Double network hydrogel based on curdlan and flaxseed gum with photothermal antibacterial properties for accelerating infectious wound healing.

The healing of infected wounds has always been a clinical challenge. With the increasing threat of drug resistance due to antibiotic overuse, it is imperative to improve antibacterial wound dressings. In this study, we designed a double network (DN) hydrogel via a "one pot method" with antibacterial activity, and natural polysaccharides with the potential to promote skin wound healing were used. That is, a DN hydrogel matrix was formed by the hydrogen bond crosslinking of curdlan and the covalent crosslinking of flaxseed gum under the action of borax. We added ε-polylysine (ε-PL) as a bactericide. Tannic acid/ferric ion (TA/Fe3+) complex was also introduced into the hydrogel network as a photothermal agent to induce photothermal antibacterial properties. The hydrogel had fast self-healing, tissue adhesion, mechanical stability, good cell compatibility and photothermal antibacterial activity. In vitro studies of hydrogel showed its ability to inhibit S. aureus and E. coli. In vivo experiments also demonstrated the significant healing effect of hydrogel when used to treat wounds infected by S. aureus by promoting collagen deposition and accelerating the formation of skin appendage. This work provides a new design for the preparation of safe antibacterial hydrogel wound dressings and demonstrates great potential for promoting wound healing of bacterial infections.

Fabrication and Separation of EGaIn Microparticles from Human Blood Based on Dielectrophoresis Force and a W-Type Electrode.

Harmful particles such as heavy metal particles in the human body can cause many problems such as kidney stones, gallstones, and cerebrovascular diseases. Therefore, it is critical to separate them from the blood and perform a systematic analysis as early as possible. Here, we apply eutectic gallium indium (EGaIn) microparticles as a model to study the separation of particles from blood, thanks to their properties of low toxicity, excellent degradability, and negligible vapor pressure. In particular, the dielectrophoresis (DEP) separation method is employed to separate EGaIn of different sizes and characteristics in blood. First, the screen-printing method is used to create EGaIn microparticles with diameters of 15, 23, 18, and 11 µm. According to the lifetime test, these microparticles can last more than 1 month, as evidenced by their surface oxidation characteristics. Moreover, a DEP platform with W-type electrodes is developed to sort EGaIn particles from whole human blood. The results show that a sorting efficiency of 95% can be attained, which is similar to the separation efficiency of 98% achieved by finite element analysis (FEA) using COMSOL software based on the orthogonal array experiment method. The proposed study successfully validates the use of the DEP method to separate particles from human blood, providing insights into heavy metal particle separating, drug screening, and cell sorting and potentially broadening the applications in environmental analysis, food engineering, and bioengineering.

Liquid Metal-Doped Conductive Hydrogel for Construction of Multifunctional Sensors.

Interest in wearable and stretchable multifunctional sensors has grown rapidly in recent years. The sensing elements must accurately detect external stimuli to expand their applicability as sensors. However, the sensor's self-healing and adhesion to a target object have been major challenges in developing such practical and versatile devices. In this study, we prepared a hydrogel (LM-SA-PAA) composed of liquid metal (LM), sodium alginate (SA), and poly(acrylic acid) (PAA) with ultrastretchable, excellent self-healing, self-adhesive, and high-sensitivity sensing capabilities that enable the conformal contact between the sensor and skin even during dynamic movements. The excellent self-healing performance of the hydrogel stems from its double cross-linked networks, including physical and chemical cross-linked networks. The physical cross-link formed by the ionic interaction between the carboxyl groups of PAA and gallium ions provide the hydrogel with reversible autonomous repair properties, whereas the covalent bond provides the hydrogel with a stable and strong chemical network. Alginate forms a microgel shell around LM nanoparticles via the coordination of its carboxyl groups with Ga ions. In addition to offering exceptional colloidal stability, the alginate shell has sufficient polar groups, ensuring that the hydrogel adheres to diverse substrates. Based on the efficient electrical pathway provided by the LM, the hydrogel exhibited strain sensitivity and enabled the detection of various human motions and electrocardiographic monitoring. The preparation method is simple and versatile and can be used for the low-cost fabrication of multifunctional sensors, which have broad application prospects in human-machine interface compatibility and medical monitoring.

