Recent Advances in Calcium-Based Anticancer Nanomaterials Exploiting Calcium Overload to Trigger Cell Apoptosis

Calcium ion is vital for the regulation of many cellular functions and serves as a second messenger in the signal transduction pathways. Once the intracellular Ca²⁺ level exceeds the tolerance of cells (called Ca²⁺ overload), oxidative stress, mitochondrial damage, and cell/mitochondria apoptosis happen. Therefore, Ca²⁺ overload has started to be deeply exploited as a new strategy for cancer therapy due to its high efficiency and satisfactory safety. This review aims to highlight the recent development of Ca²⁺-based nanomaterials (such as Ca₃(PO₄)₂, CaCO₃, CaO₂, CaH₂, CaS, and others) able to trigger intracellular Ca²⁺ overload and apoptosis in cancer therapy. The intracellular mechanisms of varied Ca²⁺-based nanomaterials and the different types of strategies to enhance Ca²⁺ overload are discussed in detail. Moreover, the design of more efficient Ca²⁺ overload-mediated cancer therapies is prospected mainly based on 1) the enhanced cellular uptake by surface modification and morphology optimization of nanomaterials, 2) the accelerated Ca²⁺ release from nanomaterials by increasing the intracellular H⁺ level and by photothermal effect, and 3) the overload maintenance by Ca²⁺ efflux inhibition, Ca²⁺ influx promotion, or promoting Ca²⁺ release from the endoplasmic reticulum.     

A Robust ROS Generation Strategy for Enhanced Chemodynamic/Photodynamic Therapy via H2O2/O2 Self-Supply and Ca2+ Overloading

The efficacy of cancer therapy with reactive oxygen species (ROS) as the main therapeutic medium suffers from a deficiency of oxy-substrates, for example, insufficient endogenous hydrogen peroxide (H₂O₂) in chemodynamic therapy (CDT) and inherent hypoxia in photodynamic therapy (PDT). Herein, a smart polyethylene glycol (PEG)-ylated nanosystem CaO₂@ZIF-Fe/Ce6@PEG (abbreviation as CaZFCP) is constructed to achieve H₂O₂/O₂ self-supply and Ca²⁺ overloading in tumor cells simultaneously for enhanced CDT/PDT. Under the weakly acidic tumor microenvironment, the activity components inside CaZFCP, that is, CaO₂ nanoparticles, Fe²⁺, and photosensitizer Chlorin e6 (Ce6) are released by the degradation of zeolitic imidazole framework-90 (ZIF-90). Thereinto, CaO₂ nanoparticles are further decomposed to generate H₂O₂ and O₂, which alleviates both the insufficient endogenous H₂O₂ and hypoxia in tumor area, thus enhancing the efficiency of CDT and PDT by producing more hydroxyl radicals and singlet oxygen. Furthermore, Ca²⁺ overloading induced by the decomposition of CaO₂ is available for amplifying intracellular oxidative stress, resulting in mitochondrial dysfunction, which further improves the efficacy of combined CDT/PDT. In vitro and in vivo experimental results confirm excellent tumor inhibition effect, which also provides a facile paradigm in ROS-involved cancer therapies.     

Precise Starving Therapy via Physiologically Dependent Photothermal Conversion Promoted Mitochondrial Calcification Based on Multi-Functional Gold Nanoparticles for Effective Tumor Treatment

Starving therapy based on tumor calcification has been considered as a promising strategy with high biosafety for tumor treatment. However, the limited calcium (Ca²⁺) concentration in/around tumor tissue as well as the slow and uncontrollable process of the physiological calcification are all challenges for its application. Herein, a sialic acid (SA, Ca²⁺ chelator), folic acid (FA, tumor targeting agent) and triphenylphosphine (TPP, mitochondrial targeting agent) co-modified gold nanoparticles (SFT-Au) are fabricated to take advantage of the abundant Ca²⁺ in mitochondria as well as the Ca²⁺ collection and Ca²⁺ dependent photothermal property of SFT-Au to achieve a precise and promoted calcification of tumor mitochondria for effective starving therapy. During therapy, the SFT-Au will first accumulate in tumor mitochondria through stepwise targeting processes medicated by FA and TPP. After that, the SA further binds with the over-expressed Ca²⁺ in tumor mitochondria to induce the aggregation of SFT-Au, which not only gathers Ca²⁺ to initiate the calcification of mitochondria, but in situ generates photothermal agent to perform photothermal conversion under 808 nm irradiation to promote the calcification, resulting in effective prohibition of the energy metabolism in tumor cells for starving therapy and continuously photothermal damage of tumor cells to enhance the therapeutic efficiency.     

