Hybrid Double Perovskite Derived Halides Based on Bi and Alkali Metals (K,Rb): Diverse Structures,Tunable Optical Properties and Second Harmonic Generation Responses

Double perovskites (DP) have attracted extensive attention due to their rich structures and wide application prospects in the field of optoelectronics. Here, we report 15 new Bi-based double perovskite derived halides with the general formula of A₂BBiX₆ (A=organic cationic ligand, B=K or Rb, X=Br or I). These materials are synthesized using organic ligands to coordinate with metal ions with a sp³ oxygen, and diverse structure types have been obtained with distinct dimensionalities and connectivity modes. The optical band gaps of these phases can be tuned by changing the halide, the organic ligand and the alkali metal, varying from 2.0 to 2.9 eV. The bromide phases exhibit increasing photoluminescence (PL) intensity with decreasing temperature, while the PL intensity of iodide phases changes nonmonotonically with temperature. Because the majority of these phases are non-centrosymmetric, second harmonic generation (SHG) responses are also measured for selected non-centrosymmetric materials, showing different particle-size-dependent trends. Our findings give rise to a series of new structural types to the DP family, and provide a powerful synthetic handle for symmetry breaking.     

Novel fluorescent chemosensor for Ag^ ＋ based on coumarin fluorophore

A novel chemosensor 1 （CS1） bearing one coumarin and two carbodithioate groups was synthesized and its fluorescent sensing behavior toward metal ions was investigated. Ag^＋ addition to a CH3COCH3/H2O （3：7, v：v） solution of CS1 gave a significantly quenched fluorescence. Other ions including Pb^2＋, Zn^2＋, Cu^2＋, Ca^2＋, Cd^2＋, Co^2＋, Mg^2＋, Mn^2＋, Hg^2＋, Ag^＋, Ni^2＋ induced no or much smaller spectral changes. This constitutes an ON-OFF Ag^＋-selective fluorescent chemosensor.     

Engineered Bacteria Labeled with Iridium(III) Photosensitizers for Enhanced Photodynamic Immunotherapy of Solid Tumors

Despite metal-based photosensitizers showing great potential in photodynamic therapy for tumor treatment, the application of the photosensitizers is intrinsically limited by their poor cancer-targeting properties. Herein, we reported a metal-based photosensitizer-bacteria hybrid, Ir-HEcN , via covalent labeling of an iridium(III) photosensitizer to the surface of genetically engineered bacteria. Due to its intrinsic self-propelled motility and hypoxia tropism, Ir-HEcN selectively targets and penetrates deeply into tumor tissues. Importantly, Ir-HEcN is capable of inducing pyroptosis and immunogenic cell death of tumor cells under irradiation, thereby remarkably evoking anti-tumor innate and adaptive immune responses in vivo and leading to the regression of solid tumors via combinational photodynamic therapy and immunotherapy. To the best of our knowledge, Ir-HEcN is the first metal complex decorated bacteria for enhanced photodynamic immunotherapy.     

Didepside Formation by the Nonreducing Polyketide Synthase Preu6 of Preussia isomera Requires Interaction of Starter Acyl Transferase and Thioesterase Domains

Orsellinic acid (OA) derivatives are produced by filamentous fungi using nonreducing polyketide synthases (nrPKSs). The chain-releasing thioesterase (TE) domains of such nrPKSs were proposed to also catalyze dimerization to yield didepsides, such as lecanoric acid. Here, we use combinatorial domain exchanges, domain dissections and reconstitutions to reveal that the TE domain of the lecanoric acid synthase Preu6 of Preussia isomera must collaborate with the starter acyl transferase (SAT) domain from the same nrPKS. We show that artificial SAT-TE fusion proteins are highly effective catalysts and reprogram the ketide homologation chassis to form didepsides. We also demonstrate that dissected SAT and TE domains of Preu6 physically interact, and SAT and TE domains of OA-synthesizing nrPKSs may co-evolve. Our work highlights an unexpected domain–domain interaction in nrPKSs that must be considered for the combinatorial biosynthesis of unnatural didepsides, depsidones, and diphenyl ethers.     

Synthetic K+ Channels Constructed by Rebuilding the Core Modules of Natural K+ Channels in an Artificial System

Different types of natural K⁺ channels share similar core modules and cation permeability characteristics. In this study, we have developed novel artificial K⁺ channels by rebuilding the core modules of natural K⁺ channels in artificial systems. All the channels displayed high selectivity for K⁺ over Na⁺ and exhibited a selectivity sequence of K⁺≈Rb⁺ during the transport process, which is highly consistent with the cation permeability characteristics of natural K⁺ channels. More importantly, these artificial channels could be efficiently inserted into cell membranes and mediate the transmembrane transport of K⁺, disrupting the cellular K⁺ homeostasis and eventually triggering the apoptosis of cells. These findings demonstrate that, by rebuilding the core modules of natural K⁺ channels in artificial systems, the structures, transport behaviors, and physiological functions of natural K⁺ channels can be mimicked in synthetic channels.     

