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The cover illustrates a multifunctional gene delivery system interacting with cancer cells. Small interfering RNA (siRNA) is an emerging class of therapeutics, which works by regulating the expression of a specifi c gene involved in disease progression. Effective transport of siRNA with minimal side effects remains a challenge. In this study, a nonviral nanoparticle gene carrier was developed which contains a core of clustered superparamagnetic iron oxide nanoparticles and a shell of alkylated polyethyleneimine. This composite effectively binds siRNA with good protection, as demonstrated by an enzymatic degradation assay. Signifi cant down-regulation of luciferase by loaded nanocarriers was observed both in vitro and in vivo. In addition, transfected cells showed signifi cant MR imaging contrast compared to nontransfected ones. For more information, please read the Full paper “N-Alkyl-PEI-Functionalized Iron Oxide Nanoclusters for Effi cient siRNA Delivery” by H. Ai, X. Chen, and co-workers beginning on page 2742.

The cover picture conceptualizes nanoparticles, quantum dots, or biomolecules being controlled in a multilayer, nanofl uidic chip architecture using electrokinetic forces to capture, hold, and release them by controlling the potential difference across the channels. The nanomaterials are delivered into the top microfl uidic channel and are captured onto the vertical nanochannels. Such dynamic control of the fl ow and placement of nanomaterials in a biocompatible, aqueous environment will have a profound impact on the fi elds of nanoplasmonics, nanophotonics, and medicine. With this architecture it is possible to capture and align nanoparticles into a 2D structure. For more information, please read the Full Paper “Real-Time Template-Assisted Manipulation of Nanoparticles in a Multilayer Nanofl uidic Chip” by L. Pang, Y. Fainman, and co-workers, beginning on page 2750.

Synthesis of monodisperse nanocrystals is an important key to control physical and chemical properties on the nanoscale. Herein, two major synthetic methods for uniform nanocrystals, hot injection and heat-up, are reviewed. Mechanistic studies supported by theoretical background and simulation works show that both hot injection and heat-up have similar size distribution control mechanisms, namely, burst nucleation and diffusion-controlled growth.

The picture shows an inorganic glass fi lm with multiple photonic band gaps (MPBGs). The fi lm is fabricated by sol-gel processing of TiO₂, SiO₂, and mixed SiO₂-TiO₂ films. In the visible region, the spectral characteristics of MPBGs can be controlled by adjusting fabrication parameters. Using the film with engineered MPBGs, pixelated redgreenblue lasing emissions are achieved in a single sol-gel resonator with three kinds of dye-doped nematic liquid crystals. With easy fabrication via wet-processing, unique optical characteristics, and the advantages of an inorganic glass, the new sol-gel film is a functional substrate with enhanced optical performance for wide-band photonic applications such as refl ective displays, organic lasers, and organic light-emitting diodes.

An inorganic glass film with engineered multiple photonic bandgaps (MPBGs) is fabricated by sol–gel processing. This sol–gel film consists of TiO₂, SiO₂, and mixed SiO₂–TiO₂ films and has controllable characteristics of MPBGs in the overall visible region. By using the sol–gel film as a resonator, a red–green–blue pixelated liquid-crystal laser is also demonstrated.

Photoactive nanowires: A novel photo-electrochemical nanowire diode that catalyzes the conversion of methanol and water to hydrogen under UV light is demonstrated. The wire consists of a metal and a metal oxide segment that are connected via a Schottky barrier. Other functions, such as remote- controlled autonomous movement, can be easily added to these wires in a modular fashion.

The synthesis of Bi₂WO₆ inverse opal photonic crystals is performed via a facile and economical method. Bi₂WO₆ inverse opals exhibit much higher photocatalytic activities for the degradation of methylene blue and salicylicic acid under visible light illumination as compared with a reference nanofilm. The photon-to-hydrogen conversion efficiencies of photoelectrochemical water splitting exhibit an almost threefold increase due to the inverse-opal structure.

A simple diblock copolymer, polystyrene-block-poly(acrylic acid), can be used to create toroidal micelles with and without inserted gold nanoparticles. Achievement of this elusive morphology at narrow ranges of DMF/H₂O ratio can be attributed to an experimental setup that locks the solvent ratio while allowing sufficient time and kinetic energy for the polymer to evolve at high temperature.