Localized Excitation of Neural Activity via Rapid Magnetothermal Drug Release

Hysteretic heat dissipation by magnetic nanoparticles (MNPs) in alternating magnetic fields (AMFs) allows these materials to act as local transducers of external stimuli. Commonly employed in cancer research, MNPs have recently found applications in remote control of heat‐dependent cellular pathways. Here, a thermally labile linker chemistry is adapted for the release of neuromodulatory compounds from the surfaces of MNPs via local nanoscale heating. By examining a range of MNP sizes, and considering individual particle loss powers, AMF conditions and nanomaterials suitable for rapid and complete release of a payload from MNP surfaces are selected. Local release of allyl isothiocyanate, an agonist of the Ca²⁺ channel TRPV1 (transient receptor potential vanilloid cation channel subfamily member 1), from iron oxide MNPs results in pharmacological excitation of neurons with latencies of ≈12 s. When targeted to neuronal membranes, these MNPs trigger Ca²⁺ influx and action potential firing at particle concentrations three orders of magnitude less than those previously used for magnetothermal neuromodulation accomplished with bulk heating.     

A Checkpoint-Regulatable Immune Niche Created by Injectable Hydrogel for Tumor Therapy

Current programmed death-1 ligand (PD-L1)-based therapy focuses on local tumors. However, circulating exosomal PD-L1 possesses inherent anti-PD-L1 blockade resistance and dominates tumor metastasis, playing a critical role in systemic immunosuppression. Therefore, the efficacy of immune checkpoint therapy depends on simultaneously decreasing tumoral and circulating exosomal PD-L1. However, such therapeutic platforms have never been reported so far. Herein, a PD-L1 checkpoint-regulatable immune niche created by an injectable hydrogel is reported to reprogram PD-L1 of both tumor and circulating exosomes. Oxidized sodium alginate-armored tumor membrane vesicle (O-TMV) as a gelator, with Ca²⁺ channel inhibitor dimethyl amiloride (DMA) and cyclin-dependent kinase 5 (Cdk5) inhibitor roscovitine formed hydrogel (O-TMV@DR) in vivo, work as an antigen depot to create an immune niche. O-TMV chelates Ca²⁺ within the tumor environment and DMA continuously prevents cellular Ca²⁺ influx, suppressing Ca²⁺-governed exosome secretion with decreased exosome number. Roscovitine not only down-regulates tumor cell PD-L1 expression along with decreasing exosomal PD-L1 expression inherited from parental tumor cells via a genetic blockade effect, but also blunts the cascade connection between PD-L1 up-regulation and interferon-γ stimulation, achieving down-regulated PD-L1 expression in both tumor cells and exosomes. Therefore, a full-scale reprogramming of both tumoral PD-L1 and exosomal PD-L1 is achieved, offering an innovative immune checkpoint-regulatable cancer immunotherapy     

Up‐Conversion Luminescent and Porous NaYF4:Yb3+, Er3+@SiO2 Nanocomposite Fibers for Anti‐Cancer Drug Delivery and Cell Imaging

Up‐conversion (UC) luminescent and porous NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanocomposite fibers are prepared by electrospinning process. The biocompatibility test on L929 fibrolast cells reveals low cytotoxicity of the fibers. The obtained fibers can be used as anti‐cancer drug delivery host carriers for investigation of the drug storage/release properties. Doxorubicin hydrochloride (DOX), a typical anticancer drug, is introduced into NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanocomposite fibers (denoted as DOX‐NaYF₄:Yb³⁺, Er³⁺@SiO₂). The release properties of the drug carrier system are examined and the in vitro cytotoxicity and cell uptake behavior of these NaYF₄:Yb³⁺, Er³⁺@SiO₂ for HeLa cells are evaluated. The release of DOX from NaYF₄:Yb³⁺, Er³⁺@SiO₂ exhibits sustained, pH‐sensitive release patterns and the DOX‐NaYF₄:Yb³⁺, Er³⁺@SiO₂ show similar cytotoxicity as the free DOX on HeLa cells. Confocal microscopy observations show that the composites can be effectively taken up by HeLa cells. Furthermore, the fibers show near‐infrared UC luminescence and are successfully applied in bioimaging of HeLa cells. The results indicate the promise of using NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanocomposite fibers as multi‐functional drug carriers for drug delivery and cell imaging.     

