Aggregation of Cyclodextrins: Fundamental Issues and Applications

The aggregation of cyclodextrins (CD) in aqueous solution is an old, yet still vastly unexplored topic that has been studied at least since the 1980s. At that time, few authors took into consideration the possibility of formation of aggregates for the interpretation of thermodynamic and thermophysical properties of CDs in aqueous solution. The aggregates appear at quite low CD concentrations and seem to encompass only a small number of CD molecules. They also occur in water in the presence of hydrophobic or amphiphilic moieties, including surfactants, assuming a preassembled state with the hydrophobic chains threading through one or two CDs. After a long period in which it has been neglected, CD aggregation is now a hot topic and one far from gathering consensus. In this chapter, a timely and critical review on the phenomenon of CD aggregation and the respective supramolecular properties, including some computational rationales, will be presented. A comprehensive summary of CD aggregates studied to date, indicating the formation conditions, characterization techniques, and applications, is also provided

Use of an acoustic wave sensor to follow lead absorption by porcine skin

A new acoustic wave sensor capable of detecting and quantifying lead is presented, and fully characterized in terms of sensitivity, selectivity, and linear calibration range. The sensor was used to quantify lead absorption by pig stratum corneum and to follow in real time, both the absorption and desorption of lead by the skin. Values of lead absorption of 29.6 mg Pb2+/g of stratum corneum were obtained. Lead in solution was also quantified by atomic absorption spectrometry (AAS). The results obtained by both methods, AAS and the sensor, were compared and no statistical differences in the accuracy and precision of the results were found.http://www.sciencedirect.com/science/article/B6THH-4P4NPG3-2/1/5b7ff13690528fc99df11246c971c26

Optimization of levofloxacin-loaded crosslinked chitosan microspheres for inhaled aerosol therapy

International audienc

Lysine-based surfactants as chemical permeation enhancers for dermal delivery of local anesthetics

The aim of this study is to investigate the efficacy of new, biocompatible, lysine-based surfactants as chemical permeation enhancers for two different local anesthetics, tetracaine and ropivacaine hydrochloride, topically administered. Results show that this class of surfactants strongly influences permeation, especially in the case of the hydrophilic and ionized drug, ropivacaine hydrochloride, that is not easily administered through the stratum corneum. It is also seen that the selected permeation enhancers do not have significant deleterious effects on the skin structure. A cytotoxicity profile for each compound was established from cytotoxicity studies. Molecular dynamics simulation results provided a rationale for the experimental observations, introducing a mechanistic view of the action of the surfactants molecules upon lipid membranes.info:eu-repo/semantics/publishedVersio

1,3-Dipolar cycloaddition of azomethine ylides generated from aziridines in supercritical carbon dioxide

The 1,3-dipolar cycloaddition of azomethine ylides with DMAD in supercritical carbon dioxide is reported. The photolysis reaction conditions were optimized with a suitable adjustment of pressure, temperature, irradiation time and co-solvent concentration leading to a more efficient reaction than in neat acetonitrile. Similar results were observed using thermal reaction conditions. Supercritical carbon dioxide with a minute co-solvent addition is shown to be a very efficient medium for promoting this type of cycloadditions.http://www.sciencedirect.com/science/article/B6THS-4K7FJ88-D/1/e5b9b60b4e9f3055fb5a425dfc75939

Novel serine-based gemini surfactants as chemical permeation enhancers of local anesthetics: a comprehensive study on structure–activity relationships, molecular dynamics and dermal delivery

This work aims at studying the efficacy of a series of novel biocompatible, serine-based surfactants as chemical permeation enhancers for two different local anesthetics, tetracaine and ropivacaine, combining an experimental and computational approach. The surfactants consist of gemini molecules structurally related, but with variations in headgroup charge (nonionic vs. cationic) and in the hydrocarbon chain lengths (main and spacer chains). In vitro permeation and molecular dynamics studies combined with cytotoxicity profiles were performed to investigate the permeation of both drugs, probe skin integrity, and rationalize the interactions at molecular level. Results show that these enhancers do not have significant deleterious effects on the skin structure and do not cause relevant changes on cell viability. Permeation across the skin is clearly improved using some of the selected serine-based gemini surfactants, namely the cationic ones with long alkyl chains and shorter spacer. This is noteworthy in the case of ropivacaine hydrochloride, which is not easily administered through the stratum corneum. Molecular dynamics results provide a mechanistic view of the surfactant action on lipid membranes that essentially corroborate the experimental observations. Overall, this study suggests the viability of these serine-based surfactants as suitable and promising delivery agents in pharmaceutical formulations.info:eu-repo/semantics/publishedVersio

Aggregation and gelation in hydroxypropylmethyl cellulose aqueous solutions

http://www.sciencedirect.com/science/article/B6WHR-4TC923M-1/2/012a59092ead1ce270813efcf98c1fb

Cationic agents for DNA compaction

Fluorescence microscopy was used to investigate the conformational changes of individual T4 DNA molecules induced by different compacting agents, namely the cationic surfactants, cetyltrimethylammonium bromide (CTAB) and chloride (CTAC), iron(III), lysozyme, and protamine sulfate. A protocol for establishing size estimates is suggested to obtain reproducible results. Observations show that in the presence of lysozyme and protamine sulfate, DNA molecules exhibit a conformational change from an elongated coil structure to compact globules, usually interpreted as a first-order transition. The maximum degree of compaction that is attained when iron(III) or CTAB (CTAC) are used as compacting agents is considerably smaller, and intermediate structures (less elongated coils) are visible even for high concentrations of these agents. Dynamic light scattering experiments were carried out, for some of the systems, to assess the reliability of size estimates from fluorescence microscopy.http://www.sciencedirect.com/science/article/B6WHR-4S7SV46-1/1/4fec487f09e6c653d0e22a0669f4e0d

Characterization of Isomeric Cationic Porphyrins with β-Pyrrolic Substituents by Electrospray Mass Spectrometry: The Singular Behavior of a Potential Virus Photoinactivator

Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) have been used to differentiate the 2- and 4-methylpyridyl isomers of free-base and metallated cationic β-vinylpyridylporphyrins. The analysis by ESI-MS/MS of the deuterated analogs and semiempirical calculations of structural and electronic parameters were also undertaken. The two free-base isomers are easily differentiated by ESI-MS/MS but the presence of a metallic center renders differentiation of the metallated isomers less effective. The data acquired show that of all the studied compounds, the free-base 2-methylpyridyl isomer, which was operative in the in vitro photoinactivation of Herpes simples virus, has a different gas-phase behavior. Local distortion of the macrocycle due to the presence of the β-vinylpyridyl substituent occurs for all the compounds, but a different electron density distribution can account for the observed gas-phase behavior of this potential virus photoinactivator