Search results for "Bioengineering"

Toxicity test of a dental commercial composite

2015

BACKGROUND: International rules must be followed for testing biosecurity in dental materials. A new brand of restorative material appeared in the market and regulations indicated that it should be tested for toxicity. OBJECTIVES: The aim of this study was to determine the 90-day sub chronic toxicity of one triethylene glycol dimethacrylate containing composite (MEDENTAL Light-Cure Composite™) orally administered to rats according to Organization for Economic Co-Operation and Development no. 48 guidelines and the requirements specified in the ISO 10993-11. MATERIAL AND METHODS: Wistar rats ate the polymerized composite during 90 days and were observed to determine changes in their behavior, …

Noninvasive cardiovascular imaging for evaluating subclinical target organ damage in hypertensive patients: a consensus article from the European Ass…

2017

International audience; : Arterial hypertension accounts for the largest amount of attributable cardiovascular mortality worldwide, and risk stratification in hypertensive patients is of crucial importance to manage treatment and prevent adverse events. Asymptomatic involvement of different organs in patients affected by hypertension represents an independent determinant of cardiovascular risk, and the identification of target organ damage is recommended to further reclassify patients' risk. Noninvasive cardiovascular imaging is progressively being used and continues to provide new technological opportunities to target organ damage evaluation at early stage. The aim of this article is to pr…

Influence of some physicochemical factors on the viscosity of aqueous levan solutions ofZymomonas mobilis

1998

Zymomonas mobilis strain 113 “S” produces levan – an extracellular, viscous, biologically active, non-toxic fructose polymer with a unique structure and extraordinary properties. This polysaccharide was isolated at two different degrees of purity by alcohol precipitation from aqueous solutions and was characterized with respect to some rheological properties and stability of viscous solutions. The effects of temperature, pH and salt concentration on the viscosity of 1–3% levan solutions were examined. The viscosity of levan solutions was found to be quite stable and reversible at room temperature over a wide range of pH from 4 to 11. The viscosity was slightly affected by increased salt con…

Polyaspartamide-graft- Polymethacrylate Nanoparticles for Doxorubicin Delivery

2011

A new PHEA-IB-PMANa + copolymer has been synthesized and its pH-induced self-assembly has been investigated in an aqueous medium. PHEA-IB-PMANa + formed nanoparticles with diameters from 25 to 50 nm upon protonation of the carboxylic acid moieties dislocated along the grafted polymethacrylate sodium salt side chains. The physico-chemical characterization of the nanoparticles was performed using light scattering, zeta-potential measurements, SEM, and AFM. Doxorubicin-loaded nanoparticles were prepared and drug release profiles were evaluated under conditions mimicking physiological media. A biological characterization was carried out by testing the cytotoxicity on Caco-2 cells, and cellular …

Thermal diffusion of dextran in aqueous solutions in the absence and the presence of urea.

2006

The Ludwig-Soret effect was studied for aqueous solutions of dextran in the temperature range 15T55 degrees C taking into account the effect of the addition of urea. In the absence of urea, the Soret coefficient S(T) changes sign; it is positive for T45.0 degrees C but negative for T45.0 degrees C. The positive sign of S(T) means that the dextran molecules migrate toward the cold side of the fluid; this behavior is typical for polymer solutions, whereas a negative sign indicates the macromolecules move toward the hot side. The addition of urea to the aqueous solution of dextran rises S(T) and reduces the inversion temperature. For 2 M urea the change in the sign of S(T) is observed at T = 2…

Stabilization of anti-leukemic enzyme l-asparaginase by immobilization on polysaccharide levan

2001

Abstract Biologically active fructose polymer levan from Zymomonas mobilis of different molecular mass (75 and 2000 kDa) was covalently coupled to anti-leukemic enzyme Erwinia carotovora l -asparaginase. The method used for the immobilization of the enzyme involved periodate oxidation of the polysaccharide, followed by reductive alkylation. A gentle periodate oxidation of levan (oxidation degree ≤24%) resulted in the highest residual enzyme activity (≥55%). The K m(app.) of glycoconjugates was higher than the K m of native l -asparaginase. The conjugation of l -asparaginase widened the optimum pH range of the enzyme. The electrophoretic mobility in polyacrylamide gel of glycoconjugates obta…

Radioactive labeling of defined HPMA-based polymeric structures using [18F]FETos for in vivo imaging by positron emission tomography.

2009

During the last decades polymer-based nanomedicine has turned out to be a promising tool in modern pharmaceutics. The following article describes the synthesis of well-defined random and block copolymers by RAFT polymerization with potential medical application. The polymers have been labeled with the positron-emitting nuclide fluorine-18. The polymeric structures are based on the biocompatible N-(2-hydroxypropyl)-methacrylamide (HPMA). To achieve these structures, functional reactive ester polymers with a molecular weight within the range of 25,000-110,000 g/mol were aminolyzed by 2-hydroxypropylamine and tyramine (3%) to form (18)F-labelable HPMA-polymer precursors. The labeling procedure…

l-Valine biosynthesis during batch and fed-batch cultivations of Corynebacterium glutamicum: Relationship between changes in bacterial growth rate an…

2007

Abstract A transition in the bacterial growth rate to below maximum was found to be an optimum parameter of cellular physiology to increase the activity of acetohydroxy acid synthase, a regulatory enzyme in l -valine synthesis, and amino acid overproduction by Corynebacterium glutamicum ATCC 13032 recombinants under batch and fed-batch cultivation conditions. An increase in l -valine synthesis under transient situations when cellular growth rate was downregulated was correlated to a decrease in the activity of aconitase, a key enzyme in the tricarboxylic acid cycle (TCA) of C. glutamicum , and, in contrast, to an increase in the activity of glucose-6-phosphate dehydrogenase, a key enzyme in…

Cell Adhesive and Antifouling Polyvinyl Chloride Surfaces Via Wet Chemical Modification

2012

Polyvinyl chloride (PVC) is one of the most frequently used polymers for the manufacturing of medical devices. Limitations for its usage are based upon unfavorable surface properties of the polymer including its hydrophobicity and lack of functionalities in order to increase its versatility. To address this issue, wet chemical modification of PVC was performed through surface amination using the bifunctional compound ethylene diamine. The reaction was conducted in order to achieve maximum surface amination while leaving the bulk material unaffected. The initial activation step was characterized by means of various methods including contact angle measurements, colorimetric amine quantificati…

2003

Resting cells of the yeast Rhodosporidium toruloides (UOFS Y-0471) were immobilised in calcium alginate beads for the enantioselective kinetic resolution of racemic-1,2-epoxyoctane. The initial activity exhibited by immobilised cells was almost 50% lower than that of the free counterpart but was extremely stable when compared to the free cells. The concentration of the immobilised biomass had no effect on apparent enzyme activity but did lead to a decrease in single cell activity. An increase in both the alginate and CaCl2 concentrations used for bead preparation led to a decrease in enzyme stability. An increase in the alginate concentration led to an increase in bead diameter. The stoichi…