A carbon dot-based nanoscale covalent organic framework as a new emitter combined with a CRISPR/Cas12a-mediated electrochemiluminescence biosensor for ultrasensitive detection of bisphenol A.

Exploring new highly efficient electrochemiluminescence (ECL) luminophores is a necessary condition for developing ultrasensitive ECL biosensors. Therefore, a luminescent carbon dot-based covalent organic framework (CD-COF) was prepared using aldehyde-based carbon dots (CDs) and 1,3,5-tris (4-aminophenyl) benzene (TPB). Because the CD-COF made the regular arrangement of CDs conducive to improving the ECL response, CD-COF had a higher ECL intensity and efficiency than CDs. What's more, the ECL intensity of the CD-COF/S2O82-/Bu4N+ system was about 2.98, 7.50, and 28.08 times higher than those of the CD-COF/S2O82-, CDs/S2O82- and S2O82- systems, respectively. Considering the remarkable ECL performance, the CD-COF/S2O82-/Bu4N+ system was employed combined with the CRISPR/Cas12a trans-cutting strategy to construct an "off-on" ECL biosensor for BPA detection. The proposed ECL biosensor exhibited excellent performance with a wide linear range from 1.0 × 10-14 mol L-1 to 1.0 × 10-5 mol L-1 with a low detection limit of 2.21 fM (S/N = 3) under the optimized conditions. The biosensor demonstrated that CD-COF can be used as an efficient ECL emitter, thus expanding the application field of COFs. In addition, the good stability and specificity of the biosensor enabled the rapid detection of BPA, which will provide valuable insights into promising ultrasensitive ECL biosensors.

Mitochondria-targetable ratiometric fluorescence probe for carbon monoxide based on naphthalimide derivatives.

The design of ratiometric probes for imaging of carbon monoxide (CO) in subcellular organelles is critical to elucidate its biological and pathological functions. In this work, we establish a ratiometric fluorescent probe (Mito-NIB-CO) for imaging of CO in mitochondria. The mitochondria-targeting unit (triphenylphosphonium moiety) and CO-responsive unit (allyl ether moiety) are covalently linking into the single molecule (Mito-NIB-CO) to achieve the multifunctional effect. Upon being treated with CO, Mito-NIB-CO underwent the cleavage of allyl ether element in the presence of PdCl2, resulting in the structural and spectral conversion. This characteristic afforded Mito-NIB-CO to be a ratiometric probe for CO with two fluorescent emission bands. Additionally, the probe Mito-NIB-CO exhibited other distinct merits, including preeminent selectivity and sensitivity. What's more, profiting from triphenylphosphonium moiety, the probe Mito-NIB-CO can specifically target the mitochondria and realize quantitative detection of exogenous/endogenous CO in mitochondria. Graphical abstract.

A water-soluble fluorescent probe for detecting creatinine in totally aqueous media and imaging exogenous creatinine in living cells.

The design of vigorous tools for creatinine determination is extremely important in the diagnosis and treatment of kidney diseases. In the study, we examine a robust fluorescent turn-on probe (NCP-Pd) for creatinine detection in a completely aqueous solution based on the metal palladium-catalyzed reaction. In the presence of creatinine, the NCP-Pd dissociates and subsequently restores the fluorescence due to elimination of the heavy atom quenching effect and prevention of the photoinduced electron transfer effect. The probe NCP-Pd displays excellent detecting performance with respect to creatinine such as good water solubility, high selectivity, and a low detection limit (0.16 µM). Additionally, in order to ensure its clinical application, this probe is operated in blood serum samples for detecting creatinine and compared with a commercial clinical method. The results indicate an extremely high agreement with the commercial clinical method. Furthermore, the results confirm that the probe NCP-Pd exhibits satisfactory cell permeability and low cytotoxicity and can detect creatinine in L929 and HCT116 cells. The study provides a potential application for detecting creatinine and conducting pathological research on creatinine-involved diseases.

A targeted and FRET-based ratiometric fluorescent nanoprobe for imaging mitochondrial hydrogen peroxide in living cells.

