Benzothiazole-Based Fluorescent Sensor for Ratiometric Detection of Zn(II) Ions and Secondary Sensing PPi and Its Applications for Biological Imaging and PPase Catalysis Assays

In this paper, we designed and synthesized three benzothiazole-based fluorescent probes <b>L</b>_<b>1</b>, <b>L</b>_<b>2</b>, and <b>L</b>_<b>3</b> for zinc ion detection. Among various metal ions, only the zinc ion exhibited fluorescence enhancement at 475 nm accompanied by the blue-shift emission wavelength in HEPES buffer solution containing probes. Through titration experiment, the detection limit of <b>L</b>_<b>1</b> for zinc ion sensing was calculated to be as low as 7 nM, which showed a high sensitivity. Furthermore, the confocal laser scanning micrographs of HeLa cells demonstrate good cell permeability of probe <b>L</b>_<b>1</b> and selective detection of zinc ion in living cells. The <b>L</b>_<b>1</b><b>–Zn</b>^<b>2+</b> complex was further used for pyrophosphate (PPi) sensing in HEPES buffer solution, the limit of detection was calculated to be as low as 60 nM. <b>L</b>_<b>1</b><b>–Zn</b>^<b>2+</b> can monitor the enzyme catalyzed degradation process of PPi, thus providing a meaningful way for tracking of zinc ion and pyrophosphate in biological systems

Highly Sensitive and Selective Fluorescent Probes for the Detection of HOCl/OCl^– Based on Fluorescein Derivatives

Developing highly sensitive and selective methods for HOCl/OCl^– detection is of significant interest. In this work, two fluorescent probes based on mono- and bis-formylated fluorescein, FN-1 and FN-2, were developed. The probes exhibit rapid response and high selectivity to HOCl/OCl^– over other reactive oxygen species (ROS)/reactive nitrogen species (RNS). Furthermore, a good linearity between the fluorescent intensity at 529 nm and the concentration of HOCl/OCl^– in the range 0–10 μM were presented. The probes FN-1 and FN-2 showed detection limits as low as 0.21 and 0.23 μM, respectively. The confocal laser scanning micrographs of HeLa cells confirmed cell permeability of the two probes and their abilities to detect HOCl/OCl^– in living cells. Compared to compound FN-1, FN-2 has lower background fluorescence and a higher speed of the reaction with HOCl/OCl^– which made it a better option for the detection of HOCl/OCl^– in aqueous solution

Filtration-Based Synthesis of Micelle-Derived Composite Membranes for High-Flux Ultrafiltration

Ideal membrane configurations for efficient separation at high flux rates consist of thin size-selective layers connected to macroporous supports for mechanical stabilization. We show that micelle-derived (MD) composite membranes combine efficient separation of similarly sized proteins and water flux 5–10 times higher than that of commercial membranes with similar retentions. MD composite membranes were obtained by filtration of solutions of amphiphilic block copolymer (BCP) micelles through commercially available macroporous supports covered by sacrificial nanostrand fabrics followed by annealing and removal of the nanostrand fabrics. Swelling-induced pore generation in the BCP films thus covering the macroporous supports yielded ∼210 nm thin nanoporous size-selective BCP layers with porosities in the 40% range tightly connected to the macroporous supports. Permselectivity and flux rates of the size-selective BCP layers were adjusted by the BCP mass deposited per membrane area and by proper selection of swelling times. The preparation methodology described here may pave the way for a modular assembly system allowing the design of tailored separation membranes

Colorimetric and Fluorometric Assays Based on Conjugated Polydiacetylene Supramolecules for Screening Acetylcholinesterase and Its Inhibitors

Polydiacetylene supramolecules (PDAs) are unique sensing materials. Upon environmental stimulation, blue PDAs can undergo a colorimetric transition from blue to red accompanied by fluorescence enhancement. In this paper, we report a new PDA system polymerized from a mixed liposome comprising 2-(2-(2-hydroxyethoxy)­ethoxy)­ethyl pentacosa-10,12-diynoate and pentacosa-10,12-diynoic acid at a 3:7 ratio. The PDA system provided new colorimetric and fluorometric assay methods for screening acetylcholinesterase and its inhibitors through three processes. First, myristoylcholine reacted with PDAs, which then underwent colorimetric and fluorometric transition. Second, acetylcholinesterase catalyzed the hydrolysis of myristoylcholine into tetradecanoic acid, which reduced the myristoylcholine concentration and led to faded color and fluorescence. Third and last, acetylcholinesterase inhibitors retarded the activity of acetylcholinesterase, thereby inducing the recovery of color and fluorescence

