Mustapha Jouiad

Synthesis of silver nanoparticles for the dual delivery of doxorubicin and alendronate to cancer cells

We present the synthesis of a silver nanoparticle (AgNP) based drug-delivery system that achieves the simultaneous intracellular delivery of doxorubicin (Dox) and alendronate (Ald) and improves the anticancer therapeutic indices of both drugs. Water, under microwave irradiation, was used as the sole reducing agent in the size-controlled, bisphosphonate-mediated synthesis of stabilized AgNPs. AgNPs were coated with the bisphosphonate Ald, which templated nanoparticle formation and served as a site for drug attachment. The unreacted primary ammonium group of Ald remained free and was subsequently functionalized with either Rhodamine B (RhB), through amide formation, or Dox, through imine formation. The RhB-conjugated NPs (RhB-Ald@AgNPs) were studied in HeLa cell culture. Experiments involving the selective inhibition of cell membrane receptors were monitored by confocal fluorescence microscopy and established that macropinocytosis and clathrin-mediated endocytosis were the main mechanisms of cellular uptake. The imine linker of the Dox-modified nanoparticles (Dox-Ald@AgNPs) was exploited for acid-mediated intracellular release of Dox. We found that Dox-Ald@AgNPs had significantly greater anti-cancer activity in vitro than either Ald or Dox alone. Ald@AgNPs can accommodate the attachment of other drugs as well as targeting agents and therefore constitute a general platform for drug delivery.

Multifunctional redox-tuned viologen-based covalent organic polymers

The immobilization of molecular switches within materials can give rise to new bulk properties that are useful for a variety of applications. Here, we report the synthesis and characterization of covalent organic polymers composed of cyclotriphosphazene core moieties linked together by redox-switchable viologen units. The polymers are isolated as non-porous, micro- and nano-sized spherical particles whose constituent viologens allow access to three distinct redox states: dicationic, radical-cationic and neutral. With viologens in their dicationic state, the particles were used for magic printing, gaseous ammonia sensing, and efficient oxoanion capture. With viologens in any oxidation state, the polymers were capable of capturing 200 to 380% of their weight of iodine vapor. Iodine capture within all of the viologen-based polymers was fast, requiring minutes, as compared to capture by previously reported polymers, which requires hours. With viologens in their neutral state, the polymers exhibited the highest iodine loadings reported to date. Upon one and two-electron reduction, the polymers partially or completely lost their cationic character and, concomitantly, their anion removal capability.

Synthesis and morphology analysis of electrospun copper nanowires

We report the fabrication of copper nanowires (NWs) using electrospinning technique. This processing technique was used successfully to synthesize copper NWs with various morphologies using a precursor composed of copper acetate salt and poly(vinyl) alcohol. The obtained NWs were characterized through high resolution scanning electron microscopy and atomic force microscopy and it was found that their morphology is sensitive to the applied voltage and solution flow rate. Their diameter decreased with increasing voltage and increasing flow rate. Moreover, at higher flow rate and lower voltage, the roughness of NWs became more pronounced. In addition, further improvement in NW morphology may be obtained with appropriate heat treatment. These copper NWs with varying morphologies and microstructures have potential applications in different engineering domains such as electronics, optoelectronics, and catalysis.

Viologen-Templated Arrays of Cucurbit[7]uril-Modified Iron Oxide Nanoparticles

Magnetic and fluorescent assemblies of iron-oxide nanoparticles (NPs) were constructed by threading a viologen-based ditopic ligand, DPV(2+), into the cavity of cucurbituril (CB[7]) macrocycles adsorbed on the surface of the NPs. Evidence for the formation of 1:2 inclusion complexes that involve DPV(2+) and two CB[7] macrocycles was first obtained in solution by (1)H NMR and emission spectroscopy. DPV(2+) was found to induce self-assembly of nanoparticle arrays (DPV(2+)⊂CB[7]NPs) by bridging CB[7] molecules on different NPs. The resulting viologen-crosslinked iron-oxide nanoparticles exhibited increased saturation magnetization and emission properties. This facile supramolecular approach to NP self-assembly provides a platform for the synthesis of smart and innovative materials that can achieve a high degree of functionality and complexity and that are needed for a wide range of applications.

An ultra-absorbent alkyne-rich porous covalent polycalix[4]arene for water purification

The development of novel materials for removal of organic contaminants from water is of global importance for the preservation of the environment. Here, we describe the synthesis and characterization of the first porous covalent calix[4]arene-based polymer (CalP) and its use for water purification. CalP has a high surface area, large pore volume and excellent sorption capacity for a range of organic solvents, oils, and toxic dyes. The polymer can selectively absorb up to seven times its weight of oil from oil/water mixtures. From aqueous solutions, it can adsorb both anionic and cationic dyes in under 15 minutes. Its uptake capacity is significantly higher than those of the most adsorbent materials reported to date, including commercial activated carbon. Additionally, the polymer can be easily regenerated using mild washing procedures and reused several times with no loss of absorption efficiency.