Hydrogen peroxide (H2 O2 ) is a prominent member of the reactive oxygen species family and plays crucial roles in living organisms, thus detecting H2 O2 and elucidating its biological functions has become an important area of biological and biomedical research. Herein, a multifunctional fluorescent nanoprobe is demonstrated for detecting mitochondrial H2 O2 . The nanoprobe is prepared by covalently linking a mitochondria-targeting ligand (triphenylphosphonium, TPP) and a H2 O2 recognition element (PFl) onto carbon dots (CDs). For this nanoprobe, the CD serves as the carrier and the FRET donor. In the presence of H2 O2 , the PFl moieties on a CD undergo structural and spectral conversion, affording the nanoplatform a FRET-based ratiometric probe for H2 O2 . The nanoprobe displays excellent water dispersibility, high sensitivity and selectivity, satisfactory cell permeability, and very low cytotoxicity. Following the living cell uptake, this nanoprobe can specifically target and stain the mitochondria; and it can detect the exogenous H2 O2 in L929 cells, as well as the endogenously produced mitochondrial H2 O2 in Raw 264.7 cells upon stimulation by PMA. This study shows that CDs can serve as promising nano-carriers for fabricating practical multifunctional fluorescent nanosensors.

Carbon-dot-based fluorescent turn-on sensor for selectively detecting sulfide anions in totally aqueous media and imaging inside live cells.

Sulfide anions are generated not only as a byproduct from industrial processes but also in biosystems. Hence, robust fluorescent sensors for detecting sulfide anions which are fast-responding, water soluble and biocompatible are highly desirable. Herein, we report a carbon-dot-based fluorescent sensor, which features excellent water solubility, low cytotoxicity and a short response time. This sensor is based on the ligand/Cu(II) approach so as to achieve fast sensing of sulfide anions. The carbon dot (CD) serves as the fluorophore as well as the anchoring site for the ligands which bind with copper ions. For this CD-based system, as copper ions bind with the ligands which reside on the surface of the CD, the paramagnetic copper ions efficiently quench the fluorescence of the CD, affording the system a turn-off sensor for copper ions. More importantly, the subsequently added sulfide anions can extract Cu(2+) from the system and form very stable CuS with Cu(2+), resulting in fluorescence enhancement and affording the system a turn-on sensor for sulfide anions. This fast-responding and selective sensor can operate in totally aqueous solution or in physiological milieu with a low detection limit of 0.78 µM. It displays good biocompatibility, and excellent cell membrane permeability, and can be used to monitor S(2-) levels in running water and living cells.

A low cytotoxic and ratiometric fluorescent nanosensor based on carbon-dots for intracellular pH sensing and mapping.

Intracellular pH plays a critical role in the function of cells, and its regulation is essential for most cellular processes. In this study, we demonstrate a fluorescence resonance energy transfer (FRET)-based ratiometric pH nanosensor with carbon-dot (CD) as the carrier. The sensor was prepared by covalently linking a pH-sensitive fluorescent dye (fluorescein isothiocyanate, FITC) onto carbon-dot. As the FRET donor, the carbon-dot exhibits bright fluorescence emission as well as λex-dependent photoluminescence emission, and a suitable excitation wavelength for the donor (CD) can be chosen to match the energy acceptor (fluorescein moiety). The fluorescein moieties on a CD undergo structural and spectral conversion as the pH changes, affording the nanoplatform a FRET-based pH sensor. The CD-based system exhibits a significant change in fluorescence intensity ratio between pH 4 and 8 with a pKa value of 5.69. It also displays excellent water dispersibility, good spectral reversibility, satisfactory cell permeability and low cytotoxicity. Following the living cell uptake, this nanoplatform with dual-chromatic emissions can facilitate real-time visualization of the pH evolution involved in the endocytic pathway of the nanosensor. This reversible and low cytotoxic fluorescent nanoplatform may be highly valuable in a variety of biological studies, such as endocytic trafficking, endosome/lysosome maturation, and pH regulation in subcellular organelles.

Construction of a ratiometric fluorescent sensing platform based on near-infrared carbon dots for organophosphorus pesticides detection.

In this work, a convenient ratiometric fluorescent platform was designed to measure organophosphorus pesticides (OPs) based on acetylcholinesterase (AChE), acetylthiocholine (ATCh), manganese dioxide nanosheets (MnO2), near-infrared carbon dots (RCDs) and o-phenylenediamine (OPD). In this platform, a direct oxidation of OPD by MnO2 generated the luminescent product 2,3-diaminophenolazine (DAP) through intrinsic oxidase activity, while RCDs served as a fluorescent reference indicator. In the presence of AChE and ATCh, the enzymatic hydrolysate thiocholine (TCh) would reduce MnO2 nanosheets to Mn2+, leading to the quenching of DAP fluorescence. On the other hand, OPs can inhibit the catabolism of ATCh by AChE thus acting as a recognizer of OPs. According to these reactions, OPs were quantitatively analyzed by the intensity ratio of fluorescence emitted from RCDs and DAP (F560/F676). The constructed platform can detect OPs with the range of 0.2-0.6 µM with a detection limit of 4.3 nM. Figure A ratiometric fluorescent probe based on carbon dots was obtained and using it to determine the concentration of organophosphorus pesticides.

