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%

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

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

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%

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

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

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

A Dual-Targeting Upconversion Nanoplatform for Two-Color Fluorescence Imaging-Guided Photodynamic Therapy

The targetability of a theranostic probe is one of the keys to assuring its theranostic efficiency. Here we show the design and fabrication of a dual-targeting upconversion nanoplatform for two-color fluorescence imaging-guided photodynamic therapy (PDT). The nanoplatform was prepared from 3-aminophenylboronic acid functionalized upconversion nanocrystals (APBA-UCNPs) and hyaluronated fullerene (HAC₆₀) via a specific diol-borate condensation. The two specific ligands of aminophenylboronic acid and hyaluronic acid provide synergistic targeting effects, high targetability, and hence a dramatically elevated uptake of the nanoplatform by cancer cells. The high generation yield of ¹O₂ due to multiplexed Förster resonance energy transfer between APBA-UCNPs (donor) and HAC₆₀ (acceptor) allows effective therapy. The present nanoplatform shows great potential for highly selective tumor-targeted imaging-guided PDT

Penetrating Peptide-Bioconjugated Persistent Nanophosphors for Long-Term Tracking of Adipose-Derived Stem Cells with Superior Signal-to-Noise Ratio

Reliable long-term in vivo tracking of stem cells is of great importance in stem cell-based therapy and research. Fluorescence imaging with in situ excitation has significant autofluorescence background, which results in poor signal-to-noise ratio (SNR). Here we report TAT penetrating peptide-bioconjugated long persistent luminescence nanoparticles (LPLNP-TAT) for long-term tracking of adipose-derived stem cells (ASC) without constant external excitation. LPLNP-TAT exhibits near-infrared emitting, red light renewable capability, and superior in vivo imaging depth and SNR compared with conventional organic dye and quantum dots. Our findings show that LPLNP-TAT can successfully label ASC without impairing their proliferation and differentiation and can effectively track ASC in skin-regeneration and tumor-homing models. We believe that LPLNP-TAT represents a new generation of cell tracking probes and will have broad application in diagnosis and therapy

Microporous Organic Network: Superhydrophobic Coating to Protect Metal–Organic Frameworks from Hydrolytic Degradation

Despite the rapid development of versatile metal–organic frameworks (MOFs), the synthesis of water-stable MOFs remains challenging, which significantly limits their practical applications. Herein, a novel engineering strategy was developed to prepare superhydrophobic MOFs by an in situ fluorinated microporous organic network (FMON) coating. Through controllable modification, the resulting MOF@FMON retained the porosity and crystallinity of the pristine MOFs. Owing to the superhydrophobicity of the FMON and the feasibility of MOF synthesis, the FMON coating could be in situ integrated with various water-sensitive MOFs to provide superhydrophobicity. The coating thickness and hydrophobicity of the MOF@FMON composites were easily regulated by changing the FMON monomer concentration. The MOF@FMON composites exhibited excellent oil/water separation and catalytic activities and enhanced durability in aqueous solutions. This study provides a general approach for the synthesis of superhydrophobic MOFs, expanding the application scope of MOFs