Interaction of amphiphilic derivatives of chitosan with DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine)

The interaction of chitosan and its N-dodecyl and poly(ethylene glycol) derivatives with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles was studied to evaluate the influence of molecular architecture of the polymers on the liposomes. The study was carried out in aqueous solution using differential scanning microcalorimetry (DSC) and dynamic light scattering. The interaction of these polymers with DPPC vesicles altered the gel-liquid crystalline phase transition temperature and decreased both the enthalpy (Delta H) and cooperativity of the phase transition. The results obtained indicate that perturbations in the vesicles surface and the incorporation of chitosan and its derivatives into the lipid bilayer upon polysaccharides interaction are responsible for the formation of large vesicles.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Synthesis, Characterization, and Antifungal Activities of Amphiphilic Derivatives of Diethylaminoethyl Chitosan against Aspergillus flavus

Amphiphilic derivatives of diethylaminoethyl chitosan (DEAE-CH) were synthesized using a two-step process involving initial substitution with diethylaminoethyl (DEAE) groups followed by reductive amination with dodecylaldehyde. The synthesized derivatives were characterized by ¹H NMR, gel permeation, and FTIR. The associative behaviors of these compounds in aqueous solution were studied using fluorescence spectroscopy, whereas their antifungal activities against Aspergillus flavus were evaluated in terms of mycelial growth. The effects of deacetylated chitosans and their derivatives on the mycelial growth of <i>A. flavus</i> were evaluated at several polymer concentrations (0.05–1.0 g/L), and the results were compared. The inhibition indices of the deacetylated chitosans increased with increasing <i>M</i>_w (16.9 kDa < 176 kDa < 517.7 kDa); however, derivatives with a combination of either a high molecular weight (<i>M</i>_w) and low hydrophobicity or a low <i>M</i>_w and high hydrophobicity were the most effective in inhibiting the in vitro radial growth of <i>A. flavus</i>

The Interaction Between N-Isopropylacrylamide-Acrylic Acid-Ethyl Methacrylate Thermosensitive Polymers and Cationic Surfactants

The interaction between cationic surfactants and isopropylacrylamide-acrylic acid-ethyl methacrylate (IPA:AA:EMA) terpolymers has been investigated using steady-state fluorescence and spectrophotometric measurements to assess the effect of the polymer composition on the aggregation process and terpolymers' thermosensitivities. Micropolarity studies using pyrene show that the interaction of cationic surfactants with IPA:AA:EMA terpolymers occurs at surfactant concentrations much smaller than that observed for the pure surfactant in aqueous solution. The critical aggregation concentration (CAC) values decrease with both the hydrocarbon length of the surfactant and the content of ethyl methacrylate. These results were interpreted as a manifestation of the increasing contribution of attractive hydrophobic and electrostatic forces between negatively charged polymer chains and positively charged surfactant molecules. The increase of ethyl methacrylate in the copolymers lowers the CAC due to the larger hydrophobic character of the polymer backbone. The cloud point determination reveals that the lower critical solution temperatures (LCST) depend strongly on the copolymer composition and surfactant nature. The binding of surfactants molecules to the polymer chain screens the electrostatic repulsion between the carboxylic groups inducing a conformational transition and the dehydration of the polymer chain

Beeinflussen Diabetestherapien das Krebsrisiko?

Undergraduate students on the first year of Chemistry Courses are unfamiliar with the representation of acid-base reactions using the ionic equation H+ + OH- → H2O. A chemistry class was proposed about acid-base reactions using theory and experimental evaluation of neutralization heat to discuss the energy involved when water is formed from H+ and OH- ions. The experiment is suggested using different strong acids and strong base pairs. The presentation of the theme within a chemistry class for high school teachers increased the number of individuals that saw the acid-base reaction from this perspective

Synthesis, characterization and antifungal activity of quaternary derivatives of chitosan on Aspergillus flavus

Two series of new chitosan derivatives were synthesized by reaction of deacetylated chitosan (CH) with propyl (CH-Propyl) and pentyl (CH-Pentyl) trimethylammonium bromides to obtain derivatives with increasing degrees of substitution (DS). The derivatives were characterized by 1H NMR and potentiometric titration techniques and their antifungal activities on the mycelial growth of Aspergillus flavus were investigated in vitro. The antifungal activities increase with DS and the more substituted derivatives of both series, CH-Propyl and CH-Pentyl, exhibited antifungal activities respectively three and six times higher than those obtained with commercial and deacetylated chitosan. The minimum inhibitory concentrations (MIC) were evaluated at 24, 48 and 72h by varying the polymer concentration from 0.5 to 16g/L and the results showed that the quaternary derivatives inhibited the fungus growth at polymer concentrations four times lower than that obtained with deacetylated chitosan (CH). The chitosans modified with pentyltrimethylammonium bromide exhibited higher activity and results are discussed taking into account the degree of substitution (DS). © 2012 Elsevier GmbH

Synthesis and evaluation of diethylethylamine-chitosan for gene delivery: Composition effects on the in vitro transfection efficiency