Graphene‐Oxide‐Conjugated Polymer Hybrid Materials for Calmodulin Sensing by Using FRET Strategy

The conformation of calmodulin (CaM) changes from closed configuration to open one, converting to a claviform dumbbell‐shaped biomolecule upon Ca²⁺‐binding. A hybrid probe of graphene oxide (GO) cationic conjugated polymer for detection of the conformation transition of CaM by using FRET technique is demonstrated. The stronger hydrophobic interaction and weaker electrostatic repulsion leads to more CaM adsorption to the surface of GO upon binding with Ca²⁺ than that of CaM in the absence of Ca²⁺ (apoCaM), resulting in much farther proximity between poly[(9,9‐bis(6′‐N,N,N‐trimethy­lammonium)hexyl)‐fluorenylene phenylene dibromide] (PFP) and green fluorescent protein labeled at the N‐terminus of CaM and therefore much weaker FRET efficiency for PFP/Ca²⁺/CaM in comparison with that of PFP/apoCaM in the presence of GO. Notably, the assembly of CaM with GO is quantitatively and reversibly controlled by Ca²⁺ ions.     

Bioactive Bacteria/MOF Hybrids Can Achieve Targeted Synergistic Chemotherapy and Chemodynamic Therapy against Breast Tumors

The hypoxic tumor microenvironment (TME) significantly affects cancer treatment. Conventional chemotherapeutic agents cannot effectively target hypoxic tumor tissue, which decreases efficacy and results in severe toxic side effects. To alleviate this problem, a self-driving biomotor is developed by functionalizing MCDP nanoparticles containing calcium peroxide and doxorubicin (DOX) loaded onto polydopamine-coated metal–organic frameworks（MOF）, with the anaerobic Bifidobacterium infantis (Bif) for synergistic chemotherapy and chemodynamic therapy (CDT) against breast cancer. The materials of institute Lavoisier (MIL) frameworks + CaO₂ + DOX + polydopamine (MCDP)@Bif biohybrid actively targets hypoxic regions of solid tumors via the inherent targeting ability of Bif. Once it has accumulated in the tumor tissue, MCDP generates hydroxyl radicals through the enhanced Fenton-type reactions between Fe²⁺ and self-generated hydrogen peroxide in the acidic TME. The disruption of Ca²⁺ homeostasis and resulting mitochondrial Ca²⁺ overload triggers apoptosis and enhances oxidative stress, promoting tumor cell death. The results found that the DOX concentration in MCDP@Bif-treated tumors is 3.8 times higher than that in free-DOX-treated tumors, which significantly prolongs the median survival of the tumor-bearing mice to 69 days and reduces the toxic side effects of DOX. Therefore, the novel bacteria-driven drug delivery system is highly effective in achieving synergistic chemotherapy and CDT against solid tumors.     

Selective Zinc(II)‐Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological Applications

A highly ordered 2D‐hexagonal mesoporous silica material is functionalized with 3‐aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4‐methyl‐2,6‐diformyl phenol. Powder X‐ray diffraction, transmission electron microscopy, N₂ sorption, Fourier transform infrared spectroscopy, and UV‐visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn²⁺ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn²⁺‐bound mesoporous material increases significantly upon addition of various concentrations of Zn²⁺, while the introduction of other biologically relevant (Ca²⁺, Mg²⁺, Na⁺, and K⁺) and environmentally hazardous transition‐metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn²⁺, evident from the large binding constant value (0.87 × 10⁴ M ^?1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn²⁺ from a mixture of ions that contains Zn²⁺ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy.     

