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31.
M. Portaccio M. Lepore B. Della Ventura O. Stoilova N. Manolova I. Rashkov D. G. Mita 《Journal of Sol-Gel Science and Technology》2009,50(3):437-448
A monolithic silica gel matrix with entrapped glucose oxidase was constructed as a bioactive element in an optical biosensor
for glucose determination. Physicochemical and biochemical characterizations of the catalytic matrix were performed, and the
intrinsic fluorescence of immobilised glucose oxidase (GOD) was investigated in the UV and visible range by performing steady
state and time course measurements. In all cases, the silica gel matrix proved to be a suitable support for optical biosensing
owing to its superior optical properties (e.g., high transmittance and reliable fluorescence and GOD absorption spectra after
immobilisation). From steady state measurements, calibration curves were obtained as a function of glucose concentration.
When time course measurements were performed, the silica gel support displayed a larger linear calibration range and higher
sensitivity than other immobilisation systems. In addition, a glucose optical biosensor was developed and characterised using
as catalytic element GOD immobilised on a gel disk bound to a bundle of optical fibres. 相似文献
32.
We study rigid string solutions rotating in AdS5×S5 background. For particular values of the parameters of the solutions we find multispin solutions corresponding to giant magnons and single spike strings. We present an analysis of the dispersion relations in the case of three spin solutions distributed only in S5 and the case of one spin in AdS5 and two spins in S5. The possible relation of these string solutions to gauge theory operators and spin chains are briefly discussed. 相似文献
33.
Hristo Penchev Dilyana Paneva Nevena Manolova Iliya Rashkov 《Macromolecular rapid communications》2008,29(8):677-681
A simple method to obtain novel nanofibers composed of polyelectrolyte complexes (PECs) has been proposed. It consists of the electrospinning of a mixed homogeneous solution of polyelectrolyte partners, and the formation of PEC during the electrospinning. This was achieved by careful choice of the composition of the spinning solutions. Chitosan was the polycationic partner, with either a weak polyacid [poly(acrylic acid), PAA] as a counterpart or a strong one [poly(2‐acrylamido‐2‐methylpropanesulfonic acid), PAMPS]. The fibrous mats were composed of nanofibers with mean diameters of ca. 100 nm. They retained their integrity over the pH range which is typical of the corresponding PEC.
34.
Iliya B. Rashkov Ivan Gitsov Ivan M. Panayotov 《Journal of polymer science. Part A, Polymer chemistry》1983,21(4):937-941
The structural changes in the potassium graphitide KC24 in its interaction with ?-caprolactone, γ-butyrolactone and pivalolactone are examined by profilometric measurement and electron scanning microscopy. The interaction of KC24 with a nonpolymerizable lactone-γ-butyrolactone proceeds without delamination of the graphitide. The polymerization of ?-caprolactone and pivalactone in the interlayer spaces of KC24 leads to destruction of the initiators structure. An increase in the temperature and monomer concentration enhances the delamination of the graphitide. 相似文献
35.
36.
Rosica Mincheva François Bougard Dilyana Paneva Magali Vachaudez Charles‐André Fustin Jean‐François Gohy Nevena Manolova Iliya Rashkov Philippe Dubois 《Journal of polymer science. Part A, Polymer chemistry》2009,47(8):2105-2117
For the first time, the polyelectrolyte complex (PEC) formation tool was used for preparation of core‐shell nanoparticles form the natural polyampholyte N‐carboxyethylchitosan (CECh) and weak polycationic (protonated) polyoxyethylene‐b‐poly[2‐(dimethyl‐amino)ethyl methacrylate] (POE‐b‐PDMAEMA) diblock copolymers. The performed dynamic light scattering analyses revealed that nanoparticles with a PEC core and a POE shell could be formed at mixing ratio between the oppositely charged groups equal to 1/1 depending on CECh molar mass, polymerization degree of PDMAEMA block and ionic strength. The results were confirmed by the performed AFM and cryo‐TEM analyses. When high molar mass CECh was used, core‐shell nanoparticles were obtained with the diblock copolymer of the shortest PDMAEMA block at ionic strength (I) of 0.01. At ionic strength value close to the physiological one (I = 0.1) secondary aggregation occurred. Spherical nanoparticles at I = 0.1 were obtained upon lowering the CECh molar mass. Depending on the polymer partners and medium parameters the size of the obtained particles varied from 60 to 600 nm. The X‐ray photoelectron spectra evidenced the hydrophilic POE‐block shell—coacervate CECh/PDMAEMA‐block core structure. The nanoparticles are stable in a rather narrow pH range around 7.0, thus revealing the high pH‐sensitivity of the obtained core‐shell particles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2105–2117, 2009 相似文献
37.
