Rapid and Ratiometric Fluorescent Detection of Cysteine with High Selectivity and Sensitivity by a Simple and Readily Available Probe

We report a simple and readily available fluorescent probe for rapid, specific, and ratiometric fluorescent detection of the biologically important cysteine (Cys). This probe uses a visible-light excitable excited-state intramolecular proton transfer (ESIPT) dye (4′-dimethylamino-3-hydroxyflavone) as the fluorophore and an acrylate group as the ESIPT blocking agent as well as the recognition unit. Cleavage of the acrylate moiety can be achieved specifically and rapidly by Cys in aqueous solution under mild conditions, which leads to restore the ESIPT process and enables the probe to show a rapid, ratiometric fluorescent detection process for Cys with high selectivity over various analytes, including homocysteine (Hcy) and glutathione (GSH). The detection limit of this probe for Cys was found to be ∼0.2 μM and bioimaging of intracellular Cys by this probe was successfully applied in living cells, indicating that this probe holds great potential for biological applications

Homogeneous Entropy Catalytic-Driven DNA Hydrogel as Strong Signal Blocker for Highly Sensitive Electrochemical Detection of Platelet-Derived Growth Factor

In this work, an elegantly designed electrochemical biosensor was constructed for platelet-derived growth factor (PDGF) detection based on homogeneous entropy catalytic-induced DNA hydrogel as a strong signal blocker to significantly inhibit the electrochemical signal of g-C₃N₄@Au@Fc-NH₂ nanomaterials as signal tag. First, the good film-forming nanomaterials of g-C₃N₄@Au@Fc-NH₂, containing large numbers of Fc-NH₂ with low resistance and high electric conductivity, were directly immobilized on an electrode surface to provide a strong original electrochemical signal, then the DNA hydrogel blocker formed by target-induced homogeneous entropy catalytic amplification was captured onto the modified electrode surface for significantly reducing the electrochemical signal, in which both the efficient conversion of the single protein to large numbers of DNA strands and the amplification of cycling products could doubly improve the detection sensitivity. As a result, the detection limit could reach 3.5 fM at the range of 0.01 pM to 10 nM. The present strategy by integration of a strong signal blocker to sharply reduce the electrochemical signal of signal tag initiates a new thought to realize the highly sensitive detection of biomarkers and possesses potential applications in clinical diagnosis, sensing, and other related subjects

Protein-Metal Organic Framework Hybrid Composites with Intrinsic Peroxidase-like Activity as a Colorimetric Biosensing Platform

Artificial enzyme mimetics have received considerable attention because natural enzymes have some significant drawbacks, including enzyme autolysis, low catalytic activity, poor recovery, and low stability to environmental changes. Herein, we demonstrated a facile approach for one-pot synthesis of hemeprotein-metal organic framework hybrid composites (H-MOFs) by using bovine hemoglobin (BHb) and zeolitic imidazolate framework-8 (ZIF-8) as a model reaction system. Surprisingly, the new hybrid composites exhibit 423% increase in peroxidase-like catalytic activity compared to free BHb. Taking advantages of the unique pore structure of H-MOFs with high catalytic property, a H-MOFs-based colorimetric biosensing platform was newly constructed and applied for the fast and sensitive detection of hydrogen peroxide (H₂O₂) and phenol. The corresponding detection limits as low as 1.0 μM for each analyte with wide linear ranges (0–800 μM for H₂O₂ and 0–200 μM for phenol) were obtained by naked-eye visualization. Significantly, a sensitive and selective method for visual assay of trace H₂O₂ in cells and phenol in sewage was achieved with this platform. The stability of H-MOFs was also examined, and excellent reproducibility and recyclability without losing in their activity were observed. In addition, the general applicability of H-MOFs was also investigated by using other hemeproteins (horseradish peroxidase, and myoglobin), and the corresponding catalytic activities were 291% and 273% enhancement, respectively. This present work not only expands the application of MOFs but also provides an alternative technique for biological and environmental sample assay

Homoadamantane-Fused Tetrahydroquinoxaline as a Robust Electron-Donating Unit for High-Performance Asymmetric NIR Rhodamine Development

