Alexandre Barras

Formulation and characterization of polyphenol-loaded lipid nanocapsules.

The purpose of this study was to design and characterize two flavonoid-loaded lipid nanocapsules (LNC) by applying the phase inversion process, and to enhance their apparent solubility and/or the stability. The flavonoid-loaded LNC were characterized by particle size, encapsulation efficiency, drug leakage rates, stability and spectroscopic studies. It was observed that quercetin-loaded LNC30 (3%) and LNC60 (2%) carried a particle size of 30.3 and 55.1 nm, respectively and significant higher entrapment efficiency. Encapsulation of quercetin (QC) in LNC enabled us to increase its apparent aqueous solubility by a factor of 100. And in view of calculations and results, it seems most probable that QC is arranged at this LNC interface between the oil phase and the hydrophilic polyethylene glycol moieties of the surfactant. In addition, colloidal suspensions proved to be stable in term of encapsulation for at least 10 weeks and QC was not oxidised. With simple chemical modification of (-)-epigallocatechin-3-gallate or (-)-EGCG, it was possible to reach very high encapsulation rates (95%). Thus we obtained stable colloidal suspensions of (-)-EGCG in water over 4 weeks while free (-)-EGCG solubilised in water exhibited 100% degradation within 4h. The initial problems (solubility and stability) of these flavonoids were resolved thanks to drug-loaded LNC.

Direct Functionalization of Nanodiamond Particles Using Dopamine Derivatives

The article reports on the strong linking of dopamine derivatives as a simple and a versatile strategy for the surface functionalization of hydroxyl-terminated nanodiamond (ND-OH) particles. Azide- (ND-N(3)) or poly-N-isopropylacrylamide-terminated (ND-PNIPAM) particles were obtained from ND-OH particles through the reaction with the corresponding dopamine derivatives. The azide-terminated ND particles were further derivatized with a fluorescent probe, alkynyl-pyrene, via copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition. The modified ND particles were characterized using transmission Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy, electrochemical measurements, thermogravimetric analysis (TGA), and particle size measurements. The surface loading of ND particles with dopamine was estimated from TGA and UV-vis spectroscopy and was found to be around 0.27 mmol g(-1). Because of its simple, gentle nature and versatility, the chemistry developed in this work can be used as an avenue for the preparation of functional nanodiamond particles for various applications.

Functionalization of Diamond Nanoparticles Using “Click” Chemistry

The paper reports on covalent linking of different alkyne-containing (decyne, ethynylferrocene, and N-propargyl-1-pyrenecarboxamide) compounds to azide-terminated nanodiamond (ND) particles. Azide-terminated particles (ND-N(3)) were obtained from amine-terminated nanodiamond particles (ND-NH(2)) through the reaction with 4-azidobenzoic acid in the presence of a carbodiimide coupling agent. Functionalized ND particles with long alkyl chain groups can be easily dispersed in various organic solvents without any apparent precipitation after several hours. The course of the reaction was followed using Fourier transform infrared (FT-IR) spectroscopy, UV/vis spectroscopy, fluorescence, cyclic voltammetry, thermogravimetric analysis (TGA), and particle size measurements. The surface loading of pyrene bearing a terminal acetylene group was found to be 0.54 mmol/g. Because of its gentle nature and specificity, the chemistry developed in this work can be used as a general platform for the preparation of functional nanoparticles for various applications.

Approach for Plasmonic Based DNA Sensing: Amplification of the Wavelength Shift and Simultaneous Detection of the Plasmon Modes of Gold Nanostructures

In this article, the detection of DNA hybridization taking advantage of the plasmonic properties of gold nanostructures is described. The approach is based on the amplification of the wavelength shift of a multilayered localized surface plasmon resonance (LSPR) sensor interface upon hybridization with gold nanorods and nanostars-labeled DNA. The amplification results in a significant decrease of the limit of detection from ≈40 nM as observed for unlabeled DNA to 0.2 nM for labeled DNA molecules. Furthermore, the plasmonic band, characteristic of the labeled DNA, is different from that of the LSPR interface. Indeed, next to the plasmon band at around 550 nm, being in resonance with the plasmon band of the LSPR interface, additional plasmonic peaks at 439 nm for gold nanostar-labeled DNA and 797 nm for gold nanorod-labeled DNA are observed, which were used as plasmonic signatures for successful hybridization.

Green chemistry approach for the synthesis of ZnO-carbon dots nanocomposites with good photocatalytic properties under visible light.

We report on a simple and one-pot synthetic method to produce ZnO/carbon quantum dots (ZnO/CQDs) nanocomposites. The morphological features and chemical composition of the nanocomposites were characterized using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analyses (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical properties of the nanocomposites were examined using UV-visible (UV-vis) spectrophotometry. The photocatalytic activity of the ZnO/CQDs was evaluated for the degradation of a model organic pollutant, rhodamine B, under visible light irradiation at room temperature. The highly efficient photodegradation capability of the nanocomposite was demonstrated by comparison with ZnO particles, prepared using identical experimental conditions. Overall, the present approach adheres to green chemistry principles and the nanocomposite holds promise for the development of remarkably efficient catalytic systems.