Chitosan has been indicated as a safe and promising polycation vector for gene delivery. However its low transfection efficiency has been a challenging obstacle for its application. To address this limitation, we synthesized chitosan derivatives which had increasing amounts of diethylethylamine groups (DEAE) attached to the chitosan main chain. The plasmid DNA VR1412 (pDNA), encoding the ß-galactosidase (ß-gal) reporter gene was used to prepare nanoparticles with the chitosan derivatives, and the transfection studies were performed with HeLa cells. By means of dynamic light scattering and zeta potential measurements, it was shown that diethylethylamine-chitosan derivatives (DEAEx-CH) were able to condense DNA into small particles having a surface charge depending on the polymer/DNA ratio (N/P ratio). Nanoparticles prepared with derivatives containing 15 and 25% of DEAE groups (DEAE15-CH and DEAE25-CH) exhibited transfection efficiencies ten times higher than that observed with deacetylated chitosan (CH). For derivatives with higher degrees of substitution (DS), transfection efficiency decreased. The most effective carriers showed low cytotoxicity and good transfection activities at low charge ratios (N/P). Vectors with low DS were easily degraded in the presence of lysozyme at physiological conditions in vitro and the nontoxicity displayed by these vectors opens up new opportunities in the design of DEAE-chitosan-based nanoparticles for gene delivery. © 2013 IOP Publishing Ltd

Acid-base reactions: concept, representation and generalization from the energy involved in transformations

Undergraduate students on the first year of Chemistry Courses are unfamiliar with the representation of acid-base reactions using the ionic equation H+ + OH- &#8594; H2O. A chemistry class was proposed about acid-base reactions using theory and experimental evaluation of neutralization heat to discuss the energy involved when water is formed from H+ and OH- ions. The experiment is suggested using different strong acids and strong base pairs. The presentation of the theme within a chemistry class for high school teachers increased the number of individuals that saw the acid-base reaction from this perspective

Chitosan derivatives targeting lipid bilayers: Synthesis, biological activity and interaction with model membranes

The antimicrobial activity of chitosan and derivatives to human and plant pathogens represents a high-valued prospective market. Presently, two low molecular weight derivatives, endowed with hydrophobic and cationic character at different ratios were synthesized and characterized. They exhibit antimicrobial activity and increased performance in relation to the intermediate and starting compounds. However, just the derivative with higher cationic character showed cytotoxicity towards human cervical carcinoma cells. Considering cell membranes as targets, the mode of action was investigated through the interaction with model lipid vesicles mimicking bacterial, tumoral and erythrocyte membranes. Intense lytic activity and binding are demonstrated for both derivatives in anionic bilayers. The less charged compound exhibits slightly improved selectivity towards bacterial model membranes, suggesting that balancing its hydrophobic/hydrophilic character may improve efficiency. Observing the aggregation of vesicles, we hypothesize that the "charge cluster mechanism", ascribed to some antimicrobial peptides, could be applied to these chitosan derivatives.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), BrasilUniv Estadual Paulista Unesp, Dept Quim & Ciencias Ambientais, Inst Biociencias Letras & Ciencias Exatas Ibilce, Campus Sao Jose do Rio Preto, BR-15054000 Sao Jose Do Rio Preto, SP, BrazilUniv Estadual Paulista Unesp, Dept Fis, Inst Biociencias Letras & Ciencias Exatas Ibilce, Campus Sao Jose do Rio Preto, BR-15054000 Sao Jose Do Rio Preto, SP, BrazilUniv Fed Sao Paulo, Lab Neurobiol Estrutural & Func LaNEF, Dept Biofis, R Botucatu 862, BR-04023062 Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Lab Neurobiol Estrutural & Func LaNEF, Dept Biofis, R Botucatu 862, BR-04023062 Sao Paulo, SP, BrazilFAPESP: 2009/11707-2, 2012/03619-9, 2012/02065-0, 2010/11823-0, 2012/24259-0, 2014/08372-7Web of Scienc

Synthesis and Physicochemical Characterization of Multiwalled Carbon Nanotubes/Hydroxamic Alginate Nanocomposite Scaffolds

In this study, the preparation of porous nanocomposite scaffolds (HX-CNT) from a combination of a hydroxamic derivative of alginate (HX) and an amine-functionalized multiwalled carbon nanotube (CNT) at different concentrations is described. The structure of HX was investigated by FTIR, and the degree of substitution around 9% was confirmed by elemental analysis. The interaction between CNT and alginate derivative in the nanocomposite crosslinked with calcium was confirmed by FTIR, Raman spectroscopy, and SEM. The results obtained in this study showed that scaffolds based on HX-CNT composites with a 4 wt% concentration level exhibited improved physical and mechanical properties compared to plain alginate (Young’s modulus increased from 2.2 to 5.1 MPa and elastic strength from 0.13 to 0.25 MPa) and decreased the swelling ratios from ~900 to ~673. The cytotoxicity assays using the L929 cell line proved that the nanocomposite scaffolds were nontoxic, even at the highest CNT concentration