Investigation on the mechanical properties of polyurea (PU)/melamine formaldehyde (MF) microcapsules prepared with different chain extenders.

There is lack of understanding on controlling of mechanical properties of moisture-curing PU/MF microcapsules which limited its further application. PU/MF microcapsules containing a core of isophorone diisocyanate (IPDI) were prepared with different chain extenders, polyetheramine D400, H2O, triethylenetetramine and polyetheramine (PEA) D230 by following a two-step synthesis method in this study. Fourier transform infra-red (FTIR) spectroscopy, Malvern particle sizing, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). And micromanipulation technique was used to identify chemical bonds in the shell, size distributions, structure, thickness, and mechanical properties of microcapsules. The results show that PU/MF microcapsules were successfully prepared. Tr increased from 46.4 ± 13.9 N/m to 75.8 ± 23.3 N/m when extender changed from D400 to D230. And the Tr increased from 51.3 ± 14.1 to 94.8 ± 17.5 N/m when the swelling time increased from 1 to 3h. Morphologies of the shell were utilised to understand the mechanism of reactions in forming the shell materials.

Preparation of polyurea/melamine formaldehyde double-layered self-healing microcapsules and investigation on core fraction.

Moisture curing type self-healing microcapsules become more attractive, while instability of active core material crippled the efficiency of self-healing behaviour. Polyurea (PU)/melamine formaldehyde (MF) double-layered self-healing microcapsules containing isophorone diisocyanate (IPDI) core with high and stable core fraction were prepared. The structure, morphology, particle size and distribution were studied with Fourier transform infra-red spectroscopy, optical microscopy, scanning electron microscopy and Mastersizer 3000. The influences of process conditions were investigated to uncover the principle of core fraction and morphology of microcapsules. The core fraction of microcapsules was reduced with the increase of ageing time, and microcapsules prepared with ice-bath, polyetheramine (PEA) and prepolymer of melamine formaldehyde (P-MF) had higher core fraction and better morphology. PEA D230 and 1500 rpm agitation rate were chosen according to optimised trade-offs in the core fraction and morphology of the microcapsules.

Fluorescent sensors based on quinoline-containing styrylcyanine: determination of ferric ions, hydrogen peroxide, and glucose, pH-sensitive properties and bioimaging.

A novel styrylcyanine-based fluorescent probe 1 was designed and synthesized via facile methods. Ferric ions quenched the fluorescence of probe 1, whereas the addition of ferrous ions led to only small changes in the fluorescence signal. When hydrogen peroxide was introduced into the solution containing probe 1 and Fe(2+) , Fe(2+) was oxidized to Fe(3+), resulting in the quenching of the fluorescence. The probe 1/Fe(2+) solution fluorescence could also be quenched by H2 O2 released from glucose oxidation by glucose oxidase (GOD), which means that probe 1/Fe(2+) platform could be used to detect glucose. Probe 1 is fluorescent in basic and neutral media but almost non-fluorescent in strong acidic environments. Such behaviour enables it to work as a fluorescent pH sensor in both the solution and solid states and as a chemosensor for detecting volatile organic compounds with high acidity and basicity. Subsequently, the fluorescence microscopic images of probe 1 in live cells and in zebrafish were achieved successfully, suggesting that the probe has good cell membrane permeability and a potential application for imaging in living cells and living organisms.

A benzothiophene-based fluorescent probe with dual-functional to polarity and cyanide for practical applications in living cells and real water samples.

Polarity is a significant intracellular environmental parameter associated with cancer, while cyanide (CN-) is known to be highly toxic to humans. In this work, we designed a dual-functional fluorescent probe (TPABT) for simultaneous detection of polarity and CN-. As a polarity sensor, the probe exhibits NIR emission at 766 nm in 1,4-dioxane (non-polar solvent), whose emission intensity is 71-fold stronger than that in water (polar solvent). Meanwhile, the fluorescence intensity and quantum yield are linearly related to solvent polarity, confirming the polarity response ability of TPABT. For cell polarity detection, low cytotoxicity and polarity sensitivity of probe enable the applications for differentiating cancer cells (HeLa, 4TI) from normal cells (HUV, 3 T3) and monitoring the polarity changes of 4TI cells. As a CN- sensor, TPABT displays a turn-on fluorescence at 640 nm upon the addition of CN-, with advantages of anti-interference, response in aqueous media and low detection limit (22 nM). Additionally, we further explored the practical applications of TPABT for CN- determination in three types of real water samples (drinking water, tap water and lake water) and living cells. Notably, TPABT responses to polarity and CN- in two independent fluorescence channels of 766 and 640 nm, respectively, ensuring the dual functions for polarity and CN- sensing. Consequently, this multi-responsive fluorescent probe TPABT is promising to diagnose polarity-related diseases and detect CN- in real environments.

