Probing the Outer Mitochondrial Membrane in Cardiac Mitochondria with Nanoparticles
Vadim V. Salnikov 1, Yevgeniya O Lukyanenko 2, Cecilia A. Frederick 1, W. Jonathan Lederer 1 and Valeriy I Lukyanenko 3*
1 niversity of Maryland Biotechnology Institute
2 University of Maryland
3 University of Maryland Biotechnology Institute
* To whom correspondence should be addressed. E-mail: lukyanen{at}umbi.umd.edu.
Submitted on July 31, 2006
Revised on August 29, 2006
Accepted on 20 October 2006
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Abstract |
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The outer mitochondrial membrane (OMM) is the last barrier between the mitochondrion and the cytoplasm. Breaches of OMM integrity result in the release of cytochrome c oxidase, triggering apoptosis. In this study we used calibrated gold nanoparticles to probe the OMM in rat permeabilized ventricular cells and in isolated cardiac mitochondria (ICM) under quasi-physiological ionic conditions and during permeability transition (PT). Our experiments showed that under control conditions the OMM is not permeable to 6-nm particles. However, 3-nm particles could enter the mitochondrial intermembrane space (MIMS) in mitochondria of permeabilized cells and ICM. Known inhibitors of the voltage-dependent anion channel (VDAC), König polyanion and 4, 4'-diisothiocyanatostilbene-2, 2'-disulfonic acid (DIDS), inhibited this entrance. Thus, 3-nm particles must have entered the MIMS through the VDAC. The transparency of the OMM for 3-nm particles was ~20 times that in permeabilized cells, suggesting low availability of VDAC pores within the cell. Experiments with expressed green fluorescent protein showed the existence of intracellular barriers restricting the VDAC pore availability in vivo. Thus, our data showed that: 1) the physical diameter of VDAC pores in cardiac mitochondria is 
3 nm but 
6 nm; and 2) PT-related mitochondrial swelling results in breaching and disruption of the OMM.
Key Words:
distribution of green fluorescent protein, gold nanoparticles, nanobiology, permeability transition, targeted delivery of nano-objects, voltage-dependent anion channel
