Synthesis, characterization and bio-functionalization of magnetic nanoparticles to improve the diagnosis of tuberculosis.

Mycobacterium tuberculosis is the cause of one of the diseases with the highest mortality and morbidity rate in the Americas and in the world. In developing countries, the diagnosis of tuberculosis (TB) is based on baciloscopy and bacteriological cultures. The first method has a low sensitivity, and the second can take several weeks to reach a confirmatory diagnosis. The lack of a rapid diagnosis compromises the efforts to control this disease and favors the transmission of tuberculosis to the susceptible population. In this work, we present the synthesis, amine-silanization, characterization and bio-functionalization of magnetic nanoparticles (MNPs) to develop a sandwich ELISA to detect and concentrate antigens from M. tuberculosis. For this purpose, a recombinant mycobacterial heat shock protein Hsp16.3, which contributes to the persistence of TB, was cloned and expressed in the E. coli system. Polyclonal antibodies anti-Hsp16.3 were produced in a rabbit and in mice. Magnetic nanoparticles were synthesized by co-precipitation, amine-functionalized and characterized by several physical-chemical methods. The XRD, Mossbauer spectroscopy, zeta potential, TEM, and FTIR all proved the successful preparation of the MNPs showing a diffraction crystal diameter of 10.48 ± 2.56 nm, superficial net charge of [Formula: see text]: +23.57 ± 2.87 mV, characteristic patterns of magnetite and a structure similar to a sphere. Additionally, it showed a magnetization saturation of 37.06 emu.g-1. For the functionalization of nanoparticle surfaces with anti-Hsp16.3, the active ester method was used for bond formation, and parameters such as time of incubation, coupling agents ratio (EDC/NHS) and concentration as well as surface saturation level of amine-silanized MNPs (MNP@Si@NH2) were standardized. Finally, bio-functionalized MNPs were used to detect, fix and concentrate the recombinant antigen Hsp16.3 from M. tuberculosis in a sandwich ELISA-MNP assay.

Optically Active Polyoxometalate-Based Silica Nanohelices: Induced Chirality from Inorganic Nanohelices to Achiral POM Clusters.

In order to investigate the principle of chiral induction from nanometric silica helices to polyoxometalate (POM) clusters, a series of optically active silica POM-based nanohelices (NANOPOMs) have been prepared by electrostatic grafting and direct adsorption of α-Keggin polyoxometalate [α-PW12 O40 ]3- to well-defined left- and right-handed silica nanohelices. UV/Vis, Raman, DRIFT, TEM, HR-TEM, EDS and circular dichroism (CD) spectroscopy were used to characterize these NANOPOMs, and confirm the presence of POM clusters as well as their interactions with the helical support. The optical activity of the left-handed and right-handed NANOPOMs has been proven by CD spectroscopy. Their CD spectra are mirror images of one another, showing cotton effects at around 214 and 276 nm, this last contribution corresponding to the oxygen-to-tungsten charge-transfer bands of Keggin polyoxoanions. The CD signal of POM clusters is strongly enhanced for NANOPOMs built by adsorption of POM onto silica nanohelices, indicating a better induced optical activity to POM clusters. These nanohelices are stable, recoverable and active catalysts in the oxidation of sulfides. To the best of our knowledge, the present research represents the first examples of optically active POM-containing silica nanohelices in which achiral POM clusters have been grafted onto silica nanohelices, and display chiroptical effects.

Probing some organic ukiyo-e Japanese pigments and mixtures using non-invasive and mobile infrared spectroscopies.

Non-invasive identification of organic colourants in paintings still remains a challenging issue, especially in the case of extremely thin layers of paint on printed paper such as Japanese ukiyo-e prints. Because prints are fragile artworks, various non-invasive analytical methods need to be employed. The present work focuses on results obtained by combining fibre optic reflectance spectroscopy in the near-infrared range (FORS NIR) with mid-infrared (MIR) spectroscopy. The first step consists of identifying spectroscopic marker bands typical of some organic pigments (indigo, gamboge, cochineal, turmeric, safflower, dragon's blood). Some reference printouts involving paper substrate, binder and pigments (seldom used or as mixtures) were then investigated in order to establish a straightforward way to extract the marker bands of the pigments. Some data post-treatments were applied to the spectra, such as spectral subtraction, in order to abstract the signal from overlapping bands originating from both substrate and binder, and second derivative calculation to emphasise the pigment marker bands' frequency positions. These data treatments turned out to be relevant to extract information on the organic pigments of interest, even within complex mixtures.

