No abstract

To predict potential medical value or toxicity of nanoparticles (NPs), it is necessary to understand the chemical transformation during intracellular processes of NPs. However, it is a grand challenge to capture a high-resolution image of metallic NPs in a single cell and the chemical information on intracellular NPs. Here, by integrating synchrotron radiation-beam transmission X-ray microscopy (SR-TXM) and SR-X-ray absorption near edge structure (SR-XANES) spectroscopy, we successfully capture the 3D distribution of silver NPs (AgNPs) inside a single human monocyte (THP-1), associated with the chemical transformation of silver. The results reveal that the cytotoxicity of AgNPs is largely due to the chemical transformation of particulate silver from elemental silver (Ag(0))n, to Ag(+) ions and Ag-O-, then Ag-S- species. These results provide direct evidence in the long-lasting debate on whether the nanoscale or the ionic form dominates the cytotoxicity of silver nanoparticles. Further, the present approach provides an integrated strategy capable of exploring the chemical origins of cytotoxicity in metallic nanoparticles.

Zinc oxide nanoparticles (ZnO NPs) have been widely used in cosmetics and sunscreens, advanced textiles, self-charging and electronic devices; the potential for human exposure and the health impact at each stage of their manufacture and use are attracting great concerns. In addition to pulmonary damage, nanoparticle exposure is also strongly correlated with the increase in incidences of cardiovascular diseases; however, their toxic potential remains largely unclear. Herein, we investigated the cellular responses and endoplasmatic reticulum (ER) stress induced by ZnO NPs in human umbilical vein endothelial cells (HUVECs) in comparison with the Zn2+ ions and CeO2 NPs. We found that the dissolved zinc ion was the most significant factor for cytotoxicity in HUVECs. More importantly, ZnO NPs at noncytotoxic concentration, but not CeO2 NPs, can induce significant cellular ER stress response with higher expression of spliced xbp-1, chop, and caspase-12 at the mRNA level, and associated ER marker proteins including BiP, Chop, GADD34, p-PERK, p-eIF2α, and cleaved Caspase-12 at the protein levels. Moreover, ER stress was widely activated after treatment with ZnO NPs, while six of 84 marker genes significantly increased. ER stress response is a sensitive marker for checking the interruption of ER homeostasis by ZnO NPs. Furthermore, higher dosage of ZnO NPs (240 μM) quickly rendered ER stress response before inducing apoptosis. These results demonstrate that ZnO NPs activate ER stress-responsive pathway and the ER stress response might be used as an earlier and sensitive end point for nanotoxicological study.

Multiwall carbon nanotubes (MWCNTs) have been widely used in many disciplines due to their unique physical and chemical properties, but have also raised great concerns about their possible negative health impacts, especially through occupational exposure. Although recent studies have demonstrated that MWCNTs induce granuloma formation and/or fibrotic responses in the lungs of rats or mice, their cellular and molecular mechanisms remain largely unaddressed. Here, it is reported that the TGF-β/Smad signaling pathway can be activated by MWCNTs and play a critical role in MWCNT-induced pulmonary fibrosis. Firstly, in vivo data show that spontaneously hypertensive (SH) rats administered long MWCNTs (20-50 μm) but not short MWCNTs (0.5-2 μm) exhibit increased fibroblast proliferation, collagen deposition and granuloma formation in lung tissue. Secondly, the in vivo experiments also indicate that only long MWCNTs can significantly activate macrophages and increase the production of transforming growth factor (TGF)-β1, which induces the phosphorylation of Smad2 and then the expression of collagen I/III and extracellular matrix (ECM) protease inhibitors in lung tissues. Finally, the present in vitro studies further demonstrate that the TGF-β/Smad signaling pathway is indeed necessary for the expression of collagen III in fibroblast cells. Together, these data demonstrate that MWCNTs stimulate pulmonary fibrotic responses such as fibroblast proliferation and collagen deposition in a TGF-β/Smad-dependent manner. These observations also suggest that tube length acts as an important factor in MWCNT-induced macrophage activation and subsequent TGF-β1 secretion. These in vivo and in vitro studies further highlight the potential adverse health effects that may occur following MWCNT exposure and provide a better understanding of the cellular and molecular mechanisms by which MWCNTs induce pulmonary fibrotic reactions.

