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991.
Costa D Valente AJ Miguel MG Queiroz J 《Langmuir : the ACS journal of surfaces and colloids》2011,27(22):13780-13789
In the last 5 years, we have gained further insight on the physical/chemical field of DNA gels. Our expertise on the gel swelling behavior, compaction of DNA by cationic entities, as lipids and surfactants, as well as on the assembly structures of these complexes allow us for the development of novel systems to be used in a variety of biomedical applications. In our previous reports, the physicochemical characterization has been well-established, and now one can evolve to the challenge of using DNA-based carriers in the biological area. Moreover, a new plasmid DNA (pDNA) hydrogel that is porous, is able to swell in the presence of additives, is biocompatible and, thus, is suitable to be used therapeutically was prepared. Here, the dual release of pDNA and solutes with pharmaceutical interest was the main challenge, and thus, we report on the photodisruption of plasmid DNA (pDNA) gels cross-linked with ethylene glycol diglycidyl ether (EGDE) as a strategy for this simultaneous release. The disruption over time, after the irradiation of the gel with ultraviolet light (400 nm), was characterized through the cumulative plasmid DNA release, the evolution in dry weight, the extent of swelling, and also the variations in the gel mesh size. The controlled release of different molecular weight solutes from plasmid DNA gels was investigated, and the influence of both the hydrogel degradation and cross-linker density on the release kinetics were addressed. While the release of lysozyme follows a Fickian process, the release of bovine serum albumin (BSA) and fluoresceinisothiocyanato-dextran (FITC-dextran) is characteristic of a Super Case II release phenomena. In addition, the size of the three solutes partially influences the release behavior; polymer chain mobility and the degree of swelling also play a role. To gain a fundamental understanding of drug release profile from pDNA matrices, in vitro release studies were evaluated using several anti-inflammatory drugs. The quantification of the release mechanism indicates a Super Case II release profile, which can be related with the gel swelling degree. A correlation between the drug release trend and the drug hydrophobicity can be found, with more hydrophobic drugs showing a slower release rate. In brief, this new pDNA gel system is biocompatible, is degradable upon light irradiation, and allows for the controlled and sustained release of plasmid DNA and incorporated solutes. This codelivery of pDNA and drugs would find relevant clinical uses due to the possibility of gene and nongene therapy combination in order to improve the therapeutic efficiency. 相似文献
992.
Maneval JE Bernin D Fabich HT Seymour JD Codd SL 《Magnetic resonance in chemistry : MRC》2011,49(10):627-640
The formation of heterogeneous structures in biopolymer gels is of current interest for biomedical applications and is of fundamental interest to understanding the molecular level origins of structures generated from disordered solutions by reactions. The cation-mediated physical gelation of alginate by calcium and copper is analyzed using magnetic resonance measurements of spatially resolved molecular dynamics during gel front propagation. Relaxation time and pulse-field gradient methods are applied to determine the impact of ion front motion on molecular translational dynamics. The formation of capillaries in alginate copper gels is correlated to changes in translational dynamics. 相似文献
993.
Rufino RD Luna JM Sarubbo LA Rodrigues LR Teixeira JA Campos-Takaki GM 《Colloids and surfaces. B, Biointerfaces》2011,84(1):1-5
In the last years, researches developed with biosurfactants for application in the medical area have been revealing the promising biological activities of these biomolecules. In this work the antimicrobial and anti-adhesive properties of a biosurfactant Rufisan isolated from the yeast Candida lipolytica UCP 0988, growth in a medium supplemented with ground nut refinery residue was determined against several microorganisms. The biosurfactant was able to reduce the water surface tension from 70 to 25.3 mN/m and showed a critical micelle concentration (CMC) of 0.03%. The biosurfactant was isolated after 72 h of fermentation and was tested in concentrations varying from 0.75 to 12 mg/l. The highest antimicrobial activities were observed against Streptococcus agalactiae, Streptococcus mutans, Streptococcus mutans NS, Streptococcus mutans HG, Streptococcus sanguis 12, Streptococcus oralis J22 at a concentration superior to the biosurfactant critical micelle concentration. Moreover, the biosurfactant showed anti-adhesive activity against most of the microorganisms tested. As far as we know, this is the first compilation of data on antimicrobial and anti-adhesive activities of a biosurfactant obtained from a Candida strain against such a broad group of microorganisms. The results obtained in this work showed that the biosurfactant from C. lipolytica is a potential antimicrobial and/or anti-adhesive agent for several biomedical applications. 相似文献
994.
995.
Débora A. Soares Maia J. C. Alexandre de Oliveira Juan Pablo Toso Karim Sapag Raul H. López Diana C. S. Azevedo Célio L. CavalcanteJr. Giorgio Zgrablich 《Adsorption》2011,17(5):853-861
Controlled series of microporous carbons were prepared through chemical activation with phosphoric acid from peach stones
as the precursor material, corresponding to different preparation conditions. Adsorption isotherms of N2 at 77 K and of CO2 at 273 K were measured to be used in the characterization of the samples. The recently proposed mixed-geometry model (MGM),
which assumes that the activated carbon is better represented by a mixture of slit and triangular geometry pores, is used
to obtain the PSDs of the samples, on the basis of Grand Canonical Monte Carlo (GCMC) simulated ideal isotherms, both for
N2 at 77 K and of CO2 at 273 K. Our results emerging from the analysis of two families of activated carbons reveal a consistent picture supporting
the thesis that the PSDs of the same sample obtained trough N2 and CO2 adsorption are different, a still controversial issue in the literature. Comparison of predictions from the MGM with those
of the pure slit geometry model (PSGM) shows that the former gives a more consistent picture and more similar PSDs for the
two adsorbates used. 相似文献
996.
