Norman Lu

Silica nanohybrids integrated with CuInS2/ZnS quantum dots and magnetite nanocrystals: Multifunctional agents for dual-modality imaging and drug delivery

A strategy is presented for the synthesis of dual-modality and theranostic silica (SiO2) nanohybrids that exert excellent properties for drug delivery vehicles as well as optical and magnetic resonance imaging. SiO2 nanohybrids are composed of CuInS2/ZnS quantum dots and magnetite nanocrystals, with an outside SiO2 shell grafted with poly(ethyleneglycol) and amine groups to provide better biocompatibility and allow subsequent bioconjugation, respectively. The synthesized nanohybrids are of ultra-small size (diameter < 30 nm) and highly monodispersed and stable in aqueous suspension. In vitro results showed that the SiO2 nanohybrids were efficiently taken up by the cells and localized in the intracellular vesicles, emitting strong fluorescence from the cytoplasm and nearby nucleus. It was also demonstrated that SiO2 nanohybrids could be used as a new class of magnetic resonance imaging probes, demonstrating a high spin–spin (T2) relaxivity (r2 = 214 mM−1 s−1). The Pt(IV) anticancer drug, c,c,t-[Pt(NH3)2Cl2(O2CCH2CH2CO2H)2], was used as a model drug to attach to the surface of dual-modality SiO2 nanohybrids by using n-ethyl-N′-(3-dimethylaminopropyl)carbodiimide and hydroxysuccinimide as the activating agents. The drug readily formed amide linkages with amines on the surface of the SiO2 nanohybrids, resulting in Pt(IV)-conjugated SiO2 nanohybrids. The results reveal that the Pt(IV)-conjugated SiO2 nanohybrids show higher cytotoxicity than the free Pt(IV) anticancer drug, indicating the potential for using the obtained multifunctional SiO2 nanohybrids simultaneously as highly effective dual-modality imaging probes for cancer diagnosis and chemotherapy.

The intramolecular blue-shifting C–H⋯F–C hydrogen bond: crystal structure of [4,4′-bis(HCF2CF2CF2CF2CH2OCH2)-2,2′-bpy]MCl2 where M = Pt, Pd

In the solid state, the two fluorous ponytails in [4,4′-bis(HCF2CF2CF2CF2CH2OCH2)-2,2′-bpy]MCl2 (M = Pt 2; Pd 3) reveal one with a transoidal HCF2CF2CF2CF2CH2– chain on carbon backbone, similar to that with a normal fluorous alkyl group, and the other with a cisoidal HCF2CF2CF2CF2CH2– chain on a carbon backbone, exhibiting an intramolecular blue-shifting C–H⋯F–C hydrogen-bond. With the contraction of C–H bond, the increase in C–H stretch and the short H⋯F distance, these two examples are among the blue-shifting hydrogen bonds as defined by Hobza et al. The calculated C–H stretches using periodic density functional theory (DFT) are in good agreement with IR observations.

Molecular tuning of the closed shell C-H···F-C hydrogen bond.

The existence of the rare six-membered and intramolecular C-H···F-C hydrogen-bond has been experimentally proven in the gas phase and in the solid state recently. However, the effect of the substituents on this C-H···F-C hydrogen-bond system has never been reported. In view of the importance of this type of C-H···F-C H-bonding whose weak interaction has been found critical in nanotechnology and biological systems, the nine functional groups composed of electron donating and electron withdrawing groups are inserted into this C-H···F-C interaction to study the group effect on the hydrogen bonding. Group effects on this C-H···F-C H-bonding system have been found, and their effects on the H-bonding system have been found to be tunable.

Targeting to overexpressed glucose-regulated protein 78 in gastric cancer discovered by 2D DIGE improves the diagnostic and therapeutic efficacy of micelles-mediated system.

The survivals of gastric cancer (GC) patients are associated with early diagnosis and effective treatments. Therefore, it is urgent for the discovery of early GC biomarkers and tumor‐targeting therapeutics. The aim of this study was to uncover putative tissue biomarkers of GC using 2D DIGE and then apply one of these specific markers in GC treatment. We found three putative biomarkers of GC with significant differences in expression level compared to adjacent normal tissue, including glucose‐regulated protein 78 (GRP78) and glutathione s‐transferase pi (GSTpi) with increased expression level, and alpha‐1 antitrypsin (A1AT) with reduced expression level. The overexpressed GRP78 was used as a targeted protein for guiding the drugs to tumor cells, leading to more effective treatment for GC xenografts. Our results demonstrated that the designated GRP78‐binding peptide based on the sequence, WIFPWIQL, was selectively prone to recognize and bind to GC MKN45 cells in vitro, and also improve the delivery efficiency of polymeric micelles‐encapsulated drugs into tumor cells and displayed better therapeutic outcome in experimental animals. This strategy of GRP78‐mediated drug targeting system may bring chemotherapeutic drugs with more precise targeting to tumor cells, leading to minimize side effects on patients after chemotherapy.

Polyfluorinated bipyridine cisplatins manipulate cytotoxicity through the induction of S-G2/M arrest and partial intercalation mechanism.

