| Abstract
| - Carbon nanotubes (CNTs) constitute a class of nanomaterials that possess characteristics suitablefor a variety of possible applications. Their compatibility with aqueous environments has been made possibleby the chemical functionalization of their surface, allowing for exploration of their interactions with biologicalcomponents including mammalian cells. Functionalized CNTs (f-CNTs) are being intensively explored inadvanced biotechnological applications ranging from molecular biosensors to cellular growth substrates.We have been exploring the potential of f-CNTs as delivery vehicles of biologically active molecules inview of possible biomedical applications, including vaccination and gene delivery. Recently we reportedthe capability of ammonium-functionalized single-walled CNTs to penetrate human and murine cells andfacilitate the delivery of plasmid DNA leading to expression of marker genes. To optimize f-CNTs as genedelivery vehicles, it is essential to characterize their interactions with DNA. In the present report, we studythe interactions of three types of f-CNTs, ammonium-functionalized single-walled and multiwalled carbonnanotubes (SWNT-NH3+; MWNT-NH3+), and lysine-functionalized single-walled carbon nanotubes (SWNT-Lys-NH3+), with plasmid DNA. Nanotube−DNA complexes were analyzed by scanning electron microscopy,surface plasmon resonance, PicoGreen dye exclusion, and agarose gel shift assay. The results indicatethat all three types of cationic carbon nanotubes are able to condense DNA to varying degrees, indicatingthat both nanotube surface area and charge density are critical parameters that determine the interactionand electrostatic complex formation between f-CNTs with DNA. All three different f-CNT types in this studyexhibited upregulation of marker gene expression over naked DNA using a mammalian (human) cell line.Differences in the levels of gene expression were correlated with the structural and biophysical data obtainedfor the f-CNT:DNA complexes to suggest that large surface area leading to very efficient DNA condensationis not necessary for effective gene transfer. However, it will require further investigation to determine whetherthe degree of binding and tight association between DNA and nanotubes is a desirable trait to increasegene expression efficiency in vitro or in vivo. This study constitutes the first thorough investigation into thephysicochemical interactions between cationic functionalized carbon nanotubes and DNA toward constructionof carbon nanotube-based gene transfer vector systems.
|