Dual-Site Chemosensor for Monitoring ·OH-Cysteine Redox in Cells and In Vivo.

The reaction between hydroxyl radical (·OH) and cysteine (Cys) plays an important role in the redox balance of living cells. A deeper insight into this intracellular reaction modulation and process is necessary and draws great interest. A highly effective technique consists of the real-time visualization of the two bioactive species and the perception of their respective changes by using a fluorescent probe. In this study, a dual-site chemosensor SPI based on phenothiazine-cyanine was developed, which realized quantitative detection and real-time imaging of ·OH and Cys at their own fluorescence channels (·OH: λex = 485 nm, λem = 608 nm; Cys: λex = 426 nm, λem = 538 nm) without spectral crosstalk. The fluorescent sensor showed excellent anti-interference and selectivity for common biological substances, apart from the successful imaging of exogenous and endogenous ·OH and Cys. We further visualized the redox dynamic reaction and explored the correlation of ·OH and Cys generated by different inhibitors (sulfasalazine and (1S, 3R)-RSL3). Notably, the chemosensor also possesses the capacity to clearly monitor ·OH and Cys in living mice and zebrafish. This study reports on the first chemosensor to investigate the process of intracellular redox modulation and control between ·OH and Cys, which show potential to further explore some metabolic and physiological mechanisms.

A multifunctional chitosan composite aerogel for PPCPs adsorption.

Pharmaceuticals and personal care products (PPCPs) are gaining attention due to their persistence in the environment. Therefore, the development of novel adsorbents to remove them is strongly anticipated. In this study, an improved dual ice-template assembly method had been used for the preparation of ZIF-67/QGO/SB-CS aerogel through ZIF-67, benzoquinone-modified graphene oxide (QGO), and sulfobetaine-modified chitosan (SB-CS) for the adsorption and removal of PPCPs in water. We reported for the first time that the chitosan composite aerogel has antifouling, bacterial filtration and oil-water separation abilities with excellent PPCPs adsorption performance and reusable, which would be a viable option for long-lasting adsorbents for PPCPs in water.

A highly selective and sensitive CdS fluorescent quantum dot for the simultaneous detection of multiple pesticides.

The abuse of pesticides has introduced a large number of residues in soil and drinking water, which can then enter the food chain and the human body. Monitoring pesticide residues and developing simple and fast detection systems for pesticide residues is urgently needed. In this study, we presented one-pot prepared CdS fluorescent quantum dots (QDs) and explored their sensing application for organic pesticides. The CdS QDs can sensitively and selectively detect three different pesticides, dichlorvos (DDVP), paraquat, and glufosinate-ammonium, through different fluorescence responses. Paraquat can effectively quench the fluorescence of the QDs and DDVP can cause remarkable fluorescent enhancement. Glufosinate-ammonium can induce both 150 nm fluorescent blueshifting and 30-fold fluorescent enhancement. The probe exhibited low detection limits for the three pesticides: 1.44 µM for paraquat, 0.23 mM for DDVP, and 49.8 µM for glufosinate-ammonium. Furthermore, based on the results, we utilized the powerful functions of smartphones to establish a concentration-gray value standard curve through RGB values and gray values to realize the qualitative detection and quantitative analysis of DDVP. It is believed that this work presents a new platform for the simultaneous detection of multiple pesticides using a single QDs probe. The present on-site method using a smartphone is of great potential for water monitoring in rural areas.

Di-(2-picolyl)amine functionalized tetraphenylethylene as multifunctional chemosensor.