Resende DI Silva EM Barros C Domingues MR Silva AM Cavaleiro JA 《Rapid communications in mass spectrometry : RCM》2011,25(20):3185-3195
Cinnamylideneacetophenones have been extensively used as versatile starting materials in numerous different transformations. The structural characterization of this type of compounds is, therefore, of crucial importance since it can give information on the chemistry, reactivity and also the potential biological activity of this type of compounds. Thus, 24 derivatives were systematically studied by tandem mass spectrometry (MS2) with electrospray ionization (ESI), in positive ion mode. The protonated molecules, [M + H]+, formed under ESI conditions were induced to dissociate and the fragmentation patterns were studied. The information collected provided important structural information on the type of substituents present and constitute an important database concerning this family of compounds. Overall, it was found that the substitution pattern of the cinnamylideneacetophenone derivatives changes the ESI‐MS2 fragmentation considerably. These results indicate that ESI‐MS2 is a useful technique for distinguishing positional isomers of these cinnamylideneacetophenone derivatives. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
997.
Diana Ciolacu Selestina Gorgieva Daniel Tampu Vanja Kokol 《Cellulose (London, England)》2011,18(6):1527-1541
This paper investigates the enzymatic hydrolysis of three main allomorphic forms of microcrystalline cellulose using different
cellulases, from Trichoderma reesei and from Aspergillus niger, respectively. It was demonstrated that both the morphological and crystalline structures are important parameters that have
a great influence on the course of the hydrolysis process. The efficiency of the enzymatic hydrolysis of cellulosic substrates
was estimated by the amounts of reducing sugar and by the yield of the reaction. Changes in the average particle sizes of
the cellulose allomorphs were determined during enzymatic hydrolysis. The accumulation of soluble sugar within the supernatant
was used as a measure of the biodegradation process’s efficiency, and was established by HPLC-SEC analysis. Any modifications
in the supramolecular structure of the cellulosic residues resulting from the enzymatic hydrolysis were determined by X-ray
diffraction. The action of each cellulase was demonstrated by a reduction in the crystalline index and the crystallite dimensions
of the corresponding allomorphic forms. The crystalline structure of allomorphic forms I and II did not suffer significant
modifications, while cellulose III recorded a partial return to the crystalline structure of cellulose I. The microstructures
of cellulose allomorph residues were presented using optical microscopy and scanning electron microscopy. 相似文献
998.
Luciane dos Santos Teixeira Andréa Nastri Grasso Andrea Moreira Monteiro Antonio M. Figueiredo Neto Nilson Dias VieiraJr. Magnus Gidlund Juliana Steffens Lilia Coronato Courrol 《Journal of fluorescence》2011,21(3):887-892
Low-Density Lipoprotein (LDL), often known as “bad cholesterol” is one of the responsible to increase the risk of coronary
arterial diseases. For this reason, the cholesterol present in the LDL particle has become one of the main parameters to be
quantified in routine clinical diagnosis. A number of tools are available to assess LDL particles and estimate the cholesterol
concentration in the blood. The most common methods to quantify the LDL in the plasma are the density gradient ultracentrifugation
and nuclear magnetic resonance (NMR). However, these techniques require special equipments and can take a long time to provide
the results. In this paper, we report on the increase of the Europium emission in Europium-oxytetracycline complex aqueous
solutions in the presence of LDL. This increase is proportional to the LDL concentration in the solution. This phenomenum
can be used to develop a method to quantify the number of LDL particles in a sample. A comparison between the performances
of the oxytetracycline and the tetracycline in the complexes is also made. 相似文献
999.
Formation of gold(III) complexes with the synthetic antibiotic norfloxacin (NF) was investigated in aqueous solution at pH
4.0, 7.5 and 10.6, with the ligand in cationic, zwitterionic and anionic forms, respectively. UV-Visible spectroscopy, steady
state and time-resolved fluorometry were used to characterize the complexes. Binding sites, association constants and fluorescence
lifetimes of the complexes were obtained. Au3+ binding to zwitterionic NF produced a fluorescence decrease and a small red shift. Fluorescence changes as a function of
Au3+ concentration were fitted using a one-site binding model and the association constant was obtained,
Kbzw = 1.7 ×105 \textM1 K_b^{{zw}} = {1}.{7} \times {1}{0^{{5}}}\;{{\text{M}}^{{1}}} . The association of Au3+ with cationic NF was much weaker, the obtained binding constant being
Kbcat = 2.4 ×103 \textM1 K_b^{{cat}} = {2}.{4} \times {1}{0^{{3}}}\;{{\text{M}}^{{1}}} . The Au3+ binding site for these species involves the carboxyl group, in agreement with a much stronger association of the cation with
the carboxylate anion than with the neutral acid. Association of Au3+ with nonfluorescent anionic NF presented a clear evidence of two binding sites. The highest affinity site is the unprotonated
piperazinyl group with
Kbpip \geqslant 5 ×107 \textM - 1 K_b^{{pip}} \geqslant {5} \times {1}{0^{{7}}}\;{{\text{M}}^{{ - {1}}}} , and the low affinity site includes the carboxylate anion. The results point out to important pH dependent differences in
complex formation between transition metal ions and fluoroquinolones, leading to different binding sites and association constants
that change by several orders of magnitude. 相似文献
1000.