Atomic layer deposition coating of carbon nanotubes with zinc oxide causes acute phase immune responses in human monocytes in vitro and in mice after pulmonary exposure.
Atomic layer deposition (ALD) is a method for applying conformal nanoscale coatings on three-dimensional structures. We hypothesized that surface functionalization of multi-walled carbon nanotubes (MWCNTs) with polycrystalline ZnO by ALD would alter pro-inflammatory cytokine expression by human monocytes in vitro and modulate the lung and systemic immune response following oropharyngeal aspiration in mice.



Pristine (U-MWCNTs) were coated with alternating doses of diethyl zinc and water over increasing ALD cycles (10 to 100 ALD cycles) to yield conformal ZnO-coated MWCNTs (Z-MWCNTs). Human THP-1 monocytic cells were exposed to U-MWCNTs or Z-MWCNTs in vitro and cytokine mRNAs measured by Taqman real-time RT-PCR. Male C57BL6 mice were exposed to U- or Z-MWCNTs by oropharyngeal aspiration (OPA) and lung inflammation evaluated at one day post-exposure by histopathology, cytokine expression and differential counting of cells in bronchoalveolar lavage fluid (BALF) cells. Lung fibrosis was evaluated at 28 days. Cytokine mRNAs (IL-6, IL-1β, CXCL10, TNF-α) in lung, heart, spleen, and liver were quantified at one and 28 days. DNA synthesis in lung tissue was measured by bromodeoxyuridine (BrdU) uptake.



ALD resulted in a conformal coating of MWCNTs with ZnO that increased proportionally to the number of coating cycles. Z-MWCNTs released Zn(+2) ions in media and increased IL-6, IL-1β, CXCL10, and TNF-α mRNAs in THP-1 cells in vitro. Mice exposed to Z-MWCNTs by OPA had exaggerated lung inflammation and a 3-fold increase in monocytes and neutrophils in BALF compared to U-MWCNTs. Z-MWCNTs, but not U-MWCNTs, induced IL-6 and CXCL10 mRNA and protein in the lungs of mice and increased IL-6 mRNA in heart and liver. U-MWCNTs but not Z-MWCNTs stimulated airway epithelial DNA synthesis in vivo. Lung fibrosis at 28 days was not significantly different between mice treated with U-MWCNT or Z-MWCNT.



Pulmonary exposure to ZnO-coated MWCNTs produces a systemic acute phase response that involves the release of Zn(+2), lung epithelial growth arrest, and increased IL-6. ALD functionalization with ZnO generates MWCNTs that possess increased risk for human exposure.
Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, 27695, USA.
Erinn C
EC
Dandley
Toxicology Program, Department of Biological Sciences, North Carolina State University, Campus Box 7633, Raleigh, North Carolina, 27695-7633, USA.
Alexia J
AJ
Taylor
Toxicology Program, Department of Biological Sciences, North Carolina State University, Campus Box 7633, Raleigh, North Carolina, 27695-7633, USA.
Katherine S
KS
Duke
Toxicology Program, Department of Biological Sciences, North Carolina State University, Campus Box 7633, Raleigh, North Carolina, 27695-7633, USA.
Mark D
MD
Ihrie
Toxicology Program, Department of Biological Sciences, North Carolina State University, Campus Box 7633, Raleigh, North Carolina, 27695-7633, USA.
Kelly A
KA
Shipkowski
Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, 27695, USA.
Gregory N
GN
Parsons
Toxicology Program, Department of Biological Sciences, North Carolina State University, Campus Box 7633, Raleigh, North Carolina, 27695-7633, USA. jcbonner@ncsu.edu.
James C
JC
Bonner
D000210:Acute-Phase Reaction / Q000139:chemically induced* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D000393:Air Pollutants / Q000737:chemistry / Q000633:toxicity*; D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D018450:Disease Progression; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects*; D008168:Lung / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D017348:Microscopy, Electron, Scanning Transmission; D009000:Monocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D037742:Nanotubes, Carbon / Q000737:chemistry / Q000633:toxicity* / Q000648:ultrastructure; D011658:Pulmonary Fibrosis / Q000209:etiology; D012333:RNA, Messenger / Q000378:metabolism; D020545:Respiratory Mucosa / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D013499:Surface Properties; D015034:Zinc Oxide / Q000737:chemistry / Q000633:toxicity*
D000393:Air Pollutants; D016207:Cytokines; D037742:Nanotubes, Carbon; D012333:RNA, Messenger; D015034:Zinc Oxide
Atomic layer deposition; Carbon nanotubes; Inflammation; Pulmonary fibrosis