Dual-Functional Eu2+/3+-Complex@ZIF-67 Nanocatalyst Derived from a Green Reduction of Eu3+ Compound.

The Eu2+/3+ mixed-valent complexes have aroused attention because of their potential application in the catalytic field endowed by the variable valence. Herein, we develop an ingenious green strategy to achieve the partial reduction of Eu3+ to Eu2+ ions in the complex of pyrenol-containing cyclen (H4(Pyr)4cyclen, H4[PC]) via a ligand-to-metal charge transfer (LMCT) effect in air at room temperature. To reveal the inherent regulated capacity of the Eu2+/3+ complex in catalysis, we prepared the nanocomposites assembled by the lanthanide complexes encapsulated into ZIF-67 to successively realize the decomposition of H2O2, including europium, gadolinium, and terbium complexes. Among the nanocomposites, Eu2+/3+[PC]H@ZIF-67 exhibits the best catalytic performance due to the achievement of dual regulation of Co3+/Co2+ ratio by the mixed-valent complex. Because of extremely abundant Co2+ active sites, the Eu2+/3+[PC]H@ZIF-67 after catalyzing H2O2 sample was further utilized to degrade organic dye rhodamine B (RhB). The rather outstanding catalytic degradation efficiency was still present in Eu2+/3+[PC]H@ZIF-67. This research presents a facile strategy of Eu3+ reduction based on the ligand design and a new direction for the future development of the composite catalytic materials with mixed-valent complexes.

A smart nanoprobe based on a gadolinium complex encapsulated by ZIF-8 with enhanced room temperature phosphorescence for synchronous oxygen sensing and photodynamic therapy.

The phosphorescence lifetime approach based on the room temperature phosphorescence (RTP) property has received considerable attention in recent years due to its excellent performance in the precise measurement of oxygen. Herein, a smart nanoprobe, Gd[PC]@ZIF-8, was designed and assembled by homogenously encapsulating a rare-earth complex phosphor Gd[(Pyr)4cyclen] (Pyr = pyrenol) into a zeolitic imidazolate framework (ZIF-8). Because of the restriction of the metal-organic framework (MOF) matrix and host-guest interactions, the nanoprobe Gd[PC]@ZIF-8 exhibited highly enhanced RTP properties, including intensity, quantum yield, and elongated decay lifetime. It displayed an outstanding linear relationship between the phosphorescence decay lifetime, intensity and oxygen concentration, which can be applied in the field of oxygen sensing. Moreover, the complex Gd[(Pyr)4cyclen] in the nanoprobe Gd[PC]@ZIF-8 served as a favorable photosensitizer that resulted in the simultaneous conversion of sufficient oxygen molecules into single state oxygen (1O2) under irradiation during the phosphorescence quenching process, which is conducive to photodynamic therapy (PDT). Thus, the design of the smart nanoprobe Gd[PC]@ZIF-8 in this study provides an ingenious strategy of utilizing a MOF as a matrix to enhance the RTP properties of phosphors for synchronous oxygen sensing and PDT.

A Smart Photosensitizer-Cerium Oxide Nanoprobe for Highly Selective and Efficient Photodynamic Therapy.

Cerium oxide (CeO x) with a reversible surface Ce3+/Ce4+ redox pair has played an important role in catalytic reactions, whereas catalase mimetics of CeO x have attracted little attention in the field of biotherapy. Herein, a smart photosensitizer-cerium oxide nanoprobe was developed to represent a promising paradigm in high-performance photodynamic therapy. The photosensitizer was linked to CeO x nanoparticles through a substrate peptide (EGPLGVRGK) of matrix metalloproteinase-2 (MMP-2). The smart nanoprobe could be converted from the "silent state" before arriving at the cancer cells to the "activated state" within the cells to turn on the fluorescence and 1O2 generation when the peptide linker (EGPLGVRGK) was cut by the cancer biomarker MMP-2. Moreover, CeO x played the role of an excellent catalase-like compound to decompose endogenous hydrogen peroxide to relieve tumor hypoxia. Via the conventional application of CeO x, our study showed innovatively how a smart nanoprobe could relieve tumor hypoxia and achieve a therapeutic effect for highly selective and efficient personalized treatment.

Smart All-in-One Thermometer-Heater Nanoprobe Based on Postsynthetical Functionalization of a Eu(III)-Metal-Organic Framework.