Rhodamines have emerged as a useful class of dye for bioimaging. However, intrinsic issues such as short emission wavelengths and small Stokes shifts limit their widespread applications in living systems. By taking advantage of the homoadamantane-fused tetrahydroquinoxaline (HFT) moiety as an electron donor, we developed a new class of asymmetric NIR rhodamine dyes, NNR1–7. These new dyes retained ideal photophysical properties from the classical rhodamine scaffold and showed large Stokes shifts (>80 nm) with improved chemo/photostability. We found that NNR1–7 specifically target cellular mitochondria with superior photobleaching resistance and improved tolerance for cell fixation compared to commercial mitochondria trackers. Based on NNR4, a novel NIR pH sensor (NNR4M) was also constructed and successfully applied for real-time monitoring of variations in lysosomal pH. We envision this design strategy would find broad applications in the development of highly stable NIR dyes with a large Stokes shift

Efficient Removal of Cationic and Anionic Radioactive Pollutants from Water Using Hydrotalcite-Based Getters

Hydrotalcite (HT)-based materials are usually applied to capture anionic pollutants in aqueous solutions. Generally considered anion exchangers, their ability to capture radioactive cations is rarely exploited. In the present work, we explored the ability of pristine and calcined HT getters to effectively capture radioactive cations (Sr²⁺ and Ba²⁺) which can be securely stabilized at the getter surface. It is found that calcined HT outperforms its pristine counterpart in cation removal ability. Meanwhile, a novel anion removal mechanism targeting radioactive I^– is demonstrated. This approach involves HT surface modification with silver species, namely, Ag₂CO₃ nanoparticles, which can attach firmly on HT surface by forming coherent interface. This HT-based anion getter can be further used to capture I^– in aqueous solution. The observed I^– uptake mechanism is distinctly different from the widely reported ion exchange mechanism of HT and much more efficient. As a result of the high local concentrations of precipitants on the getters, radioactive ions in water can be readily immobilized onto the getter surface by forming precipitates. The secured ionic pollutants can be subsequently removed from water by filtration or sedimentation for safe disposal. Overall, these stable, inexpensive getters are the materials of choice for removal of trace ionic pollutants from bulk radioactive liquids, especially during episodic environmental crisis

Thermoelectric Energy Conversion Using Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) Fibers Based on Low-Temperature In Situ Polymerization and the Freeze–Thaw Method

Wearable devices based on organic thermoelectric (TE) fibers or textiles are attracting widespread attention because of their impressive structural features and high heat-to-electricity conversion capability. However, the production of low-cost, high-TE, and high-mechanical-performance TE fibers is still a challenge. Herein, a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) spinning solution were synthesized by low-temperature in situ polymerization and freeze–thaw (FT) treatment. Also PEDOT:PSS TE fibers were prepared by wet spinning. PEDOT:PSS fibers with excellent properties were obviously improved by regulating the polymerization reaction temperature and number of FT cycles. The optimized PEDOT:PSS fibers obtained at a pretty low in situ polymerization temperature (−18 °C) and FT2 cycles excited a considerably high Seebeck coefficient of 40.8 μV·K–1, a high electrical conductivity of 980 S·cm–1, and a tensile breaking strength of 57.42 cN. The method is cost-effective and could be realized in mass production, demonstrating its potential application in wearable electronic devices

Direct Photocatalytic Conversion of Aldehydes to Esters Using Supported Gold Nanoparticles under Visible Light Irradiation at Room Temperature

Visible light can drive esterification from aldehydes and alcohols using supported gold nanoparticles (Au/Al₂O₃) as photocatalysts at ambient temperatures. The gold nanoparticles (AuNPs) absorb visible light due to the localized surface plasmon resonance (LSPR) effect, and the conduction electrons of the AuNPs gain the energy of the incident light. The energetic electrons, which concentrate at the NP surface, facilitate the activation of a range of aldehyde and alcohol substrates. The photocatalytic efficiencies strongly depend on the Au loading, particle sizes of the AuNPs, irradiance, and wavelength of the light irradiation. Finally, a plausible reaction mechanism was proposed, and the Au/Al₂O₃ catalysts can be reused several times without significantly losing activity. The knowledge acquired in this study may inspire further studies in new efficient recyclable photocatalysts and a wide range of organic synthesis driven by sunlight

