Interactions of nitroxide-labeled polyamidoamine dendrimers of generations 2 and 6 (2SBD-T and 6SBD-T, respectively) with double-stranded polynucleotidessCalf Thymus DNA (C.T.DNA), poly-(deoxyadenylic-deoxythymidylic acid) (termed Poly(AT)), poly(deoxyguanylic-deoxycytidylic acid) (termed Poly(GC)), and a double-stranded oligonucleotide of 12 base pairs (DNA-12mer)swere investigated by EPR. Computer-aided analysis of the EPR spectra provided information on the mobility of the nitroxide labels and their partition in different environments, which, in turn, gave information on the interactions between dendrimers and polynucleotides. After complexes were formed between DNA and SBD, the labels retained fast mobility at room temperature. On the basis of EPR analysis at 258 K, interaction of oligoor polynucleotides with SBDs decreased in the following order: DNA-12mer > C.T.DNA > Poly(GC) > Poly(AT). Small dendrimers (2SBD-T) at low pH (5.5) showed significant interaction with the polynucleotides, which decreased with an increase in concentration due to self-aggregation of dendrimer molecules. Conversely, interaction between large dendrimers (6SBD-T) and polynucleotides increased with an increase in SBD concentration until saturation of the interacting sites occurred. Comparison with previous studies on nSBD-T-vesicle systems indicated that interaction of dendrimers with vesicles is stronger than dendrimer-polynucleotide interaction. This study provides some insights into dendrimer-DNA interactions of particular interest in understanding the mechanism of gene transfer to mammalian cells by SBDs.

The interactions between polyamidoamine starburst dendrimers (SBDs) and vesicles consisting of dimyristoylphosphatidylcholine (DMPC) and its phosphatidylcholate salt (DMPA-Na) in various relative ratios (from 0% to 40% of DMPA-Na) were studied by electron paramagnetic resonance (EPR) and by transmission electron microscopy (TEM). The EPR spectra were computer-simulated to extract mobility and structural parameters of the probes and labels. The systems were analyzed as a function of the level of protonation of SBDs and generation (G ) 2SBD and G ) 6SBD). Both the hydrophobic 5doxylstearic spin probe (5DSA) and the positively charged nitroxide CAT16, a cationic surfactant with a C16 chain, inserted in the vesicles and monitored the formation of dendrimer-mixed vesicle (DMPC/DMPA-Na) complexes. 5DSA revealed a partial ordering of a double-layer-like structure occurring at the dendrimer surface. The spin labels at the vesicle/dendrimer interface modified the structural and mobility parameters upon complexation with the dendrimer. At high levels of protonation, dendrimers showed a larger interaction with the vesicles, especially for the mixed vesicles, compared to dendrimers at a lower level of protonation. In agreement with EPR results, TEM micrographs showed that the addition of DMPA-Na to DMPC modifies the vesicle shape from spherical to rodlike. The EPR analysis suggested that the vesicles wrap around the large dendrimers whereas the small dendrimer directly interacts with the vesicle surface. The results are very promising for a better understanding of the mechanism of interaction of dendrimers with cell membranes which may be an important feature in the role of SBDs as drug and gene carriers to target cells.

No abstract

A series of sixteen fluoro-functionalized poly (lactic acid)s were synthesised using two commercial fluorinated alcohols [3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1octanol and 4-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)benzyl alcohol] as co-initiators in the ring-opening polymerization of L-lactide and rac-lactide (the racemic mixture of L-and D-lactide) catalyzed by Tin(II) 2-ethylhexanoate. The polymers were characterized by NMR, IR, GPC, DSC and tested as potential protective coating for stone. The performances were comparatively evaluated in terms of water protection efficacy and colour changes of the treated stone. Furthermore, the photo-stability of nine selected polymers under Solar Box condition was also investigated. It has been shown that the presence of fluorine makes the stone more water-repellent. The polymers showed also interesting photo-stability and some of them provided a behavior close to PLA-FLK-PLA block copolymers recently reported in the literature, in spite of their lower fluorine content V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: [3125][3126][3127][3128][3129][3130][3131][3132][3133] 2012

No abstract