High-Conductivity and Ultrastretchable Self-Healing Hydrogels for Flexible Zinc-Ion Batteries.

Aqueous zinc-ion batteries are promising candidates for flexible energy storage devices due to their safety, economic efficiency, and environmental friendliness. However, the uncontrollable dendrite growth and side reactions at the zinc anode hinder their commercial application. Herein, we designed and synthesized a dual network self-healing hydrogel electrolyte with zwitterionic groups (PAM-PAAS-QCS), which can be used for the large deformations of flexible devices due to its excellent stretchability (ε = 5100%). The incorporation of zwitterionic groups into the PAM-PAAS-QCS hydrogel electrolyte endows it with high ionic conductivity (33.61 mS/cm), a wide electrochemical stability window, and the ability to suppress zinc dendrite formation and side reactions. Besides, the Zn//Zn symmetric cell with PAM-PAAS-QCS can stably plate and strip zinc for 1500 h at 0.5 mA/cm2, and the Zn//Polyaniline full cell retains 82.4% of its capacity after 1500 cycles at 1 A/g. Additionally, flexible batteries based on both the original and self-healed PAM-PAAS-QCS hydrogel electrolytes demonstrate good cycling stability and stable charge-discharge performance under various bending conditions. This self-healing hydrogel electrolyte with excellent stretchability and high ionic conductivity is expected to pave the way for the development of high-performance flexible energy storage and wearable devices.

Cell Membrane-Targeting Type I/II Photodynamic Therapy Combination with FSP1 Inhibition for Ferroptosis-Enhanced Photodynamic Immunotherapy.

An imbalance in reactive oxygen species (ROS) levels in tumor cells can result in the accumulation of lipid peroxide (LPO) which can induce ferroptosis. Moreover, elevated ROS levels in tumors present a chance to develop ROS-based cancer therapeutics including photodynamic therapy (PDT) and ferroptosis. However, their anticancer efficacies are compromised by insufficient oxygen levels and inherent cellular ROS regulatory mechanism. Herein, a cell membrane-targeting photosensitizer, TBzT-CNQi, which can generate 1O2, •OH, and O2 •- via type I/II process to induce a high level of LPO for potent ferroptosis and photodynamic therapy is developed. The FSP1 inhibitor (iFSP1) is incorporated with TBzT-CNQi to downregulate FSP1 expression, lower the intracellular CoQ10 content, induce a high level of LPO, and activate initial tumor immunogenic ferroptosis. In vitro and in vivo experiments demonstrate that the cell membrane-targeting type I/II PDT combination with FSP1 inhibition can evoke strong ICD and activate the immune response, which subsequently promotes the invasion of CD8+ T cells infiltration, facilitates the dendritic cell maturation, and decreases the tumor infiltration of tumor-associated macrophages. The study indicates that the combination of cell membrane-targeting type I/II PDT and FSP1 inhibition holds promise as a potential strategy for ferroptosis-enhanced photodynamic immunotherapy of hypoxia tumors.

NIR-II Emissive Superoxide Radical Photogenerator for Photothermal/Photodynamic Therapy against Hypoxic Tumor.

Due to the "Achilles' heels" of hypoxia, complicated location in solid tumor, small molecular photosensitizers with second near-infrared window (NIR-II) fluorescence, type-I photodynamic therapy (PDT), and photothermal therapy (PTT) have attracted great attention. However, these photosensitizers are still few but yet challenging. Herein, an "all in one" NIR-II acceptor-donor-acceptor fused-ring photosensitizer, Y6-Th, is presented for the in-depth diagnosis and efficient treatment of cancer. Benefiting from the strong intramolecular charge transfer, promoted highly efficient intersystem crossing, largely p-conjugated fused-ring structure, and reduced planarity, the fabricated nanoparticles (Y6-Th nanoparticles) can emit NIR-II fluorescence with the peak located at 1020 nm, exclusively generate O2•- for type-I PDT, and display excellent PTT performance under an 808 nm laser stimulation. These characteristics make Y6-Th a distinguished NIR-wavelength-triggered phototheranostic agent, which can effectively therapy the hypoxic tumor using NIR-II-fluorescence-guided type-I PDT/PTT. This work provides a valuable guideline for fabricating high-performing NIR-II emissive superoxide radical photogenerators.

A naked-eye chemosensor for fluoride ions: a selective easy-to-prepare test paper.

