol was not affected by the coexistence of 30 μM resorcinol and 50 μM hydroquinone at pH 8.0. The detection limit of this RTP method was 53 nM catechol, and the precision was 3.2% (relative standard deviation) for five replicate detections of 1 μM catechol. The discrimination mechanism was ascribed to the weak bonded ligand of STPP-Mn-ZnS QDs and the different interaction between the three isomers and STPP-Mn-ZnS QDs. The strong binding of catechol to Zn resulted in the extraction of Zn from the surface of STPP-Mn-ZnS QDs and the generation of holes that were trapped by Mn²⁺ to form Mn³⁺. Catechol also promoted the reduction of Mn³⁺ into Mn²⁺ excited state, thus ultimately inducing the enhanced RTP response of STPP-Mn-ZnS QDs