Engineering sensitive gas sensor based on MOF-derived hollow metal-oxide semiconductor heterostructures.

Metal-organic frameworks (MOFs) derived hollow heterostructured metal oxide semiconductors (MOSs) are a class of functional porous materials exhibiting distinctive physiochemical properties. Owing to the unique advantages, including large specific surface, high intrinsic catalytic performance, abundant channels for facilitating electron transfer and mass transport, and strong synergistic effect between different components, MOF-derived hollow MOSs heterostructures can work as promising candidates for gas sensing, which have thus attracted increasing attention. Aiming to provide a deep understanding on the design strategy and MOSs heterostructure, this review presents a comprehensive overview on the advantages and applications of MOF-derived hollow MOSs heterostructures when they used n for the detection of toxic gases. In addition, a deep discussion about the perspective and challenge of this interesting field is also well organized, hoping to provide guidance for the future design and development of more accurate gas sensors.

Terminal protection of peptides by interactions with proteins: A "signal-on" peptide-templated gold nanocluster beacon for label-free protein detection.

Characterization of the protein-peptide interactions are a critical for understanding the functions and signal pathways of proteins. Herein, a new finding of universal terminal protection that protein bind specifically with peptide and provide a protective coating to prevent peptide hydrolysis in the presence of peptidase. On the basis of this mechanism, we first reported a novel label-free fluorescence biosensor strategy that utilizes the protection of specific terminal protein on peptide-templated gold nanocluster (AuNCs) beacon for the detection of proteins. The fluorescence quenching of peptide-templated AuNCs can be effectively inhibited with increasing concentration of the specific protein, exhibiting a satisfactory sensitivity and selectivity toward protein with the detection limit of MDM2 and gp120 are 0.0019 U/mL and 0.0012 U/mL, respectively. The developed label-free fluorescence biosensor strategy provides new ideas to detect and screen protein for analyzing protein-peptide interaction in biomedical applications.

A sensitive "Switch-on" phosphorescent probe for ferrous iron quantification in drug and In vitro imaging of living cells.

Iron plays an important role in various physiological processes. However, the detailed biological functions of iron have not been sufficiently explored because of a lack of effective methods to monitoring iron, especially the labile ferrous ion (Fe2+). In the current study, a novel turn-on phosphorescent probe for Fe2+ quantification and visualization has been proposed based on the hybrid nanocomposite of manganese dioxide and gemini iridium complex (MnO2-GM-Ir). The surfactant-like GM-Ir with positive charges was beneficial to combine with the negatively charged manganese dioxide (MnO2) nanosheets, and thus endowing the MnO2-GM-Ir nanocomposite excellent dispersion ability in the water as well as efficiently avoiding the interference to the detection caused by the agglomeration of nanocomposite. Phosphorescence of GM-Ir was effectively quenched by MnO2 nanosheets through fluorescence resonance energy transfer (FRET) and the inner filter effect (IFE), while the phosphorescence could be significantly recovered in the presence of Fe2+via a selective Fe2+-mediated reduction of MnO2 nanosheets, indicating a highly-specific selectivity towards Fe2+ with a low detection limit (80 nM). The drug test assay and in vitro imaging studies further proved that the MnO2-GM-Ir nanocomposite could be employed as a promising probe for the quantitative detection of exogenous Fe2+ in drug and in vitro imaging of living cells.

A novel mitochondria-targeted phosphorescence probe for hypochlorite ions detection in living cells.

Monitoring hypochlorite anion (ClO-) in living cells is particularly meaningful and valuable, because over-exposure of the ClO- may cause a potential health hazard towards animals and humans. Considering the special structure and properties of the gemini surfactant, a novel amphiphilic gemini-iridium complex Ir[(ppy-iso)2(bpy-tma2Br2)] (Ir-iso) with isoniazide as a recognition site for ClO- was designed. The Ir-iso possessed an excellent water-solubility as well as a strong ClO- binding capacity, as revealed from the rapid response of emission signal towards ClO-. It was worth noting that such probe had a highly-specific selectivity with a low detection limit (20.5 nM) and was suitable in physiological environment. The cell viability assay, cell imaging, and co-location studies further proved that the Ir-iso had little cytotoxicity and was specifically localized in the mitochondria of breast cancer cells, being a promising candidate of chemo-sensor to detect the endogenous ClO- in living cells.

Amphiphilic gemini-iridium (III) complex for rapid and selective detection of picric acid in water and intracellular.

Inspired by the structure and properties of gemini surfactant, a novel amphiphilic gemini-iridium complex (GIC-Ir) has been developed, which can spontaneously form vesicles by self-assembly and exhibit excellent dispersibility and high emission intensity in water. The emission of GIC-Ir can be rapidly and selectively quenched by picric acid (PA) due to the aromatic groups and two long-chain quaternary ammonium (QA) groups with positive charge, which endow GIC-Ir vesicles outstanding capability to capture negatively charged PA, and greatly promote the interaction between GIC-Ir and PA. Theoretical calculations and spectral studied indicated that the photoinduced electron transfer and resonance energy transfer may be responsible to the emission quenching. Furthermore, the real water samples and in vitro studies further prove that GIC-Ir can be used as a promising chemosensor for the detection of PA both in water and intracellular.

Amphiphilic Gemini Iridium(III) Complex as a Mitochondria-Targeted Theranostic Agent for Tumor Imaging and Photodynamic Therapy.

Clinical diagnostics and therapeutics of tumors are significantly benefitted by the development of multifunctional theranostic agents, which integrate tumor targeting, imaging, and therapeutics. However, the integration of imaging and therapy functionalities to a unimolecular framework remains a great challenge. Herein, a family of amphiphilic gemini iridium(III) complexes (GIC), Ir1-Ir6, are synthesized and characterized. The presence of quaternary ammonium (QA) groups endows GIC with adjustable water solubility and excellent self-assembly properties. Spectroscopic and computational results reveal that introducing QA groups into cyclometalating ligands (CN ligands) can overcome the drawback of aggregation-caused emission quenching and ensure Ir1-Ir3 with high emission intensity and excellent singlet oxygen (1O2) generation ability in aqueous media. Cell-based assays indicate that Ir3 shows higher cellular uptake efficiency and localizes specifically in the mitochondria, as well as exhibits outstanding photostability and an impressive phototoxicity index with satisfactory performance in mitochondria-targeted imaging and photodynamic therapy (PDT) of tumor cells. Furthermore, in vivo studies further prove that Ir3 possesses excellent antitumor activity and remarkably inhibits the growth of the HepG2 cells under PDT treatment. Consequently, this study presents a promising strategy for designing clinical application potential multifunctional iridium complex theranostic agents for mitochondria-targeted imaging and PDT in a single molecular framework.