Lung Macrophages “Digest” Carbon Nanotubes Using a Superoxide/Peroxynitrite Oxidative Pathway

Abstract

In contrast to short-lived neutrophils, macrophages display persistent presence in the lung of animals after pulmonary exposure to carbon nanotubes. While effective in the clearance of bacterial pathogens and injured host cells, the ability of macrophages to “digest” carbonaceous nanoparticles has not been documented. Here, we used chemical, biochemical, and cell and animal models and demonstrated oxidative biodegradation of oxidatively functionalized single-walled carbon nanotubes via superoxide/NO* → peroxynitrite-driven oxidative pathways of activated macrophages facilitating clearance of nanoparticles from the lung.

Magnetic Fe3O4 nanoparticle catalyzed chemiluminescence for detection of nitric oxide in living cells

“…The reaction rate constant between O 2 ·− and NO is as high as 6.7 × 10 9 L mol −1 s −1 , which is about 30 times of that between O 2 ·− and luminol radical (2.3 × 10 8 L mol −1 s −1 ) [32,33]. Moreover, the produced ONOO − is a much stronger oxidant (with a redox potential of 1.4 V) than O 2 ·− [34,35] and can first react with luminol to produce an unstable endoperoxide intermediate, which decays to ground state aminophthalate with emission of light [36]. Thus, CL signal in the reaction system is mainly emitted from endoperoxide intermediate oxidized by ONOO − .…”

Defect density in multiwalled carbon nanotubes influences ovalbumin adsorption and promotes macrophage activation and CD4^+ T-cell proliferation

“…Recent evidence has also reported the possibility of the degradation of CNTs by cells, such as neutrophils, 32 microglia, 33 and macrophages. [34][35][36] Overall, the current data suggest that the toxicity of MWCNTs can be at least partly reduced or minimized by improving design strategies of short-length MWCNT with appropriate surface modifications that are feasible for degradation by cells after the delivery of loaded proteins or drugs.…”

Hybrids of Iron-Filled Multiwall Carbon Nanotubes and Anticancer Agents as Potential Magnetic Drug Delivery Systems: In Vitro Studies against Human Melanoma, Colon Carcinoma, and Colon Adenocarcinoma

“…The outer and inner Fe@MWCNT diameters (ODs and IDs) were nonuniform and varied not only between different but also for particular nanotubes; ODs and IDs were found to be equal to 44 ± 25 and 12 ± 6 nm, respectively. The length of pristine nanotubes was 100±20 m, while oxidation led to their partial cutting and the length was reduced to 50±30 m yielding nanotubes which fall into a biocompatible and water-dispersible category [19][20][21]. Raman spectrum of Fe@MWCNT (Figure 1(c)) shows three dominating signals at 1332, 1579, and 2662 cm −1 which can be assigned to D-(disorder), G-(tangential graphite), and G -(second-order harmonic) bands, respectively [45].…”

“…On the other hand, today, there is no doubt that short, functionalized with polar moieties, and individualized MWCNTs offer a hope to be tested clinically [16]. But earlier in vitro [17] and in vivo [18] reports confirmed that, after functionalization, even >40 m long Fe@MWCNTs, providing individualized (i.e., not aggregated) nanotubes, could be considered as enzymatically degradable [19,20] and hence excretable drug vehicles [21].…”