ABSTRACT
We report a method for the preparation of ordered patterns of Pd species on a substrate based on the use of polystyrene-block-poly(ethylene oxide) copolymer (PS-b-PEO) templates and selective inclusion of palladium (Pd) species in the PEO domains. PS-b-PEO samples of different total molecular masses self-assemble in a cylindrical microphase-separated morphology, in which vertically aligned PEO cylinders, with different diameters depending on the molecular mass, are organized in a hexagonal array of different lateral spacings. The cylindrical nanostructure is maintained after the selective inclusion of Pd species (Pd acetate and Pd nanoparticles (NPs) after reduction of Pd ions of the salt) in the PEO cylinders so that the characteristic sizes (diameters and lateral spacings) of the included Pd species are tuned by the characteristic sizes of the block copolymer (BCP) template, which are regulated by molecular mass. Treatment of nanocomposites at elevated temperatures in air removes the polymer matrix and leads to the formation of arrays of palladium oxide (PdO) NPs covering a solid support. The patterns of PdO NPs are characterized by different particle diameters and gap distances, mirroring the patterns and characteristic nanodimensions of the parent BCPs used as templates.
ABSTRACT
Chitosan and gelatin are biodegradable and biocompatible polymers which may be used in the preparation of 3D scaffolds with applications in biomedicine. Chitosan/gelatin scaffolds crosslinked with glutaraldehyde were prepared by ice segregation induced self-assembly (ISISA); a unidirectional freezing at -196°C followed freeze-drying to produce macroporous materials with a well-patterned structure. This process may be included within the green chemistry by the preparation of the porous structures without using organic solvents, moreover is a versatile, non-difficult and cheap process. The scaffolds prepared by ISISA were characterized by scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, and their stability was evaluated by degree swelling and degradation tests. The scaffolds present properties as high porosity, high degree swelling and good stability which make them suitable of applications as biomaterials.
Subject(s)
Chitosan/chemistry , Gelatin/chemistry , Hydrogels/chemical synthesis , Tissue Scaffolds/chemistry , Biocatalysis , Cross-Linking Reagents/chemistry , Freezing , Green Chemistry Technology , Hydrogels/chemistry , Hydrolysis , Hydrophobic and Hydrophilic Interactions , Muramidase/metabolism , PorosityABSTRACT
The GB virus C/hepatitis G virus (GBV C/HGV) is a Flaviviridae member that despite its non pathogenicity, has become of great interest given that it could inhibit the replication of the human immunodeficiency virus (HIV). Therefore, a better knowledge of the virus peptides involved in the cellular membrane fusion mechanism has become our aim. The selected peptide, named E2(347-363), corresponds to the GBV-C/HGV E2 protein and has been synthesized in order to study its interaction with in vitro membrane models. Two phospholipids, varying the charge and the unsaturations of the hydrocarbon chain have been chosen: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (DOPG). For our porpoise, we have used the Langmuir monolayer technique and Brewster angle microscopy (BAM) to gain deeper insight into the peptide/lipid interactions. The results obtained allow us to argue in favour of considering E2(347-363) a success candidate for developing further experiments in order to determine its potential role in the GBV C/HGV virus/cell membrane fusion process.
Subject(s)
1,2-Dipalmitoylphosphatidylcholine/metabolism , Membranes, Artificial , Peptide Fragments/metabolism , Phosphatidylglycerols/metabolism , Viral Envelope Proteins/metabolism , GB virus C , Models, Molecular , Pressure , Surface Properties , Viral Envelope Proteins/chemical synthesisABSTRACT
The 3D phase formation was monitored in relaxation experiments of the collapsed Langmuir monolayers of selected partially fluorinated tetracosanes, that is, F6H18, F8H16, and F10H14. To carry out these experiments, the classical method of surface manometry, such as pi-A isotherms registration and the molecular area-time dependencies, under quasi-static monitoring conditions were applied. The evolution of 3D structures at the water/air interface was observed with Brewster angle microscopy (BAM). The obtained data were interpreted according to the nucleation-growth-collision theory model. It occurred that, even though the investigated chemicals are not classical surfactants and do not possess any polar headgroup, their evolution from a 2D monolayer to 3D structures can be successfully modeled with the above-mentioned theory. The influence of the subphase temperature on the nucleation process is also discussed.
