Release of DNA and surfactant from gel particles: The receptor solution effect and the dehydration-hydration aspects

DNA and cetyltrimethylammonium bromide (CTAB) have been used to prepare gel particles for controlled release studies. This article reports on the release of DNA and CTAB in four different solutions: in sodium bromide, in strong acid, pH 2 and pH 9 solutions for salmon testes DNA-CTAB gel particles. Also, compares results at extreme acid media and 10. mM NaBr solution with higher molecular weight DNA gel particles. The direct surfactant release was followed for the first time and shows the need of using biocompatible surfactants for the preparation of these gel particles. The release behavior depends on the receptor solution pH and the molecular weight of DNA. The first stage of the release corresponds to the so-called normal release profile and after this period, the release changed to a slow release profile. Also, the effect of dehydration and rehydration on the gel particles structure has been studied for the first time. The last process was observed visually and by SAXS measurements as a function of time. This process maintains the particle membrane integrity, structure and barrier function. The rehydration of dry gel particle in water occurs in only a few hours.Pau Güell is acknowledged for experimental assistance during his fellowship at our laboratory. Jaume Caelles from IQAC SAXS-WAXS Service is also acknowledged. This work was supported by CSIC through a JAE-DOC2010-097 contract co-financed by FSE 2007-2013. The authors acknowledge financial support from Spanish MINECO CTQ2010-14897 and Generalitat de Catalunya 2009SGR-1331.Peer reviewe

The nanostructure of surfactant-DNA complexes with different arrangements

The nanostructure of DNA with different cationic surfactant has been studied in order to elucidate the detailed arrangement concerning the position of DNA and surfactant domains in the complexes. Also, the orientation of the DNA cylinders in the thin films of the complexes was investigated. Attention was directed on the preparation methods of the complexes and to how the different surfactant structure affects the compaction of the DNA. The cationic surfactant-DNA complexes were investigated by X-ray scattering, polarized light microscopy and elemental microanalysis. It was observed that the molecular organization of the complexes between DNA and cationic surfactant corresponds to a hexagonal structure with different packing arrangements. The nanostructure of the complexes depends on the hydrophobic/hydrophilic balance of the cationic surfactant. In particular the use of arginine derived surfactants, with a large polar head group able to interact not only by electrostatics but also by hydrogen bonding, allows for the formation of more compact structures. The results suggest that the smaller the lattice parameter the more compact and stable is the complex implying slower DNA release.Imma Carrera is acknowledged for technical assistance. Jaume Caelles from the IQAC SAXS-WAXS Service and the Microanalysis Service from IQAC are acknowledged for measurements. This work was supported by CSIC through a JAE-DOC2010-097 contract co-financed by FSE 2007-2013. Financial support by CTQ2010-14897 from MINECO (Spain) and 2009SGR1331 from Generalitat de Catalunya is 18 acknowledged. M.C. Morán acknowledges the support of the MICINN (Ramon y Cajal contract RyC 2009-04683).Peer reviewe

Self assembly of pH-sensitive cationic lysine based surfactants

Three cationic surfactants of the type N(ε)-acyl lysine methyl ester hydrochloride have been studied with respect to solution behavior and adsorption on the air/water interface, as well as the thermolyotropic behavior. The self-assembly of these surfactants, which have the cationic charge on amine protonated groups, was assessed by different physicochemical methods. Depending on the pH value, these surfactants can dissociate in aqueous solutions, losing the cationic charge. Therefore, knowledge of the pK(a) of these compounds is essential to explain their behavior in aqueous solutions. The bulk techniques, conductivity, and nuclear magnetic resonance diffusion (NMR) obtained similar critical micellar concentration (CMC) values, which were well above those obtained from surface tension. Surface tension measurements were strongly dependent on the technique used, namely, Wilhelmy plate and pendant drop. The phase behavior at medium to high concentrations has been studied by optical polarizing microscopy and small angle x-ray scattering (SAXS). The X-ray studies showed that the lysine-based surfactants at low hydration have rich thermotropic liquid crystalline behavior. The results are discussed in terms of the structure of the compounds and the cationic charge of the molecule. We will show how apparently small changes in molecule structure have a large influence on phase behavior.This work was supported by CSIC through a JAE-DOC2010-097 contract cofinanced by FSE 2007-2013, Project CTQ2009-14151-C02-02, and CTQ2010-14897 from Ministerio de Economía y Competitividad (Spain)Peer reviewe