期刊
ACS NANO
卷 13, 期 1, 页码 187-202出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.8b05151
关键词
endosomal escape; polyplexes; proton sponge effect; stochastic optical reconstruction microscopy; STORM; glycogen
类别
资金
- Australian Research Council (ARC) [FT140100873]
- National Health and Medical Research Council [APP1135806]
- University of Melbourne Establishment Grant
- University of Melbourne Endeavour Research Fellowship - Australian Government, Department of Education and Training [5574]
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology [CE140100036]
- Australian Research Council [FT140100873] Funding Source: Australian Research Council
The intracellular delivery of nucleic acids and proteins remains a key challenge in the development of biological therapeutics. In gene therapy, the inefficient delivery of small interfering RNA (siRNA) to the cytosol by lipoplexes or polyplexes is often ascribed to the entrapment and degradation of siRNA payload in the endosomal compartments. A possible mechanism by which polyplexes rupture the endosomal membrane and release their nucleic acid cargo is commonly defined as the proton sponge effect. This is an osmosis-driven process triggered by the proton buffering capacity of polyplexes. Herein, we investigate the molecular basis of the proton sponge effect through direct visualization of the siRNA trafficking process, including analysis of individual polyplexes endosomes, using stochastic optical reconstruction microscopy. We probe the sequential siRNA trafficking steps through single molecule super-resolution analysis of subcellular structures, polyplexes, and silencing RNA molecules. Specifically, individual intact polyplexes released in the cytosol upon rupture of the endosomes, the damaged endosomal vesicles, and the disassembly of the polyplexes in the cytosol are examined. We find that the architecture of the polyplex and the rigidity of the cationic polymer chains are crucial parameters that control the mechanism of endosomal escape driven by the proton sponge effect. We provide evidence that in highly branched and rigid cationic polymers, such as glycogen or polyethylenimine, immobilized on silica nanoparticles, the proton sponge effect is effective in inducing osmotic swelling and rupture of endosomes.
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