Epoxy-terminated self-assembled monolayers containing internal urea or amide groups.

We report the synthesis of new coupling agents with internal amide or urea groups possessing an epoxy-terminal group and trimethoxysilyl-anchoring group. The structural characterizations of the corresponding self-assembled monolayers (SAMs) were performed by polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS). The molecular assembly is mainly based on the intermolecular hydrogen-bonding between adjacent amide or urea groups in the monolayers. Because of the steric hindrance of amide or urea groups, the distance between the alkyl chains is too large to establish van der Waals interactions, inducing their disorder. The reactivity of the epoxy-terminal groups was successfully investigated through reaction with a fluorescent probe. We show that SAMs containing internal urea or amide groups exhibited a higher density of accessible epoxide groups than the corresponding long-chain (C22) glycidyl-terminated SAM.

Functionalized hydrogen-bonding self-assembled monolayers grafted onto SiO2 substrates.

A novel urea coupling agent possessing a vinyl-terminal group and trimethoxysilyl anchoring group was synthesized and grafted onto SiO(2)/Au substrates. This ureido coupling agent exhibits a good capacity to directly yield homogeneous SAMs with a surface smoothing. Polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) was used to monitor these SAMs. Indeed, the different functional groups (alkyl chain, urea, and vinyl) of this coupling agent were clearly observed in the PM-IRRAS spectra. Chemical modifications of the terminal function for the covalent immobilization of biomolecules were monitored by PM-IRRAS for the first time. We have demonstrated the successful reactions of the conversion of the vinyl-terminated SAMs successively into SAM-COOH and SAM-NHS without any degradation of the monolayer. The reactivity of activated esters was successfully investigated in order to immobilize the protein A.

PM-IRRAS investigation of self-assembled monolayers grafted onto SiO2/Au substrates.

Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was used to characterize self-assembled monolayers (SAMs). Novel ester-terminated organosilicon coupling agents possessing a trialkoxysilyl headgroup and a urea group in the linear alkyl chains (4) were synthesized and grafted onto SiO(2)/Au substrates (SiO(2) film of 200 Å thickness deposited on gold mirror). This composite substrate allowed the anchoring of SAMs and preserved the high reflectivity for infrared radiation. PM-IRRAS spectra with very high signal-to-noise ratios have been obtained in the mid-infrared spectral range allowing monitoring of the grafted SAMs. Quantitative analysis of the measured signal is described to compare PM-IRRAS and conventional IRRAS spectra. This quantitative analysis has been validated since the band intensities in the corrected PM-IRRAS and conventional IRRAS spectra are identical. Orientation information on the different functional groups has been obtained comparing the corrected PM-IRRAS spectrum with the one calculated using isotropic optical constants of ester-terminated organosilicon coupling agents 4. The carbonyls of the urea groups are preferentially parallel to the substrate surface favoring intermolecular hydrogen bonding and consequently a close packing of the molecules attached to the surface. By contrast, the alkyl chains present gauche defects and are poorly oriented.

Interaction process between gaseous CH3I and NaCl particles: implication for iodine dispersion in the atmosphere.

Gaseous iodomethane (CH3I) is naturally emitted into the atmosphere by biological activity in oceans and during severe accidents (SAs) in nuclear power plants. In this latter case, a part of radioactive iodine such as 131I may be released. Improving the knowledge of CH3I transport and reactivity in the atmosphere is important since they are strongly linked to first the cycle of ozone and second to the dispersion of radioactive CH3I with potential radiological consequences on both the environment and human health. Here, the interaction process of CH3I with NaCl as a surrogate of atmospheric aerosols was investigated under ambient air conditions by using Diffuse Reflectance Fourier Transform Spectroscopy (DRIFTS). The DRIFTS spectra of NaCl clearly evidenced CH3I adsorption on the NaCl particle surface. A part of CH3I ((1.68 ± 0.85) × 1014 molecule per mgNaCl) was found to be strongly bonded to NaCl since no desorption was observed. The CH3I adsorption on the NaCl surface presented a 1st order kinetics relative to its gas phase concentration. The uptake coefficient was determined to be in the order of 10-11. These results show a low probability of CH3I to be taken up by halide-containing aerosols. These data are crucial for completing the iodine atmospheric chemical scheme.

