Mass transport in low Tg azo-polymers: Effect on the surface relief grating induction and stability of additional side chain groups able to generate physical interactions

International audienceThe nanostructuration ability of low glass transition temperature (Tg) azo-polysiloxanes films is investigated at working temperatures close or higher than the film Tg. The behavior of materials incorporating additional side chain nitrobenzene or naphthalene groups and as a result presenting different Tg is compared in terms of the surface modulation dynamics and stability of the induced topographic modifications.This comparison is carried out under light exposure and in dark environment. We demonstrate the ability to optically generate surface modulations on these materials even at operating temperatures corresponding to the film Tg. Along with a modification of the opto-mechanic properties correlated with the materials chemical structure, a collapse of the surface structures occurring with different dynamics in materials of similar Tg is highlighted. These observations suggest the existence of an additional mechanism rather than a purely thermal redistribution of the polymer chains in the films

Azo-polymers modified with nucleobases and their interactions with DNA molecules

The photo-fluidization process which is specific for azo-materials opens a new perspective for their use in the field of molecules nano manipulation at the surface of the azo polymer films. This is possible considering that in the case of the UV irradiation from a polarized laser source the azo material has an unidirectional flow. Here, we investigated the structuring phenomena occurring on the surface of the azo-polysiloxanes films modified with nucleobases, upon UV irradiation. Measurements of topography and adhesive forces between polymeric substrates and a hydrophilic probe have been done by atomic force microscopy (AFM). The response of the material upon irradiation has been investigated also by using UV-VIS spectroscopy. This method allowed us to draw the photo-isomerization and relaxation curves. Also, preliminary tests were conducted to determine the capacity of the film surface to immobilize DNA molecules

Dynamic constitutional frameworks (DCFs) as nanovectors for cellular delivery of DNA

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Eco-Friendly Synthesis and Comparative In Vitro Biological Evaluation of Silver Nanoparticles Using <i>Tagetes erecta</i> Flower Extracts

The present study reports an eco-friendly synthesis method of silver nanoparticles (AgNPs) using two different extracts (aqueous and ethanolic) of Tagetes erecta flowers. When exposed to different biocompounds found in the plant, silver ions are reduced, thus, resulting in the green synthesis of nanoparticles. After performing the optimization of synthesis, the obtained AgNPs were characterized using various techniques. The UV–Vis spectrum of the synthesized nanoparticles showed maximum peaks at 410 and 420 nm. TEM analysis revealed that the particles were spherical with a size ranging from 10 to 15 nm, and EDX analysis confirmed the presence of silver metal. The average diameter value obtained through DLS analysis for the two types of AgNPs (obtained using aqueous and ethanolic extracts) was 104 and 123 nm. The Zeta potentials of the samples were −27.74 mV and −26.46 mV, respectively, which indicates the stability of the colloidal solution. The antioxidant and antimicrobial activities assays showed that nanoparticles obtained using the aqueous extract presented enhanced antioxidant activity compared to the corresponding extract, with both types of AgNPs exhibiting improved antifungal properties compared to the initial extracts

New Hydrogels Nanocomposites Based on Chitosan, 2-Formylphenylboronic Acid, and ZnO Nanoparticles as Promising Disinfectants for Duodenoscopes Reprocessing

New hydrogels nanocomposites, based on iminoboronate hydrogels and ZnO nanoparticles (ZnO–NPs), were obtained and characterised in order to develop a new class of disinfectants able to fight the nosocomial infections produced by duodenoscopes investigation procedures. The formation of the imine linkages between chitosan and the aldehyde was demonstrated using NMR and FTIR spectroscopy, while the supramolecular architecture of the developed systems was evaluated via wide-angle X-ray diffraction and polarised optical microscopy. The morphological characterisation of the systems via scanning electron microscopy revealed the highly porous structure of the materials, in which no ZnO agglomeration could be observed, indicating the very fine and homogenous encapsulation of the nanoparticles into the hydrogels. The newly synthetised hydrogels nanocomposites was proven to have synergistic antimicrobial properties, being very efficient as disinfectants against reference strains as: Enterococcus faecalis, Klebsiella pneumoniae, and Candida albicans

Azobenzene based polymers as photoactive supports and micellar structures for applications in biology

International audienceAzo-polymers have been investigated for the large structural modifications occurring under light excitation. Photo induced isomerizations of the azobenzene molecular units can provide cooperative forces able to affect self-assembling processes in the liquid state or leading to an efficient mass transport in the solid state, which results in large deformations of film surfaces. We introduce here our studies on azopolymers based on a polysiloxane matrix bearing specific chemical functions, whose composition can be finely tuned for applications in the biological field. Depending on their chemical structure, these materials are able to form photoactive surfaces with adjustable topographic properties or photosensitive micellar architectures in aqueous solvents. In the first case, the ability to control the surface shape at the optical wavelength scale aims to provide photoactive cell growth supports with tuneable properties, for the investigation of the environment influence on cell development. The optical properties of the materials are presented, as well as the preliminary studies showing the materials potential to modify the cell response to the surface. The stability of the films surface in contact with biological media and the implications on the cell behavior are also addressed. The second property involving formation of micellar structures is demonstrated by showing the ability of the materials to encapsulate and provide controlled release of small molecules pointing to their potential use in drug delivery applications

In Vitro and In Vivo Antioxidant Activity of the New Magnetic-Cerium Oxide Nanoconjugates

Background. Cerium oxide nanoparticles present the mimetic activity of superoxide dismutase, being able to inactivate the excess of reactive oxygen species (ROS) correlated with a large number of pathologies, such as stents restenosis and the occurrence of genetic mutations that can cause cancer. This study presents the synthesis and biological characterisation of nanoconjugates based on nanoparticles of iron oxide interconnected with cerium oxide conjugates. Methods. The synthesis of magnetite-nanoceria nanoconjugates has been done in several stages, where the key to the process is the coating of nanoparticles with polyethyleneimine and its chemical activation-reticulation with glutaraldehyde. The nanoconjugates are characterised by several techniques, and the antioxidant activity was evaluated in vitro and in vivo. Results. Iron oxide nanoparticles interconnected with cerium oxide nanoparticles were obtained, having an average diameter of 8 nm. Nanoconjugates prove to possess superparamagnetic properties and the saturation magnetisation varies with the addition of diamagnetic components in the system, remaining within the limits of biomedical applications. In vitro free-radical scavenging properties of nanoceria are improved after the coating of nanoparticles with polyethylenimine and conjugation with magnetite nanoparticles. In vivo studies reveal increased antioxidant activity in all organs and fluids collected from mice, which demonstrates the ability of the nanoconjugates to reduce oxidative stress. Conclusion. Nanoconjugates possess magnetic properties, being able to scavenge free radicals, reducing the oxidative stress. The combination of the two properties mentioned above makes them excellent candidates for theranostic applications