Evoking Ferroptosis by Synergistic Enhancement of a Cyclopentadienyl Iridium-Betulin Immune Agonist

Ferroptosis is a form of programmed cell death driven by iron-dependent lipid peroxidation (LPO) with the potential for antitumor immunity activation. In this study, a nonferrous cyclopentadienyl metal-based ferroptosis inducer [Ir(Cp*)(Bet)Cl]Cl ( Ir-Bet ) was developed by a metal-ligand synergistic enhancement (MLSE) strategy involving the reaction of [Ir(Cp*)Cl]₂Cl₂ with the natural product Betulin. The fusion of Betulin with iridium cyclopentadienyl (Ir-Cp*) species as Ir-Bet not only tremendously enhanced the antiproliferative activity toward cancer cells, but also activated ferritinophagy for iron homeostasis regulation by PI3K/Akt/mTOR cascade inhibition with a lower dosage of Betulin, and then evoked an immune response by nuclear factor kappa-B (NF-κB) activation of Ir-Cp* species. Further immunogenic cell death (ICD) occurred by remarkable ferroptosis through glutathione (GSH) depletion, glutathione peroxidase 4 (GPX4) deactivation and ferritinophagy. An in vivo vaccination experiment demonstrated desirable antitumor and immunogenic effects of Ir-Bet by increasing the ratio of cytotoxic T cells (CTLs)/regulatory T cells (Tregs).     

1H NMR study on pre-micellization of quaternary ammonium gemini surfactants

Two quaternary ammonium Gemini surfactant series, 12-s-12, ([C(12)H(25)N+ (CH(3))(2)](2)(CH(2))(s).(2)Br(-)) and 14-s-14 ([C(14)H(29)N(+)(CH(3))(2)](2)(CH(2))(s).(2)Br(-)), where s = 2, 3, and 4, have been studied by the use of (1)H NMR in aqueous solution at concentrations below their critical micelle concentrations (CMC) at 25 degrees C. The appearance of a second set of peaks for the 14-s-14 series and the changes in chemical shifts, line widths, and line shapes of the 12-s-12 series with increasing concentration below the CMC are interpreted as evidence for the formation of premicelle aggregates (oligomers) that appear at approximately one-half their CMC values. Self-diffusion coefficients (D) and transverse relaxation times (T(2)) have also been detected and support the results obtained by (1)H NMR.     

Mechanism of surfactant micelle formation

The mechanism of micelle formation of surfactants sodium dodecyl sulfate (SDS), n-hexyldecyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) in heavy water solutions was studied by 1H NMR (chemical shift and line shape) and NMR self-diffusion experiments. 1H NMR and self-diffusion experiments of these three surfactants show that their chemical shifts (delta) begin to change and resonance peaks begins to broaden with the increase in concentration significantly below their critical micelle concentrations (cmc's). At the same time, self-diffusion coefficients ( D) of the surfactant molecules decrease simultaneously as their concentrations increase. These indicate that when the concentrations are near and lower than their cmc's, there are oligomers (premicelles) formed in these three surfactant systems. Carefully examining the dependence of chemical shift and self-diffusion coefficient on concentration in the region just slightly above their cmc's, one finds that the pseudophase transition model is not applicable to the variation of physical properties (chemical shift and self-diffusion coefficient) with concentration of these systems. This indicates that premicelles still exist in this concentration region along with the formation of micelles. The curved dependence of chemical shift and self-diffusion coefficient on the increase in concentration suggests that the premicelles grow as the concentration increases until a definite value when the size of the premicelle reaches that of the micelle, i.e., the system is likely dominated by the monomers and micelles. Additionally, the approximate values of premicelle coming forth concentration (pmc) and cmc were obtained by again fitting chemical shifts to reciprocals of concentrations at a different perspective, and are in good accordant with experimental results and literature values and prove the former conclusion.     

New biocompatible polypyrrole-based films with good blood compatibility and high electrical conductivity

A novel O-butyryl chitosan (OBCS)-grafted polypyrrole (PPy) film was described. The immobilization was accomplished by photocrosslinking the OBCS onto PPy films under ultraviolet light irradiation. The surfaces of OBCS-grafted PPy film were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and electron spectroscopy for chemical analysis (ESCA). The blood compatibility of the OBCS-grafted PPy film was evaluated by platelet-rich plasma (PRP) contacting experiments and protein adsorption experiments in vitro. These results have demonstrated that the surface with immobilized OBCS shows much less platelet adhesive and fibrinogen adsorption compared to the control surface. The bulk conductivity values of PPy films were measured by a modified four-probe method. The composite films have both good blood compatibility and high electrical conductivity that make them suitable for using as potential biomaterials, such as electrically conducting blood vessel and functionally haemocompatible substrate of biosensor used directly in whole blood.     

New fluorescent benzocrown ether derivatives of tetrathiafulvalene: facile synthesis and recognition properties

Two new fluorescent crown ether derivatives of tetrathiafulvalene (TTF) (2a and 2b) were synthesized and characterized; their electrochemical response to Na⁺ ions and fluorescence properties were investigated. The mechanism of the strong fluorescence has also been explored.