Search results for "Biomaterials"
showing 10 items of 1265 documents
A DC and small signal AC model for organic thin film transistors including contact effects and non quasi static regime
2017
Abstract We present a compact model for the DC and small signal AC analysis of Organic Thin Film Transistors (OTFTs). The DC part of the model assumes that the electrical current injected in the OTFT is limited by the presence of a metal/organic semiconductor junction that, at source, acts as a reverse biased Schottky junction. By including this junction, modeled as a reverse biased gated diode at source, the DC model is able to reproduce the scaling of the electrical characteristics even for short channel devices. The small signal AC part of the model uses a transmission line approach in order to compute the impedances of the channel and parasitic regions of the device. The overlap capacit…
Auto-assembly of nanometer thick, water soluble layers of plasmid DNA complexed with diamines and basic amino acids on graphite: Greatest DNA protect…
2017
Abstract We have investigated the ability of diamines as well as basic amino acids to condense DNA onto highly ordered pyrolytic graphite with minimum damage after re-dissolution in water. Based on a bibliographic survey we briefly summarize DNA binding properties with diamines as compared to basic amino acids. Thus, solutions of DNA complexed with these linkers were drop-cast in order to deposit ultra-thin layers on the surface of HOPG in the absence or presence of Tris buffer. Atomic Force Microscopy analyses showed that, at a fixed ligand-DNA mixing ratio of 16, the mean thickness of the layers can be statistically predicted to lie in the range 0–50 nm with a maximum standard deviation ±…
Tuning the pH-Switch of Supramolecular Polymer Carriers for siRNA to Physiologically Relevant pH
2017
The preparation of histidine enriched dendritic peptide amphiphiles and their self-assembly into multicomponent pH-switchable supramolecular polymers is reported. Alternating histidine and phenylalanine peptide synthons allow the assembly/disassembly to be adjusted in a physiologically relevant range of pH 5.3-6.0. Coassembly of monomers equipped with dendritic tetraethylene glycol chains with monomers bearing peripheral primary amine groups leads to nanorods with a tunable cationic surface charge density. These surface functional supramolecular polycations are able to reversibly bind short interfering RNA (siRNA). The nanorod-like supramolecular polymers, their complexation with siRNA, and…
A Polyphenylene Dendrimer Drug Transporter with Precisely Positioned Amphiphilic Surface Patches
2014
The design and synthesis of a polyphenylene dendrimer (PPD 3) with discrete binding sites for lipophilic guest molecules and characteristic surface patterns is presented. Its semi-rigidity in combination with a precise positioning of hydrophilic and hydrophobic groups at the periphery yields a refined architecture with lipophilic binding pockets that accommodate defined numbers of biologically relevant guest molecules such as fatty acids or the drug doxorubicin. The size, architecture, and surface textures allow to even penetrate brain endothelial cells that are a major component of the extremely tight blood-brain barrier. In addition, low to no toxicity is observed in in vivo studies using…
Luting of ceramic crowns with a self-adhesive cement: Effect of contamination on marginal adaptation and fracture strength
2012
Objectives: This study evaluated the percentages of continuous margins (%CM) and fracture strength (FS) of crowns made out from blocs of leucite-reinforced ceramic (IPS Empress CAD) and luted with a representative self-adhesive cement (RelyX Unicem) under four contaminating agents: saliva, water, blood, a haemostatic solution containing aluminium chloride (pH= 0.8) and a control group with no contamination. Study Design: %CM at both tooth-cement (TC) and cement-crown (CC) interfaces were determined before and after a fatigue test consisting of 600’000 chewing loads and 1’500 temperature cycles changing from 5º C to 50º C. Load to fracture was recorded on fatigued specimens. Kruskal-Wallis t…
Adsorption mechanism of arsenate by zirconyl-functionalized activated carbon
2007
Arsenate [As(V)] and arsenite [As(III)] sorption at the solid-water interface of activated carbon impregnated with zirconyl nitrate (Zr-AC) was investigated using X-ray absorption spectroscopy (XAS) and surface complexation modeling. The XAS data at the Zr K-edge suggest that the structure of the zirconyl nitrate coating is built from chains of edge-sharing ZrO8 trigonal dodecahedra bound to each other through two double hydroxyl bridges. The 8-fold coordination of each Zr atom is completed by four O atoms, which share a bit less than the two theoretically possible bidentate nitrate groups. On impregnation, two of the O atoms may lose their nitrate group and be transformed to hydroxyl group…
Tuning the Structure of Galacturonate Hydrogels: External Gelation by Ca, Zn, or Fe Cationic Cross-Linkers
2019
International audience; We show here how the nature of various divalent cations M2+ (Ca2+, Zn2+, or Fe2+) influences the structure and mechanical properties of ionotropic polygalacturonate (polyGal) hydrogels designed by the diffusion of cations along one direction (external gelation). All hydrogels exhibit strong gradients of polyGal and cation concentrations, which are similar for all studied cations with a constant ratio R = [M2+]/[Gal] equal to 0.25, showing that every M2+ cation interacts with four galacturonate (Gal) units all along the gels. The regions of the hydrogels formed in the early stages of the gelation process are also similar for all cations and are homogeneous, with the s…
Monitoring of the action of drugs in melanoma cells by dynamic laser speckle
2014
Abstract. This work presents the development of a protocol based on the dynamic laser speckle designed tomonitor the reaction of cancer cells of line MEL-RC08 to the application of the drug Colcemid in two differentconcentrations: 0.2 and 0.4 μg∕mL. The protocol was designed using the forward scattering approach with anHe-Ne laser of 632.8 nm illuminating the samples, a control, and two variations of Colcemid, being monitoredalong 8 h. The data were analyzed numerically in the time and in the frequency domain, and the results pre-sented the ability of the technique to monitor the action of the drug, particularly Colcemid (0.4 μg∕mL). © 2014Society of Photo-Optical Instrumentation Engineers …
Towards noncontact skin melanoma selection by multispectral imaging analysis
2011
A clinical trial comprising 334 pigmented and vascular lesions has been performed in three Riga clinics by means of multispectral imaging analysis. The imaging system Nuance 2.4 (CRi) and self-developed software for mapping of the main skin chromophores were used. Spe- cific features were observed and analyzed for malignant skin melanomas: notably higher absorbance (especially as the difference of optical density relative to the healthy skin), uneven chromophore distribution over the lesion area, and the possibility to select the "melanoma areas" in the correla- tion graphs of chromophores. The obtained results indicate clinical potential of this technology for noncontact selec- tion of mel…
Semiautomated quantification of the fibrous tissue response to complex three‐dimensional filamentous scaffolds using digital image analysis
2021
Fibrosis represents a relevant response to the implantation of biomaterials, which occurs not only at the tissue-material interface (fibrotic encapsulation) but also within the void fraction of complex three-dimensional (3D) biomaterial constructions (fibrotic ingrowth). Usual evaluation of the biocompatibility mostly depicts fibrosis at the interface of the biomaterial using semiquantitative scores. Here, the relations between encapsulation and infiltrating fibrotic growth are poorly represented. Virtual pathology and digital image analysis provide new strategies to assess fibrosis in a more differentiated way. In this study, we adopted a method previously used to quantify fibrosis in visc…