In this study, we successfully developed a new multifunctional chemosensor 4',4‴-(2,2-diphenylethene-1,1-diyl)bis(N,N-bis (pyridin-2-ylmethyl)-[1,1'-biphenyl]-4-amine (T-D), based on the cooperation of tetraphenylethylene and di-(2-picolyl)amine (DPA), for sensitive, selective, and quick detection of Cu2+, PO43- and pesticide glyphosate in aqueous solution. In our research, we made full use of the Cu2+-indicator displacement strategy to achieve the construction of an "on-off-on" fluorescent switch platform. Due to the presence of the DPA moiety in T-D, Cu2+ could be captured quickly to form the complex T-D-Cu and caused fluorescence quenching. With the addition of PO43- and glyphosate, the system could rapidly restore the fluorescence by squeezing Cu2+ from T-D-Cu and blocking the photo induced electron transfer (PET) process to display the aggregation-induced emission. To demonstrate the possibility of practical applications, we detected PO43- and glyphosate in spiked real samples. The detection limit for PO43- and glyphosate reached 19 nM and 25 nM, respectively. Furthermore, test strips using T-D-Cu solution simplified the detection process of glyphosate. More importantly, the sensor could be used in visual semi-quantitative determination of PO43- concentrations in both living cells and living zebra fish. Therefore, the chemosensor presented here will not only be a powerful tool for the detection of phosphate anions in aqueous solution and biological systems, but also provides a new template for the design of other multifunctional chemosensors.

Non-biological fluorescent chemosensors for pesticides detection.

The ongoing poisoning of agricultural products has pushed the security problem to become an important issue. Among them, exceeding the standard rate of pesticide residues is the main factor influencing the quality and security of agricultural products. Moreover, the abuse of pesticides has introduced a large amount of residues in soil and drinking water, which will enter the food chain to the human body, leading to neurological disorders and cancer. Therefore, great efforts have been devoted to developing fluorescent sensors for detecting pesticide in a facile, quickly, sensitive, selective, accurate manner, which exhibit greater advantages than some traditional methods. In this review, we mainly focus on summarizing the non-biological fluorescent probes for organic pesticides detection with the detection limit of micromole to nanomole, including organic functional small molecules, calixarenes and pillararenes, metal organic framework systems, and nanomaterials. Meanwhile, we described the different sensing mechanisms for pesticides detection of these mentioned fluorescent sensors, the detection limit of each pesticide, the application in detecting actual samples, as well as their respective advantages and development prospects associated with present non-biological fluorescent sensors.

Organic Crystal Growth: Directly from Amorphous Solid Powder to Single Crystals.

Preparation of organic crystals mainly depends on solution-deposition, sublimation, and melt-deposition techniques. Solid-state growth methods are generally not suitable for organic crystal growth due to the unprocurable mass transfer. Herein, we report two pyridine-substituted fluorenone compounds with extraordinary crystal-growth capacity, and these compounds can directly and quickly form single crystals from their amorphous solid powder by heating under antisolvent-assistance conditions. The novel experimental phenomenon and crystal growth mechanism were investigated in depth. The results indicate that multiple intermolecular hydrogen-bonding sites and planar aromatic structure (prone to π-π interactions) of these molecules dominate the mass transfer during crystal growth by providing enough energy. This discovery enhances our knowledge of solid-state methods for single-crystal growth.

Photophysical properties and stimuli-responsive crystal-state luminescence switching of morpholine-modified naphthalic anhydride derivative.

