M. Sastry et al., Studies on the formation of DNA - Cationic lipid composite films and DNA hybridization in the composites, J PHYS CH B, 105(19), 2001, pp. 4409-4414
The formation of composite films of double-stranded DNA and cationic lipid
molecules (octadecylamine, ODA) and the hybridization of complementary sing
le-stranded DNA molecules in such composite films are demonstrated. The imm
obilization of DNA is accomplished by simple immersion of a thermally evapo
rated ODA film in the DNA solution at close to physiological pH. The entrap
ment of the DNA molecules in the cationic lipid film is dominated by attrac
tive electrostatic interaction between the negatively char ed phosphate bac
kbone of the DNA molecules and the protonated amine molecules in the therma
lly evaporated film and has been quantified using quartz crystal microgravi
metry (QCM). Fluorescence studies of DNA-ODA composite films obtained by se
quential immersion of the ODA matrix in the complementary single-stranded D
NA solutions using ethidium bromide intercalator clearly showed that the hy
bridization of the DNA single strands had occurred within the composite fil
m. Furthermore, fluorescence studies of the preformed double-stranded DNA-O
DA biocomposite film indicated DNA entrapment without distortion to the nat
ive double-helical structure. The DNA-ODA biocomposite films have been furt
her characterized with Fourier transform infrared (FTIR) and X-ray photoele
ctron spectroscopy (XPS) measurements. The DNA-fatty lipid composite films
would serve as model systems for understanding DNA-membrane interactions as
well as in the study of DNA-drug/protein interactions. This approach also
shows promise for the synthesis of patterned DNA films and consequent appli
cation in disease detection and genome sequencing.