Controlled template-assisted assembly of plasmid DNA into nanometric particles with high DNA concentration

A series of novel cationic detergents that contain cleavable hydrophilic is othiuronium headgroups was synthesized, and their utility in controlled ass embly of plasmid DNA into small stable particles with high DNA concentratio n investigated. The detergents have alkyl chains of C-8-C-12 and contain hy drophilic isothiuronium headgroups that give relatively high critical micel le concentration (CMC) to the detergents (>10 mM). The isothiuronium group masks a sulfhydryl group on the detergent and can be cleaved in a controlle d manner under basic conditions to generate a reactive thiol group. The thi ol group can undergo a further reaction after the! detergents have accumula ted on a DNA template to form a disulfide-linked lipid containing two alkyl chains. The pH-dependent kinetics of cleavage of the isothiuronium group, the CIVIC of the surfactants, the formation of the complexes, and the trans fection efficiency of the DNA complexes have been investigated. Using the C -12 detergent, a similar to 6 kilo-basepair plasmid DNA was compacted into a small particle with an average diameter of around 40 nm with a similar to -13 mV xi-potential at high DNA concentration (up to 0.3 mg/mL). The compo unds were well tolerated in cell culture and showed no cytotoxicity under t heir CMCs. Under appropriate conditions, the small particle retained transf ection activity.