Stimuli-response organic solid-state luminescence switching materials are attracting increasing interest due to their smart photophysical properties. In this study, a morpholine-modified naphthalic anhydride derivative, 4-(4-morpholinyl)naphthalic anhydride (MBC), was synthesized and studied. Its two crystal polymorphs, MBC-G and MBC-O, were obtained under different crystallization conditions. These two distinct crystals show significantly different solid-state luminescence behaviors: a green emission at 535 nm for MBC-G, and an orange emission at 572 nm for MBC-O. Upon fiercely grinding the MBC-G crystal or melting and then quickly cooling it, a phase transition occurs from MBC-G to MBC-O, accompanied by a fluorescence change from green to orange. The reverse transformation from MBC-O to MBC-G can be achieved by recrystallization. The X-ray single crystal structures show that the green emission should be attributed to molecular J-aggregation in the crystal packing, and the orange emission may originate from molecular H-aggregation. This switchable color nature gives MBC the promising candidate for potential smart anti-counterfeiting and light-emitting materials.

Employing a fluorescent and colorimetric picolyl-functionalized rhodamine for the detection of glyphosate pesticide.

The ongoing poisoning of agricultural products has pushed the security problem to become an important issue. Among them, exceeding the standard rate of pesticide residues is the main factor influencing the quality and security of agricultural products. Monitoring pesticide residues and developing simple, yet ultrasensitive detection systems for pesticide residues are urgently needed. In this study, we successfully developed a novel rhodamine derivative as fluorescent and colorimetric chemosensor R-G for the rapid, selective and ultrasensitive detection of glyphosate pesticide residue in aqueous solution. Through a Cu2+-indicator displacement strategy, glyphosate can displace an indicator (R-G) from a Cu2+-indicator complex due to its strong affinity to bind with Cu2+ to give a turn-on fluorescence and distinct color change. Moreover, a test strip was also fabricated to achieve a facile detection of glyphosate pesticide. To demonstrate the possibility of practical applications, glyphosate was detected on the surface of cabbage and in a spiked soil sample. The detection limit of 4.1 nM and the response time of 2 min indicate that the method is enough sensitive and rapid to detect the glyphosate residue at or below levels that pose a health risk.

An "OR-AND" logic gate based multifunctional colorimetric sensor for the discrimination of Pb2+ and Cd2.

Pb2+ and Cd2+ are the most ubiquitous heavy metal ion pollutants, and they have aroused much attention due to their irreversible and significant damage to human organ. In this work, a new fluorescein-based "OR-AND" logic gate colorimetric probe 3',6'-bis((tert-butyldiphenylsilyl)oxy)-2-(2-((2-hydroxyphenyl)imino)ethylidene)aminspiro[isoindoline-1,9'-xanthen]-3-one (FP) was designed and synthesized via attaching 2-(2-((2-hydroxyphenyl)imino)ethylidene)amino and tert-butyldiphenylsilyl to fluorescein as the specific identification groups. This sensor can rapidly and sensitively discriminate Pb2+ and Cd2+ by utilizing F- as an auxiliary reagent. When Pb2+ or Cd2+ was added into the FP solution, the absorption band at 533 nm increased and the peak at 374 nm decreased, the color changed from colorless to pale-purple, resulting in a ratiometric spectral change. However, adding fluoride ion to the FP solution containing Pb2+ or Cd2+ resulted in a distinct phenomenon in which the pale purple color fades out to colorless for a Pb2+-containing solution and deepen to dark purple for a Cd2+-containing solution, which is attributable to the different coordination mechanisms. In aqueous solution, the detection limits of FP can reach 0.42 µM for Pb2+ and 0.53 µM for Cd2+. The probe exhibited rapid responses for these analytes. Moreover, FP was successfully used to rapidly detect trace amounts of hazardous Pb2+ and Cd2+ in tap water with good relative recovery and the relative standard deviations (RSD) were 1.8% for Pb2+ and 0.3% for Cd2+, providing a novel approach for detecting Pb2+ and Cd2+ in practical application.

Carboxyl hydrogel particle film as a local pH buffer for voltammetric determination of luteolin and baicalein.