A Ca-Ion Electrochromic Battery via a Water-in-Salt Electrolyte

Multivalent-ion batteries with electrochromic functionality are an emerging green technology for development of low-carbon society. Compared to Mg²⁺, Zn²⁺ and Al³⁺, Ca²⁺ has a low polarization strength similar to that of Li⁺, therefore Ca²⁺ for electrochromism and battery can avoid kinetic issues caused by other multivalent-ions with high polarization strength. Here, by exploiting Ca-ion carriers for electrochromism and a water-in-salt (WIS) Ca(OTF)₂ electrolyte for the first time, a new and safe aqueous Ca-ion electrochromic battery (CIEB) has been demonstrated. The WIS Ca(OTF)₂ electrolyte demonstrates enhanced anion-cation interactions and decreased water activity. Vanadium oxide (VO_x) and indium hexacyanoferrate (InHCF) films are respectively developed as anode and cathode because of their stable and high-rate Ca²⁺ insertion/extraction, as well as matched electrochromism. The CIEB demonstrates a stable and high-rate capability, a high energy density of 51.4 mWh m⁻² at a power density of 1737.3 mW m⁻², and a greenish yellow-to-black electrochromism. The presented results are beneficial for understanding redox kinetics in WIS electrolytes, and inspire researches on batteries and electrochromism with multivalent-ions.     

Four Birds with One Stone: A Multifunctional Polypeptide Nanocomposite to Unify Ferroptosis,Nitric Oxide,and Photothermia for Amplifying Antitumor Immunity

Tumor metastasis and relapse mainly results in therapy failure and becomes a big challenge in oncology. Immunogenic cell death (ICD) of tumors mediated immunotherapy (IT) is attracting widely for solving that problem although achieving sufficient ICD and strong immune response is challenging for nanoparticles-based cancer IT. Herein, a multifunctional polypeptide coordinate nanocomposite that possesses near infrared photothermia (PT) and responsive releases of nitric oxide (NO) and iron ions is constructed, which synergistically kills cancer cells and highly prohibits metastatic 4T1 cells invasion and migration by PT-boosted NO release and ferroptosis (FT). Remarkably, triple FT-NO-PT treatment amplifies the ICD effects and outperforms combo/monotherapy FT-PT and FT in cancer cells and tumors, which further activates dendritic cells maturation, and primed CD4⁺T and CD8⁺T cells immune responses and memory effects, playing four birds with one stone (i.e., FT-NO-PT-IT). The PCSFG-based FT-NO-PT not only fully eradicates 4T1 primary tumors, but also induces strong ICD, immune priming, and memory effects to reject rechallenged 4T1 tumors and inhibit malignant tumor metastasis, demonstrating synergistic amplified ICD effects with strong cell immunities and memory effects by a unified FT-NO-PT-IT.     

Great Enhancement in the Thermopower of Ionic Liquid by a Metal-Organic Framework

To efficiently harvest the abundant waste heat on earth is of great significance for sustainable development. Thermoelectric materials can be used to directly convert heat into electricity, and ionic thermoelectric materials like ionic liquids (ILs) are considered as the next-generation thermoelectric materials. It is important to develop novel methods to improve the overall thermoelectric properties particularly the thermopower. Herein, the great enhancement in the thermopower of 1-ethyl-3-methylimidazolium dicyanamide (EMIM:DCA) is reported that is an IL by introducing zeolitic imidazolate framework (ZIF-8) that is a metal-organic framework (MOF) for the first time. The presence of 40 wt.% ZIF-8 can greatly increase the ionic thermopower of EMIM:DCA from 8.8 to 31.9 mV K⁻¹ at room temperature, and the ZIF-8/EMIM:DCA mixture at the ZIF-8 loading of 10 wt.% can exhibit a ZT_i value of 3.1, notably higher than that (0.59) of neat EMIM:DCA. The enhancement in the thermopower is attributed to the increase in the difference of the mobilities of EMIM⁺ and DCA⁻ by ZIF-8. Because DCA⁻ is smaller while EMIM⁺ is larger than the pore size of ZIF-8, the DCA⁻ transport is hindered by ZIF-8, while EMIM⁺ can bypass ZIF-8.     