A Benzothiazole-Based Fluorescent Probe for Ratiometric Detection of Al³⁺ in Aqueous Medium and Living Cells

Aluminum is the third (after O and Si) most abundant metal in the earth’s crust and associates with neurological diseases when abnormal level of Al³⁺ occurs in nervous center. Developing highly sensitive and selective methods for Al³⁺ detection is of significant interest. In this work, we developed an excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) active fluorescent probe for ratiometric detection of Al³⁺ in aqueous medium and living cells. The <b>BTZ-SF</b> can detect Al³⁺ with high selectivity and a good linear relationship (<i>R</i>² = 0.9911) between fluorescence intensity ratio (<i>I</i>_476 nm/<i>I</i>_568 nm) and Al³⁺ concentration (0–100 μM). In addition, the detection limit was calculated as low as 2.2 μM. The single crystal structure of <b>BTZ-SF</b>–Al clearly exhibited the interaction between <b>BTZ-SF</b> and Al³⁺ with a hexa-coordinated structure. Furthermore, confocal fluorescence images of HeLa cell indicated that <b>BTZ-SF</b> could be used for monitoring Al³⁺ in living cells. Finally, a test strips experiment suggests that the <b>BTZ-SF</b> can recognize the Al³⁺ selectively accompanied by remarkable color change

Lighting up Pyruvate Metabolism in Saccharomyces cerevisiae by a Genetically Encoded Fluorescent Biosensor

Monitoring intracellular pyruvate is useful for the exploration of fundamental metabolism and for guiding the construction of yeast cell factories for chemical production. Here, we employed a genetically encoded fluorescent Pyronic biosensor to light up the pyruvate metabolic state in the cytoplasm, nucleus, and mitochondria of Saccharomyces cerevisiae BY4741. A strong correlation was observed between the pyruvate fluctuation in mitochondria and cytoplasm when exposed to different metabolites. Further metabolic analysis of pyruvate uptake and glycolytic dynamics showed that glucose and fructose dose-dependently activated cytoplasmic pyruvate levels more effectively than direct exposure to pyruvate. Meanwhile, the Pyronic biosensor could visually distinguish phenotypes of the wild-type S. cerevisiae BY4741 and the pyruvate-hyperproducing S. cerevisiae TAM at a single-cell resolution, having the potential for high-throughput screening. Overall, Pyronic biosensors targeting different suborganelles contribute to mapping and studying the central carbon metabolism in-depth and guide the design and construction of yeast cell factories

Highly Efficient Photosensitizers with Molecular Vibrational Torsion for Cancer Photodynamic Therapy

The development of highly effective photosensitizers (PSs) for photodynamic therapy remains a great challenge at present. Most PSs rely on the heavy-atom effect or the spin–orbit charge-transfer intersystem crossing (SOCT-ISC) effect to promote ISC, which brings about additional cytotoxicity, and the latter is susceptible to the interference of solvent environment. Herein, an immanent universal property named photoinduced molecular vibrational torsion (PVT)-enhanced spin–orbit coupling (PVT-SOC) in PSs has been first revealed. PVT is verified to be a widespread intrinsic property of quinoid cyanine (QCy) dyes that occurs on an extremely short time scale (10–10 s) and can be captured by transient spectra. The PVT property can provide reinforced SOC as the occurrence of ISC predicted by the El Sayed rules (1ππ*–3nπ*), which ensures efficient photosensitization ability for QCy dyes. Hence, QTCy7-Ac exhibited the highest singlet oxygen yield (13-fold higher than that of TCy7) and lossless fluorescence quantum yield (ΦF) under near-infrared (NIR) irradiation. The preeminent photochemical properties accompanied by high biosecurity enable it to effectively perform photoablation in solid tumors. The revelation of this property supplies a new route for constructing high-performance PSs for achieving enhanced cancer phototherapy