Mihri Ozkan

Synthesis and characterization of polyamidoamine dendrimer-coated multi-walled carbon nanotubes and their application in gene delivery systems

With the aim of improving the amount and delivery efficiency of genes taken by carbon nanotubes into human cancer cells, different generations of polyamidoamine dendrimer modified multi-walled carbon nanotubes (dMNTs) were fabricated, and characterized by high-resolution transmission electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis, revealing the presence of dendrimer capped on the surface of carbon nanotubes. The dMNTs fully conjugated with FITC-labeled antisense c-myc oligonucleotides (asODN), those resultant asODN-dMNTs composites were incubated with human breast cancer cell line MCF-7 cells and MDA-MB-435 cells, and liver cancer cell line HepG2 cells, and confirmed to enter into tumor cells within 15 min by laser confocal microscopy. These composites inhibited the cell growth in time- and dose-dependent means, and down-regulated the expression of the c-myc gene and C-Myc protein. Compared with the composites of CNT-NH(2)-asODN and dendrimer-asODN, no. 5 generation of dendrimer-modified MNT-asODN composites exhibit maximal transfection efficiencies and inhibition effects on tumor cells. The intracellular gene transport and uptake via dMNTs should be generic for the mammalian cell lines. The dMNTs have potentials in applications such as gene or drug delivery for cancer therapy and molecular imaging.

Size Control of Gold Nanoparticles Grown on Polyaniline Nanofibers for Bistable Memory Devices

Controlling reaction temperature for a set time enables the size of gold nanoparticles autoreduced on the surface of polyaniline nanofibers to be controlled. The size of the gold nanoparticles can be used to tune the electrical bistable memory effect in gold/polyaniline nanofiber composite devices. Turn-on voltages and on/off ratios improve with decreasing nanoparticle size, making this a promising method to enhance performance and create smaller devices. Long-term stability of the composites can be improved by the addition of stabilizers following autoreduction of the gold nanoparticles.

Patterning and templating for nanoelectronics.

The semiconductor industry will soon be launching 32 nm complementary metal oxide semiconductor (CMOS) technology node using 193 nm lithography patterning technology to fabricate microprocessors with more than 2 billion transistors. To ensure the survival of Moores law, alternative patterning techniques that offer advantages beyond conventional top-down patterning are aggressively being explored. It is evident that most alternative patterning techniques may not offer compelling advantages to succeed conventional top-down lithography for silicon integrated circuits, but alternative approaches may well indeed offer functional advantages in realising next-generation information processing nanoarchitectures such as those based on cellular, bioinsipired, magnetic dot logic, and crossbar schemes. This paper highlights and evaluates some patterning methods from the Center on Functional Engineered Nano Architectonics in Los Angeles and discusses key benchmarking criteria with respect to CMOS scaling.

Heterogeneous Graphene Nanostructures: ZnO Nanostructures Grown on Large‐Area Graphene Layers

In this work, the synthesis and characterization of three-dimensional hetergeneous graphene nanostructures (HGN) comprising continuous large-area graphene layers and ZnO nanostructures, fabricated via chemical vapor deposition, are reported. Characterization of large-area HGN demonstrates that it consists of 1-5 layers of graphene, and exhibits high optical transmittance and enhanced electrical conductivity. Electron microscopy investigation of the three-dimensional heterostructures shows that the morphology of ZnO nanostructures is highly dependent on the growth temperature. It is observed that ordered crystalline ZnO nanostructures are preferably grown along the <0001> direction. Ultraviolet spectroscopy and photoluminescence spectroscopy indicates that the CVD-grown HGN layers has excellent optical properties. A combination of electrical and optical properties of graphene and ZnO building blocks in ZnO-based HGN provides unique characteristics for opportunities in future optoelectronic devices.

Delivery of a peptide via poly(D,L-lactic-co-glycolic) acid nanoparticles enhances its dendritic cell-stimulatory capacity.

UNLABELLED Nanoparticles (NPs) are attractive carriers for vaccines. We have previously shown that a short peptide (Hp91) activates dendritic cells (DCs), which are critical for initiation of immune responses. In an effort to develop Hp91 as a vaccine adjuvant with NP carriers, we evaluated its activity when encapsulated in or conjugated to the surface of poly(d,l-lactic-co-glycolic) acid (PLGA) NPs. We found that Hp91, when encapsulated in or conjugated to the surface of PLGA-NPs, not only activates both human and mouse DCs, but is in fact more potent than free Hp91. Hp91 packaged within NPs was about fivefold more potent than the free peptide, and Hp91 conjugated to the surface of NPs was ∼20-fold more potent than free Hp91. Because of their capacity to activate DCs, such NP-Hp91 systems are promising as delivery vehicles for subunit vaccines against infectious disease or cancer. FROM THE CLINICAL EDITOR In this paper, nanoparticle-based dendritic cell activating vaccines are described and discussed. The authors report that the presented PLGA NP based vaccine constructs increase the potency of the studied vaccine by up to 20-fold, making them promising as delivery vehicles for subunit vaccines against infectious diseases or cancer.