Real-time temperature feedback in tissue based on photothermal therapy is an urgent problem to be solved in cancer treatment. Herein, a smart all-in-one nanoprobe THA@Eu-NMOF@Fe/TA was designed and assembled by postsynthetical functionalization of an Eu(III)-based nanoscale metal-organic framework (Eu-NMOF) with a two-photon-absorbing ß-diketonate ligand 4,4,4-trifluoro-1-(9-hexylcarbazol-3-yl)-1,3-butanedione (HTHA) and Fe(III)/tannic acid assembly (Fe/TA). Such a functionalized material can simultaneously achieve the temperature-sensing and optical heating under a single beam of near-infrared (NIR) light. Under 808 nm laser excitation, real-time feedback of temperature by monitoring thermoresponsive fluorescence emission ratio ( I616/ I590) and fluorescence lifetime of Eu(III) ions were realized. Meantime, Fe/TA served as the photothermal agent and antibacterial agent to implement photothermal therapy (PTT) and antibacteria simultaneously. The functions of the nanoprobe were proved with ex vivo experiments, and the antibacterial activity against Gram-positive and Gram-negative bacteria of the probe was also elaborately evaluated. Our work paves a new avenue for engineering a new cancer treatment probe which can achieve real-time temperature sensing feedback during PTT and antibacterial process.

Smart MMP2-Responsive Nanoprobe for Activatable Fluorescence Imaging-Guided Local Triple-Combination Therapies with Single Light.

Elaborately designed stimuli-responsive smart systems simultaneously enabling activatable imaging and selective treatment are highly desirable for precise diagnosis and therapy of cancer. Herein, such a smart theranostic nanoprobe composed of hollow gold nanospheres (HAuNs), photosensitizer (PS), matrix metalloproteinase 2 (MMP2) substrate peptide, and model drug doxorubicin (DOX) was designed. In the design, HAuNs served as the acceptor of Förster resonance energy transfer (FRET), photothermal therapy (PTT) reagent, and nanocarrier. The fluorescence and 1O2 generation of PS were inhibited by HAuNs through FRET effect, avoiding phototoxicity to normal tissues during circulation. Meanwhile, owing to the MMP2-triggered peptide cleavage, the PS could be efficiently activated in a tumor for selective fluorescence imaging and photodynamic therapy (PDT). The recovered fluorescence could be applied for detecting MMP2, locating tumor in vivo, and further guiding the local triple-combination therapies including PDT, PTT, and chemotherapy. The synergistic treatments of activated PDT, PTT, and controlled DOX release were achieved with single light, which provided the best therapeutic effects with enhanced stability and remarkably reduced nonspecific toxicity of PS and anticancer drug. This study helps to design novel stimuli-responsive systems for precise molecular sensing and site-specific cancer treatment.

A novel drug-drug nanohybrid for the self-delivery of porphyrin and cis-platinum.

The thriving development of nanotechnology has greatly promoted the development of drug delivery systems (DDSs) in the past decades. However, most DDSs themselves cannot serve as diagnostic reagents and must be metabolized, by which they may become poisonous and even cause immune reactions. In this study, a novel self-delivery drug-drug system (SDDS) nanohybrid based on the coordination assembly of a photodynamic reagent, tetra-(4-carboxyphenyl)porphyrin (TCPP), and a chemotherapy reagent, cis-platinum, was designed and synthesized. The four carboxyl groups of TCPP can compete with the chloride ions of cis-platinum by coordination interactions, forming a TCPP-cis-platinum nanohybrid (PCNH) for the purpose of photodynamic/chemotherapeutic synergistic treatment with a combinational index of 0.28. Meanwhile, the PCNH system can effectively protect the photosensitizer TCPP from photobleaching when irradiated continuously in the photodynamic therapy (PDT) process, which is very crucial for PDT. Furthermore, introduction of the heavy atom platinum can greatly enhance the producing efficiency of 1O2 by 46%. In addition, the red emission fluorescence of TCPP is beneficial for monitoring and tracing the process of drug delivery when used in vitro. This work may pave a new way for the design of new integrated nanohybrids for diagnosis and synergistic treatment.

Eu2+/Eu3+-Based Smart Duplicate Responsive Stimuli and Time-gated Nanohybrid for Optical Recording and Encryption.