Electrochemical determination of luteolin and baicalein always needs acidic supporting electrolyte to guarantee good sensitivity. Therefore, most of the reported electrochemical sensors of luteolin and baicalein are unsuitable for detection of neutral actual samples. It is necessary to design a highly sensitive sensor for direct determination of them in neutral conditions. In this study, poly(N-isopropylacrylamide-acrylic acid) hydrogel particles (NIPA/AA) and multiwall carbon nanotubes (MWCNTs) composite modified glassy carbon electrode (GCE) was fabricated by a simple casting method. The voltammetric results showed that the NIPA/AA particle film provided acidic environment for proton-electron coupled reaction in neutral mediums. The near-surface pH of the electrode was related on the loaded amount of the NIPA/AA particles in pH range from 4.2 to 5.9. The voltammetric behaviors of luteolin and baicalein at the NIPA/AA-MWCNTs-GCE were studied by cyclic voltammetry. The peak separations between cathodic and anodic peaks were decreased and peak currents were increased because of decrease in pH and increase in ion conductivity at the local electrode surface. The sensitivity of the electrode was investigated by differential pulse voltammetry. Even under neutral conditions, the plots of the oxidation currents of luteolin and baicalein were dependent linearly on their concentration with detection limit of 14.5 pM and 44.4 pM, respectively. Moreover, the proposed NIPA/AA-MWCNTs-GCE was also successfully applied for determination of luteolin and baicalein in peanut shell, Huang-qin and tomato samples.

A fluorescein-based AND-logic FPSi probe for the simultaneous detection of Hg2+ and F.

In this study, we have designed and synthesized a novel 'AND' logic based fluorescence probe,1-(3',6'-bis((tert-butyldiphenylsilyl)oxy)-3-oxospiro (isoindoline-1,9'-xanthen)-2-yl)-3-phenylthiourea (FPSi), for the rapid (3 min) simultaneous detection of F- and Hg2+ in DMSO/H2O solution (7:3, v/v). The FPSi probe, synthesized over three steps starting from commercially available fluorescein, was constructed by attaching tert-butyldiphenylsilyl and thiosemicarbazide (as the specific identification groups for F- and Hg2+) to the skeleton of fluorescein, respectively. FPSi produced no fluorescence response towards the addition of F- or Hg2+ separately. However, when the probe was exposed to a solution containing both F- and Hg2+, there was a significant yellow-green fluorescence. FPSi demonstrated an excellent selectivity towards both F- and Hg2+ in the presence of interfering substances. The results of TOF-MS-EI analysis indicated that the response of FPSi towards F- and Hg2+ was mainly aroused by the F- promoted cleavage of Si-O bond, and Hg2+ triggered an irreversible desulfurization reaction leading to the spiral ring opening. Furthermore, the FPSi probe has been successfully used to detect F- and Hg2+ ions in tap water and cropland soil.

A benzothiazole-rhodol based luminophor: ESIPT-induced AIE and an application for detecting Fe2+ ion.

Herein, we designed and synthesized a luminophor, Rh-F, which is an intergrant of rhodol and 2-hydroxy benzothiazole by introducing a benzothiazole unit onto the ortho-position of the phenolic hydroxy of rhodol. Rh-F exhibited excellent fluorescence properties such as a large Stokes shift (>180 nm) and the synergistic effect of aggregation-induced emission (AIE) and an excited state intramolecular proton transfer (ESIPT) feature. The AIE/ESIPT mechanism was thoroughly explored using X-ray single-crystal structures and photophysical determinations. Furthermore, Rh-F showed a sensitive fluorescence response to Fe2+ with low detection limits of 115.2 nM and high selectivity. Studies of its sensing mechanism indicated that the Fe2+-induced blue-green fluorescence-quenched at 525 nm originates from an irreversible Fe2+ chelate with the oxygen atom of the hydroxyl group and the N atom of the benzothiazole moiety. This blocked the ESIPT process of Rh-F which resulted in the quenching of the fluorescence sensor for Rh-F.

Tri-(2-picolyl)amine-modificated triarylborane: Synthesis, photophysical properties and distinguish for cyanide and fluoride anions in aqueous solution.