Anovel therapy model with mitochondria- targeting single-walled carbon nanotubes (SWNTs), which convert laser energy into heat and selectively destroy the target mitochondria, is explored. The procedure induces cytochrome c release and cell apoptosis. The laser–SWNT method could be a promising selective local treatment modality, while minimizing adverse side effects.

Electron beam-induced shrinkage of metal-coated membrane nanopores for single-molecule fluorescence spectroscopy is achieved using only a scanning electron microscope. Shrinkage occurs on both the Al and Si₃N₄ sides, with carbon deposition being the dominant mechanism. The process is time-dependent and can be fine-tuned by optimizing the electron beam settings.

Iron oxide nanoclusters (IOs) functionalized with alkylated polyethyleneimine of 2000 kDa molecular weight (Alkyl-PEI2k) are synthesized using Alkyl-PEI2k as the phase transfer material, which binds siRNA to form well-dispersed nanoparticles with uniform structure and narrow size distribution. With siRNA loading, Alkyl-PEI2k-IOs induce enhanced luciferase gene (fluc) silencing in fluc-4T1 cells in cell culture and in a fluc-4T1 tumor xenograft model with good biocompatibility.

A multilayer nanophotonic, microfluidic, nanofluidic platform is demonstrated, in which nanoparticles are manipulated in real time by electrokinetic forces (via voltage potential) to form a nanoparticle structure above the underlying nanochannel membrane when an electric field is applied. Simulations of the nanoparticles' motion validate the approach, as confirmed by experiments in creating 200-nm nanoparticle 2D arrays.

Three isomers of chondroitin sulfate (CS), i.e., CS-A, CS-B, and CS-C, are investigated as single-walled carbon nanotube (SWNT) dispersants in water. CS-C and CS-A, which have lower alpha-helix secondary structure contents, disperse the SWNTs much better than CS-B. The helical wrappings of CS-A and CS-C around the nanotubes was confirmed by atomic force microscopy and transmission electron microscopy.

Composite nanopost arrays are fabricated by combining colloidal lithography and surface-initiated atom-transfer radical polymerization. Both the resultant nanoarchitecture and color of the composite nanopost arrays can be precisely tuned by adjusting the time of polymerization. The final composite nanopost arrays can be used as highly stable and repeatable sensors to rapidly detect water vapor.

Oxygen reacts with active sites on graphenic carbon surfaces to produce surface-bound oxygen intermediates that react heterogeneously with the antioxidant glutathione to restore the carbon surface and complete a catalytic cycle. This catalytic reaction is seen for a wide range of graphenic carbon materials and may contribute to oxidative stress pathways in nanotoxicity.

In vivo tumor targeting and drug delivery properties of small polymerized polydiacetylene (PDA) micelles (∼10 nm) is investigated in a murine MDA-MB-231 xenograft model of breast cancer. Uptake of (2000 Da poly(ethylene glycol))–PDA micelles in tumors is confirmed by co-localization with [¹⁸F]-fluorodeoxyglucose positron emission tomography and the tumor growth was significantly decreased when mice are treated with micelles loaded with paclitaxel.

Parabolic-mirror-assisted confocal far- field optical microscopy and high-resolution tip-enhanced near-field spectroscopic mapping are used to study the phase separation due to 1,8-octanedithiol (ODT) addition to a polymer:fullerene (PCPDTBT:PCBM) blend model system. The morphology, photoluminescence, Raman spectra, and nanoscale photophysics properties of the blend films with respect to the absence and presence of ODT are discussed.

Water molecule deficiency in the channel cores of bioinspired hierarchical peptide nanotubes not only modifies the bandgap of the subnanometer-scale crystalline structure formed by self-assembly, but also induces a characteristic ultraviolet photoluminescence peak, which is tunable and recoverable depending on incorporation or loss of water molecules.

The antiviral or anticancer properties of polyoxometalate (POM)/carboxymethyl chitosan (CMC) nanocapsules significantly reduce the cytotoxicity of bioactive POMs. They are used in a combined drug carrier-and-monitoring approach to track the unknown cellular pathways of POMs. Fluorescently labeled POM/CMC nanocomposites are detected in the perinuclear region of HeLa cells and nonlabeled nanospheres are tracked there with transmission electron microscopy.