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Carbon nanotubes (CNTs) consist of carbon atoms arranged in sheets of graphene rolled up into cylindrical shapes. This class of nanomaterials has attracted attention because of their extraordinary properties, such as high electrical and thermal conductivity. In addition, development in CNT functionalization chemistry has led to an enhanced dispersibility in aqueous physiological media which indeed broadens the spectrum for their potential biological applications including gene delivery. The aim of this study is to determine the capability of different cationic polymer-grafted multiwalled carbon nanotubes (MWNTs) (polymer-g-MWNTs) to efficiently complex and transfer plasmid DNA (pCMV-βGal) in vitro without promoting cytotoxicity. Carboxylated MWNT is chemically conjugated to the cationic polymers polyethylenimine (PEI), polyallylamine (PAA), or a mixture of the two polymers. In order to explore the potential of these polymer-g-MWNTs as gene delivery systems, we first study their capacity to complex plasmid DNA (pDNA) using agarose gel electrophoresis. Gel migration studies confirm pDNA binding to polymer-g-MWNT with different affinities, highest for PEI-g-MWNT and PEI/PAA-g-CNT constructs. β-galactosidase expression is assessed in human lung epithelial (A549) cells, and the cytotoxicity is determined by modified LDH assay after 24 h incubation period. Additionally, PEI-g-MWNT and/or PEI/PAA-g-MWNT reveal an improvement in gene expression when compared to the naked pDNA or to the equivalent amounts of PEI polymer alone. Mechanistically, pDNA was delivered by the polymer-g-MWNT constructs via a different pathway compared to those used by polyplexes. In conclusion, polymer-g-MWNTs may be considered in the future as a versatile tool for efficient gene transfer in cancer cells in vitro, provided their toxicological profile is established.

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A comprehensive study of the chemical vapor codeposition of silica, alumina, and aluminosilicates from SiCl 4 -AlCl 3 -H 2 -CO 2 mixtures is presented. A hot-wall reactor, coupled to an electronic microbalance, is used to investigate the dependence of the deposition rate on temperature, pressure, composition, and total flow rate over a broad range of operating conditions. The experimental observations are discussed in the context of the results obtained in independent deposition experiments of silica and alumina from mixtures of SiCl 4 -H 2 -CO 2 and AlCl 3 -H 2 -CO 2 , respectively, in the same apparatus. The results show that the deposition of silica proceeds at very low rates that are by more than an order of magnitude lower than those of alumina deposition at the same temperature, pressure, total flow rate, and carbon dioxide and chloride mole fractions in the feed. When both chlorides (SiCl 4 and AlCl 3 ) are fed to the reactor, that is, in the codeposition process, the rate of SiO 2 deposition is much higher than that seen in the single species deposition experiments, while the opposite behavior is observed for the rate of deposition of Al 2 O 3 . The results of deposition experiments conducted on refractory wires, in order to obtain information on the effect of the substrate position in the reactor, show that manipulation of residence time offers a way to control the composition of the codeposited films in alumina and silica. The experimental results are compared with those obtained in a past study using methyltrichlorosilane as silicon source.