With the rapid development of information science, it is urgent that memory devices possessing high security, density, and desirable storage ability should be developed. In this work, a smart duplicate response of stimuli has been developed and a time-gate nanohybrid based on variable valence Eu2+/Eu3+ coencapsulated has been fabricated and acts as active material in the multilevel and multidimensional memory devices. The luminescence lifetime of Eu3+ in this nanohybrid gave a stimuli response due to which the energy level of the coordinated ligand could be modulated. Furthermore, by a simple sintering procedure, Eu3+ was partially in situ reduced to Eu2+ with a short lifetime in the system. And the in situ reduction ensured both Eu3+ and Eu2+ ions' uniform distribution in the nanohybrid and simultaneous response upon light excitation of variable valence Eu ions. Interestingly, Eu3+ revealed a prolonged lifetime because of the presence of an energy-transfer effect of Eu2+ → Eu3+. Such a nanohybrid had abundant luminescent properties, including the short lifetime of Eu2+, the energy transfer from the Eu2+ to Eu3+ ions, and the stimuli response of the Eu3+ lifetimes when exposed to acidic or basic vapor, thus giving birth to interesting recording and encryption performance in spatial-temporal dimensions. We believe that this research will point out a new direction for the future development of multilevel and multidimensional optical recording and encryption materials.

Plant Sunscreen and Co(II)/(III) Porphyrins for UV-Resistant and Thermally Stable Perovskite Solar Cells: From Natural to Artificial.

The poor UV, thermal, and interfacial stability of perovskite solar cells (PSCs) makes it highly challenging for their technological application, and has drawn increasing attention to resolving the above issues. In nature, plants generally sustain long exposure to UV illumination without damage, which is attributed to the presence of the organic materials acting as sunscreens. Inspired by the natural phenomenon, a natural plant sunscreen, sinapoyl malate, an ester derivative of sinapic acid, is employed to modify the surface of electron transport materials (ETMs). The interfacial modification successfully resolved the UV stability and reduced the poor interfacial contact between ETM and perovskite. The best efficiency of fabricated PSCs is up to 19.6%. Furthermore, we employed a mixture of Co(II) and Co(III)-based porphyrin compounds containing the excellent Co(II)/Co(III) redox couple to substitute the commonly used hole transport material, 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spiro-bifluorene (spiro-OMeTAD), to resolve the thermal degradation of PSCs noted at and above 80 °C that originates from ion diffusion of I- and CH3 NH3+ (MA+ ) ions from perovskite into spiro-OMeTAD. Finally, the stable PSCs with the best efficiency up to 20.5% are successfully fabricated.

MOF-Derived Hollow CoS Decorated with CeOx Nanoparticles for Boosting Oxygen Evolution Reaction Electrocatalysis.

Transition-metal sulfides (TMSs) have emerged as important candidates for oxygen evolution reaction (OER) electrocatalysts. Now a hybrid nanostructure has been decorated with CeOx nanoparticles on the surface of ZIF-67-derived hollow CoS through in situ generation. Proper control of the amount of CeOx on the surface of CoS can achieve precise tuning of Co2+ /Co3+ ratio, especially for the induced defects, further boosting the OER activity. Meanwhile, the formation of protective CeOx thin layer effectively inhibits the corrosion by losing cobalt ion species from the active surface into the solution. It is thus a rare example of a hybrid hetero-structural electrocatalyst with CeOx NPs to improve the performance of the hollow TMS nanocage.

Ce-Doped NiFe-Layered Double Hydroxide Ultrathin Nanosheets/Nanocarbon Hierarchical Nanocomposite as an Efficient Oxygen Evolution Catalyst.

Developing convenient doping to build highly active oxygen evolution reaction (OER) electrocatalysts is a practical process for solving the energy crisis. Herein, a facile and low-cost in situ self-assembly strategy for preparing a Ce-doped NiFe-LDH nanosheets/nanocarbon (denoted as NiFeCe-LDH/CNT, LDH = layered double hydroxide and CNT = carbon nanotube) hierarchical nanocomposite is established for enhanced OER, in which the novel material provides its overall advantageous structural features, including high intrinsic catalytic activity, rich redox properties, high, flexible coordination number of Ce3+, and strongly coupled interface. Further experimental results indicate that doped Ce into NiFe-LDH/CNT nanoarrays brings about the reinforced specific surface area, electrochemical surface area, lattice defects, and the electron transport between the LDH nanolayered structure and the framework of CNTs. The effective synergy prompts the NiFeCe-LDH/CNT nanocomposite to possess superior OER electrocatalytic activity with a low onset potential (227 mV) and Tafel slope (33 mV dec-1), better than the most non-noble metal-based OER electrocatalysts reported. Therefore, the combination of the remarkable catalytic ability and the facile normal temperature synthesis conditions endows the Ce-doped LDH nanocomposite as a promising catalyst to expand the field of lanthanide-doped layered materials for efficient water-splitting electrocatalysis with scale-up potential.

