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The discrete coordination-driven self assemblies have received continuous attention due to their molecular architecture esthetics and applications in recognition, catalysis, storage, etc. [ 1 ] Among these self assemblies, one species that has emerged recently is the porous coordination nanocages formed between carboxylate ligands and metal clusters, which are also known as metal-organic polyhedra (MOP). [ 2 ] Due to the robust porous structure and versatile functionality, they have found applications as plasticizer, gas sponge, ion channel, coatings, and building units. [ 3 ] Presumably, the porous shell and uniform yet tunable cavity make them good candidates for drug delivery purpose. However, almost all the coordination nanocages reported so far are hydrophobic, which greatly limits their applications in aqueous condition. We hypothesize this problem can be circumvented by turning these nanocages into colloids through surface functionalization with hydrophilic polymers. In this Communication, we report a porous coordination nanocage covered with alkyne groups and its surface functionalization by grafting with azide-terminated polyethylene glycol (PEG) through "click chemistry". In addition, its drug load and release capacity has been evaluated using an anticancer drug 5-fl uorouracil as a model.The metal-organic cuboctahedron was chosen as the prototype of nanocage in this study. [ 2a , 2c ] It is composed of 12 dicopper paddlewheel clusters and 24 isophthalate moieties, with 8 triangular and 6 square windows that are roughly 8 and 12 Å across, respectively. The internal cavity has a diameter of around 15 Å. The 5-position of isophthalate moieties would be the reaction site for surface functionalization. The Cu(I)-catalyzed Huisgen cycloaddition between azide and alkyne, a so-called "click reaction", was chosen as the synthetic tool in this study due to its high yield, mild reaction condition, and easy operation. [ 4 ] Based on the retrosynthetic analysis and the convenience of implementation, alkyne-covered nanocage and azide-terminated PEG are two prerequisites. The synthesis and characterization of alkyne-covered metal-organic cuboctahedron is not as straightforward as it seems to be. Since NMR signal would be elusive due to the presence of paramagnetic Cu(II) in these nanocages, [ 5 ] single crystal X-ray diffraction might be the only characterization tool available. Therefore, obtaining a single crystal of the nanocage would be of paramount importance for characterization. Figure 1a illustrates all the ligand precursors we've tried in synthesizing this "clickable" nanocage, which comprise isophthalate moiety capable of forming metalorganic cuboctahedron and alkyne group suitable for click reaction. Solvothermal reaction, a process involving heating the ligand/metal mixture solution within sealed environment at high temperature, is often used in synthesizing these coordination nanocages. [ 2a ] The solvothermal reaction between 5-ethynylisophthalic acid (H 2 ei) and copper salt ended up with a coordin...

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We have used an infrared laser for desorption of material and ionization by interaction with electrosprayed solvent. Infrared laser-assisted desorption electrospray ionization (IR LADESI) mass spectrometry was used for the direct analysis of water-containing samples under ambient conditions. An ion trap mass spectrometer was modified to include a pulsed Er:YAG laser at 2.94 microm wavelength coupled into a germanium oxide optical fiber for desorption at atmospheric pressure and a nanoelectrospray source for ionization. Analytes in aqueous solution were placed on a stainless steel target and irradiated with the pulsed IR laser. Material desorbed and ablated from the target was ionized by a continuous stream of charged droplets from the electrosprayed solvent. Peptide and protein samples analyzed using this method yield mass spectra similar to those obtained by conventional electrospray. Blood and urine were analyzed without sample pretreatment to demonstrate the capability of IR LADESI for direct analysis of biological fluids. Pharmaceutical products were also directly analyzed. Finally, the role of water as a matrix in the IR LADESI process is discussed.

A novel polyphosphoester (PPE) with vinyl ether side chain functionality was developed as a versatile template for postpolymerization modifications, and its degradability and biocompatibility were evaluated. An organo-catalyzed ring-opening polymerization of ethylene glycol vinyl ether-pendant cyclic phosphotriester monomer allowed for construction of poly(ethylene glycol vinyl ether phosphotriester) (PEVEP). This vinyl ether-functionalized PPE scaffold was coupled with hydroxyl- or thiol-containing model small molecules via three different types of conjugation chemistries—thiol—ene “click” reaction, acetalization, or thio-acetalization reaction—to afford modified polymers that accommodated either stable thio–ether or hydrolytically labile acetal or thio–acetal linkages. Amphiphilic diblock copolymers of poly(ethylene glycol) and PEVEP formed well-defined micelles with a narrow and monomodal size distribution in water, as confirmed by dynamic light scattering (DLS), transmission electron microscopy, and atomic force microscopy. The stability of the micelles and the hydrolytic degradability of the backbone and side chains of the PEVEP block segment were assessed by DLS and nuclear magnetic resonance spectroscopy (1H and 31P), respectively, in aqueous buffer solutions at pH values of 5.0 and 7.4 and at temperatures of 25 and 37 °C. The hydrolytic degradation products of the PEVEP segments of the block copolymers were then identified by electrospray ionization, gas chromatography, and matrix-assisted laser desorption/ionization mass spectrometry. The parent micelles and their degradation products were found to be non-cytotoxic at concentrations up to 3 mg/mL, when evaluated with RAW 264.7 mouse macrophages and OVCAR-3 human ovarian adenocarcinoma cells.