Core–Satellite Mesoporous Silica–Gold Nanotheranostics for Biological Stimuli Triggered Multimodal Cancer Therapy

A core–satellite nanotheranostic agent with pH‐dependent photothermal properties, pH‐triggered drug release, and H₂O₂‐induced catalytic generation of radical medicine is fabricated to give a selective and effective tumor medicine with three modes of action. The nanocomplex (core–satellite mesoporous silica–gold nanocomposite) consists of amino‐group‐functionalized mesoporous silica nanoparticles (MSN‐NH₂) linked to L‐cysteine‐derivatized gold nanoparticles (AuNPs‐Cys) with bridging ferrous iron (Fe²⁺) ions. The AuNPs‐Cys serve as both removable caps that control drug release (doxorubicin) and stimuli‐responsive agents for selective photothermal therapy. Drug release and photothermal therapy are initiated by the cleavage of Fe²⁺ coordination bonds at low pH and the spontaneous aggregation of the dissociated AuNPs‐Cys. In addition, the Fe²⁺ is able to catalyze the decomposition of hydrogen peroxide abundant in cancer cells by a Fenton‐like reaction to generate high‐concentration hydroxyl radicals (·OH), which then causes cell damage. This system requires two tumor microenvironment conditions (low pH and considerable amounts of H₂O₂) to trigger the three therapeutic actions. In vivo data from mouse models show that a tumor can be completely inhibited after two weeks of treatment with the combined chemo‐photothermal method; the data directly demonstrate the efficiency of the MSN–Fe–AuNPs for tumor therapy.     

Ultra-High Capacity and Cyclability of β-phase Ca0.14V2O5 as a Promising Cathode in Calcium-Ion Batteries

Crystalline water-free β-phase Ca_0.14V₂O₅ is reported for the first time as a viable cathode material for calcium-ion batteries (CIBs). In contrast to layered α-V₂O₅ and δ-Ca_xV₂O₅·nH₂O, which have limited capacity, the β-phase delivers a reversible capacity of ≈247 mAh g⁻¹, which corresponds to the insertion/extraction of Ca²⁺ between Ca_0.14V₂O₅ and Ca_1.0V₂O₅. The process of Ca²⁺ insertion process and the accompanying structural relaxation are theoretically and experimentally verified. The initial insertion of Ca²⁺ into Ca_0.14V₂O₅ causes a slight shift of oxygen atoms surrounding hepta-coordination sites, creating penta-coordinated sites that are then partially filled up to Ca_0.33V₂O₅. Further insertion occurs through the stepwise occupation of up to 50% of neighboring hexa- and tetra-coordination sites to form Ca_0.67V₂O₅ and Ca_1.0V₂O₅, respectively. The rearrangement of oxygen atoms in Ca_0.14V₂O₅ also minimizes dimensional changes, leading to high cyclic stability during repeated charge/discharge cycles. The remarkable electrochemical performance of full cells containing a Ca_0.14V₂O₅ cathode and a K metal anode in Ca²⁺/K⁺ hybrid electrolytes, is also demonstrated, thanks to the inertness of K⁺ insertion into Ca_0.14V₂O₅ and the absence of calcium plating/stripping. The cyclic stability and high capacity of Ca_0.14V₂O₅ is not compromised in hybrid electrolytes, making it a viable CIB cathode.     

Preparation of Tortuous 3D γ‐CsPbI3 Films at Low Temperature by CaI2 as Dopant for Highly Efficient Perovskite Solar Cells