A novel nitidine chloride nanoparticle overcomes the stemness of CD133+EPCAM+ Huh7 hepatocellular carcinoma cells for liver cancer therapy.

BACKGROUND: Stemness of CD133+EPCAM+ hepatocellular carcinoma cells ensures cancer resistance to apoptosis,which is a challenge to current liver cancer treatments. In this study, we evaluated the tumorcidal activity of a novel nanoparticle of nitidine chloride (TPGS-FA/NC, TPGS-FA: folic acid modified D-α-tocopheryl polyethylene glycol 1000 succinate, NC: nitidine chloride), against human hepatocellular carcinoma (HCC) cell line Huh7 growth in vitro and in vivo. METHODS: Huh7 cells were treated with TPGS-FA/NC. Cell proliferation was assessed using MTT and colony assays. The expression of cell markers and signaling proteins was detected using western blot analyses. A sphere culture technique was used to enrich cancer stem cells (CSC) in Huh7 cells. TPGS-FA/NC (7.5, 15, 30, 60, 120 µg/mL) dose-dependently inhibited the proliferation of HCC cells, which associated with a reduction in AQP3 and STAT3 expression. Importantly,TPGS-FA/NC (10, 20, and 40 µg/mL) significantly reduced the EpCAM+/CD133+cell numbers, suppressed the sphere formation. The in vivo antitumor efficacy of TPGS-FA/NC was proved in Huh7 cell xenograft model in BALB/c nude mice, which were administered TPGS-FA/NC(4 mg· kg - 1· d - 1, ig) for 2 weeks. RESULTS: TPGS-FA/NC dose-dependently suppressed the AQP3/STAT3/CD133 axis in Huh7 cells. In Huh7 xenograft bearing nude mice, TPGS-FA/NC administration markedly inhibited Huh7 xenograft tumor growth . CONCLUSIONS: TPGS-FA/NC inhibit HCC tumor growth through multiple mechanisms, and it may be a promising candidate drug for the clinical therapy of hepatocellular carcinoma.

A highly efficient Fe-Ni-S/NF hybrid electrode for promoting oxygen evolution performance.

In this study, a Fe-Ni-S/NF hybrid electrode with a hierarchical structure was fabricated via a simple hydrothermal and ion exchange method, and it exhibited remarkable OER performance in an alkaline solution at an ultralow overpotential (1000 mA cm-2@384 mV) and outstanding operational stability.

Electrochemiluminescence aptasensor for multiple determination of Hg2+ and Pb2+ ions by using the MIL-53(Al)@CdTe-PEI modified electrode.

An aptasensor based on MIL-53(Al)@CdTe was designed for multiple determination of Hg2+ and Pb2+ by electrochemiluminescence (ECL). Upon the recognition of Hg2+, aptamer 2-AuNPs form hairpin structures and are removed from the electrode. While in the presence of Pb2+, aptamer 1-PtNPs capture the target ions and form G-quadruplexes, and then bring PtNPs close enough to CdTe QDs to produce ECL resonance energy transfer. Upon aptamer interaction with Hg2+ and Pb2+, decreased ECL intensity was observed due to enhanced resonance energy transfer (ERET) and attenuated surface plasmon resonance (SPR). The ECL intensity difference (ΔECL) could therefore be used to detect heavy-metal ions with detection limits of 4.1 × 10-12 M (path 1, Hg2+), 3.7 × 10-11 M (path 2, Pb2+), and 2.4 × 10-11 M (path 3, Pb2+). The aptasensor could also be used for detecting Hg2+ and Pb2+ in fish and shrimp samples with good recoveries.

An AIE fluorescent probe with a naphthalimide derivative and its application for detection of hypochlorite and imaging inside living cells.

