title: Phosphate-enhanced cytotoxicity of zinc oxide nanoparticles and agglomerates.
abstract: Zinc oxide (ZnO) nanoparticles (NPs) have been found to readily react with phosphate ions to form zinc phosphate (Zn3(PO4)2) crystallites. Because phosphates are ubiquitous in physiological fluids as well as waste water streams, it is important to examine the potential effects that the formation of Zn3(PO4)2 crystallites may have on cell viability. Thus, the cytotoxic response of NIH/3T3 fibroblast cells was assessed following 24h of exposure to ZnO NPs suspended in media with and without the standard phosphate salt supplement. Both particle dosage and size have been shown to impact the cytotoxic effects of ZnO NPs, so doses ranging from 5 to 50 μg/mL were examined and agglomerate size effects were investigated by using the bioinert amphiphilic polymer polyvinylpyrrolidone (PVP) to generate water-soluble ZnO ranging from individually dispersed 4 nm NPs up to micron-sized agglomerates. Cell metabolic activity measures indicated that the presence of phosphate in the suspension media can led to significantly reduced cell viability at all agglomerate sizes and at lower ZnO dosages. In addition, a reduction in cell viability was observed when agglomerate size was decreased, but only in the phosphate-containing media. These metabolic activity results were reflected in separate measures of cell death via the lactate dehydrogenase assay. Our results suggest that, while higher doses of water-soluble ZnO NPs are cytotoxic, the presence of phosphates in the surrounding fluid can lead to significantly elevated levels of cell death at lower ZnO NP doses. Moreover, the extent of this death can potentially be modulated or offset by tuning the agglomerate size. These findings underscore the importance of understanding how nanoscale materials can interact with the components of surrounding fluids so that potential adverse effects of such interactions can be controlled.
authors.affiliation: Mechanical Engineering, Texas A&M University, College Station, TX 77843, United States; Chemical Engineering, Texas A&M University, College Station, TX 77843, United States.
authors.forename: W Neil
authors.initials: WN
authors.lastname: Everett
authors.affiliation: Chemical Engineering, Texas A&M University, College Station, TX 77843, United States.
authors.forename: Christina
authors.initials: C
authors.lastname: Chern
authors.affiliation: Mechanical Engineering, Texas A&M University, College Station, TX 77843, United States.
authors.forename: Dazhi
authors.initials: D
authors.lastname: Sun
authors.affiliation: Chemical Engineering, Texas A&M University, College Station, TX 77843, United States.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: McMahon
authors.affiliation: Mechanical Engineering, Texas A&M University, College Station, TX 77843, United States.
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center College of Medicine, Bryan, TX 77807, United States.
authors.forename: Wei-Jung A
authors.initials: WJ
authors.lastname: Chen
authors.affiliation: Chemical Engineering, Texas A&M University, College Station, TX 77843, United States; Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, United States. Electronic address: hahnm@rpi.edu.
authors.forename: Mariah S
authors.initials: MS
authors.lastname: Hahn
authors.affiliation: Mechanical Engineering, Texas A&M University, College Station, TX 77843, United States. Electronic address: hjsue@tamu.edu.
authors.forename: H-J
authors.initials: HJ
authors.lastname: Sue
mesh_terms: D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D053768:Metal Nanoparticles; D051379:Mice; D041681:NIH 3T3 Cells; D010316:Particle Size; D010710:Phosphates / Q000633:toxicity*; D011205:Povidone / Q000737:chemistry; D012995:Solubility; D015034:Zinc Oxide / Q000737:chemistry / Q000633:toxicity*
chemical_list: D010710:Phosphates; D007770:L-Lactate Dehydrogenase; D011205:Povidone; D015034:Zinc Oxide
keywords: AAS; Aggregation; Culture media byproduct; DLS; DMEM without phosphates; DMEM(+phos); DMEM(−phos); Dulbecco's modified Eagle's medium (DMEM) with phosphates; FBS; HRTEM; ICP-MS; NP; Nanohazard; PBS; PS; PSG; PVP; X-ray diffraction; XRD; Zinc oxide toxicity; Zinc phosphate toxicity; atomic absorption spectrometry; dynamic light scattering; fetal bovine serum; high-resolution transmission electron microscopy; inductively coupled plasma-mass spectrometry; nanoparticle; penicillin streptomycin; penicillin streptomycin l-glutamine; phosphate buffered saline; polyvinylpyrrolidone