Long Term Influence of Carbon Nanoparticles on Health and Liver Status in Rats.

Due to their excellent biocompatibility, carbon nanoparticles have been widely investigated for prospective biomedical applications. However, their impact on an organism with prolonged exposure is still not well understood. Here, we performed an experiment investigating diamond, graphene oxide and graphite nanoparticles, which were repeatedly administrated intraperitoneally into Wistar rats for four weeks. Some of the animals was sacrificed after the last injection, whereas the rest were sacrificed twelve weeks after the last exposure. We evaluated blood morphology and biochemistry, as well as the redox and inflammatory state of the liver. The results show the retention of nanoparticles within the peritoneal cavity in the form of prominent aggregates in proximity to the injection site, as well as the presence of some nanoparticles in the mesentery. Small aggregates were also visible in the liver serosa, suggesting possible transportation to the liver. However, none of the tested nanoparticles affected the health of animals. This lack of toxic effect may suggest the potential applicability of nanoparticles as drug carriers for local therapies, ensuring accumulation and slow release of drugs into a targeted tissue without harmful systemic side effects.

Biodistribution and toxicity of nanodiamonds in mice after intratracheal instillation.

Nanodiamonds (NDs) are receiving increasing attention in materials science and nanotechnology-based industries for a large variety of applications, including protein immobilization, biosensors, therapeutic molecule delivery, and bioimaging. However, limited information is known about their biokinetic behavior and toxicity in vivo. In this article, we investigated the biodistribution of NDs using radiotracer techniques and evaluated its acute toxicity in Kun Ming mice after intratracheal instillation. The biodistribution showed that, besides having the highest retention in the lung, NDs were distributed mainly in the spleen, liver, bone and heart. An analysis of histological morphology and biochemical parameters indicated that NDs could induce dose-dependent toxicity to the lung, liver, kidney and blood. This work provided fundamental data for understanding the biodistribution of NDs and will provide guidance for further study of their toxicity.

Beyond the sparkle: the impact of nanodiamonds as biolabeling and therapeutic agents.

A paper by Treussart and co-workers in this issue demonstrates the application of photoluminescent nanodiamonds for intracellular labeling as well as mechanistic cellular uptake studies. Findings from this paper reveal that optimal photoluminescence of nitrogen-vacancy color centers can be attained with photostability and no photoblinking, enabling continuous tracking in the cytoplasm over sustained time scales. In addition to the fluorescent properties of the nanodiamonds, internalization assays reveal a primarily endocytic uptake process. A high degree of nanodiamond ( approximately 46 nm in diameter) and endosome colocalization as well as cytoplasmic presence of smaller nanodiamonds was observed. Several attributes of the nanodiamond particles are elucidated in this and other recent studies, ranging from their stability as imaging agents to their potential as intracellular molecular delivery vehicles. These findings give insight into the use of nanodiamonds as an emerging platform for therapeutic and diagnostic ("theranostic") nanomedicine, forging new foundations and criteria for continued nanodiamond engineering toward downstream clinical relevance and impact.

Photoluminescent diamond nanoparticles for cell labeling: study of the uptake mechanism in mammalian cells.

Diamond nanoparticles (nanodiamonds) have been recently proposed as new labels for cellular imaging. For small nanodiamonds (size <40 nm), resonant laser scattering and Raman scattering cross sections are too small to allow single nanoparticle observation. Nanodiamonds can, however, be rendered photoluminescent with a perfect photostability at room temperature. Such a remarkable property allows easier single-particle tracking over long time scales. In this work, we use photoluminescent nanodiamonds of size <50 nm for intracellular labeling and investigate the mechanism of their uptake by living cells. By blocking selectively different uptake processes, we show that nanodiamonds enter cells mainly by endocytosis, and converging data indicate that it is clathrin-mediated. We also examine nanodiamond intracellular localization in endocytic vesicles using immunofluorescence and transmission electron microscopy. We find a high degree of colocalization between vesicles and the biggest nanoparticles or aggregates, while the smallest particles appear free in the cytosol. Our results pave the way for the use of photoluminescent nanodiamonds in targeted intracellular labeling or biomolecule delivery.

The biocompatibility of fluorescent nanodiamonds and their mechanism of cellular uptake.

The labeling of cells with fluorescent nanoparticles is promising for various biomedical applications. The objective of this study is to evaluate the biocompatibility and the mechanism of the cellular uptake of fluorescent nanodiamonds (FNDs) in cancer cells (HeLa) and pre-adipocytes (3T3-L1). With flow cytometry and the use of a battery of metabolic and cytoskeletal inhibitors, we found that the mechanism of the FND uptake in both cells is by energy-dependent clathrin-mediated endocytosis. In addition, the surface charge of FND influences its cellular uptake, as the uptake of poly-L-lysine-coated FNDs is better than that of oxidative-acid-purified FNDs at the same concentration in regular medium with or without serum. We also confirm that the proliferative potential of FND-treated and untreated cells does not exhibit any significant differences when measured at bulk cultures, and more stringently at clonal cell density. Further biocompatibility studies indicate that the in vitro differentiation of 3T3-L1 pre-adipocytes and 489-2 osteoprogenitors is not affected by the FND treatment. Our results show that FNDs are biocompatible and ideal candidates for potential applications in human stem cell research.