Terbium Functionalized Micelle Nanoprobe for Ratiometric Fluorescence Detection of Anthrax Spore Biomarker.

Rapid, sensitive, and selective quantitative detection of pyridine dicarboxylic acid (DPA) as biomarker of anthrax spores is in great demand since anthrax spores are highly lethal to human beings and animals and also potential biological warfare agents. Herein, we prepared a ratiometric fluorescence lanthanide functionalized micelle nanoprobe by "one-pot" self-assembly, with an amphiphilic ligand containing ß-diketone derivative which can "immobilize" terbium ions through the coordination interaction and a fluorophore as fluorescence reference (FR). The detection strategy was ascribed to Tb3+ ions in lanthanide functionalized micelle, which can be sensitized to emit the intrinsic luminescence upon addition of DPA due to the presence of energy transfer when DPA chromophore coordinated with Tb3+ ion. The fluorescence intensity of FR remained essentially constant, leading to ratiometric fluorescence response toward DPA. The results demonstrate that the terbium functionalized micelle was able to sensitively detect DPA with a linear relation in the range of 0 µM to 7.0 µM in aqueous solution, which also showed remarkable selectivity to DPA over other aromatic ligands. Our work paves a new way in the design of ratiometric fluorescence lanthanide functionalized micelle nanoprobes which can be promising for selective and sensitive detection of bacterial spores or biomolecules.

Functionalized Eu(III)-Based Nanoscale Metal-Organic Framework To Achieve Near-IR-Triggered and -Targeted Two-Photon Absorption Photodynamic Therapy.

The postsynthetic-modified nanoscale metal-organic framework (NMOF) probes selected as potential drug delivery platforms and photodynamic therapy agents to fulfill the effective and safe treatment of neoplastic diseases have attracted increasing attention recently. Herein, a Eu(III)-based NMOF probe elaborately postsynthetically modified with a ß-diketonate two-photon-absorbing (TPA) ligand is rationally designed and further functionalized by assembling the photosensitizer molecule (methylene blue, MB) in the pores and a cyclic peptide targeting motif on the surface of the NMOF, which could achieve highly efficient near-infrared (NIR)-triggered and -targeted photodynamic therapy (PDT). On the basis of the luminescence resonance energy transfer process between the NMOF donor and the photosensitizer MB acceptor, the probe can achieve a high tissue-penetrable TPA-PDT effect. Thus, the NMOFs in this study play the role of not only the nanocontainer for the photosensitizer but also the energy-transfer donor. Studies in vitro show enhanced cellular uptake and satisfactory PDT effectiveness toward cancer cells compared to the free photosensitizer MB. It is highly expected that this study contributes to the development of smart luminescent diagnostic and therapeutic probes.

Self-Assembled Upconversion Nanoparticle Clusters for NIR-controlled Drug Release and Synergistic Therapy after Conjugation with Gold Nanoparticles.

Fabricated three-dimensional (3D) upconversion nanoclusters (abbreviated as EBSUCNPs) are obtained via an emulsion-based bottom-up self-assembly of NaGdF4:Yb/Er@NaGdF4 nanoparticles (abbreviated as UCNPs), which comprise a NaGdF4:Yb/Er core and a NaGdF4 shell. The EBSUCNPs were then coated with a thin mesoporous amino-functionalized SiO2 shell (resulting in EBSUCNPs@SiO2 precursor) and further conjugated with gold nanoparticles to give the novel EBSUCNPs@SiO2@Au material. Finally, EBSUCNPs@SiO2@Au was applied as a biocompatible and efficient drug carrier for doxorubicin (DOX), thus giving rise to a multifunctional EBSUCNPs@SiO2-DOX@Au nanocomposite. This final material, EBSUCNPs@SiO2-DOX@Au, and the precursor nanoparticles, EBSUCNPs@SiO2@Au, were both fully characterized and their luminescence was investigated in detail. In addition, the drug release properties and photothermal effects of EBSUCNPs@SiO2-DOX@Au were also discussed. Interestingly, when under NIR irradiation, an increasing DOX release was achieved owing to the thermal effect of the Au NPs after absorbing the green light from the upconversion nanoclusters based on the fluorescence resonance energy transfer (FRET) effect. Thus, a near-infrared (NIR)-controlled "on-off" pattern of drug release behavior can be achieved. Moreover, compared with a single therapy method, the assembled nanocomposites exhibit a good synergistic therapy against cancer cells that combines chemotherapy with photothermal therapy. In addition, the in vitro fluorescence microscopy images of EBSUCNPs@SiO2-DOX@Au show a higher enhancement in the red region due to the loading of DOX molecules with respect to EBSUCNPs@SiO2@Au. Therefore, this novel multifunctional 3D cluster architecture can be used in the biomedical field after modification and may pave a new way in other application areas of UCNPs clusters.