Laetitia Mespouille Olivier Coulembier Dilyana Paneva Philippe Degée Iliya Rashkov Philippe Dubois 《Journal of polymer science. Part A, Polymer chemistry》2008,46(15):4997-5013
Well‐defined adaptative and amphiphilic polymer conetworks based on hydrophilic poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PDMAEMA) and hydrophobic poly(ε‐caprolactone) (PCL) have been prepared by combination of ATRP, ROP, and “Click chemistry.” Telechelic α,ω‐alkyne terminated PCL crosslinker was obtained by ring‐opening polymerization (ROP) of CL in THF at 80 °C initiated by 1,4‐butanediol and catalyzed by tin(II) bis 2‐ethyl hexanoate (Sn(Oct)2), followed by the quantitative esterification of hydroxyl end‐groups by activated 4‐pentynoic acid. In parallel, an azido‐containing PDMAEMA‐based copolymer was obtained in a three‐step strategy involving primarily the copolymerization of DMAEMA with newly synthesized 2‐(2‐azidoethoxy)ethyl methacrylate (AEEMA) monomer. The latter was obtained by nucleophilic substitution of chloride atom from 2‐(2‐chloroethoxy)ethanol by an azide group followed by the esterification reaction of the hydroxyl group with methacrylic anhydride. The copolymerization was carried out in an equivolumic mixture of H2O and isopropanol at r.t. and initiated by a ω‐bromoisobutyryl oligo PEO macroinitiator in the presence of various ligated copper(I)‐based catalysts. In a last step, both polymer precursors were chemically linked by the Huisgen‐1,3‐dipolar cycloaddition in anhydrous THF at r.t. using CuBr complexed by 2,2′‐bipyridine ligand as catalyst. Final material was characterized by the means of DSC and SEM, both attesting of a homogeneous distribution of the PCL crosslinkers and a highly porous structure in this new amphiphilic model conetworks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4997–5013, 2008 相似文献
38.
Continuous defect-free nanofibers containing chitosan (Ch) or quaternized chitosan (QCh) were successfully prepared by one-step electrospinning of Ch or QCh solutions mixed with poly[(L-lactide)-co-(D,L-lactide)] in common solvent. XPS revealed the surface chemical composition of the bicomponent electrospun mats. Crosslinked Ch- and QCh-containing nanofibers exhibited higher kill rates against bacteria S. aureus and E. coli than the corresponding solvent-cast films. SEM observations showed that hybrid mats were very effective in suppressing the adhesion of pathogenic bacteria S. aureus. The hybrid nanofibers are promising for wound-healing applications. 相似文献
39.
Milena Ignatova Zhanina Petkova Nevena Manolova Nadya Markova Iliya Rashkov 《Macromolecular bioscience》2012,12(1):104-115
In order to impart antibacterial properties to microfibrous electrospun materials from styrene/maleic anhydride copolymers, quaternized chitosan derivatives (QCh) containing alkyl substituents of different chain lengths are covalently attached to the mats. A complete inhibition of the growth of bacteria, S. aureus (Gram‐positive) and E. coli (Gram‐negative), for a contact time of 30–120 min or a decrease of the bacterial titer by 2–3 log units is observed depending on the quaternization degree, the chain length of the alkyl substituent, and the molar mass of QCh. The modified mats are also effective in suppressing the adhesion of pathogenic S. aureus bacteria.
40.
Rosica Mincheva François Bougard Dilyana Paneva Magali Vachaudez Nevena Manolova Philippe Dubois Iliya Rashkov 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6712-6721
For the first time the possibility to obtain nanostructures by self‐assembly of chitosan polyampholytic derivative was demonstrated. The self‐assembly of N‐carboxyethylchitosan (CECh) took place only near its isoelectric point (pH 5.0–5.6). Out of the pH range 5.0–5.6, CECh aqueous solutions behaved as real solutions. Dynamic light scattering and atomic force microscopy analyses revealed that spherically shaped or rod/worm‐like nanosized assemblies were formed depending on the polymer molar mass, pH value, and polymer concentration. CECh of two different molar masses was studied in concentrations ranging from 0.01 to 0.1 mg/mL. The structures from CECh of weight‐average molar mass (Mw ) 4.5 × 103 g/mol were spherical regardless the pH and polymer concentration. In contrast, CECh of high molar mass (HMMCECh, Mw = 6.7 × 105 g/mol) formed self‐assemblies with spherical shape only at pH 5.0 and 5.6. At pH 5.2 spherical nanoparticles were obtained only at polymer concentration 0.01 mg/mL. The mean hydrodynamic diameter (Dh) of the obtained nanoparticles was in the range from 30 to 980 nm. On increasing the concentration, aggregation of the nanoparticles appeared, and at HMMCECh concentration 0.1 mg/mL, rod/worm‐like structures were obtained. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6712–6721, 2008 相似文献