There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

Aggregation-Induced Emission: Together We Shine, United We Soar!

비만아 부모의 돌봄 경험: q 방법론

Metal-organic frameworks (MOFs)-an emerging class of hybrid porous materials built from metal ions or clusters bridged by organic linkers-have attracted increasing attention in recent years. The superior properties of MOFs, such as well-defined pore aperture, tailorable composition and structure, tunable size, versatile functionality, high agent loading, and improved biocompatibility, make them promising candidates as drug delivery hosts. Furthermore, scientists have made remarkable achievements in the field of nanomedical applications of MOFs, owing to their facile synthesis on the nanoscale and alternative functionalization via inclusion and surface chemistry. A brief introduction to the applications of MOFs in controlled drug/cargo delivery and cancer therapy that have been reported in recent years is provided here.

Metal-Organic Framework (MOF)-Based Drug/Cargo Delivery and Cancer Therapy.

Mesoporous silica nanoparticles, capable of storing a payload of small molecules and releasing it following specific catalytic activation by an esterase, have been designed and fabricated. The storage and release of the payload is controlled by the presence of [2]rotaxanes, which consist of tri(ethylene glycol) chains threaded by α-cyclodextrin tori, located on the surfaces of the nanoparticles and terminated by a large stoppering group. These modified silica nanoparticles are capable of encapsulating guest molecules when the [2]rotaxanes are present. The bulky stoppers, which serve to hold the tori in place, are stable under physiological conditions but are cleaved by the catalytic action of an enzyme, causing dethreading of the tori and release of the guest molecules from the pores of the nanoparticles. These snap-top covered silica nanocontainers (SCSNs) are prepared by a modular synthetic method, in which the stoppering unit, incorporated in the final step of the synthesis, may be changed at will to target the response of the system to any of a number of hydrolytic enzymes. Here, the design, synthesis, and operation of model SCSNs that open in the presence of porcine liver esterase (PLE) are reported. The empty pores of the silica nanoparticles were loaded with luminescent dye molecules (rhodamine B), and stoppering units that incorporate adamantyl ester moieties were then attached in the presence of α-cyclodextrin using the copper-catalyzed azide−alkyne cycloaddition (CuAAC), closing the SCSNs. The release of rhodamine-B from the pores of the SCSN, following PLE-mediated hydrolysis of the stoppers, was monitored using fluorescence spectroscopy.

Enzyme-Responsive Snap-Top Covered Silica Nanocontainers

The ability to control the release of molecules from mesoporous silica nanoparticles promises to have far-reaching consequences for drug-delivery applications. Both molecular and supramolecular nanovalves, which regulate the release of guest molecules from nanopores of mesostructured silica nanoparticles, and operate under a range of stimuli including pH, competitive binding, light, and redox control, have been designed and their successful operation demonstrated in organic solvents. These systems are based upon the switching of components that have been tethered to the nanoparticle surfaces, such that access to the entrances of the nanopores can be opened and gated on demand. Since most of the traditional nanovalve designs have been based on [2]pseudorotaxanes and bistable [2]rotaxanes that rely upon donor–acceptor and hydrogen-bonding interactions between the ring and stalk components, they are limited largely to use in organic solvents. However, to realize the potential of nanovalves in therapeutic applications, it is imperative that they not only employ biocompatible components but that they also operate under physiological conditions. For nanovalves to be viable in biological environments, a recognition and binding motif which operates in aqueous media has to be identified, and then tried and tested. Herein, we describe a pH-responsive nanovalve that relies on the ion–dipole interaction between cucurbit[6]uril (CB[6]) and bisammonium stalks, and operates in water. CB[6], a pumpkin-shaped polymacrocycle with D6h symmetry consisting of six glycouril units strapped together by pairs of bridging methylene groups between nitrogen atoms, has received considerable attention because of its highly distinctive range of physical and chemical properties. Of particular interest in the field of supramolecular chemistry is the ability of CB[6] to form inclusion complexes with a variety of polymethylene derivatives, especially diaminoalkanes: the stabilities of these 1:1 complexes are highly pHdependent. The pH-dependent complexation/decomplexation behavior of CB[6] with diaminoalkanes has enabled the preparation of dynamic supramolecular entities which can be controlled by pH. Another important characteristic of CB[6] is its ability to catalyze 1,3-dipolar cycloadditions, such that the reaction between an azide-substituted ammonium ion and an alkyne-containing ammonium ion yields a disubstituted 1,2,3-triazole derivative encircled by a CB[6] ring. In view of these particular properties of CB[6], we set about to employ it as a catalyst for the formation of monolayers of [2]pseudorotaxanes on the surfaces of mesoporous silica nanoparticles so as to generate ultimately pHresponsive, biocompatible nanovalves capable of executing different missions. Mesoporous silica has proven to be an excellent support for the formation of dynamic nanosystems, including nanovalves, because it is chemically stable and optically transparent. In this current study, [2]pseudorotaxanes consisting of bisammonium stalks and CB[6] rings were constructed (Figure 1a,b) on the surface of mesoporous silica nanoparticles, and the pH-dependent binding of CB[6] with the bisammonium stalks is exploited to control the release of guest molecules from the pores of the silica nanoparticles. At neutral and acidic pH values, the CB[6] rings encircle the bisammonium stalks tightly, thereby blocking the nanopores efficiently when employing tethers of suitable lengths. Deprotonation of the stalks upon addition of base results in spontaneous dethreading (Figure 1b,c) of the CB[6] rings and unblocking of the silica nanopores. The silica supports employed were approximately 400nm-diameter spherical particles which contain ordered 2D hexagonal arrays of tubular pores (pore diameters of ca. 2 nm with a lattice spacing of ca. 4 nm) prepared by using a basecatalyzed sol–gel method. The nanopores were templated by cetyltrimethylammonium bromide (CTAB) surfactants, and tetraethylorthosilicate (TEOS) was used as the silica precursor. Empty nanopores were obtained by removal of the templating agents by solvent extraction. The ordered structure and particle morphology were confirmed (Figure 2) by X-ray diffraction (XRD) and scanning electron microscopy. This system was designed (Scheme 1a) such that the nanovalve components could be assembled in a stepwise, divergent manner from the nanoparticle surface outwards. Following solvent extraction, the nanoparticles were heated under reflux in an aminopropyltriethoxysilane (APTES) solution, which afforded the amino-modified nanoparticles 1. These nanoparticles were recovered by vacuum filtration [*] S. Angelos, Dr. Y.-W. Yang, K. Patel, Prof. J. F. Stoddart, Prof. J. I. Zink California NanoSystems Institute and Department of Chemistry and Biochemistry University of California, Los Angeles 405 Hilgard Avenue, Los Angeles, CA 90095-1569 (USA) Fax: (+1)310-206-1843 E-mail: stoddart@chem.ucla.edu zink@chem.ucla.edu Homepage: http://stoddart.chem.ucla.edu http://www.chem.ucla.edu/dept/Faculty/jzink/ [] These authors have contributed equally and both should be considered first author.