Porosity-induced relaxation of strains in GaN layers studied by means of micro-indentation and optical spectroscopy

We report the fabrication of porous GaN nanostructures using UV-assisted electroless etching of bulk GaN layer grown on c-plane sapphire substrate in a solution consisting of HF:CH3OH:H2O2. The morphology of the porous GaN nanostructures was characterized for different etching intervals using high resolution scanning electron microscopy. The geometry and size of resultant pores do not appear to be affected by the etching time; however, the pore density was augmented for longer etching time. Micro-indentation tests were carried out to quantify the indentation modulus for different porous GaN nanostructures. Our results reveal a relationship between the elastic properties and the porosity kinetics, i.e., a decrease of the elastic modulus was observed with increasing porosity. The photoluminescence (PL) and Raman measurements carried out at room temperature for the etched samples having a high degree of porosity revealed a strong enhancement in intensity. Also, the peak of the PL wavelength was shifted towar...

Facile synthesis of copper oxide nanoparticles via electrospinning

A novel approach for synthesizing copper oxide (CuO) nanoparticles (NPs) through electrospinning is reported. The approach is based on producing rough and discontinuous electrospun nanofibers from a precursor based on copper acetate salt and polyvinyl alcohol (PVA) polymer. Selectively removing the polymeric phase from the fibers produced highly rough CuO nanofibers, which were composed of NPs that are weakly held together in a one-dimensional (1D) manner. Sonication in a suitable liquid under controlled conditions completely disintegrated the nanofibers into NPs, resulting in the formation of uniform CuO NPs suspension. Aberration corrected high resolution transmission electron microscope (HRTEM) showed that the obtained NPs are highly crystalline and nearly sphere-like with a diameter of 30 to 70 nm. Thus, electrospinning, which is a low cost and industrially scalable technique, can also be employed for economic and large scale synthesis of NPs.

Surface plasmon assisted hot electron collection in wafer-scale metallic-semiconductor photonic crystals

Plasmon assisted photoelectric hot electron collection in a metal-semiconductor junction can allow for sub-bandgap optical to electrical energy conversion. Here we report hot electron collection by wafer-scale Au/TiO2 metallic-semiconductor photonic crystals (MSPhC), with a broadband photoresponse below the bandgap of TiO2. Multiple absorption modes supported by the 2D nano-cavity structure of the MSPhC extend the photon-metal interaction time and fulfill a broadband light absorption. The surface plasmon absorption mode provides access to enhanced electric field oscillation and hot electron generation at the interface between Au and TiO2. A broadband sub-bandgap photoresponse centered at 590 nm was achieved due to surface plasmon absorption. Gold nanorods were deposited on the surface of MSPhC to study localized surface plasmon (LSP) mode absorption and subsequent injection to the TiO2 catalyst at different wavelengths. Applications of these results could lead to low-cost and robust photo-electrochemical applications such as more efficient solar water splitting.

Mesoporous γ-Iron Oxide Nanoparticles for Magnetically Triggered Release of Doxorubicin and Hyperthermia Treatment.

Mesoporous iron-oxide nanoparticles (mNPs) were prepared by using a modified nanocasting approach with mesoporous carbon as a hard template. mNPs were first loaded with doxorubicin (Dox), an anticancer drug, and then coated with the thermosensitive polymer Pluronic F108 to prevent the leakage of Dox molecules from the pores that would otherwise occur under physiological conditions. The Dox-loaded, Pluronic F108-coated system (Dox@F108-mNPs) was stable at room temperature and physiological pH and released its Dox cargo slowly under acidic conditions or in a sudden burst with magnetic heating. No significant toxicity was observed in vitro when Dox@F108-mNPs were incubated with noncancerous cells, a result consistent with the minimal internalization of the particles that occurs with normal cells. On the other hand, the drug-loaded particles significantly reduced the viability of cervical cancer cells (HeLa, IC50 =0.70 μm), wild-type ovarian cancer cells (A2780, IC50 =0.50 μm) and Dox-resistant ovarian cancer cells (A2780/AD, IC50 =0.53 μm). In addition, the treatment of HeLa cells with both Dox@F108-mNPs and subsequent alternating magnetic-field-induced hyperthermia was significantly more effective at reducing cell viability than either Dox or Dox@F108-mNP treatment alone. Thus, Dox@F108-mNPs constitute a novel soft/hard hybrid nanocarrier system that is highly stable under physiological conditions, temperature-responsive, and has chemo- and thermotherapeutic modes of action.

Metal/metal-oxide nanocoatings on black silicon nanograss for enhanced solar absorption and photochemical activity

In this work, we present experimental results showing optical absorption enhancement of silicon wafer through etching and metal/metal-oxide nanolayers deposition. Black silicon nanograss were fabricated from single crystalline silicon by reactive ion etching, and ZnO, Pt, and CeO2 nanolayers were deposited through atomic layer deposition as well as magnetron sputtering. The resulting structure exhibits less than 8% reflection over broadband solar spectrum. The fabricated structures are analyzed by scanning electron microscope, focused ion beam milling slice and view and transverse electron microscope sample preparation. The results are compared to finite difference time domain simulations based on the actual fabricated structures. A study of the influence of various parameters on the geometry of the fabricated micro and nanostructures and the corresponding change in optical properties is also presented. Applications of such highly absorbing metamaterials to solar photocatalysis is discussed.