Synthesis, Characterization, and Anticancer Activity of a Series of Ketone‑N⁴‑Substituted Thiosemicarbazones and Their Ruthenium(II) Arene Complexes

A series of ketone-N⁴-substituted thiosemicarbazone (TSC) compounds (<b>L1–L9</b>) and their corresponding [(η⁶-<i>p</i>-cymene)­Ru^II(TSC)­Cl]^+/0 complexes (<b>1</b>–<b>9</b>) were synthesized and characterized by NMR, IR, elemental analysis, and HR-ESI-mass spectrometry. The molecular structures of <b>L4</b>, <b>L9</b>, <b>1</b>–<b>6</b>, and <b>9</b> were determined by single-crystal X-ray diffraction analysis. The compounds were further evaluated for their <i>in vitro</i> antiproliferative activities against the SGC-7901 human gastric cancer, BEL-7404 human liver cancer, and HEK-293T noncancerous cell lines. Furthermore, the interactions of the compounds with DNA were followed by electrophoretic mobility spectrometry studies

Aptamer-Targeted Dendrimersomes Assembled from Azido-Modified Janus Dendrimers “Clicked” to DNA

Amphiphilic Janus dendrimers (JDs), synthetic alternatives to lipids, have the potential to expand the scope of nanocarrier delivery systems. JDs self-assemble into vesicles called dendrimersomes, encapsulate both hydrophobic cargo and nucleic acids, and demonstrate enhanced stability in comparison to lipid nanoparticles (LNPs). Here, we report the ability to enhance the cellular uptake of Janus dendrimersomes using DNA aptamers. Azido-modified JDs were synthesized and conjugated to alkyne-modified DNAs using copper-catalyzed azide alkyne cycloaddition. DNA-functionalized JDs form nanometer-sized dendrimersomes in aqueous solution via thin film hydration. These vesicles, now displaying short DNAs, are then hybridized to transferrin receptor binding DNA aptamers. Aptamer-targeted dendrimersomes show improved cellular uptake as compared to control vesicles via fluorescence microscopy and flow cytometry. This work demonstrates the versatility of using click chemistry to conjugate functionalized JDs with biologically relevant molecules and the feasibility of targeting DNA-modified dendrimersomes for drug delivery applications

Enhancing Catalytic Performance of Palladium in Gold and Palladium Alloy Nanoparticles for Organic Synthesis Reactions through Visible Light Irradiation at Ambient Temperatures

The intrinsic catalytic activity of palladium (Pd) is significantly enhanced in gold (Au)-Pd alloy nanoparticles (NPs) under visible light irradiation at ambient temperatures. The alloy NPs strongly absorb light and efficiently enhance the conversion of several reactions, including Suzuki-Miyaura cross coupling, oxidative addition of benzylamine, selective oxidation of aromatic alcohols to corresponding aldehydes and ketones, and phenol oxidation. The Au/Pd molar ratio of the alloy NPs has an important impact on performance of the catalysts since it determines both the electronic heterogeneity and the distribution of Pd sites at the NP surface, with these two factors playing key roles in the catalytic activity. Irradiating with light produces an even more profound enhancement in the catalytic performance of the NPs. For example, the best conversion rate achieved thermally at 30 °C for Suzuki-Miyaura cross coupling was 37% at a Au/Pd ratio of 1:1.86, while under light illumination the yield increased to 96% under the same conditions. The catalytic activity of the alloy NPs depends on the intensity and wavelength of incident light. Light absorption due to the Localized Surface Plasmon Resonance of gold nanocrystals plays an important role in enhancing catalyst performance. We believe that the conduction electrons of the NPs gain the light absorbed energy producing energetic electrons at the surface Pd sites, which enhances the sites’ intrinsic catalytic ability. These findings provide useful guidelines for designing efficient catalysts composed of alloys of a plasmonic metal and a catalytically active transition metal for various organic syntheses driven by sunlight