We designed and synthesized a tri-(2-picolyl) amine (TPA) functionalized triarylborane, 1-(6-(4-(dimesitylboryl)phenyl)pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine (PB2). The photophysical properties of PB2 were thoroughly explored. Moreover, PB2 can capture CN- and F- in aqueous solution through strong chelation induced by the synergy of a boron atom and metal ion gripped by TPA to display entirely different fluorogenic responses such as fluorescence enhancement for CN- and fluorescence quenching for F-. The results of TOF-MS-EI analysis and theoretical calculations indicate that the complexing of PB2 with CN- formed a 2-to-2 adduct with a stabilized configuration, resulting in strong emission. The complexing of PB2 with F- formed a 1-to-1 adduct with a loose configuration, resulting in weak emission. In pure water, the detection limit of PB2 for CN- is 0.79 µM, and in H2O/THF (1:9 v/v) system, the detection limits of PB2 for CN- and F- can reach 0.39 and 2.12 µM, respectively, indicating its potential application for effective detection and discrimination of CN- and F-.

Colorimetric hydrazine detection and fluorescent hydrogen peroxide imaging by using a multifunctional chemical probe.

Among organic small molecules, hydrogen peroxide (H2O2) and hydrazine (NH2NH2) often cause concern because they are widely used in biological and chemical industries. Here, we present a novel probe RH-1 for colorimetric detection of NH2NH2 and fluorescent imaging of H2O2. In this probe, rhodamine was used as the main skeleton due to its favorable spectroscopic performance and stable absorption. Importantly, a benzoic acid group is present in the rhodamine skeleton, which can react with NH2NH2 by amidation. The rhodamine skeleton can also be modified with chromogens to detect H2O2. Results showed that RH-1 can be used for colorimetric detection of NH2NH2 and fluorescent monitoring of H2O2 with high selectivity and sensitivity. The detection limits for NH2NH2 and H2O2 were 0.27 and 0.16 µM, respectively. Moreover, RH-1 can fluorescently image H2O2 in living cells with low cytotoxicity.

Tricolor Luminescence Switching by Thermal and Mechanical Stimuli in the Crystal Polymorphs of Pyridyl-substituted Fluorene.

Stimuli-responsive organic luminescence-switching materials have attracted much attention for a decade. Most of the reported examples display a reversible two-color luminescence switching, and multicolor-switching materials remain extremely rare. Herein, we report a simple organic molecule, 4,4'-(9,9-dimethyl-9H-fluorene-2,7-diyl)dipyridine (MFDP), which exhibits three different crystal polymorphs (V-MFDP, B-MFDP and G-MFDP) with different luminescent colors. Furthermore, the three crystal polymorphs show a reversible tricolor fluorescent switching from violet to blue and to green upon physical stimuli. The single-crystal structures of the three polymorphs were obtained, and the results indicate that the stimuli-responsive properties of the three polymorphs come from the different stacking modes induced by intermolecular interactions. The competition between weak π-π stacking and weak hydrogen bonding is the main reason for the the phase transformations among the three crystal polymorphs.

Benzothiazole modified rhodol as chemodosimeter for the detection of sulfur mustard simulant.

In this paper, we introduced a new sensor for detecting sulfur mustard (SM) and its simulant through the functionalization of a rhodol chromophore with benzothiazole, followed by thionation of the spirolactam. The synthesized chemodosimeter (RHBT) exhibited an obvious green-yellow fluorescence enhancement and chromogenic change from colorless to fuchsia in the presence of SM and its simulant stimuli, which is based on the spirothiolactam ring opening of rhodol induced by the synergy of S-alkylation of thiolactam and the excited state intramolecular proton transfer (ESIPT) of rhodol-benzothiazole. Furthermore, the chemodosimeter was successfully demonstrated for the rapid detection of SM and its simulant in solution, soil and air at ambient temperature, indicating its potential application for on-site detection of sulfur mustard.