Inorganic cubic CsPbI₃ perovskite (α‐CsPbI₃) has been widely explored for perovskite solar cells (PSCs) due to its thermal stability and suitable bandgap of 1.73 eV. However, α‐CsPbI₃ usually requires high synthesis temperatures (>320 °C). Additionally, it usually undergoes phase transition to the nonperovskite structure phase (β‐CsPbI₃), which results in poor photoelectric performance in devices. In this study, it is first found that the tortuous 3D CsPbI₃ phase (γ‐CsPbI₃) can be prepared and used for PSCs by solution process without any additive at low temperature (60 °C). The γ‐CsPbI₃ exhibits suitable bandgap of 1.75 eV and favorable photoelectric properties. However, γ‐CsPbI₃ is a metastable phase and easily transforms into β‐CsPbI₃ in ambient moisture. In order to improve the stability of γ‐CsPbI₃, calcium ions (Ca²⁺) with a relatively small radius of 100 pm are used to partially substitute lead ions (119 pm). This research proves that Ca²⁺ can effectively improve the stability of the γ‐CsPbI₃ at room temperature. By optimizing the doping concentration of Ca²⁺ (CsPb_1?xCa_xI₃, x is from 0% to 2%), the Ca²⁺‐doped γ‐CsPbI₃ PSCs achieve a hysteresis‐free J–V curve and a maximum power conversion efficiency (PCE) of 9.20%.     

Luminescence properties of Ca4GdO(BO3)3:Eu in ultraviolet and vacuum ultraviolet regions

The luminescent properties of Ca₄GdO(BO₃)₃:Eu³⁺ were investigated under excitation of UV and VUV light. Separate two broad bands at around 259 and 184 nm were observed in the excitation spectrum of Ca₄GdO(BO₃)₃:Eu³⁺. These peaks were assigned to the charge transfer transition of Eu³⁺-O²⁻ and Gd³⁺-O²⁻, respectively. Owing to the favorable spectral position in their broad intense excitation band, Eu³⁺ ions show a intense emission under 258 nm excitation in Ca₄GdO(BO₃)₃:Eu³⁺. This spectral position was determined by the free oxygen ions O (1). Ca₄GdO(BO₃)₃ doped with Eu³⁺ ion seems to be a preferable candidate as red lamp phosphor. On the other hand, a weak band with a maximum at about 184 nm was observed below 200 nm in the excitation spectrum of Ca₄GdO(BO₃)₃:Eu³⁺. This phosphor do not emit effectively under the 147 nm excitation. This unfavorable profile was also due to the O (1) ions, which played a role to the shifting towards the lower energy sides. The luminescence of Eu³⁺ ions in Ca₄GdO(BO₃)₃ was somewhat different from that observed in the other borates phosphors, but resembled to those observed in the oxide phosphors (e.g. Gd₂O₃, Y₂O₃ and Gd₂SiO₅). Such behavior was recognized by the detailed analysis of crystallographical surroundings around activator.     

Biodegradable Fe(III)@WS2‐PVP Nanocapsules for Redox Reaction and TME‐Enhanced Nanocatalytic,Photothermal, and Chemotherapy

In this study, biocompatible Fe(III) species‐WS₂‐polyvinylpyrrolidone (Fe(III) @ WS₂‐PVP) nanocapsules with enhanced biodegradability and doxorubicin (DOX) loading capacity are one‐pot synthesized. In this nanocapsule, there exists a redox reaction between Fe(III) species and WS₂ to form Fe²⁺ and WO₄^2?. The formed Fe²⁺ could be oxidized to Fe³⁺, which reacts with Fe(III) @ WS₂‐PVP again to continuously produce Fe²⁺ and WO₄^2?. Such a repeated endogenous redox reaction leads to an enhanced biodegradation and DOX release of DOX @ Fe(III) @ WS₂‐PVP. More strikingly, the Fe²⁺ generation and DOX release are further accelerated by the overexpressed H₂O₂ and the mild acidic tumor microenvironment (TME), since H₂O₂ and H⁺ can accelerate the oxidation of Fe²⁺. The continuously generated Fe²⁺ catalyzes a fast Fenton reaction with the innate H₂O₂ in tumor cells and produces abundant highly toxic hydroxyl radicals for nanocatalytic tumor therapy. Together with the high photothermal transforming capability, the DOX @ Fe(III) @WS₂‐PVP nanocapsules successfully achieve the endogenous redox reaction and exogenous TME‐augmented tumor photothermal therapy, chemo and nanocatalytic therapy outcome. The concept of material design can be innovatively extended to the synthesis of biodegradable Fe(III) @ MoS₂‐PVP nanocomposite, thus paving a promising novel way for the rational design of intelligent theranostic agents for highly efficient treatment of cancer.     