A core-shell metal-organic-framework (MOF)-based smart nanocomposite for efficient NIR/H2O2-responsive photodynamic therapy against hypoxic tumor cells.

Core-shell MOF-based smart nanocomposite UCNPs/MB@ZIF-8@catalase (UCNPs = upconversion nanoparticles; MB = methylene blue; ZIF = zeolitic imidazolate framework) has been constructed for bio-imaging and efficient NIR/H2O2-responsive photodynamic therapy against hypoxic tumor cells. The nanoporous MOF shell can prevent aggregation of photosensitizers and serve as an efficient self-sufficient oxygen gas acceptor.

An Elaborate Supramolecular Assembly for a Smart Nanodevice for Ratiometric Molecular Recognition and Logic Gates.

Ingenious approaches to supramolecular assembly for fabricating smart nanodevices is one of the more significant topics in nanomaterials research. Herein, by using surface quaternized cationic carbon dots (CDots) as the assembly and fluorescence platform, anionic sulfonatocalix[4]arene with modifiable lower and upper rims as a connector, as well as in situ coordination of Tb(3+) ions, we propose an elaborate supramolecular assembly strategy for the facile fabrication of a multifunctional nanodevice. The dynamic equilibrium characteristics of the supramolecular interaction can eventually endow this nanodevice with functions of fluorescent ratiometric molecular recognition and as a nano-logic gate with two output channels.

A novel fluorescent chemosensor based on tetra-peptides for detecting zinc ions in aqueous solutions and live cells.

A fluorescent chemosensor is a powerful analytical tool for the visualization and quantitation of analytes in living cells, tissue slices, and whole bodies. Peptides with a reporter ionophore are very valuable as fluorescent chemosensors, because of their higher biological compatibility and solubility compared to organic dyes, and they are more stable than proteins in aqueous solutions. Herein, we report a novel peptide fluorescent chemosensor (HL) based on tetra-peptides conjugated with dansyl groups, which was synthesized by solid phase peptide synthesis. This chemosensor selectively and sensitively detects Zn2+ based on the photo-induced electron transfer (PET) effect by turn-on response in 100% aqueous solutions. As designed, HL can penetrate live HeLa cells and image intracellular Zn2+ by turn-on response. Moreover, HL exhibits low biotoxicity with a limit of detection (LOD) of about 32 nM for Zn2+, implying that HL acts as a highly useful peptide fluorescent chemosensor for biological systems.

Versatile rare-earth oxide nanocomposites: enhanced chemo/photothermal/photodynamic anticancer therapy and multimodal imaging.

The development of novel nanocomposites that combine multiple imaging and therapeutic strategies has recently attracted considerable attention because of their cumulative and synergistic therapeutic effects. In this study, doxorubicin (DOX)- and indocyanine green (ICG)-loaded Gd2O3:Eu3+@P(NIPAm-co-MAA)@THA@cRGD nanocomposites {abbreviated as DOX-ICG-TPNPs@cRGD; P(NIPAm-co-MAA): poly[(N-isopropylacrylamide)-co-(methacrylic acid)]; THA: 4,4-trifluoro-1-(9-pentylcarbazole-3-yl)-1,3-butanedione; cRGD: cyclic(Arg-Gly-Asp-d-Phe-Lys)} were designed, assembled, fully characterized, and successfully applied in multimodal imaging diagnosis and therapy. The designed nanocomposites display a versatile, multifunctional platform that includes (a) simultaneous targeting with cRGD, (b) multimodal imaging, including two-photon luminescence (TPL), magnetic resonance imaging (MRI), computed tomography (CT), and photothermal imaging (PTI), and (c) stimuli-responsive coordinated drug delivery; this results in a highly efficient synergistic chemo/photothermal/photodynamic anticancer therapy (chemo/PTT/PDT). An important feature of the obtained nanocomposites is the enhancement of both the PTT and PDT effects of ICG due to the effective light protection of a two-photon sensitized Eu3+ complex. This integrated strategy shows an excellent synergistic inhibition of tumor growth triggered by NIR laser irradiation, as confirmed by both in vitro and in vivo tests. The present study emphasizes the influence and interaction of every component in the nanocomposites and demonstrates that the systematic design of nanocarriers can lead to an assembly of smart nanomaterials with enhanced antitumor efficacy.