A new naked-eye chromogenic chemosensor based on 2-thiohydantoin shows high selectivity for fluoride ions and is used to develop a test paper for detection of fluoride ions in the solid state.

Colorimetric and fluorescent dual-signals probes for naked-eye detection of hydrogen peroxide and applications in milk samples and in vivo.

Excessive residual hydrogen peroxide (H2O2) disinfectant in food is harmful to human health. Therefore, it is necessary to develop efficient detection methods for H2O2 detection. In this work, we designed and synthesized five D-A molecules 3a-3e by introducing electron-donor substituents (-OCH3 and -CH3) to the electron-acceptor dicyanoisophorone skeleton in order to find out the suitable probes for H2O2 detection. Among them, two promising probes, 3a and 3c, are screened out according to structure-property relationships. Based on the principle of intramolecular charge transfer (ICT), 3a and 3c express colorimetric and fluorescent dual-signals towards H2O2 with low detection limits (0.20 µM and 0.14 µM) and rapid response (within 20 mins). The reaction mechanism between probes and H2O2 is determined by 1H NMR and HRMS. Density functional theory (DFT) calculations are measured to study the regulation mechanism of structure adjustment on probs performance. Furthermore, a smartphone RGB analysis is utilized as a portable platform for the quantitative detection of H2O2 without complicated instruments, indicating a high efficiency and on-site detection method for H2O2. In addition, probes are applied to detect H2O2 in milk samples, HepG-2 cells and zebrafish, suggesting the promising applications in food samples and physiological systems.

Copperphosphotungstate Doped Polyanilines Nanorods for GSH-Depletion Enhanced Chemodynamic/NIR-II Photothermal Synergistic Therapy.

Introduction: The high concentration of glutathione (GSH) and hydrogen peroxide (H2O2) levels within the tumor microenvironment (TME) are the major obstacle to induce the unsatisfactory anticancer treatment efficiency. The synergistic cancer therapy strategies of the combination the GSH depletion enhanced chemodynamic therapy (CDT) with photothermal therapy (PTT) have been proved to be the promising method to significantly improve the therapeutic efficacy. Methods: The copperphosphotungstate was incorporated into polyanilines to design copperphosphotungstate doped polyaniline nanorods (CuPW@PANI Nanorods) via chemical oxidant polymerization of aniline. The low long-term toxicity and biocompatibility were evaluated. Both in vitro and in vivo experiments were carried out to confirm the GSH depletion enhanced CDT/NIR-II PTT synergistic therapy. Results: CuPW@PANI Nanorods feature biosafety and biocompatibility, strong NIR-II absorbance, and high photothermal-conversion efficiency (45.14%) in NIR-II bio-window, making them highly applicable for photoacoustic imaging and NIR-II PTT. Moreover, CuPW@PANI Nanorods could consume endogenous GSH to disrupt redox homeostasis and perform a Fenton-like reaction with H2O2 to produce cytotoxic •OH for the enhanced CDT. Furthermore, NIR-II photothermal-induced local hyperthermia accelerates •OH generation to enhance CDT, which realizes high therapeutic efficacy in vivo. Conclusion: This study provides a proof of concept of GSH-depletion augmented chemodynamic/NIR-II photothermal therapy.

Inhibition of Q235 corrosion in sodium chloride solution by chitosan derivative and its synergistic effect with ZnO.

A novel chitosan Schiff base derivative (CVZ) doped with ZnO nanoparticles (ZnONPs) was synthesized and investigated. The corrosion protection performance was evaluated via electrochemical measurements and surface analyses. Compared to the undoped derivative (CV), the results show that the corrosion inhibition efficiency of CVZ sharply increases from 67.7 % to 99.6 %. The surface mean roughness decreases from 1.2350 µm of the blank sample to 0.7004 µm with CVZ protection. Additionally, the inhibition mechanism of the inhibitor and the synergistic effect between CV and ZnONPs were discussed. The strategy of organic/inorganic hybrid and the synergistic effect can inspire the development of chitosan as a green corrosion inhibitor with low concentration and high efficiency.

Conductive Hydrogels with Ultrastretchability and Adhesiveness for Flame- and Cold-Tolerant Strain Sensors.