Novel Multi‐functional Mixed‐oxide Catalysts for Effective NOx Capture,Decomposition, and Reduction

In this paper, novel multi‐functional mixed‐oxide catalysts have been rationally designed and developed for the effective abatement of NO_x. Ca_xCo_{3 – x}Al hydrotalcite‐like compounds (where x = 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) are first synthesized by co‐precipitation and calcined at 800 °C for 4 h in air to derive the mixed oxides. The resultant mixed oxides are generally of spinel phase, where the CaO phase is segregated when x ≥ 2.5. It has subsequently been found that the derived oxides are catalytically multi‐functional for NO_x decomposition, capture, and reduction. For example, the mixed Ca₂Co₁Al₁‐oxide can decompose 55 % NO at 300 °C in 8 % oxygen, completely trap NO for 750 s, and capture 12.88 and 18.06 mg g^–1 NO within 30 and 60 min, respectively. The catalytic activities of the Ca₂Co₁Al₁‐oxide catalyst have been further improved by incorporating La to form a quaternary catalyst Ca₂Co₁La_0.1Al_0.9‐oxide. This catalyst significantly enhances the NO decomposition to 75 %, extends the complete trapping time to 1100 s, and captures more NO at 300 °C in 8 % O₂ (19.02 mg g^–1 NO within 60 min). The in‐situ IR spectra of the catalysts with adsorbed NO indicates that the major nitrogen species formed on the catalysts are various kinds of nitrites and nitrates, which can be readily reduced by H₂ within 6 min at 350 °C. Therefore, the excellent catalytic activity of layered double hydroxide (LDH)‐based mixed oxides for NO decomposition, storage, and reduction can be achieved by the elegant combination of normal transition metals.     

Structural and Spectroscopic Characterization of Nominal Yb3+:Ca8La2(PO4)6O2 Oxyapatite Single Crystal Fibers Grown by the Micro‐Pulling‐Down Method

Yb‐doped Ca₈La₂(PO₄)₆O₂ (CLPA) single crystals with the apatite‐type structure and having <0001> orientation were grown by the micro‐pulling‐down (μ‐PD) method. The apatite structure is represented by the monophased field of Ca₈(La_2–xYb_x)‐(PO₄)₆O₂ (CLYPA) where it is assumed that 2 Ca²⁺ sites are substituted by La³⁺ and Yb³⁺ cations. Its monophased range was found to be from x = 0.0 to 0.2. The segregation of Yb³⁺ in CLPA single crystals and the maximum Yb³⁺ concentration are discussed. The crystallinity was studied using X‐ray rocking curve analysis. Absorption, emission and fluorescence decay studies of Yb³⁺ ions in CLPA were also carried out both at low temperature and room temperature. Spectroscopic data reveal Yb³⁺ ion occupation within different crystallographic sites of the apatite‐type structure. The potential for a diode‐pumped Yb³⁺ laser is evaluated.     

Luminescent Metal‐Organic Frameworks for Selectively Sensing Nitric Oxide in an Aqueous Solution and in Living Cells

Cu²⁺‐based metal‐organic framework (Cu? TCA ) (H₃ TCA = tricarboxytriphenyl amine) having triphenylamine emitters was assembled and structurally characterized. Cu? TCA features a three‐dimensional porous structure consolidated by the well‐established Cu₂(O₂CR)₄ paddlewheel units with volume of the cavities approximately 4000 nm³. Having paramagnetic Cu²⁺ ions to quench the luminescence of triphenylamine, Cu? TCA only exhibited very weak emission at 430 nm; upon the addition of NO up to 0.1 mM , the luminescence was recovered directly and provided about 700‐fold fluorescent enhancement. The luminescence detection exhibited high selectivity – other reactive species present in biological systems, including H₂O₂, NO₃^?, NO₂^?, ONOO^?, ClO^? and ¹O₂, did not interfere with the NO detection. The brightness of the emission of Cu? TCA also led to its successful application in the biological imaging of NO in living cells. As a comparison, lanthanide metal‐organic framework Eu? TCA having triphenylamine emitters and characteristic europium emitters was also assembled. Eu? TCA exhibited ratiometric fluorescent responses towards NO with the europium luminescence maintained as the internal standard and the triphenylamine emission exhibited more than 1000‐fold enhancement.