title: Toxicity evaluation of biodegradable chitosan nanoparticles using a zebrafish embryo model.
abstract: BACKGROUND
  Although there are a number of reports regarding the toxicity evaluation of inorganic nanoparticles, knowledge on biodegradable nanomaterials, which have always been considered safe, is still limited. For example, the toxicity of chitosan nanoparticles, one of the most widely used drug/gene delivery vehicles, is largely unknown. In the present study, the zebrafish model was used for a safety evaluation of this nanocarrier.
  
  
  METHODS
  Chitosan nanoparticles with two particle sizes were prepared by ionic cross-linking of chitosan with sodium tripolyphosphate. Chitosan nanoparticles of different concentrations were incubated with zebrafish embryos, and ZnO nanoparticles were used as the positive control.
  
  
  RESULTS
  Embryo exposure to chitosan nanoparticles and ZnO nanoparticles resulted in a decreased hatching rate and increased mortality, which was concentration-dependent. Chitosan nanoparticles at a size of 200 nm caused malformations, including a bent spine, pericardial edema, and an opaque yolk in zebrafish embryos. Furthermore, embryos exposed to chitosan nanoparticles showed an increased rate of cell death, high expression of reactive oxygen species, as well as overexpression of heat shock protein 70, indicating that chitosan nanoparticles can cause physiological stress in zebrafish. The results also suggest that the toxicity of biodegradable nanocarriers such as chitosan nanoparticles must be addressed, especially considering the in vivo distribution of these nanoscaled particles.
  
  
  CONCLUSIONS
  Our results add new insights into the potential toxicity of nanoparticles produced by biodegradable materials, and may help us to understand better the nanotoxicity of drug delivery carriers.
authors.affiliation: Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, People's Republic of China.
authors.forename: Yu-Lan
authors.initials: YL
authors.lastname: Hu
authors.forename: Wang
authors.initials: W
authors.lastname: Qi
authors.forename: Feng
authors.initials: F
authors.lastname: Han
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Shao
authors.forename: Jian-Qing
authors.initials: JQ
authors.lastname: Gao
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D048271:Chitosan / Q000633:toxicity*; D004337:Drug Carriers / Q000633:toxicity*; D004625:Embryo, Nonmammalian; D047108:Embryonic Development / Q000187:drug effects*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D053758:Nanoparticles / Q000633:toxicity*; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism; D018675:Toxicity Tests; D015027:Zebrafish; D015034:Zinc Oxide / Q000633:toxicity
chemical_list: D004337:Drug Carriers; D018840:HSP70 Heat-Shock Proteins; D017382:Reactive Oxygen Species; D048271:Chitosan; D015034:Zinc Oxide