Search results for "bioengineering"

Reconstitution of a protein monolayer on thiolates functionalized gaas surface

2012

International audience; In the aim to realize an efficient resonant biosensor, gallium arsenide (GaAs) presents many advantages. In addition to its properties of transduction, GaAs is a crystal for which microfabrication processes were developed, conferring the possibility to miniaturize the device and integrate electronic circuit. Moreover, the biofunctionalization could be realized on the crystalline surface without layer deposition, constituting a real advantage to perform reusable sensor. The functionalization of GaAs surface was engaged in order to immobilize a protein monolayer on this substrate. Functionalization was done using a mixed self assembled monolayer of thiolate molecules. …

Complexes of an anionic poly(p-phenylene) polyelectrolyte and dioctadecylammonium bromide at the air–water interface

1999

Abstract By spreading dioctadecyldimethylammonium bromide on a subphase containing rigid rod-like anionic poly( p -phenylene) sulfonate, a complex monolayer is formed in situ at the air–water interface. Complexation results in an increase of the area per amphiphile molecule compared to the amphiphile on pure water. The change in structural order upon complexation and subsequent compression of the monolayer can be demonstrated employing UV/Vis spectroscopy: A red-shift of the polymer absorption band upon compression and a subsequent partial reversion of this shift after monolayer collapse can be observed. The peak shift is discussed to be a result of the electronic interaction of the π -syst…

Viscoelastic Behavior of an Epoxy Resin Modified with Recycled Waste Particles Analyzed through a Fractional Model

2021

It is well-known that the addition of randomly dispersed particles in polymers influences their linear viscoelastic behavior and dynamic mechanical properties. The aim of this study was to describe the viscoelastic behavior of an epoxy resin modified by waste glass and rubber particles using the linear fractional spring-pot model. Unlike complex classical exponential models, fractional models, being only two-parameter dependent, make it easier to characterize the viscoelastic behavior of materials. Isothermal relaxation and single frequency sweep temperature dynamic tests were carried out in a dynamic mechanical analyzer DMA150 by varying the content of the particles from 0 to 20% by weight…

Epoxy Resin/Carbon Black Composites Below the Percolation Threshold

2013

International audience; A set of epoxy resin composites filled with 0.25-2.0 wt.% of commercially available ENSACO carbon black (CB) of high and low surface area (CBH and CBL respectively) has been produced. The results of broadband dielectric spectroscopy of manufactured CB/epoxy below the percolation threshold in broad temperature (200 K to 450 K) and frequency (20 Hz to 1 MHz) ranges are reported. The dielectric properties of composites below the percolation threshold are mostly determined by alpha relaxation in pure polymer matrix. The glass transition temperature for CB/epoxy decreases in comparison with neat epoxy resin due to the extra free volume at the polymer-filler interface. At …

Behavior Modification of Nanostructured PbO2 Electrodes in Lead Acid Batteries Changing Electrolyte Concentration and Separator

2019

Currently, lead acid battery is extensively investigated owing to its prevalent use as a startinglighting and ignition device. An essential role for electrochemical reactions is played by the surface area available for conversion reactions and a possible approach is the use of nanostructured electrodes. In this work, lead dioxide nanostructured electrodes were tested in order to investigate the dependence of the charge and discharge behaviour on some parameters such as electrolyte concentration, and a new type of thin separator. In this last case, it is possible to reduce the size of the cell by using a very thin separator comparable to the nanostructured electrode thickness. Besides, a low…

Effect of cold drawing on mechanical properties of biodegradable fibers.

2016

Purpose Biodegradable polymers are currently gaining importance in several fields, because they allow mitigation of the impact on the environment related to disposal of traditional, nonbiodegradable polymers, as well as reducing the utilization of oil-based sources (when they also come from renewable resources). Fibers made of biodegradable polymers are of particular interest, though, it is not easy to obtain polymer fibers with suitable mechanical properties and to tailor these to the specific application. The main ways to tailor the mechanical properties of a given biodegradable polymer fiber are based on crystallinity and orientation control. However, crystallinity can only marginally be…

Modification of human platelet adhesion on biomaterial surfaces by protein preadsorption under static and flow conditions.

2004

Biomaterial-induced thrombosis remains one of the main complications of vascular implant devices. Preadsorbed proteins on the biomaterial/blood interface will modify the adhesion and activation of platelets (PTLs) during the initial contact-phase. Our results clearly show that PTL-adherence on biomaterials is influenced not only by protein preadsorption, but also by flow conditions. The covalent coating of TCPS and glass by phosphorylcholine (PC) induces a significant decrease of PTL adhesion but leads to a slight, but nevertheless significant activation of PTL, which was detected by the induction of P-selectin expression using FACS analysis. Methodologically, the visualization of PTL adhes…

Biocompatible micelles based on squalene portions linked to pegylated polyaspartamide as potential colloidal drug carriers

2011

SYNTHESIS AND CHARACTERIZATION OF POLYAMINOACIDIC POLYCATIONS FOR GENE DELIVERY

2005

The properties as non viral gene vector of a protein-like polymer, the alpha,beta-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) were exploited after its derivatization with 3-(carboxypropyl)trimethyl-ammonium chloride (CPTA) as molecule bearing a cationic group, in order to obtain stable polycations able to condense DNA. PHEA was firstly functionalized with aminic pendant groups by reaction with ethylenediamine (EDA) obtaining the alpha,beta-poly(N-2-hydroxyethyl)(2-aminoethylcarbamate)-d,l-aspartamide (PHEA-EDA) copolymer. We demonstrated that polymer functionalization degree is easily modulable by varying reaction conditions, so allowing to produce two PHEA-EDA derivatives at different mo…

Response of human endothelial cells to oxidative stress on Ti6Al4V alloy.

2007

Titanium and its alloys are amongst the most frequently used materials in bone and dental implantology. The good biocompatibility of titanium(-alloys) is attributed to the formation of a titanium oxide layer on the implant surface. However, implant failures do occur and this appears to be due to titanium corrosion. Thus, cells participating in the wound healing processes around an implanted material, among them endothelial cells, might be subjected to reactive oxygen species (ROS) formed by electrochemical processes during titanium corrosion. Therefore, we studied the response of endothelial cells grown on Ti6Al4V alloy to H(2)O(2) and compared this with the response of endothelial cells gr…