Hydrogel strain sensors with extreme temperature tolerance have recently gained great attention. However, the sensing ability of these hydrogel strain sensors changes with temperature, resulting in the variety of output signals that causes signal distortion. In this study, double-network hydrogels comprising SiO2 nanoparticles composed of polyacrylamide and phytic acid-doped polypyrrole were prepared and applied on strain sensors with a wide sensing range, high adhesiveness, and invariable strain sensitivity under flame and cold environments. The hydrogels had stable conductivity, excellent adhesive strength of up to 79.7 kPa on various substrates, and high elongation of up to 1896% at subzero temperature and after heating. They also exhibited effective flame retardancy with low surface temperature (71.2 °C) after 1200 s of heating (200 °C) and antifreezing properties at a low temperature of -20 °C. Remarkably, even under cold temperature and heat treatment, the hydrogel-based strain sensor displayed consistent sensing behaviors in detecting human motions with a broad strain range (up to 500%) and steady gauge factor (GF, ∼2.90). Therefore, this work paves the way for the applications of hydrogel sensors in robotic skin, human-mechanical interfaces, and health monitoring devices under harsh operating environments.

Two cyanoethylene-based fluorescence probes for highly efficient cyanide detection and practical applications in drinking water and living cells.

Cyanide detection methods are urgently needed due to the highly lethal to human beings. Herein, we report two fluorescence probes (Probe 1 and Probe 2) based on cyanoethylene group for cyanide anion (CN-) detection. The selective recognition for CN- was confirmed by the completely opposite green fluorescence of Probe 1 and red fluorescence of Probe 2 observed by fluorescence spectra and naked eyes. The probes take advantages of the large Stokes shift (~160 nm), rapid response (30 s), anti-interference performance and low detection limit (Probe 1: 12.4 nM, Probe 2: 101 nM). The sensing mechanism is certificated to the nucleophilic attack of CN- to electron-deficient cyanoethylene group of probes, which was demonstrated by 1H NMR titration, HR-MS, Job's plot and IR spectroscopy. Density functional theory (DFT) calculations were carried out to analyze the mechanism in theory. Further, practical applications were studied. Easy-to-use test strips treated with Probe 1 or Probe 2 are capable of CN- detection in pure drinking water. The good biocompatibility and membrane penetrability have achieved the bioimaging capability of Probe 1 and Probe 2 in living HepG-2 cells, making the probes promising for use in real lives.

Chitosan derivative corrosion inhibitor for aluminum alloy in sodium chloride solution: A green organic/inorganic hybrid.

A novel and eco-friendly chitosan derivative was synthesized as green corrosion inhibitors on C3003 aluminum alloy in 3.5 wt.% NaCl solution. In this paper, CP was prepared by Schiff Base reaction with chitosan and 4-pyridinecarboxaldehyde. Then, TiO2 was dispersed in CP to prepare CPT nanocomposite. The corrosion inhibition effect of CPT on C3003 aluminum alloy at different concentrations were studied with electrochemical techniques and surface analysis. The results showed that the maximum inhibition efficiency of CPT nanocomposite reaches to 94.5 % at 200 ppm after the immersed in 3.5 wt.% NaCl solution for 72 h. Meanwhile, the contact angle increases to 120° due to the formation of hydrophobic substances. The strategy of organic/inorganic hybrid can provide the inspiration for the development of chitosan corrosion inhibitor with low concentration and high efficiency.

Metallohydrogel with Tunable Fluorescence, High Stretchability, Shape-Memory, and Self-Healing Properties.

Aiming at the problem that the reported smart optical metallohydrogels were limited with poor mechanical properties, we reported here a novel smart optical metallohydrogel (Al-hydrogel) with excellent elongation, shape-memory ability, self-healing property, and controllable fluorescence intensity. The Al-hydrogel was obtained by the HHPMA-Al3+ and carboxylate-Al3+ coordination after one-pot micellar copolymerization of acrylic acid (AAc), acrylamide (AAm), and hydrophobic arylhydrazone-based ligand (HHPMA). This hydrogel was able to extend up to 5000% of its original length without fracture. Its emission intensity was tunable by OH-/H+ or Zn2+/AAc and increased by 500% with 0.1 M OH- or Zn2+. Its tunable fluorescence enabled us to repeatedly pattern it. A reversible system consisting of Fe3+/H+, was implemented to control the shape of the Al-hydrogel, endowing the Al-hydrogel with shape-memory ability. This highly stretchable and multifunctional Al-hydrogel has potential applications in information transmission, wearable devices, and flexible sensors.

A nucleic acid-specific fluorescent probe for nucleolus imaging in living cells.