Thiol–Yne Click Reactions on Alkynyl–Dopamine‐Modified Reduced Graphene Oxide

The large-scale preparation of graphene is of great importance due to its potential applications in various fields. We report herein a simple method for the simultaneous exfoliation and reduction of graphene oxide (GO) to reduced GO (rGO) by using alkynyl-terminated dopamine as the reducing agent. The reaction was performed under mild conditions to yield rGO functionalized with the dopamine derivative. The chemical reactivity of the alkynyl function was demonstrated by post-functionalization with two thiolated precursors, namely 6-(ferrocenyl)hexanethiol and 1H,1H,2H,2H-perfluorodecanethiol. X-ray photoelectron spectroscopy, UV/Vis spectrophotometry, Raman spectroscopy, conductivity measurements, and cyclic voltammetry were used to characterize the resulting surfaces.

MoS2/reduced graphene oxide as active hybrid material for the electrochemical detection of folic acid in human serum.

In this study, a new matrix based on a molybdenum disulfide-reduced graphene oxide hybrid (MoS2-rGO) was prepared and characterized. Modification of a glassy carbon electrode (GCE) with MoS2-rGO (MG) using drop casting allowed for the selective analysis of folic acid in the presence of a variety of interference species with a limit of detection of 10nM, a linear range between 0.01μM and 100μM with a sensitivity of 14µAµM(-1). In addition, the analytical performance of the proposed sensor was successfully conducted for the determination of folic acid in human serum samples, making MG-GC electrodes promising interfaces for bio-electrochemical applications.

Transdermal skin patch based on reduced graphene oxide: A new approach for photothermal triggered permeation of ondansetron across porcine skin

&NA; The development of a skin‐mounted patch capable of controlled transcutaneous delivery of therapeutics through thermal activation provides a unique solution for the controlled release of active principles over long‐term periods. Here, we report on a flexible transdermal patch for photothermal triggered release of ondansetron (ODS), a commonly used drug for the treatment of chemotherapy‐induced nausea and vomiting and used as model compound here. To achieve this, a dispersion of ODS‐loaded reduced graphene oxide (rGO‐ODS) nanosheets were deposited onto Kapton to produce a flexible polyimide‐based patch. It is demonstrated that ODS loaded Kapton/rGO patches have a high drug delivery performance upon irradiation with a continuous laser beam at 980 nm for 10 min due to an induced photothermal heating effect. The ability of ODS impregnated Kapton/rGO patches as transdermal delivery scaffolds for ODS across the skin is in addition investigated using porcine ear skin as a model. We show that the cumulative quantity and flux of ODS passing the skin are highly depending on the laser power density used. At 5 W cm− 2 irradiation, the ODS flux across pig skin was determined to be 1.6 &mgr;g cm− 2 h− 1 comparable to other approaches. The use of tween 20 as skin enhancer could significantly increase the ODS flux to 13.2 &mgr;g cm− 2 h− 1. While the skin penetration enhancement is comparable to that obtained using other well‐known permeation enhancers, the actual superiority and interest of the proposed approach is that the Kapton/rGO photoactivatable skin patch can be loaded with any drugs and therapeutics of interest, making the approach extremely versatile. The on demand delivery of drugs upon local laser irradiation and the possibility to reload the interface with the drug makes this new drug administration route very appealing. Graphical abstract Figure. No caption available.

Magnetic reduced graphene oxide loaded hydrogels: Highly versatile and efficient adsorbents for dyes and selective Cr(VI) ions removal

The formation of composites of reduced graphene oxide (rGO) and magnetic nanoparticles (MP) has flourished in recent years as they combine the advantages of both nanomaterials. Most of these composite materials are prepared by in situ formation of MP onto rGO or by the post-adsorption onto rGO. We report here on a simple and highly controlled method for the fabrication of different magnetic 3D rGO-loaded hydrogels. Cellulose bound magnetic nanoparticles (MP@cellulose) were synthesized by chemical co-precipitation and loaded together with rGO into poly(ethylene glycol) dimethacrylate based hydrogels during their fabrication using photo-polymerization. The magnetic rGO-loaded hydrogels proved to be highly adaptable to different applications. The as-formed composites allowed for efficient dye removal with an adsorption capacity of 111.9±4mgg-1 in the case of methylene blue (MB). Integration of poly(ethyleneimine) (PEI) allowed for the selective capturing of Cr6+ ions with an adsorption capacity of 313±12mgg-1. Most importantly, independent of the application, the magnetic rGO-loaded hydrogel can be regenerated without loss of its adsorption capacity.

Insulin loaded iron magnetic nanoparticle–graphene oxide composites: synthesis, characterization and application for in vivo delivery of insulin

One of the focal subjects in insulin delivery is the development of insulin formulations that protect the native insulin from degradation under acidic pH in the stomach. In this work we show, for the first time, that a graphene oxide (GO) based matrix can ensure the stability of insulin at low pH. GO and GO modified with 2-nitrodopamine coated magnetic particle (GO–MPdop) matrices loaded with insulin were prepared and the pH triggered release of the insulin was studied. The loading of insulin on the GO nanomaterials proved to be extremely high at pH < 5.4 with a loading capacity of 100 ± 3% on GO and 88 ± 3% on GO–MPdop. The insulin-containing GO matrices were stable at acidic pH, while insulin was released when exposed to basic solutions (pH = 9.2). Using Xenopus laevis oocytes as a model we showed that the meiotic resumption rate of GO and GO–MPdop remained unaltered when pre-treated in acidic conditions, while pre-incubated insulin (without GO nanomaterials) has lost almost entirely its maturation effect. These results suggest that GO based nanomatrices are promising systems for the protection of insulin.