Carbon nanotubes inhibit the hemolytic activity of the pore-forming toxin pyolysin

Abstract

Functionalized carbon nanotubes have already demonstrated great biocompatibility and potential for drug delivery. We have synthesized acid oxidized and non-covalently PEGlyated single-walled carbon nanotubes (SWNTs), which were previously prepared for drug delivery purposes, and explored their potential for detoxifi cation in the bloodstream. Our investigations of the binding of SWNTs to a pore-forming toxin pyolysin show that SWNTs prevented toxin-induced pore formation in the cell membrane of human red blood cells. Quantitative hemolysis assay and scanning electron microscopy were used to evaluate the inhibition of hemolytic activity of pyolysin. According to Raman spectroscopy data, human red blood cells, unlike HeLa cells, did not internalize oxidized SWNTs. Molecular modeling and circular dichroism measurements were used to predict the 3-D structure of pyolysin (domain 4) and its interaction with SWNTs. The tryptophan-rich hydrophobic motif in the membrane-binding domain of pyolysin, a common construct in a large family of cholesterol-dependent cytolysins, shows high affi nity for SWNTs.

Tethered bilayer membranes as a complementary tool for functional and structural studies: The pyolysin case

“…As seen from Figure scanning electron microscopy of red blood cells subjected to PLO [32] or with the pore sizes measured for other members of the cholesterol-dependent cytolysins family [33].…”

Nano-antidotes for drug overdose and poisoning

“…Although the good safety profile, biodegradability, and relative manufacturing simplicity make liposomes and ILEs attractive options, ILEs are often criticized for their lack of stability and limited chemical diversity. In recent years, a considerable amount of work has been invested into the development of other biodetoxifying nanostructures, including nanospheres, nanocapsules, and nanotubes (21)(22)(23). Several studies have reported good extraction efficiencies for drugs or heavy metals under in vitro conditions using nanoparticles, but most of the systems investigated so far do not possess optimal properties for an antidotal application in vivo.…”

“…Several studies have reported good extraction efficiencies for drugs or heavy metals under in vitro conditions using nanoparticles, but most of the systems investigated so far do not possess optimal properties for an antidotal application in vivo. The high surface charge (21), nonbiodegradability (23), and/ or hemolytic effects (22) of several tested systems preclude clinical use, especially considering the high doses that are often needed to counteract the overdosed drugs.…”

Toxicity of single-walled carbon nanotubes

“…Using confocal microscopy, Sachar and Saxena (2011) showed that the fluorescent-tagged SWNTs may enter into the erythrocytes through a passive mechanism after 1 h exposure (Sachar and Saxena 2011), whereas Raman spectroscopic data from Donkor et al (2009) suggests that there was no evidence of uptake by erythrocytes after 2 h incubation with SWNTs (Donkor et al 2009). Given the absence of endocytic receptors on normal mature erythrocytes, it is plausible that the uptake of SWNTs by erythrocytes, as reported by Sachar and Saxena (2011) may have been occurred through other mechanism(s), such as passive uptake, which has been shown with titanium dioxide, polystyrene, and gold nanoparticles (Geiser et al 2005;Rothen-Rutishauser et al 2006); the SWNTs might also have been associated with the erythrocyte membrane instead of entering the cells.…”