Emerging memory devices

Each memory device presented has its unique range of advantages and challenges. DRAM and FLASH have radically different characteristics; hence, they are used for different applications. Accordingly, the search for memory devices beyond CMOS comes with an important caveat: different memory for different applications. FENAs research path will continue to focus on improving our presented memory devices, and integrating with logic elements, while exploring other emerging memory devices based on nanomaterials, nanostructures, and the next generation of low-cost assembly techniques

Heparin Antagonism by Polyvalent Display of Cationic Motifs on Virus‐Like Particles

Particles to the rescue! The construction of cationic amino acid motifs on the surface of bacteriophage Qβ by genetic engineering or chemical conjugation gives particles that are potent inhibitors of the anticoagulant action of heparin, which is a common anticlotting agent subject to clinical overdose.

Molecular absorption and photodesorption in pristine and functionalized large-area graphene layers

We studied the photodesorption behavior of pristine and nitric acid (HNO(3)) treated graphene layers fabricated by chemical vapor deposition (CVD). The decrease in electrical conductivity and a negative shift of the Dirac point in graphene layers illuminated with ultraviolet light are caused by molecular photodesorption, while the UV illumination does not degrade the carrier mobility of graphene layers. When graphene layers were treated with concentrated HNO(3), the photodesorption-induced current decrease became less significant than for pristine graphene layers. We suggest this is due to the passivation of oxygen-bearing functionalities to CVD grown graphene structural defects by HNO(3) functionalization, which prevents the further absorption of gas molecules. Our results provide a new strategy for stabilizing the electrical performance of CVD grown large-area graphene layers for applications ranging from nanoelectronics to optoelectronics.

Enhanced presentation of MHC class Ia, Ib and class II-restricted peptides encapsulated in biodegradable nanoparticles: a promising strategy for tumor immunotherapy.

BackgroundMany peptide-based cancer vaccines have been tested in clinical trials with a limited success, mostly due to difficulties associated with peptide stability and delivery, resulting in inefficient antigen presentation. Therefore, the development of suitable and efficient vaccine carrier systems remains a major challenge.MethodsTo address this issue, we have engineered polylactic-co-glycolic acid (PLGA) nanoparticles incorporating: (i) two MHC class I-restricted clinically-relevant peptides, (ii) a MHC class II-binding peptide, and (iii) a non-classical MHC class I-binding peptide. We formulated the nanoparticles utilizing a double emulsion-solvent evaporation technique and characterized their surface morphology, size, zeta potential and peptide content. We also loaded human and murine dendritic cells (DC) with the peptide-containing nanoparticles and determined their ability to present the encapsulated peptide antigens and to induce tumor-specific cytotoxic T lymphocytes (CTL) in vitro.ResultsWe confirmed that the nanoparticles are not toxic to either mouse or human dendritic cells, and do not have any effect on the DC maturation. We also demonstrated a significantly enhanced presentation of the encapsulated peptides upon internalization of the nanoparticles by DC, and confirmed that the improved peptide presentation is actually associated with more efficient generation of peptide-specific CTL and T helper cell responses.ConclusionEncapsulating antigens in PLGA nanoparticles offers unique advantages such as higher efficiency of antigen loading, prolonged presentation of the antigens, prevention of peptide degradation, specific targeting of antigens to antigen presenting cells, improved shelf life of the antigens, and easy scale up for pharmaceutical production. Therefore, these findings are highly significant to the development of synthetic vaccines, and the induction of CTL for adoptive immunotherapy.

Advanced Sulfur-Silicon Full Cell Architecture for Lithium Ion Batteries

Lithium-ion batteries are crucial to the future of energy storage. However, the energy density of current lithium-ion batteries is insufficient for future applications. Sulfur cathodes and silicon anodes have garnered a lot of attention in the field due their high capacity potential. Although recent developments in sulfur and silicon electrodes show exciting results in half cell formats, neither electrode can act as a lithium source when put together into a full cell format. Current methods toward incorporating lithium in sulfur-silicon full cells involves prelithiating silicon or using lithium sulfide. These methods however, complicate material processing and creates safety hazards. Herein, we present a novel full cell battery architecture that bypasses the issues associated with current methods. This battery architecture gradually integrates controlled amounts of pure lithium into the system by allowing lithium the access to external circuit. A high specific energy density of 350 Wh/kg after 250 cycles at C/10 was achieved using this method. This work should pave the way for future researches into sulfur-silicon full cells.