Supercritical loading of gatifloxacin into hydrophobic foldable intraocular lenses - Process control and optimization by following in situ CO2 sorption and polymer swelling.

The supercritical impregnation process was used as a green technology for the elaboration of drug delivery intraocular lenses to mitigate the risk of post-operatory endophthalmitis after cataract surgery. Commercially available hydrophobic acrylic (copolymer of benzyl methacrylate and methyl methacrylate) intraocular lenses (IOLs) were impregnated with gatifloxacin, a fourth generation fluoroquinolone drug, using pure supercritical CO2 (scCO2) to obtain solvent-free loaded implants. The interaction phenomena involved in the supercritical impregnation were studied by following in situ scCO2 sorption within the polymer support and the subsequent IOL swelling, and by taking into account drug solubility in the supercritical fluid phase. The drug impregnation yields determined though in-vitro release studies varied between 0.33 and 1.07 ± 0.07 µg·mg-1IOL in the studied experimental conditions (8 to 25 MPa, 308 to 328 K and 30 to 240 min impregnation duration). An impregnation duration longer or equal to the time required for a complete CO2 uptake by the polymer as well as a higher pressure or a higher temperature over the crossover pressure delimiting the upper limit of the retrograde solubility zone, led to higher drug impregnation yields.

Adsorption of Proteins on Dual Loaded Silica Nanocapsules.

The design of nanocarriers containing hydrophobic and hydrophilic compounds represents a powerful tool for cocktail delivery. Water-in-oil-in-water emulsions constitute an attractive approach, as they offer dual encapsulation and provide a template for the constitution of a capsule. A limitation in the preparation of nano double emulsions is their instability resulting from high curvature radii. In this work, silica nanocapsules (NCs) stable over several months were synthesized. This was achieved by exploiting a double emulsion in which the oil phase is constituted by a combination of oils presenting several volatilities. The decrease of oil droplet size by evaporation favored the deposition of a silica layer at the nanoscale interface. The release of the payload obtained by drying the capsules was investigated by fluorescence spectroscopy. Understanding the interactions between proteins and nanocapsules is a fundamental point for many biological applications. Nanocapsules were exposed to two model proteins, which were bovine serum albumin (BSA) and lysozyme (Ly). These proteins, presenting differences in charges and size, showed distinctive arrangements onto the nanocapsules. Moreover, we have studied changes in α-helix and ß-sheet content, which divulged the interactions between the proteins and the nanocapsules.

Oligocarbazole-based chromophores for efficient thin-film dye-sensitized solar cells.

Carb your enthusiasm: Carbazole-based sensitizers with high extinction coefficients are synthesized for application in dye-sensitized solar cells (DSCs). The dyes perform efficiently with both iodine and cobalt electrolytes, showing power conversion efficiencies of up to 5.8% on TiO2 films of 15 µm thickness, and retaining 90% of their efficiency in devices with thinner films.

Resolving the chemical nature of nanodesigned silica surface obtained via a bottom-up approach.

The covalent grafting on silica surfaces of a functional dendritic organosilane coupling agent inserted, in a long alkyl chain monolayer, is described. In this paper, we show that depending on experimental parameters, particularly the solvent, it is possible to obtain a nanodesigned surface via a bottom-up approach. Thus, we succeed in the formation of both homogeneous dense monolayer and a heterogeneous dense monolayer, the latter being characterized by a nanosized volcano-type pattern (4-6 nm of height, 100 nm of width, and around 3 volcanos/µm(2)) randomly distributed over the surface. The dendritic attribute of the grafted silylated coupling agent affords enough anchoring sites to immobilize covalently functional gold nanoparticles (GNPs), coated with amino PEG polymer to resolve the chemical nature of the surfaces and especially the volcano type nanopattern structures of the heterogeneous monolayer. Thus, the versatile surface chemistry developed herein is particularly challenging as the nanodesign is straightforward achieved in a bottom-up approach without any specific lithography device.