A series of polyfluorinated bipyridine cisplatins 2-6 were prepared, characterized, and evaluated for their in vitro cytotoxicities against a panel of human cancer cell lines, MCF7 (breast adenocarcinoma), MDA-MB-231 (breast adenocarcinoma) and A549 (lung adenocarcinoma). The results show that a correlation between the relative order of lipophilicity of complexes 2-4 and their cytotoxicity is established by following the trend: 4>2>3. Complex 4, which is the most active compound in the series, was found to be a more effective and selective anticancer agent than cisplatin. Complex 4 inhibited cancer cell proliferation by partial intercalation to DNA, which subsequently resulted in induction of S-G2/M arrest and apoptosis.

5,5′-Bis[(2,2,2-trifluoro­eth­oxy)meth­yl]-2,2′-bipyridine

The complete molecule of the title compound, C16H14F6N2O2, is generated by crystallographic inversion symmetry, which results in two short intramolecular C—H⋯N hydrogen-bond contacts per molecule. In the crystal, aromatic π–π stacking [centroid–centroid distance = 3.457 (2) Å] and weak C—H⋯π interactions occur. A short H⋯H [2.32 (3) Å] contact is present.

Enhanced photocatalytic degradation of atrazine by platinized titanium dioxide under 352 nm irradiation

Simply coating 1 wt.% of platinum on titanium dioxide (TiO2) surface resulted in simple preparation of platinized TiO2 (Pt-TiO2). This study demonstrated the photodegradation of atrazine (ATZ) using either Pt-TiO2 or TiO2 as a photocatalyst under 352 nm light irradiation. The Pt-TiO2-catalyzed ATZ degradation reached 76% in 3 hours without adding H2O2 solution or aeration, which was more than 10% higher than the TiO2-catalyzed reaction. The decomposition product of Pt-TiO2-catalyzed ATZ degradation was mainly cyanuric acid. Thus, Pt-TiO2 as an effective photocatalyst has three main advantages in the photodegradation of ATZ under 352 nm irradiation. First, the coated Pt can facilitate the generation of appropriate amounts of OH radicals, so it can prevent the formation of over-oxidized TiO2. Second, aeration was not needed. Third, the excited electrons were mainly uni-directionally transferred to the catalyst surface to avoid recombination of electron-hole pairs.

The influence of fluoroalkyl chains in redox electrolytes for energy conversion

We discovered an unprecedented fundamental interaction originated from the fluoroalkyl chains at the interface between light harvesting chromophore and charge transport redox electrolyte in dye-sensitized solar cells (DSSCs). A fluoroalkylated Ru complexes dye (FN719) was synthesized and upon anchoring on nanoparticulate TiO2 electrodes, FN719 exhibits 5 times better photostability in humid air than that of the conventional N719 due to the hydrophobicity of the fluoroalkyl chains. Moreover, the lipophobicity of fluoroalkylated chains in organic electrolyte causes a size-selective steric hindrance with respect to the redox couple I−/I3−, leading to a more stalled diffusion of the bulky I3− towards dyes and TiO2 photoanode than that of the lean I−. As such, without sacrificing the forward electron transport and quantum efficiency, the recombination in FN719-based DSSCs is suppressed to be 1.3 times slower than N719-based DSSCs studied by the photovoltage transients and electrochemical impedance spectroscopy...

Intercalated polyfluorinated Pd complexes in α-zirconium phosphate for Sonogashira and Heck reactions

During our exploration, we have found that fluorous metal complexes can be readily and directly intercalated into α-zirconium phosphate (ZrP) layered compound. The interlayer distance of neat ZrP is 7.6 A. After the uptake of polyfluorinated Pd complexes, the original 7.6 A interlayer distance was increased to ca. 10.6 A, suggesting the successful intercalation of polyfluorinated Pd complexes within the ZrP galleries. The reason why polyfluorinated Pd complexes can be readily intercalated into ZrP is probably owing to the formation of hydrogen bonds between the hydroxyl groups of ZrP and the fluorous segments of the metal complexes. The intercalation of polyfluorinated Pd complexes into ZrP converted the metal complexes to heterogeneous catalysts, which were evaluated for Sonogashira and Heck reactions. Such intercalation compounds exhibited high performance in terms of both yield and recyclability, which suggested that intercalation into layered compounds (such as ZrP) can be a promising route to form heterogeneous catalysts for polyfluorinated metal complexes for various reactions.

4,4'-Bis(2,2,2-trifluoroethoxymethyl)-2,2'-bipyridine.

As part of a homologous series of novel polyfluorinated bipyridyl (bpy) ligands, the title compound, C(16)H(14)F(6)N(2)O(2), contains the smallest fluorinated group, viz. CF(3). The molecule resides on a crystallographic inversion centre at the mid-point of the pyridine C(ipso)-C(ipso) bond. Therefore, the bpy skeleton lies in an anti conformation to avoid repulsion between the two pyridyl N atoms. Weak intramolecular C-H...N and C-H...O interactions are observed, similar to those in related polyfluorinated bpy-metal complexes. A pi-pi interaction is observed between the bpy rings of adjacent molecules and this is probably a primary driving force in crystallization. Weak intermolecular C-H...N hydrogen bonding is present between one of the CF(3)CH(2)- methylene H atoms and a pyridyl N atom related by translation along the [010] direction, in addition to weak benzyl-type C-H...F interactions to atoms of the terminal CF(3) group. It is of note that the O-CH(2)CF(3) bond is almost perpendicular to the bpy plane.