Hypochlorite (ClO-) is a highly reactive oxygen species that plays an important role in resistance to attacks by microorganisms. Herein, we report the preparation of a fluorescence probe (NIB-M) through the integration of a naphthalimide moiety and ClO- to capture diaminomaleonitrile and employ it for the aggregation-induced emission-based (AIE-based) monitoring of ClO-. In the presence of ClO-, NIB-M undergoes sequential nucleophilic substitution and HCl elimination reactions that allow it to possess high selectivity, a fast response, and a low detection limit (0.032 µM). Due to the good AIE properties of the parent molecule, a ClO- test board was facilely prepared by loading NIB-M on a Whatman paper strip-based portable device. The test plate can conveniently and sensitively detect hypochlorite onsite. In addition, the NIB-M probe was used for the imaging of exogenous/endogenous ClO- inside living cells.

Crystallization and Temperature Driven Morphological Evolution of Bio-based Polyethylene Glycol-acrylic Rosin Polymer.

In this work, the morphological and conformational evolution of bio-based polyethylene glycol (PEG)-acrylic rosin polymer in water was studied by scanning electron microscopy (SEM), polarized optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Rayleigh light scattering (RLS) and dynamic light scattering (DLS) techniques during a heating and cooling cycle. When the concentration was higher than the critical micelle concentration (CMC), a reversible transformation process, i.e. from micelle to irregular lamella aggregations, was detected. As the concentration was equal to or below the CMC, individual unimers aggregated into needle-shaped crystals composed of acrylic rosin crystalline core in the heating run. The crystallization of acrylic rosin blocks acted as seeds and thus, in the subsequent cooling process, the PEG corona crystallized into the cube-shaped crystals. The cytotoxicity assay showed the biocompatibility of bio-based polyethylene glycol-acrylic rosin polymer. This has great potential in the application of drug delivery and release triggered by temperature.

Progressive Relaxation Behavior and Relaxation Dynamics of sPS Gels upon Controlled Heating.

Progressive relaxation behavior of syndiotactic polystyrene (sPS) chains in sPS gel was detected in the course of melting via the application of intrinsic fluorescence and fluorescence anisotropy techniques. The melting process included a dissociative process of the network at lower temperature and a relaxation process from helix to worm-like chains at higher temperature. The dynamics of structural relaxation behavior was discovered by intrinsic fluorescence technique, and an abrupt bend emerged at 58 °C on the Arrhenius plot. At temperatures lower than 58 °C, only the dissociation of the helical structure existed and the rate of relaxation from helix to worm-like conformation was negligible. At temperatures higher than 58 °C, the transition from helical chain to worm-like chain was the rate-determining step. The intrinsic fluorescence technique demonstrated its practicability in detecting kinetic processes of sPS/chloroform gel in the course of melting.

Ru(bpy)32+-Silica@Poly-L-lysine-Au as labels for electrochemiluminescence lysozyme aptasensor based on 3D graphene.

In this work, the feasibility of a novel sensitive electrochemiluminescence aptasensor for the detection of lysozyme using Ru(bpy)32+-Silica@Poly-L-lysine-Au (RuSiNPs@PLL-Au) nanocomposites labeling as an indicator was demonstrated. The substrate electrode of the aptasensor was prepared by depositing gold nanoparticles (AuNPs) on 3D graphene-modified electrode. The lysozyme binding aptamer (LBA) was attached to the 3D graphene/AuNPs electrode through gold-thiol affinity, hybridized with a complementary single-strand DNA (CDNA) of the lysozyme aptamer labeled by RuSiNPs@PLL-Au as an electrochemiluminescence intensity amplifier. Thanks to the synergistic amplification of the 3D graphene, the AuNPs and RuSiNPs@PLL-Au NPs linked to Ru(bpy)32+-ECL further enhanced the ECL intensity of the aptasensor. In presence of lysozyme, the CDNA segment of the self-assembled duplex was displaced by the lysozyme, resulting in decreased electrochemiluminescence signal. Under the optimized conditions, the decrease in electrochemiluminescence intensity varied proportionally with the logarithmic concentration of the lysozyme from 2.25 × 10-12 to 5.0 × 10-8 mol L-1, and the detection limit was estimated to 7.5 × 10-13 mol L-1. The aptasensor was further tested in real samples and found reliable for the detection of lysozyme, thus holding great potential application in food safety researches and bioassay analysis.

Novel semirigid water-soluble thermoresponsive polymers based on mesogen-jacketed liquid crystal polymers.

Two novel semirigid smart polymers based on mesogen-jacketed liquid crystal polymers were successfully synthesized via free radical polymerization, which showed both characteristic liquid crystal properties of mesogen-jacketed liquid crystal polymers and remarkably reversible thermoresponsive phase transition behaviors.