Nucleus imaging is of great importance for understanding cellular processes of genetic expression, proliferation and growth, etc. Although many nucleic-acid selective dyes for nucleus staining are available, few of them meet multiple standards. Herein, we report a cationic fluorescence dye FTI that possesses visible light excitation (436 nm), orange emission (571 nm) and a large Stokes shift (~135 nm) for nucleic-acid staining. FTI displays an obvious and sensitive fluorescent response to DNA in vitro with a 6.4-fold quantum yield increasing. Co-staining and nucleic acid digest experiments in live cells demonstrate that FTI exhibits an unexpected selectivity for the nucleolus of the cells due to the stronger affinity to RNA than DNA. Because of good photostability and low cytotoxicity, FTI can accomplish a promising stain for DNA recognition in vitro and nucleolus-specific imaging in cancer cells.

Self-Healing and Multistimuli-Responsive Hydrogels Formed via a Cooperation Strategy and Their Application in Detecting Biogenic Amines.

We reported here a new platform of supramolecular hydrogels cross-linked by the cooperation of metal-ligand coordination and hydrophobic interaction. A salicylaldehyde benzoyl hydrazone-terminal poly(ethylene glycol) (2SBH-PEG) was synthesized and formed small micelles in an aqueous environment. Addition of Ni2+ connected the low-molecular-weight 2SBH-PEG into a metallopolymer via metal-ligand coordination and led to micelle aggregation, resulting in gelation due to the enhancement of hydrophobic interaction. The forming hydrogel, Ni-PEGel, exhibited rapid self-healing ability and reversible pH-responsive property. Because of the containing metal coordination bond, it was also sensitive to the strong competing ligands, such as ethylenediaminetetraacetic acid (EDTA) and pyridine. In addition, Ni-PEGel showed colorimetric changes when exposed to biogenic amine (BA) vapor. The color development of Ni-PEGel toward BAs makes it a good candidate in monitoring food spoilage.

Real-time imaging of cancer cell generations and monitoring tumor growth using a nucleus-targeted red fluorescent probe.

Real-time and long-term nucleus labeling is of great significance for understanding and elucidating cellular and molecular processes in the life sciences, such as gene expression, replication, recombination, and repair, but remains challenging because of the lack of ideal imaging probes. Traditional commercial DNA stains for live-cell imaging either suffer from low water solubility, high cytotoxicity and photobleaching or have small Stokes shifts and low ultraviolet (UV) light excitation; these intrinsic drawbacks limit their utility. Here, a far-red DNA stain (PTB) is explored for in vitro long-term nucleus tracking and in vivo tumor growth monitoring. PTB exhibits a large Stokes shift (∼110 nm), far-red emission (625 nm), and a 73.8-fold increase in fluorescence upon binding with DNA. Compared to currently used nucleus stains, PTB also displays low cytotoxicity and good photostability and biocompatibility. More importantly, the results of in vitro studies reveal that PTB can be tracked in stained HepG-2 cancer cells for up to 11 generations. Moreover, PTB demonstrates effective long-term (i.e., 21 days) tumor growth imaging in vivo. The combination of these remarkable properties makes PTB a promising far-red DNA stain.

Aggregation-Induced Emission-Active Near-Infrared Fluorescent Organic Nanoparticles for Noninvasive Long-Term Monitoring of Tumor Growth.

Effective long-term monitoring of tumor growth is significant for the evaluation of cancer therapy. Aggregation-induced emission-active near-infrared (NIR) fluorescent organic nanoparticles (TPFE-Rho dots) are designed and synthesized for long-term in vitro cell tracking and in vivo monitoring of tumor growth. TPFE-Rho dots display the advantages of NIR fluorescent emission, large Stokes shift (∼180 nm), good biocompatibility, and high photostability. In vitro cell tracing studies demonstrate that TPFE-Rho dots can track SK-Hep-1 cells over 11 generations. In vivo optical imaging results confirm that TPFE-Rho dots can monitor tumor growth for more than 19 days in a real-time manner. This work indicates that TPFE-Rho dots could act as NIR fluorescent nanoprobes for real-time long-term in situ in vivo monitoring of tumor growth.

Precise design and synthesis of an AIE fluorophore with near-infrared emission for cellular bioimaging.

Organic fluorophores emerge as important stains for bioimaging and biosensing, especially for fluorophores with aggregation-induced emission characters. However, the development of organic fluorophores with efficient AIE properties expand to far-red and/or near-infrared is still a great challenge. Herein, we precisely design and synthesize a novel D-π-A type of near-infrared AIE fluorophore (TPE-PTZ-R) by introducing phenothiazine (PTZ) to modify the typical AIE unit (tetraphenylethylene, TPE). TPE-PTZ-R displays good optical properties including a large Stokes shift and typical AIE properties. We next fabricate the uniform and stable AIE nanoparticles by loading Pluronic F127 and apply it in cellular bioimaging with high uptake efficiency, low cytotoxicity and good photostability.