Coronaviruses belong to the family Coronaviridae, which primarily cause infection of the upper respiratory and gastrointestinal tract of hosts. Transmissible gastroenteritis virus (TGEV) is an economically significant coronavirus that can cause severe diarrhea in pigs. Silver nanomaterials (Ag NMs) have attracted great interests in recent years due to their excellent anti-microorganism properties. Herein, four representative Ag NMs including spherical Ag nanoparticles (Ag NPs, NM-300), two kinds of silver nanowires (XFJ011) and silver colloids (XFJ04) were selected to study their inhibitory effect on TGEV-induced host cell infection in vitro. Ag NPs were uniformly distributed, with particle sizes less than 20 nm by characterization of environmental scanning electron microscope and transmission electron microscope. Two types of silver nanowires were 60 nm and 400 nm in diameter, respectively. The average diameter of the silver colloids was approximately 10 nm. TGEV infection induced the occurring of apoptosis in swine testicle (ST) cells, down-regulated the expression of Bcl-2, up-regulated the expression of Bax, altered mitochondrial membrane potential, activated p38 MAPK signal pathway, and increased expression of p53 as evidenced by immunofluorescence assays, real-time PCR, flow cytometry and Western blot. Under non-toxic concentrations, Ag NPs and silver nanowires significantly diminished the infectivity of TGEV in ST cells. Moreover, further results showed that Ag NPs and silver nanowires decreased the number of apoptotic cells induced by TGEV through regulating p38/mitochondria-caspase-3 signaling pathway. Our data indicate that Ag NMs are effective in prevention of TGEV-mediated cell infection as a virucidal agent or as an inhibitor of viral entry and the present findings may provide new insights into antiviral therapy of coronaviruses.

We investigated how surface chemistry influences the interaction between gold nanorods (AuNRs) and cell membranes and the subsequent cytotoxicity arising from them in a serum-free cell culture system. Our results showed that the AuNRs coated with cetyl trimethylammonium bromide (CTAB) molecules can generate defects in the cell membrane and induce cell death, mainly due to the unique bilayer structure of CTAB molecules on the surface of the rods rather than their charge. Compared to CTAB-capped nanorods, positively charged polyelectrolyte-coated, i.e. poly(diallyldimethyl ammonium chloride) (PDDAC), AuNRs show improved biocompatibility towards cells. Thus, the present results indicate that the nature of surface molecules, especially their packing structures on the surface of AuNRs rather than surface charge, play a more crucial role in determining cytotoxicity. These findings about interfacial interactions could also explain the effects of internalized AuNRs on the structures or functions of organelles. This study will help understanding of the toxic nature of AuNRs and guide rational design of the surface chemistry of AuNRs for good biocompatibility in pharmaceutical therapy.

Under evolutionary pressure from chemotherapy, cancer cells develop resistance characteristics such as a low redox state, which eventually leads to treatment failures. An attractive option for combatting resistance is producing a high concentration of produced free radicals in situ. Here, we report the production and use of dispersible hollow carbon nanospheres (HCSs) as a novel platform for delivering the drug doxorubicine (DOX) and generating additional cellular reactive oxygen species using near-infrared laser irradiation. These irradiated HCSs catalyzed sufficiently persistent free radicals to produce a large number of heat shock factor-1 protein homotrimers, thereby suppressing the activation and function of resistance-related genes. Laser irradiation also promoted the release of DOX from lysosomal DOX@HCSs into the cytoplasm so that it could enter cell nuclei. As a result, DOX@HCSs reduced the resistance of human breast cancer cells (MCF-7/ADR) to DOX through the synergy among photothermal effects, increased generation of free radicals, and chemotherapy with the aid of laser irradiation. HCSs can provide a unique and versatile platform for combatting chemotherapy-resistant cancer cells. These findings provide new clinical strategies and insights for the treatment of resistant cancers.

The contemporary use of nanomedicines for cancer treatment has been largely limited to serving as carriers for existing therapeutic agents. Here, we provide definitive evidence that, the metallofullerenol nanomaterial Gd@C82(OH)22, while essentially not toxic to normal mammary epithelial cells, possesses intrinsic inhibitory activity against triple-negative breast cancer cells. Gd@C82(OH)22 blocks epithelial-to-mesenchymal transition with resultant efficient elimination of breast cancer stem cells (CSCs) resulting in abrogation of tumour initiation and metastasis. In normoxic conditions, Gd@C82(OH)22 mediates these effects by blocking TGF-β signalling. Moreover, under hypoxic conditions found in the tumour microenvironment, cellular uptake of Gd@C82(OH)22 is facilitated where it functions as a bi-potent inhibitor of HIF-1α and TGF-β activities, enhancing CSC elimination. These studies indicate that nanomaterials can be engineered to directly target CSCs. Thus, Gd-metallofullerenol is identified as a kind of non-toxic CSC specific inhibitors with significant therapeutic potential.