pH‐Responsive Supramolecular Nanovalves Based on Cucurbit[6]uril Pseudorotaxanes

Carboxylatopillar[5]arene (CP[5]A), a new water-soluble macrocyclic synthetic receptor, has been employed as a stabilizing ligand for in situ preparation of gold nanoparticles (AuNPs) to gain new insights into supramolecular host–AuNP interactions. CP[5]A-modified AuNPs with good dispersion and narrow size distributions (3.1 ± 0.5 nm) were successfully produced in aqueous solution, suggesting a green synthetic pathway for the application of AuNPs in biological systems. Supramolecular self-assembly of CP[5]A-modified AuNPs mediated by suitable guest molecules was also investigated, indicating that the new hybrid material is useful for sensing and detection of the herbicide paraquat.

Viologen-Mediated Assembly of and Sensing with Carboxylatopillar[5]arene-Modified Gold Nanoparticles

Metal-organic frameworks (MOFs) are an interesting and useful class of coordination polymers, constructed from metal ion/cluster nodes and functional organic ligands through coordination bonds, and have attracted extensive research interest during the past decades. Due to the unique features of diverse compositions, facile synthesis, easy surface functionalization, high surface areas, adjustable porosity, and tunable biocompatibility, MOFs have been widely used in hydrogen/methane storage, catalysis, biological imaging and sensing, drug delivery, desalination, gas separation, magnetic and electronic devices, nonlinear optics, water vapor capture, etc. Notably, with the rapid development of synthetic methods and surface functionalization strategies, smart MOF-based nanocomposites with advanced bio-related properties have been designed and fabricated to meet the growing demands of MOF materials for biomedical applications. This work outlines the synthesis and functionalization and the recent advances of MOFs in biomedical fields, including cargo (drugs, nucleic acids, proteins, and dyes) delivery for cancer therapy, bioimaging, antimicrobial, biosensing, and biocatalysis. The prospects and challenges in the field of MOF-based biomedical materials are also discussed.

Ying-Wei Yang

Papers

Metal-Organic Framework (MOF)-Based Drug/Cargo Delivery and Cancer Therapy.

Enzyme-Responsive Snap-Top Covered Silica Nanocontainers

pH‐Responsive Supramolecular Nanovalves Based on Cucurbit[6]uril Pseudorotaxanes

Viologen-Mediated Assembly of and Sensing with Carboxylatopillar[5]arene-Modified Gold Nanoparticles

Metal-Organic Frameworks for Biomedical Applications.