DQAsome/DNA complexes release DNA upon contact with isolated mouse liver mitochondria

DQAsomes are mitochondrictropic cationic vesicles, which have been develope d by us for the supposed transport of DNA to mitochondria in living cells [ Pharm. Res. 15 (1998) 334]. Our strategy for the delivery of DNA into the m atrix of mitochondria is based upon the putative transport of a DNA-signal peptide conjugate to mitochondria, the liberation of this conjugate from DQ Asomes at the mitochondrial membrane followed by DNA uptake via the mitocho ndrial protein import machinery. As a first and important step towards deli very of DNA into mitochondria of living cells, we studied the DNA release f rom DQAsomes upon contact with non-energized mitochondria in vitro. Mitocho ndria were isolated from mouse liver and characterized by electron microsco py and the determination of mitochondrial marker enzyme activity. DQAsomes were added to DNA in the presence of SYBR Green I resulting in the formatio n of DQAsome/DNA complex and the complete loss of fluorescence. Following t he addition of isolated mitochondria to DQAsome/DNA complex, the fluorescen ce signal was recovered due to the dissociation of DNA from its cationic ca rrier. Thus, DQAsome/DNA complexes were shown to release DNA upon contact w ith the surface of mitochondria thereby meeting a key requirement for our s trategy towards mitochondrial DNA delivery. (C) 2001 Elsevier Science BY. A ll rights reserved.