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1.
Carbohydr Polym ; 116: 261-6, 2015 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-25458299

RESUMO

A simple and highly reproducible synthesis of amorphous bismuth nanoparticles incorporated into a polysaccharide matrix using a photoreduction process is presented. As precursor for the generation of the Bi nanoparticles, organosoluble triphenylbismuth is used. The precursor is dissolved in toluene and mixed with a hydrophobic organosoluble polysaccharide, namely trimethylsilyl cellulose (TMSC) with high DSSi. The solution is subjected to UV exposure, which induces the homolytic cleavage of the bismuth-carbon bond in BiPh3 resulting in the formation of Bi(0) and phenyl radicals. The aggregation of the Bi atoms can be controlled in the TMSC matrix and yields nanoparticles of around 20 nm size as proven by TEM. The phenyl radicals undergo recombination to form small organic molecules like benzene and biphenyl, which can be removed from the nanocomposite after lyophilization and exposure to high vacuum. Finally, the TMSC matrix is converted to cellulose after exposure to HCl vapors, which remove the trimethylsilyl groups from the TMSC derivative. Although TMSC is converted to cellulose, the formed TMS-OH is not leaving the nanocomposite but reacts instead with surface oxide layer of the Bi nanoparticles to form silylated Bi nanoparticles as proven by TEM/EDX.


Assuntos
Bismuto/química , Celulose/química , Nanopartículas Metálicas/química , Nanocompostos/química , Compostos de Trimetilsilil/química , Interações Hidrofóbicas e Hidrofílicas , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Transmissão , Nanocompostos/ultraestrutura , Oxirredução
2.
Carbohydr Polym ; 117: 34-42, 2015 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-25498606

RESUMO

Simultaneous antibacterial and anticoagulant surfaces have been prepared by immobilization of engineered gold nanoparticles onto different kinds of surfaces. The gold nanoparticle core is surrounded by a hemocompatible, anticoagulant polysaccharide, 6-O chitosan sulfate, which serves as reduction and stabilizing agent for the generation of gold nanoparticles in a microwave mediated reaction. The particle suspension shows anticoagulant activity, which is investigated by aPTT and PT testing on citrated blood samples of three patients suffering from congenital or acquired bleeding disorders. The amount of nanoparticles deposited on the surfaces is quantified by a quartz crystal microbalance with dissipation unit. All gold containing surfaces exhibit excellent antimicrobial properties against the chosen model organism, Escherichia coli MG 1655 [R1-16]. Moreover, blood plasma coagulation times of the surfaces are increased after deposition of the engineered nanoparticles as demonstrated by QCM-D.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Anticoagulantes/química , Anticoagulantes/farmacologia , Ouro/química , Ouro/farmacologia , Nanopartículas Metálicas , Cápsulas , Celulose/química , Quitosana/química , Engenharia , Escherichia coli/efeitos dos fármacos , Humanos , Tempo de Tromboplastina Parcial , Tempo de Protrombina , Sulfatos/química , Propriedades de Superfície
3.
Chem Commun (Camb) ; 50(86): 13070-2, 2014 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-25225660

RESUMO

The anticoagulant activity of surfaces decorated with cellulose nanocrystals (CNCs) prepared via sulfuric acid hydrolysis, is explored. Such surfaces bear a high amount of negatively charged sulfate groups, which mimic the naturally occurring anticoagulant heparin in terms of charge density. It is demonstrated that CNC decorated surfaces significantly enhance the coagulation times of blood plasma and whole blood as proven by QCM-D and simple clotting tests.


Assuntos
Anticoagulantes/química , Celulose/química , Nanopartículas/química , Anticoagulantes/farmacologia , Coagulação Sanguínea/efeitos dos fármacos , Heparina/química , Heparina/farmacologia , Humanos , Hidrólise , Polietilenoimina/química , Ácidos Sulfúricos/química , Propriedades de Superfície
4.
Carbohydr Polym ; 94(1): 677-86, 2013 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-23544590

RESUMO

A green approach for the preparation of silver nanocomposites on viscose fibers using microwave and conventional heating is presented. Reduction of silver nitrate is induced by addition of 6-O chitosan sulfate (S-Chi) in aqueous media which provides steric protection and electrostatic stabilization to prevent agglomeration of the nanoparticles. The particles are formed in close spatial proximity to the fibers and adsorption of the particles via structural similarity takes place to create silver nanocomposites. All nanocomposites have been subjected to antimicrobial tests and high antimicrobial activity toward Escherichia coli bacteria has been determined. Further, the nanocomposites are characterized using different analytical techniques which reveal very similar results for both heating techniques. The only significant difference is observed concerning the shape of the nanoparticles on the viscose fibers which are slightly elongated for the microwave method in comparison to spheres observed by conventional heating. Therefore, detailed investigations on the formation of colloidal silver nanoparticles have been performed, comparing microwave dielectric and conventional heating at the exact same temperature and reaction times. These experiments resulted in nearly identical nanoparticle shape and size for both heating methods as demonstrated by dynamic light scattering, UV-vis spectroscopy and transmission electron microscopy. A wide range of parameters has been varied (temperature, AgNO3 to S-Chi ratio, reaction time, and stirring speed) to study the nanoparticle formation under microwave and conventional conditions. No evidence for the existence of so-called specific microwave effects was obtained.

5.
J Mater Chem B ; 1(15): 2022-2030, 2013 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-32260891

RESUMO

The rational design of silver nanoparticles encapsulated in an anticoagulant, hemocompatible polysaccharide, 6-O-chitosan sulfate, is presented. Three different approaches are described for the immobilization of these core shell particles on cellulosic surfaces. The mass of the immobilized particles is quantified using a quartz crystal microbalance with dissipation (QCM-D). The antimicrobial activity of the surfaces towards E. coli MG 1655 [R1-16] is investigated by live/dead assays using fluorescence staining. All surfaces treated with the designed nanoparticles exhibit excellent antimicrobial activity towards E. coli MG 1655 [R1-16]. Anticoagulant properties of blood plasma on the nanoparticle treated surfaces have been determined using QCM-D. In comparison with the unmodified substrates, the total coagulation time as well as the thrombin formation time and fibrin clotting time of surfaces modified with nanoparticles are significantly increased.

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